Descriptive Epidemiology of the Multicenter ACL Revision Study (MARS) Cohort

1. The MARS Group*†

1. †Rick W. Wright, MD, Department of Orthopaedic Surgery, Washington University School of Medicine, One Barnes-Jewish Hospital Plaza, Suite 11300, West Pavillion, St Louis, MO 63110 (e-mail: rwwright1@aol.com).

1. Rick W. Wright, MD; Laura J. Huston, MS; Kurt P. Spindler, MD; Warren R. Dunn, MD, MPH; Amanda K. Haas, MA; Christina R. Allen, MD; Daniel E. Cooper, MD; Thomas M. DeBerardino, MD; Brett (Brick) A. Lantz, MD; Barton J. Mann, PhD; Michael J. Stuart, MD; John P. Albright, MD; Annunziato (Ned) Amendola, MD; Allen F. Anderson, MD; Jack T. Andrish, MD; Christopher C. Annunziata, MD; Robert A. Arciero, MD; Bernard R. Bach Jr, MD; Champ L. Baker III, MD; Arthur R. Bartolozzi, MD; Keith M. Baumgarten, MD; Jeffery R. Bechler, MD; Jeffrey H. Berg, MD; Geoffrey A. Bernas, MD; Stephen F. Brockmeier, MD; Robert H. Brophy, MD; Charles A. Bush-Joseph, MD; J. Brad Butler V, MD; John D. Campbell, MD; James L. Carey, MD, MPH; James E. Carpenter, MD; Brian J. Cole, MD; Jonathan M. Cooper, MD; Charles L. Cox, MD; R. Alexander Creighton, MD; Diane L. Dahm, MD; Tal S. David, MD; David C. Flanigan, MD; Robert W. Frederick, MD; Charles J. Gatt Jr, MD; Steven R. Gecha, MD; James Robert Giffin, MD; Donald B. Goodfellow, MD; Sharon L. Hame, MD; Jo A. Hannafin, MD, PhD; Christopher D. Harner, MD; Norman Lindsay Harris Jr, MD; Keith S. Hechtman, MD; Elliott B. Hershman, MD; Rudolf G. Hoellrich, MD; Timothy M. Hosea, MD; David C. Johnson, MD; Timothy S. Johnson, MD; Morgan H. Jones, MD; Christopher C. Kaeding, MD; Thomas E. Klootwyk, MD; Bruce A. Levy, MD; C. Benjamin Ma, MD; G. Peter Maiers II, MD; Robert G. Marx, MD; Matthew J. Matava, MD; Gregory M. Mathien, MD; David R. McAllister, MD; Eric C. McCarty, MD; Robert G. McCormack, MD; Bruce S. Miller, MD, MS; Ali R. Motamedi, MD; Carl W. Nissen, MD; Daniel F. O’Neill, MD, EdD; Richard D. Parker, MD; Mark L. Purnell, MD; Arun J. Ramappa, MD; Michael A. Rauh, MD; Arthur Rettig, MD; Jon K. Sekiya, MD; Kevin G. Shea, MD; Orrin H. Sherman, MD; James R. Slauterbeck, MD; Matthew V. Smith, MD; LTC Steven J. Svoboda, MD; Timothy N. Taft, MD; COL Joachim J. Tenuta, MD; Edwin M. Tingstad, MD; Armando F. Vidal, MD; Darius G. Viskontas, MD; Richard A. White, MD; James S. Williams Jr, MD; Michelle L. Wolcott, MD; Brian R. Wolf, MD; James J. York, MD.

Abstract

Background: Revision anterior cruciate ligament (ACL) reconstruction has worse outcomes than primary reconstructions. Predictors for these worse outcomes are not known. The Multicenter ACL Revision Study (MARS) Group was developed to perform a multisurgeon, multicenter prospective longitudinal study to obtain sufficient subjects to allow multivariable analysis to determine predictors of clinical outcome.

Purpose: To describe the formation of MARS and provide descriptive analysis of patient demographics and clinical features for the initial 460 enrolled patients to date in this prospective cohort.

Study Design: Cross-sectional study; Level of evidence, 2.

Methods: After training and institutional review board approval, surgeons began enrolling patients undergoing revision ACL reconstruction, recording patient demographics, previous ACL reconstruction methods, intra-articular injuries, and current revision techniques. Enrolled subjects completed a questionnaire consisting of validated patient-based outcome measures.

Results: As of April 1, 2009, 87 surgeons have enrolled a total of 460 patients (57% men; median age, 26 years). For 89%, the reconstruction was the first revision. Mode of failure as deemed by the revising surgeon was traumatic (32%), technical (24%), biologic (7%), combination (37%), infection (<1%),>

Conclusion: The MARS Group has been able to quickly accumulate the largest revision ACL reconstruction cohort reported to date. Traumatic reinjury is deemed by surgeons to be the most common single mode of failure, but a combination of factors represents the most common mode of failure. Allograft graft choice is more common in the revision setting than autograft. Concomitant knee injury is extremely common in this population.

For further information: http://ajs.sagepub.com/content/38/10/1979.abstract

From Medicine and Science in Sports and Exercise®

Prevalence of Chondral Defects in Athletes' Knees: A Systematic Review

David C. Flanigan; Joshua D. Harris; Thai Q. Trinh; Robert A. Siston; Robert H. Brophy

Authors and Disclosures

Abstract

Purpose: To determine the prevalence of full-thickness focal chondral defects in the athlete's knee.
Methods: We conducted a systematic review of multiple databases, evaluating studies of the prevalence of articular cartilage defects in athletes. Because of the heterogeneity of data, a meta-analysis could not be performed.
Results: Eleven studies were identified for inclusion (931 subjects). All studies were level 4 evidence. Defects were diagnosed via magnetic resonance imaging, arthroscopy, or both. Forty percent of athletes were professionals (NBA and NFL). The overall prevalence of full-thickness focal chondral defects in athletes was 36% (range = 2.4%–75% between all studies). Fourteen percent of athletes were asymptomatic at the time of diagnosis. Patellofemoral defects (37%) were more common than femoral condyle (35%) and tibial plateau defects (25%). Medial condyle defects were more common than lateral (68% vs 32%), and patella defects were more common than trochlea (64% vs 36%). Meniscal tear (47%) was the most common concomitant knee pathological finding, followed by anterior cruciate ligament tear (30%) and then medial collateral ligament or lateral collateral ligament tear (14%).
Conclusions: Full-thickness focal chondral defects in the knee are more common in athletes than among the general population. More than one-half of asymptomatic athletes have a full-thickness defect. Further study is needed to define more precisely the prevalence of these lesions in this population.

Introduction

Articular cartilage defects of the knee demonstrate limited regenerative potential in response to injury and, therefore, have been implicated as a potential risk factor in the development of early-onset osteoarthritis.^[1,13,41]Chondral defects are seen in 34%–62% of knee arthroscopies,^[2,12,18,52] while full-thickness focal lesions of with an area of at least 1–2 cm² are seen in 4.2%–6.2% (range of prevalence among referenced studies) of all arthroscopies^[2,12,18,52] in patients younger than 40 yr. These studies document the prevalence of chondral defects in all patients within the general population, athletes and nonathletes alike, of any age requiring knee arthroscopy for any reason. Younger patients with large, isolated, full-thickness defects represent those most amenable to cartilage repair or restoration with marrow stimulation techniques, osteochondral autograft transfer system (OATS/mosaicplasty), osteochondral allograft, or cell-based therapy with autologous chondrocyte implantation (ACI).^[10,35]

The natural history of the isolated chondral defect and to what degree the isolated defect may become symptomatic is not completely understood.^[8] The presence of concomitant injuries, whether acute or chronic, further influences management of these lesions. Insufficiency of the anterior cruciate ligament (ACL),^[19,45,51]deficiency of the menisci, and malalignment of both the patellofemoral and tibiofemoral compartments must be addressed during surgery.^[10,53] Intra-articular knee injuries are known to occur more frequently in an athletic population and may lead to degenerative changes in the knee.^[26] Compared with the general population, athletes place a higher demand on the knee and, as a result, are 12 times more likely to develop osteoarthritis.^[13,41]Epidemiologic data suggest that athletes subjected to both acute contact trauma and repetitive joint loading during pivoting and twisting are more likely to show signs of joint degeneration.^[13,41]

A recent systematic review of microfracture concluded that early treatment of chondral defects with microfracture was associated with positive clinical and histologic outcomes.^[36] Another systematic review^[17b] reported that early treatment of defects with either ACI or microfracture was associated with positive clinical outcomes and earlier return to sport. Therefore, early diagnosis and treatment of chondral defects in the knee of the athlete may facilitate a quicker return to sport after injury and decrease the risk of developing osteoarthritis in the future.^[35]Although the prevalence of chondral defects in the general population, athletes and nonathletes together, has been well documented, the prevalence of chondral defects in an exclusively athletic population is currently unknown. The purpose of this systematic review was to report the prevalence of full-thickness chondral defects in athletes using the currently available evidence. We hypothesize that the prevalence of articular cartilage lesions in the athlete is higher than published standards for the general population.

For further information: http://www.medscape.com/viewarticle/729630?src=mp&spon=8&uac=45143PK

© 2010 The Journal of Bone and Joint Surgery, Inc.

Surgical Versus Functional Treatment for Acute Ruptures of the Lateral Ligament Complex of the Ankle in Young Men

A Randomized Controlled Trial

Harri Pihlajamäki, MD, PhD¹, Kalevi Hietaniemi, MD, PhD²,Mika Paavola, MD, PhD³, Tuomo Visuri, MD, PhD¹ andVille M. Mattila, MD, PhD⁴

¹ Research Department, Centre for Military Medicine, P.O. Box 50, FIN-00301, Helsinki, Finland. E-mail address for H. Pihlajamäki: Harri.Pihlajamaki@helsinki.fi. E-mail address for T. Visuri:TuomoVisuri@helsinki.fi
² Department of Orthopaedics and Traumatology, Helsinki University Hospital, Jorvi Hospital, Turuntie 150, FIN-02740 Espoo, Finland. E-mail address: kalevi.hietaniemi@hus.fi
³ Department of Orthopaedics and Traumatology, Helsinki University Hospital, Töölö Hospital, Topeliuksenkatu 5, Helsinki 00029 HUS, Finland. E-mail address: mika. paavola@hus.fi
⁴ Department of Orthopaedics, Tampere University Hospital, 33100 Tampere Finland. E-mail address: Ville.Mattila@uta.fi

Investigation performed at the Centre for Military Medicine and the Department of Orthopaedic Surgery, Central Military Hospital, Helsinki, Finland

Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate familiesreceived payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity.

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Background Some have recommended surgical treatment of Grade-III lateralligament injuries in very active individuals with high functional demands on the ankle. The purpose of this study was to establish whether surgery provides better long-term results than functional treatment for acute ruptures of the lateral ligaments of the ankle.

Methods Physically active Finnish men (mean age, 20.4 years) with an acute Grade-III lateral ligament rupture of the ankle were randomly allocated to surgical (n = 25) or functional (n = 26) treatment. Ligament injury was confirmed with stress radiographs. Surgical treatment comprised suture repair of the injured ligament(s) within the first week after injury. A below-the-knee plaster cast was worn for six weeks with full weight-bearing. Functional treatment consisted of the use of an Aircast ankle brace for three weeks. The main outcome measures included final follow-up examinations, calculation of an ankle score, stress radiographs, and magnetic resonance imaging scans.

Results Fifteen (60%) of twenty-five surgically treated patients and eighteen (69%) of twenty-six functionally treated patients returnedfor long-term follow-up (mean duration, fourteen years). All patients in both groups had recovered their preinjury activity level and reported that they could walk and run normally. The prevalence of reinjury was one of fifteen in the surgical group and seven of eighteen in the functional treatment group (risk difference: 32%; 95% confidence interval: 6% to 58%). The mean ankle score did not differ significantly between the groups (mean difference: 8.3 points; 95% confidence interval: –0.03 to 16.6 points). Stress radiographs revealed no difference between groups with regard to the mean anterior drawer (–1 mm in the surgical group and 0 mm in the functional treatment group; mean difference: 0.7 mm; 95% confidence interval: –1.4 to 2.7 mm) or mean tilt angle (0° in both groups; mean difference: 0.1°; 95% confidence interval: –3.2° to 3.5°). Grade-II osteoarthritis was observed on magnetic resonance images of four of the fifteen surgically treated patients and in none of the eighteen functionally treated patients (risk difference: 27%; 95% confidence interval: 4% to 49%).

Conclusions These findings indicate that, in terms of recovery of the preinjury activity level, the long-term results of surgical treatment of acute lateral ligament rupture of the ankle correspond with those of functional treatment. Although surgery appeared to decrease the prevalence of reinjury of the lateral ligaments, there may be an increased risk for the subsequent development of osteoarthritis.

Level of Evidence Therapeutic Level I. See Instructions to Authors for a complete description of levels of evidence.

For further information: http://www.ejbjs.org/cgi/content/abstract/92/14/2367

Posted on the ORTHOSuperSite September 24, 2010

Surgeon recommends autologous chondrocyte implantation for treatment of large knee lesions

GLASGOW — Autologous chondrocyte implantation outperformed mosaicplasty at 10 years for the treatment of symptomatic articular cartilage defects of the knee in younger patients, in a prospective, randomized comparison study conducted in the United Kingdom.

Leela C. Biant, BSc, AFRCS Ed, of the Royal National Orthopaedic Hospital Stanmore, presented the results at the 2010 Meeting of the Combined Orthopaedics Associations, here.

“ACI was significantly better,” Biant said. “We would not recommend mosaicplasty for large lesions or for salvage after other surgery. It is useful to remember that even ‘failures’ may not be failures in this group of patients if we can delay arthroplasty in the younger patient.

Study design

Biant and colleagues included 100 consecutive patients in their study with articular cartilage lesions that had been symptomatic for an average of 7.2 years. The average size of the defects following debridement was 4.66 cm², and patients ranged in age from 16 to 49 years. All but six patients had undergone previous surgery for the defect.

Patients were randomized at arthroscopy if the lesion was suitable to undergo either of the two procedures: 58 patients were treated with autologous chondrocyte implantation (ACI) and 42 with mosaicplasty, according to Biant.

Failures, functional outcomes

Biant reported failures in 23 of 42 mosaicplasty patients and 10 of 58 ACI patients. “We defined failure as a clinically poor result with arthroscopic evidence of graft failure or revision surgery of any kind.”

Modified Cincinnati functional scores among the two groups were as follows: 28 ACI patients had excellent scores, compared to 4 mosaicplasty patients; seven ACI patients and five mosaicplasty patients had good scores; six ACI patients and four mosaicplasty patients had fair scores; and two patients from each group had poor scores. Biant noted that similar results were seen when using the Stanmore and Bentley functional rating systems.

“In conclusion, this is actually the largest long-term study of either method, and it is the longest comparative study,” Biant said. “This was surgery for chronic, large lesions which may not be the sportsman come straight off the pitch. So this is a very difficult-to-treat group in whom the alternative really is arthroplasty.”

Reference:

Biant L, et al. Autologous chondrocyte implantation versus mosaicplasty for symptomatic articular cartilage defects in the young adult knee: 10-year results of a prospective randomized comparison study. Presented at the 2010 Meeting of the Combined Orthopaedic Associations. Sept. 13-17. Glasgow.

It is a very interesting paper; previous works have been done by George Bentley’s group comparing ACI to mosaicplasty, showing that ACI is probably superior. Today they have presented longer term results still showing the same trend.

I think that this is a challenging group of patients to treat and these are large lesions. Overall, one might expect that a proportion of them might be in a more arthritic group rather than isolated defects, and so one might expect worse results. I think that multiple mosaicplasty plugs to treat large lesions may cause a problem at the donor site but also because the quality of repair will not be as good as you will find with smaller defects.

I think the lesson learned here is that mosaicplasty probably doesn’t have a roll in the large defect, and we’ll wait to see the results of ACI for treating this type of defect in larger series. Very interesting and some important messages, but more data is required. - — Andrew Price, PhD, FRCS(Orth), MBBChir, Session Moderator.

For further information: http://www.orthosupersite.com/view.aspx?rid=70585

ORTHOPEDICS October 2010;33(10):758.

Acute Achilles Tendon Ruptures

by Justin M. Weatherall, MD; Kenneth Mroczek, MD; Nirmal Tejwani, MD

Acute ruptures of the Achilles tendon most commonly affect individuals in their third to fifth decade of life who are intermittently active. Previously, a bimodal age distribution was reported but a 2006 study by Suchak et al¹ reported a mean incidence of 8.3 ruptures per 100,000 people with a peak incidence in the 30- to 49-year-old age group. There is agreement in the literature that intratendinous degeneration plays a role in the underlying pathology of acute Achilles tendon ruptures. All patients in the series reported by Cetti et al² in 2003, showed degenerative changes at the site of rupture on histological examination of a biopsy taken at the time of surgical repair.

Etiology

The etiology of Acute Achilles tendon ruptures is multifactorial and includes overuse injuries, host factors, medications, or inappropriate footwear.³

Acute ruptures of the Achilles tendon are predominately overuse injuries in the recreational athlete. In runners with acute and overuse injuries, Achilles tendinopathy was the most common running-associated tendinopathy, and those running for >10 years had an increased risk for Achilles tendinopathy.⁴ Athletes with a recent change in their training schedule are also at increased risk of tendon injury. Similarly, military recruits beginning basic training, decreased plantar flexion strength and increased dorsiflexion excursion were significant predictors of an overuse injury of the Achilles tendon.⁵

Langbern et al⁶ found no alteration in the blood flow to the region of the tendon with the highest incidence of injury. In contrast, Chen et al,⁷ found the midsection of the tendon to be hypovascular, especially in patients with compromised blood supply. Patients with either a biomechanical malalignment, hyperpronation and cavus foot, or marked forefoot varus are at an increased risk of developing Achilles tendon complaints.³ Other predisposing factors include floroquinolone, hormone replacement therapy or steroid use, Ochronosis, prior Achilles tendon rupture, infection, hypertension, obesity or systemic inflammatory condition. Holmes and Lin⁸ observed that obesity, hypertension, hormone replacement therapy, birth control pills and steroids were all associated with Achilles tendinopathy. Kvist³ reported that shoe dependent factors were involved in 10% of Achilles tendon injuries in his study.

Anatomy

The Achilles tendon is a conjoined tendon composed of the gastrocnemius and soleus muscles with occasional contribution from the plantaris muscle, and it inserts on the calcaneal tuberosity. The plantaris muscle is absent in 6% to 8% of individuals. The Achilles tendon is approximately 15-cm long and is the largest and strongest tendon in the human body. The tendon spirals approximately 90° from its origin to its insertion and this twisting produces an area of stress approximately 2- to 5-cm proximal to its insertion. The tendon has no true synovial sheath; instead it is wrapped in a paratenon. The Achilles tendon experiences the highest loads of any tendon in the body, and bears tensile loads up to 10 times body weight during athletic activities.⁹ The tendon most commonly ruptures in a region 2- to 6-cm proximal to its insertion.

The Achilles tendon receives its blood supply from the posterior tibial and peroneal arteries, and its blood supply is divided into 3 regions: the musculotendinous junction, the mesotenon, and the tendon-bone junction. The posterior tibial artery supplies blood to the proximal and distal parts of the tendon with the middle part supplied by the peroneal artery. In an anatomic study the midsection of the tendon tends to be hypovascular, which may explain the high incidence of mid section tendon ruptures, especially in patients with compromised blood supply.⁷

Biomechanics

The Achilles tendon is a part of a complex myotendinous unit that spans across 3 joints, but when the muscles of the Achilles tendon contract it flexes the knee, plantarflexes the ankle, and supinates the subtalar joint. The gastrocnemius and plantaris originate proximal to the knee joint whereas the soleus originates on the proximal tibia. The gastrocnemius is composed of primarily fast twitch fibers and it plantarflexes the ankle joint and flexes the knee joint. The soleus is composed predominately of slow twitch fibers and functions as a postural muscle when then the center of gravity of the body passes anterior to the knee joint. The soleus also functions as the prime plantar flexor.⁸ During normal ambulation the subtalar joint becomes pronated and this subsequently imparts an internal rotation force to the tibia, but knee extension imparts an external rotation force to the tibia. Both combined movements translate into significant stress on the Achilles tendon.

Biochemistry and Histology

The Achilles tendon is composed of fibroblasts surrounded by an extracellular matrix of collagen, mucopolysaccarides, elastin, and glycoproteins. The collagen is primarily type I and is organized in parallel bundles of fibrils. The fibroblasts are imbedded in the bundles of fibrils. Each fibril is surrounded by an endotenon, and these units are surrounded by a highly vascular epitenon. With normal aging the structure of the Achilles tendon changes. These changes include decreased cell density, decreased collagen fibril diameter and density, and loss of fiber waviness, which may explain the higher incidence of tendon injury in older athletes.¹⁰

In patients with Achilles tendon pathology certain biochemical changes take place within the tendon, which may predispose the tendon to rupture. Biopsies of tendons in patients undergoing surgery for Achilles tendinopathy, found that in the region of the diseased tendon, the water content was highest, and the collagen content was subnormal with increased amounts of denatured and damaged collagen. They also found low pentosidine levels in the pathologic tissue, which indicates the presence young collagenous matrix. The authors concluded that based on their findings the collagen turnover rate is increased, therefore the natural biochemical composition of the collagenous matrix is compromised.¹¹

Clinical Presentation

Patients present with acute posterior ankle/heel pain and may give a history of “felt like someone kicked me from behind”. Patients may report a direct injury, or report the pain started with jumping or landing on a dorsiflexed foot. It is important to elicit in the history any recent steroid or flouroqunolone usage including local steroid injections, and also any history of endocrine disorders or systemic inflammatory conditions.

On physical examination the area will appear swollen and ecchymotic, which may inhibit the examiners ability to detect a palpable defect. The patient will be unable to perform a single heel raise. To detect the presence of a complete rupture the Thompson test can be performed. The test is done by placing the patient prone on the examination table with the knee flexed to 90°, which allows gravity and the resting tension of the triceps surae to increase the dorsiflexion at the ankle. The calf muscle is squeezed by the examiner and a lack of planar flexion is noted in positive cases (Figure 1). It is important to note that active plantar flexion may still be present in the face of a complete rupture due to the secondary flexor muscles of the foot. It has been reported that up to 25% of patients may initially be missed in the emergency department due to presence of active plantar flexion and swelling over the Achilles tendon, which makes palpation of a defect difficult.

	Figure 1: Thompson Test. The patient is placed supine on the exam table and the knee is flexed to 90° (A). Dorsiflexion of the foot with calf squeeze is a negative Thompson test (B). Failure of the foot to plantarflex with calf squeeze is a positive Thompson test (C).

Imaging

Multiple imaging modalities have been used to diagnose Achilles tendon injuries, which include plain radiography, magnetic resonance imaging (MRI), and ultrasound. Each test has its own advantages and disadvantages.

Ultrasound is approximately used 4 times more often than MRI for diagnosing Achilles tendon ruptures in the United Kingdom.¹² The advantages of ultrasound are that it is inexpensive, readily available in most hospitals, fast, repeatable, and allows for dynamic assessment of the tendon. Ultrasound is effective at evaluating the thickness of the tendon and the gap between the ends of the tendon in a complete rupture. The disadvantages are that is operator dependent and is not as effective as MRI in diagnosing partial tears.

The most widely used modality in the United States to diagnose acute ruptures of the Achilles tendon is MRI, which has the advantage of accurate detail of the soft tissue but the disadvantages of not being readily available, high cost, does not provide dynamic assessment of the injury, and does not enable the practitioner to readily evaluate tendon healing (Figure 2). Magnetic resonance imaging is also superior to other imaging modalities in diagnosing partial ruptures of the Achilles tendon Kayser et al,¹³ reported that the sensitivity was 0.5 and the specificity was .81 for detecting proximal partial ruptures of the Achilles tendon with ultrasound. The authors concluded ultrasound is a useful tool, but that it is not sufficiently reliable enough to diagnose all Achilles tendon pathologies including partial ruptures. They recommend obtaining an MRI for the definitive diagnosis. In our practice we use MRI for equivocal cases, or when we suspect a partial rupture.

Figure 2: Sagittal view of an MRI demonstrates a complete rupture of the Achilles tendon demonstrated by the arrow.

Classification

Kuwada¹⁴ in 1990 published a classification system to guide surgical treatment for Achilles tendon injuries. Type 1 is a partial tear, which he recommended treating in a cast. Type 2 is a complete rupture with a defect up to 3 cm, which he recommends treating with an end-to-end anastomosis. Type 3 injuries have a 3- to 6-cm defect after debridement of the tendon ends to healthy tissue. He recommends treating this injury with a tendon graft flap, with possibly a synthetic graft augment. A V-Y advancement, a Bosworth turndown, tendon transfer, or a combination of these may also be used for type 3 injuries. Lastly, a Type 4 injury is a defect >6 cm and requires a gastrocnemius recession, a turndown, tendon transfer, free tendon graft, and/or synthetic graft, or a combination of these (Table).¹⁴

Treatment

Recent studies have shown successful outcomes with nonoperative and operative treatment. Comparative studies between nonoperative and operative treatment show a higher rate of re-rupture with nonoperative treatment, but also show risks of wound healing, wound infection, and nerve injury with operative treatment. Studies have published a re-rupture rate of 4.3% to 23% in nonoperatively treated patients compared to 1.7% to 10% for operatively treated patients.^15-19 In a meta-analysis published by Khan et al²⁰ in 2005 of randomized controlled trials of acute Achilles tendon ruptures the authors concluded that open operative treatment results in a significant reduction in the risk of re-rupture when compared to nonoperative treatment. Operative treatment was associated with a significantly higher risk of wound complications, adhesions, infection, and nerve injury. They also concluded that the risk associated with surgical treatment may be reduced by percutaneous surgery and postoperatively splinting the limb with a functional brace; however, percutaneous treatment may be associated with a higher risk of sural nerve injury.²⁰ Recent studies have also shown improved functional outcomes with early motion and weight bearing.^21-25

Nonsurgical Treatment

The most widely used method of nonsurgical treatment involves the use of serial casting with gradual progression from plantar flexion to neutral or using a solid removable boot with heel inserts to bring the ends of the tendon closer together. The advantage of a solid removable boot is that it allows the patient to begin early motion and is removable. Wide variability exists among surgeons in regards to the period of absolute immobilization, initiating range of motion exercises, and progression of weight bearing status.

Hufner et al¹⁵ reported 73.5% good to excellent results and 17.5% poor results with functional nonoperative treatment when on ultrasound the tendon ends were <10>15

A prospective, randomized, multicenter study of 112 patients with 2-year follow-up comparing surgical treatment followed by early functional rehabilitation versus nonsurgical treatment with a plaster splint for 8 weeks. Identical rehabilitation protocols were used for both groups. The authors found that the rate of re-rupture was 20.8% in the nonoperative group compared to 1.7% in the surgical group.¹⁶

Costa et al,¹⁷ in a randomized controlled trial, compared immediate functional weight bearing versus cast immobilization in nonsurgically treated patients, and the authors found no functional benefit from immediate weight bearing. The authors showed that immediate weight bearing did not predispose the patients to a higher complication rate, and they found no evidence of tendon elongation or a higher rate of re-rupture with immediate weight bearing compared to casting and nonweight bearing.¹⁷

In a prospective randomized study by Twaddle and Poon¹⁸ the authors compared open surgical treatment versus nonoperative treatment. Twenty patients were in the operative group and 22 patients in the nonoperative group with a total of 1-year follow-up. The patients were all treated with an equinus cast for 10 days and then received an orthosis. Protected weight bearing was initiated at 6 weeks and crutches were discontinued at 8 weeks. Range of motion exercises were initiated with an orthosis. The authors found no difference in motion, calf circumference, musculoskeletal functional assessment, instrument scores, re-rupture rates, or complications. The authors concluded that controlled early motion is an important part of the treatment of Achilles tendon ruptures.¹⁸

Surgical Treatment

The essence of surgical treatment involves 2 decisions; surgical technique and the postoperative regime.

Most published reports on surgical treatment fall into 3 different surgical approach categories that include the following: direct open, minimally invasive, and percutaneous. In multiple studies surgical treatment has demonstrated a lower rate of re-rupture compared to nonoperative treatment, but surgical treatment is associated with a higher rate of wound healing problems, infection, postoperative pain, adhesions, and nerve damage. Most commonly the direct open approach involves a 10- to 18-cm posteromedial incision. The minimally invasive approach has a 3- to 10-cm incision, and the percutaneous approach involves repairing the tendon through multiple small incisions. As with nonsurgical treatment there exists wide variation in the reported literature regarding postoperative treatment protocols. Multiple comparative studies have been published comparing different surgical approaches, repair methods, or postoperative treatment protocols.

Cretnik et al²⁶ compared 132 percutaneous versus 105 open repairs of Achilles tendon ruptures and found a lower rate of major complications, equal AOFAS and Holz score, but a higher risk of re-rupture and sural nerve dysfunction with the percutaneous repair. Ceccarelli et al²⁷ reported no re-ruptures and similar results for isokinetic strength, AOFAS scores, and time for return to work for either of the 2 groups. Lansdall et al²⁸ examined the results of 163 Achilles tendon ruptures treated with a minimally invasive technique with functional after treatment. The authors reported 92% patient satisfaction, 5.5% major complications and a 9.2% incidence of sural nerve dysfunction. The major complications included re-rupture, deep infection, tendon necrosis and deep vein thrombosis (DVT).²⁸ Most recently, Maffulli et al²⁹ retrospectively examined results of 35 patients 65 years or older with the mean age of 73.4 years who underwent percutaneous repair for an acute rupture. Twenty-seven of 35 patients completed the appropriate follow-up of 49 months. The authors state that percutaneous repair of acute Achilles tendon ruptures in elderly patients produces similar outcomes to younger patients.²⁹

In a meta-analysis, Khan et al²⁰ found 14 studies with a total of 891 patients. The authors found that surgical treatment compared to nonoperative treatment resulted in a lower rate of re-rupture with a relative risk of 0.27, but surgical treatment had a higher risk of other complications with a relative risk of 10.60. The authors also compared percutaneous repair versus a direct open repair and found the percutaneous repair resulted in a shorted surgical time and a lower risk of infection with a relative risk of 10.52. Lastly, the authors compared postoperative functional bracing versus casting, and they showed that the functional bracing group had decreased inpatient stays and time off from work, returned to sports faster, and had a lower complication rate.²

Halasi et al³⁰ examined percutaneous repair with or without tendoscopic control, and their results showed a lower re-rupture rate with tendoscopy but both techniques had similar results for return to sports, plantar flexion strength, and subjective scores. Jung et al³¹ retrospectively reviewed their results of 30 consecutive patients who underwent a limited open technique and the authors reported 2 re-ruptures, 1 deep infection, and 1 sural nerve injury. They concluded that the limited open technique provided an excellent cosmetic result, satisfactory functional results, and a high level of patient satisfaction.³¹

Atkas and Kocaoglu³³ compared open repair versus a minimally invasive repair with the Achillon device (Integra LifeSciences Corp, Plainsboro, New Jersey). They showed similar functional scores between the 2 groups, improved surgical outcomes in regards to local tenderness, skin adhesions, and scar and tendon thickness in the Achillon group.³² Another study compared the strength of the Achillon tendon repair with a 2 strand Kessler repair technique with number 2 Ticron suture (Coviden, Dublin, Ireland) in a simulated sheep model. Their results demonstrated no difference between groups, suggesting the use of this specialty device is a biomechanically sound method of repair.³³

Aktas et al³⁴ treated 30 patients with acute Achilles tendon ruptures who underwent either an end-to-end repair or an end-to-end repair with plantaris augmentation with Krackow type sutures with epitendinous cross stitches. They reported no significant difference at 17 months postoperatively. A recent biomechanical study examined the difference in strength and gap resistance between a 4 strand Krakow and a epitendinous augmented 4 strand Krakow. The authors concluded that the epitendinous cross-stitch significantly increased the strength of the repair and gap resistance.³⁵ Hohendorff et al³⁶ compared fibrin glue versus suture, in a long-term follow-up study, and they reported that the patients in the fibrin glue group had higher modified Thermann scores, equal isokinetic scores, and fewer complications. In this study, the authors concluded that fibrin glue is a suitable alternative to a traditional suture repair.³⁶

Postoperative Course

Multiple studies have compared post-operative immobilization versus early functional mobilization, early weight bearing versus nonweight bearing for 6 to 8 weeks, and the need for thromboprophylaxis. The consensus among recent studies is that patients who undergo early functional weight bearing and range of motion have decreased inpatient stays and time off from work, faster return to sports, and a lower complication rate. Kangas et al,²¹ compared 2 groups, an early motion group versus casting in neutral by placing intraoperative markers. Their results showed greater tendon elongation in the immobilization group and less tendon elongation led to better outcomes. Maffulli et al,²² divided 53 patients, with acute tears repaired with absorbable suture, into 2 groups. One group was immediate weight bearing in an equinus cast for 2 weeks, and then they were placed in a dorsiflexion stop orthosis, and the other group was nonweight bearing with serial casting every 2 weeks with progression to neutral by 6 weeks postoperatively. The authors found the weight-bearing group had higher satisfaction scores, with no increase in isometric testing, and no re-ruptures in either group.²²

Suchak et al^23,24 published a level 1 study comparing 2 groups of patients. One group was nonweight bearing for 2 weeks and another group was non-weight bearing for 6 weeks. Patients were monitored for compliance by wearing a fixed-hinge AFO with a pressure sensor installed. The author’s results showed that the weight bearing group had better quality of life scores at 6 weeks and 3 months but no difference existed between the groups at 6 months. The authors concluded that early weight bearing after surgical repair of an acute Achilles tendon rupture improves health-related quality of life at 6 weeks and 3 months with no detrimental effects on recovery with 6 months of follow-up. Ozkaya et al²⁵ reviewed 25 consecutive patients after open minimally invasive repair with early rehabilitation. The authors reported 1 partial re-rupture and one superficial infection and the patients had a mean AOFAS score of 93. They concluded that open minimally invasive repair of an acute rupture of the Achilles tendon with early rehabilitation provides satisfactory results with low complication rates.

Postoperative thromboprophylaxis is indicated after many lower-extremity orthopedic procedures. Patient’s with ruptures of the Achilles tendon experience a certain amount of immobilization before and after surgical and nonsurgical treatment. Currently, there is no consensus on whether patients should receive thromboprophylaxis.

A level 1 randomized, placebo controlled, double blind study of 105 patients with acute ruptures published by Lapidus et al³⁷ compared 6 weeks of daily injections of either placebo or 5000 units of Fragmin (Pfizer, New York, New York). The patients were screened for DVTs at 3 and 6 weeks postoperatively by color dupex sonography. Postoperatively the patients were nonweight bearing in a plaster cast for 3 weeks and then were advanced to weight bearing as tolerated in a cast for an additional 3 weeks. The authors found a 34% rate of DVT with 2% being proximal DVTs in the Fragmin group and a 36% rate of DVTs with 6% being proximal DVTs in the control group. No patient in either group was diagnosed with a pulmonary embolism (PE) or demonstrated major postoperative bleeding at the surgical site. Based on the results the authors concluded that DVT is common after surgical repair of the Achilles tendon, and patients should receive effective DVT prophylaxis. The authors found that DVT prophylaxis with Fragmin did not affect the incidence of DVT.³⁷ Another prospective study examined the incidence of DVT in patients with an Achilles tendon rupture. They examined nonoperatively treated and operatively treated patients. They found the incidence of DVT is high after Achilles tendon ruptures and there was no difference in the incidence of DVT in operatively or non-operatively treated patients.³⁸ Based on the results of these two studies the incidence of DVT after an Achilles tendon rupture is high, but neither study reported a case of fatal pulmonary embolus. Currently, there is no scientific evidence to demonstrate a benefit of chemical thromboprophylaxis in reducing the risk of DVT and PE in patients with acute Achilles tendon injuries.

Surgical Technique

The patient is positioned prone after administration of either general or regional anesthesia. A longitudinal incision is made on either the medial or lateral aspect of the tendon. If a lateral incision is chosen care must be taken to identify and protect the sural nerve. Length of the incision averages 3 to 10 cm. Once the paratenon is incised longitudinally, the tendon ends are easily identifies. These are then re-approximated with either a Bunnell or Kessler or Krackow type suture technique with nonabsorbable suture. Next, the epitenon is repaired with a cross stitch technique. The paratenon should be repaired if it will be useful to prevent adhesions. Finally, a meticulous skin closure will limit wound complications.³⁹ An alternative method is to perform a percutaneous technique, with a small incision (ranging from 2-4 cm). A few salient points include: the incision should be extended as needed; no self-retaining retractors should be used; and meticulous paratenon and wound closure is essential.

Postoperatively the patient is immobilized in an equinous splint (usually 10° -15°) for 2 weeks. Immobilization may be extended if there is any concern about wound healing. At the 2-week follow-up, full weight bearing is permitted using a solid removable boot. At 6 weeks, aggressive physical therapy is prescribed and the patient uses the boot only for outdoor activity. At 12 weeks postoperatively, no further orthosis is recommended.⁴⁰

Conclusion

Acute rupture of the Achilles tendon is a common injury sustained in athletes and middle-aged patients. In some patients age related degenerative changes within the tendon may predispose the tendon to rupture. Certain conditions or drugs may weaken the tendon and make it more susceptible to injury. Achilles ruptures may be missed in an emergency room setting. Studies show successful outcomes with both nonoperative and operative treatments. The decision to pursue operative treatment should be based on patient’s pre-injury functional status and ability to undergo operative treatment. Among operative treatments, studies show a low rate of complications with open, minimally invasive, and percutaneous approaches. Early functional range of motion and weight bearing has been shown to be beneficial compared to a traditional course of casting and nonweight bearing. Deep vein thrombosis is common in these patients postoperatively, but no study has shown whether a postoperative course of pharmacologic thromboprophylaxis is indicated.^37,38

^{For further information: http://www.orthosupersite.com/view.aspx?rid=70484}

ORTHOPEDICS October 2010;33(10):724.

Intra-articular Injection of Hyaluronic Acid Following Arthroscopic Partial Meniscectomy of the Knee

by Rafael Thein, MD; Barak Haviv, MD; Amos Kidron, MD; Shlomo Bronak, MD

Abstract

The short-term recovery period post-arthroscopic meniscectomy is characterized by pain and impaired function most likely related to the irrigation of synovial fluid from the knee intraoperatively. Consequently, along with removal of harmful debris, the irrigation fluid dilutes the hyaluronic acid layer covering the joint tissues. Hyaluronic acid contributes to the homeostasis of the joint environment and is an important component of synovial fluid and cartilage matrix. Hence, the instillation of hyaluronic acid after the procedure may relieve symptoms.

This prospective, single-blind, randomized, controlled study evaluated clinical outcome after hyaluronic acid injection to patients who underwent arthroscopic meniscectomy of the knee. Patients with ligamentous injuries or severe chondral damage were excluded. Fifty-six patients with a mean age of 34 years (range, 17-44 years) were injected with Viscoseal (TRB Chemedica International S.A., Geneva, Switzerland) or normal saline immediately post-arthroscopy and divided into the Viscoseal group or control group, respectively. Patients were evaluated for pain, swelling, and function at 1, 4, and 12 weeks postoperatively. Patients in the control group reported more pain at week 1, with a mean visual analog score (VAS) of 43, than did patients in the Viscoseal group, with a mean VAS of 28 (P=.006). At 4 weeks postoperatively, none of the Viscoseal patients had consumed analgesics, where 9 (of 28) in the control group reported acetaminophen intake (P=.039). No significant difference in knee function was found between groups. Intra-articular injection of Viscoseal after arthroscopic meniscectomy reduced pain in the short-term recovery period.

Patients undergoing knee arthroscopy frequently encounter pain, swelling, and impaired function in the short-term postoperative period. Several analgesic schemes have been used to treat pain induced by arthroscopic knee surgery with partial effect.^1,2 Current practice involves lavage of the normal hyperviscous synovial fluid as an integral part of the procedure, with an irrigation fluid (normal saline) to be replaced later by the new, naturally formed synovial fluid. Consequently, along with removal of harmful debris, the irrigation fluid dilutes the hyaluronic acid layer covering the joint tissues, including the cartilage. In addition, experimental studies have shown that irrigation fluids used in arthroscopy can have a negative effect on the metabolism and structure of the joint cartilage.^3,4

The synovial fluid contains hyaluronic acid, a complex glycosaminoglycan whose viscoelastic properties serve to lubricate and allow smooth and pain-free joint motion. Hyaluronic acid contributes to the homeostasis of the joint environment and is an important component of synovial fluid and cartilage matrix. Due to its structure, it serves as a semipermeable barrier to protect the cartilage from the free movement of lytic enzymes, inflammation mediators, and inflammatory cells in the synovial fluid.^5,6

The efficacy of hyaluronic acid in osteoarthritis has been described in several studies. In a rabbit osteoarthritis model, high-molecular-weight hyaluronic acid relieved joint pain and prevented the progression of cartilage degeneration.⁷ Exogenous hyaluronic acid injected into the arthritic joint space has been shown to improve the qualitative and quantitative properties of endogenous hyaluronic acid and therefore improve joint lubrication (concept of viscosupplementation).⁸ More recent studies of human synoviocytes from osteoarthritic joints have revealed that exogenous hyaluronic acid stimulates de novo synthesis of hyaluronic acid, inhibits release of arachidonic acid, and inhibits interleukin-1α-induced prostaglandin E2 synthesis by human synoviocytes, which reduces the anti-inflammatory response.⁹ Thus, the replacement of the lost synovial fluid with a hyaluronic acid-containing synovial fluid substitute immediately after arthroscopy may be beneficial.

The purpose of this study was to assess whether the use of a hyaluronic acid-containing synovial fluid substitute (Viscoseal; TRB Chemedica International S.A., Geneva, Switzerland) after arthroscopic partial meniscectomy would relieve acute pain and result in an earlier return of joint function compared to patients undergoing standard arthroscopic partial meniscectomy.

Materials and Methods

This was a prospective, single-blind, randomized, controlled study. The inclusion criteria for this study included symptomatic patients with meniscal tear and minimal chondral damage of the knee (ie, no more than Outerbridge¹⁰ grade 2). Additional exclusion criteria were the presence of associated ligament injuries, previous surgery on the same knee, infection, or inflammatory joint disease.

During the study period (2004-2006), 452 knee arthroscopies were performed at our institution. A total of 88 patients with presurgery diagnosis of meniscal pathology requiring arthroscopic intervention were recruited. Three patients cancelled their arthroscopy for unknown reasons, while 5 patients were lost to follow-up at 3 months. Twenty-four patients presented exclusion criteria during arthroscopy (eg, anterior cruciate ligament tear, advanced chondral damage, or intact menisci) and were not randomized. Overall, 56 patients participated in this study (32 men and 24 women). Mean patient age was 34 years (range, 17-44 years). Patients were divided randomly into 2 groups. The Viscoseal group (N=28) was treated with 10 mL intra-articular of Viscoseal while the control group (N=28) was treated with normal saline. Patients were blind to this treatment.

The indication for surgery was knee pain accompanied by mechanical symptoms. All patients had meniscal injury signs on physical examination. Imaging studies included anteroposterior and lateral radiographic views of the painful knee and preoperative magnetic resonance imaging to confirm the diagnosis.

All patients received general anesthesia using pneumatic tourniquet and were randomized to the treatment groups during arthroscopy once the inclusion and exclusion criteria were confirmed. Joint irrigation was performed with the assistance of an arthroscopic pump system using 0.9% NaCl solution at room temperature. At the end of the surgery, all the remaining fluids were drained from the knee and 10 mL of Viscoseal preparation or 10 mL of saline were injected. The knee was dressed while the tourniquet was still inflated.

All surgeries were performed in a day-surgery facility. Postoperatively, full weight bearing was allowed. Crutches were recommended for the first 48 hours. Anti-inflammatory medications were avoided. However, consumption of escape medication (eg, acetaminophen) was recorded. All patients followed a rehabilitation protocol for meniscectomy and were asked to return for assessment at weeks 1, 4, and 12. At each visit they were questioned on any adverse events they may have experienced since their last visit. Their escape medication intake since the previous visit was also recorded.

Preoperative assessments were undertaken 2 days prior to and on the day of the index surgery. Postoperative assessments were then performed at 1, 4, and 12 weeks. Permission was obtained from all patients prior to surgery to use their data.

The following parameters were assessed at each time period:

• Pain (the mean at rest and squatting), using a 100-point visual analog score (VAS) (0=no pain, 100=extreme pain).
• The Knee Injury and Osteoarthritis Outcome Score, a questionnaire designed to assess short- and long-term patient-relevant outcomes following knee injury.¹¹ The questionnaire is self-administered and assesses 5 outcomes: pain, symptoms, activities of daily living, sport and recreation function, and knee-related quality of life.
• Joint swelling, evaluated as measuring and comparing the circumference of both knees at the patellar level (the broadest point).
• Analgesic consumption.

Viscoseal is a viscosified synovial fluid substitute specifically developed for use after arthroscopy. It is approved as a medical device in the European Union and other countries. It is a 0.5% isotonic solution of 1.2 million-dalton-molecular-weight hyaluronan. This concentration of sodium hyaluronate is similar to the concentration of hyaluronic acid present in normal synovial fluid.⁸ The hyaluronic acid in Viscoseal is a specific, highly purified fraction obtained by bacterial fermentation (Streptococcus zooepidemicus) and is devoid of animal proteins. The solution is sufficiently viscous (intrinsic viscosity 15 dL/g) to act as a synovial fluid substitute after arthroscopy.

Results were expressed with descriptive methods (mean, range). Nonparametric analysis was performed with the Mann-Whitney U test for comparison between corresponding parameters in each group for all available time points. P<.05 was considered statistically significant.

Results

All 56 patients completed the study. The 2 groups were homogeneous for age and sex. At arthroscopy the 2 groups had similar chondral findings. Specifically, we found no chondral damage in 13 patients in the Viscoseal group and 10 in the control group. Grade 1 chondral lesions were found in 8 patients in the Viscoseal group and 9 in the control group, while grade 2 lesions were found in 11 and 12 patients, respectively. Chondral lesions were unicompartmental in 12 patients, bicompartmental in 2, and tricompartmental in 1 in the Viscoseal group, and unicompartmental in 11, bicompartmental in 4, and tricompartmental in 3 in the control group.

Overall, the reduction in pain at 12 weeks was similar for both groups (Figure 1). However, patients in the control group reported more pain at week 1, with a mean VAS of 43, than did patients in the Viscoseal group, with a mean VAS of 28. This difference was statistically significant (P=.006). At 4 weeks postoperatively, the mean VAS was almost equal.

Figure 1: Pain in both groups at baseline and follow-up. Abbreviation: VAS, visual analog score.

Figure 2: Knee Injury and Osteoarthritis Outcome Score (KOOS) in both groups at baseline and follow-up.

The improvement in the Knee Injury and Osteoarthritis Outcome Score was also nearly equivalent in both groups at all follow-up time points (Figure 2). However, at baseline, Knee Injury and Osteoarthritis Outcome Scores were significantly lower in the Viscoseal group, with a mean of 41.8 (range, 3-79.2), compared to the control group, with a mean of 52.3 (range, 20.2-83.3) (P=.005). This was attributed mainly to the differences in joint swelling between groups. More patients in the Viscoseal group (19 of 28) had joint effusion compared to the control group (8 of 28) at baseline. However, assessments at 4 and 12 weeks showed a mild superiority in joint effusion (fewer patients with measured swelling) in the Viscoseal group.

Analgesic intake was lower throughout the follow-up period in the Viscoseal group compared to the control group, but it was significant at the second follow-up assessment. At 4 weeks postoperatively, none of the Viscoseal patients had consumed analgesics, where 9 (of 28) in the control group reported acetaminophen intake (P=.039).

No serious or unexpected adverse events were reported in either group. Viscoseal was well tolerated by all patients.

Discussion

Our results suggest that immediate postoperative hyaluronic acid injection can relieve pain in the first 4 weeks after arthroscopic meniscectomy.

Hyaluronic acid is widely used in the treatment of osteoarthritis by intra-articular injection into affected joints. Several clinical trials have shown that hyaluronic acid therapy is effective and safe for osteoarthritis patients who have ongoing pain or are unable to tolerate other conservative treatments.^12-14 To test the value of incorporating hyaluronic acid immediately after arthroscopic meniscectomy, we used a hyaluronic acid-based synovial fluid substitute (Viscoseal) after final irrigation. Viscoseal contains 0.5% hyaluronic acid, which is close to the concentration of hyaluronic acid present in normal synovial fluid (0.2%-0.4%).⁸ Pain, effusion, and function were compared between patients who received intra-articular hyaluronic acid and patients who underwent standard therapy. Follow-up time was 12 weeks based on previous studies that demonstrated rapid elimination of intra-articular hyaluronic acid injection from the synovial fluid.^15-17

Statistically significant pain reduction was found 1 week postoperatively in the Viscoseal group. Although pain had leveled in the control group at 4 weeks, patients in the control group consumed more analgesics during that period. In a similar previous study, Mathies¹⁸ found a lower increase in pain in the Viscoseal group compared to the control group, with the trend remaining in favor of Viscoseal for the first 3 days postoperatively. In his study, the Viscoseal group also had a proven superiority in diclofenac intake on days 3, 4, and 7, indicating a nonsteroidal anti-inflammatory drug-sparing effect. No significant between-group differences were observed in joint function both in Mathies’ study¹⁸ (tested by the Lysholm score) and in our study (tested by the Knee Injury and Osteoarthritis Outcome Score), although at baseline Knee Injury and Osteoarthritis Outcome Score values were significantly lower in the Viscoseal group. This was attributed mainly to the differences in joint swelling between groups. More patients in the Viscoseal group had joint effusion compared to the control group at baseline.

Our study demonstrated that patients in the Viscoseal group had a more rapid recovery from arthroscopic partial meniscectomy with less pain, less effusion, and a lower intake of analgesics compared to the control group. Other short- and long-term benefits can be found in the literature but were mainly performed on osteoarthritis patients. A prospective, randomized, controlled, double-blind study of 66 patients with various degrees of chondral damage at 2 years after treatment showed that the postarthroscopic instillation of a hyaluronic acid-based synovial fluid substitute into the joint is a suitable way of achieving long-term stabilization of the treatment outcome.¹⁹ Another multicenter, prospective, open study showed that hylan G-F 20 in knee osteoarthritis patients provides effective pain relief and improves stiffness and physical function at 4 to 12 weeks after arthroscopic meniscectomy.²⁰ Symptomatic efficacy was maximized at 12 weeks and maintained at 26 and 52 weeks.

The distinctive strength of our study is in its methodology as a prospective, randomized, controlled, single-blind study. In contrast to most other publications, the target population included patients with meniscal tear without significant chondral changes. Pain and function in both study groups were almost identical by the end of our follow-up (at 12 weeks); however, the Viscoseal group proved to be less painful within the first 4 weeks. We believe that this instant improvement with intra-articular hyaluronic acid should be considered cost effective after arthroscopic meniscectomy as it can shorten the recovery time and allow more rapid return to work or other occupations.

For further information: http://www.orthosupersite.com/view.aspx?rid=70288

ORTHOPEDICS October 2010;33(10):722.

Mechanical Evaluation of Cross Pins Used for Femoral Fixation of Hamstring Grafts in ACL Reconstructions

by Gregory E. Bellisari, MD; Christopher C. Kaeding, MD; Alan S. Litsky, MD, ScD

Abstract

The goal of this study was to test the mechanical strength of 4 different cross pins currently available for femoral fixation by loading each cross pin to failure as received and determine the effect of 1 million cycles of fatigue loading. Additionally, the strength of resorbable pins was tested after prolonged exposure to biologic conditions. Six implants each of the Arthrotek LactoSorb (Biomet, Warsaw, Indiana), Mitek RigidFix (DePuy Mitek Inc, Raynham, Massachusetts), Arthrotek Bone Mulch Screw (Biomet), cortical allograft, and control were tested for 3-point failure without prior loading and after cyclic loading between 50 to 200 N at 10 Hz for 1 million cycles. The bioabsorbable pins were placed in sterile water at 37°C and tested after 2, 4, and 6 months for 3-point failure strength. All implants tested without antecedent loading demonstrated adequate strength for initial fixation for hamstring grafts. During fatigue testing, RigidFix implants (n=6) failed at 18,893±8365 cycles (with a central deformation of 0.48±0.11 mm prior to fracture). All of the other implants tested endured 1 million cycles of loading (50-200 N) without fracture or 1.5 mm central deformation. Neither of the bioabsorbable pins demonstrated a significant change in yield strength after prolonged exposure to water.

All implants tested demonstrated adequate strength for initial fixation of hamstring grafts. The metal and bone implants far exceed the strength required to sustain mechanical fixation until biological fixation occurs; both polymeric implants demonstrated that they maintained enough mechanical strength to achieve this goal.

Epidemiologic studies estimate an increasing incidence of anterior cruciate ligament (ACL) injuries because of an increased emphasis on sporting lifestyles.¹ Good outcomes associated with ACL reconstruction rely on factors such as graft choice, surgical technique, and method of fixation. Significant morbidity has been associated with bone–patellar tendon–bone grafts such as patellofemoral pain, patellar tendonitis, quadriceps atrophy, and loss of extensor mechanism.²

When hamstring grafts are harvested, overall hamstring performance with regard to knee flexion was not affected,³ and recovery of hamstring strength to 95% of preoperative values 3 years after hamstring tendon graft ACL reconstruction have been reported.⁴ With less harvest morbidity^2,4 and higher ultimate tensile load, the hamstring graft is becoming an increasingly popular choice.^5,6 Both bone–patellar tendon–bone and quadrupled hamstring tendon autografts are viable options for ACL reconstruction. Although graft choice is still debated, both demonstrate adequate strength to be used for ACL reconstruction. Bone–patellar tendon–bone has an ultimate tensile strength of approximately 2300 N⁷ and the quadruple semitendinosus/gracilis tendon graft⁵ an ultimate tensile strength as high as 4108 N.⁵ Both of these far exceed the 500 N load reported by Grood and Noyes⁸ for strenuous activity.

Hamstring grafts are an attractive choice only if fixation of the graft is optimal. Graft fixation is usually the weakest link in ACL reconstructions. Graft fixation needs to be strong enough to protect the reconstruction from failure during activities of daily living and early rehabilitation until the graft is biologically healed in the bone tunnels.⁹ The demand for higher fixation strength has also increased with the advent of aggressive rehabilitation, including early mobilization, after ACL reconstruction.^10-12

Cross-pin femoral fixation has shown good results with a 2-year follow-up.⁵ In a study that quantified the amount of permanent elongation in response to cyclic loading, femoral fixation with a cross pin showed no significant permanent elongation, while the button/tape femoral fixation along with its sutures (whipstitches) had significantly greater permanent elongation.¹³ Clinically, permanent elongation could translate to a loss of graft function. Initial biomechanical properties of cross pins have been shown to be superior to interference screws and soft tissue fixation.¹⁴ In an in vivo sheep study, cross pins were superior to interference screw fixation both initially and at 6 weeks postoperatively.⁹

The goals of this study were (1) to test the initial mechanical strength of 4 different cross-pin products currently available for femoral fixation by loading each cross pin to failure, and (2) to determine the effect of 1 million cycles of fatigue loading on the mechanical strength. A degradation study was also conducted with the bioabsorbable implants to test the effects of being subjected to a biologic environment. Our hypothesis was that all products tested would demonstrate adequate mechanical strength to provide adequate fixation for hamstring grafts in ACL reconstructions.

Materials and Methods

The cross pins used in our study were the Arthrotek LactoSorb (50 mm long×4 mm diameter polylactic/polyglycolic acid copolymer; Biomet, Warsaw, Indiana), the Mitek RigidFix (42×3.3 mm polylactic acid; DePuy Mitek Inc, Raynham, Massachusetts), the Arthrotek Bone Mulch Screw (25×10.5 mm Ti6Al4V alloy measuring 2 mm width where the pin was tested; Biomet), cortical allograft (50×4 mm freeze dried, ethylene oxide sterilized bone), and a control consisting of 3.2 mm (1/8”) diameter stainless steel rod (Figure). Each Bone Mulch Screw was prepared for 3-point bending by separating the central pin portion from the threaded portion so the pin would lie flat across the cylindrical supports. For the RigidFix cross pins, only 1 of the 2 pin systems was used for mechanical testing, as there was no means to test both pins simultaneously. Six implants of each design were randomly tested in 3-point bending and fatigue testing.

Figure: Cross pins tested (from left): LactoSorb, RigidFix, Bone Mulch Screw, cortical allograft, control.

For the 3-point bending, each implant was placed across a 12-mm span supported by 6.3-mm-diameter cylindrical supports. A 12-mm bone tunnel was chosen to represent the upper limits of bone tunnel diameter and worst-case scenario if widening of the tunnel were to occur postoperatively. Using a servohydraulic materials testing system (Bionix 858; MTS Systems, Eden Prairie, Minnesota), each implant was centrally loaded in a linear ramp at 1 mm/min until fracture or 1.5 mm central deformation. In our study, 1.5 mm of deformation was chosen as failure of the implant. Although strict, it is important to point out that the implant is only 1 part of the construct and deformation of 3 mm with EndoButton (Smith & Nephew, Memphis, Tennessee) fixation has led to clinically unacceptable results.¹⁵

Three-point fatigue testing was accomplished by cyclic loading between 50 to 200 N at 10 Hz for 1 million cycles followed by 3-point bending to failure as described above if the implant has not previously failed. Two hundred Newtons is representative of the literature values for ACL tension in normal walking. Five hundred Newtons is the highest reported value for ACL tension during normal walking, reported by Kuster et al.¹⁶ Grood and Noyes⁸ and Noyes et al,¹⁷ however, reported values close to 500 N to occur only during strenuous athletic activities. One million cycles was chosen to approximate 1 year of in vivo loading, sufficient time for the graft to be biologically secured in the femoral bone tunnel.

The bioabsorbable implants were tested after prolonged exposure to a biological environment. Both the RigidFix and LactoSorb implants were immersed in sterile water at 37°C for 6 months to measure the effect of hydrolysis on their mechanical properties. Six of each implant were pulled out at 2, 4, and 6 months for 3-point bending as described for the time-zero specimens.

Statistical analysis was carried out on yield load, load at 1.5 mm deformation, and structural stiffness. They were compared across the different designs using analysis of variance (ANOVA) and post-hoc analysis.

Results

The results of the 3-point bending test without antecedent cyclic fatigue testing are summarized in Table 1. The mean yield load for the Bone Mulch Screw was significantly higher than the other implants (P<.001). The mean yield loads in the LactoSorb implant and the allograft were similar and significantly higher than the RigidFix implant (P<.001). The stiffness of the cortical allograft, however, was more than twice that of the LactoSorb implant. The greatest stiffness was observed in the Bone Mulch Screw.

The mode of failure for the RigidFix implants and cortical allografts was by brittle fracture. The allografts fractured at 0.3±0.03 mm central deformation; the RigidFix implants after 1.5 mm deflection. The other 3 implants bent past 1.5 mm for failure without evidence of fracture. Load at 1.5 mm central deformation was 28% to 45% greater than the yield load.

Fatigue testing revealed that the RigidFix implants (n=6) fail at 18,893±8365 cycles (with a central deformation of 0.48±0.11 mm prior to fracture). All the other implants tested endured 1 million cycles of loading (50-200 N) without fracture or 1.5 mm central deformation. Post-fatigue 3-point bending showed no changes to the Bone Mulch Screw; however, there was a statistically significant (P<.05) increase in stiffness for both the LactoSorb and the cortical allograft. The fracture load of the allograft also increased significantly with fatigue loading, which was conducted dry and at room temperature.

After exposure to a biologic environment, neither of the bioabsorbable implants showed a statistically significant change in mean yield or stiffness from their zero time values under these experimental conditions. The RigidFix implants became slightly less compliant with time and more of the specimens broke before reaching 1.5 mm central displacement (Table 2).

Discussion

Femoral fixation of quadrupled hamstring grafts is a key element to a durable ACL reconstruction, and there are many implants designed to accomplish this. There is no consensus as to which method is superior. Our study focused on the mechanical characteristics of some of the more popular cross-pin fixation devices. Fixation of the device in the femoral metaphysis was specifically not examined, nor did we compare our results to other methods of fixation on the femoral side. Clinically, the biomechanics of the final graft construct will be determined by multiple factors: tibial fixation, femoral fixation, graft characteristics, and surgical technique. None of these factors was evaluated or accounted for in our study.

Clinically, the benefits of cross-pin femoral fixation appear to outweigh the drawbacks. The benefits of cross-pin fixation are rigid fixation and its proximity to the joint line, possibly decreasing the bungee effect and preventing tunnel widening.¹⁸ Soft tissue graft fixation methods are chosen on their strength and ability to resist deformation under cyclic loading. In our study, the strength of the Bone Mulch Screw and the LactoSorb implant/pin/device would be sufficient to withstand the reported values of normal walking. The Bone Mulch Screw displayed superior mechanical properties to the other cross pins. The RigidFix values for yield load are likely not representative of the final construct values because of its 2-pin configuration. The LactoSorb implant yield load (449±23 N) approaches the 454 N needed for daily activities reported by Grood and Noyes⁸ and Noyes et al.¹⁷ There are limitations to cross-pin fixation and reported complications. Marx and Spock¹⁹ reported a series of 2 cases with medial and lateral irritation of proud cross pins that required reoperation for hardware removal.

Several recent studies^20-23 have investigated the biomechanics of femoral fixation for ACL grafts. These studies have mostly compared cross-pin fixation to other forms of femoral fixation such as interference screws, considered the gold standard by many, and the EndoButton.

Kousa et al,¹³ in an ex vivo study, found no statistically significant difference between the Bone Mulch Screw and RigidFix cross pins when tested under a 50 mm/min bending load to failure before or after 1500 cycles of fatigue loading (50-200 N). Their test was performed with cadaveric quadrupled hamstring grafts looped over the femoral fixation devices in porcine femora. They concluded that the aforementioned cross pins provided greater fixation strength than 3 types of interference screws included in their protocol and that “the rigidity of the device itself improves the fixation characteristics of the implant.”

Our results show lower mean yield strength (187 N) compared to the findings of Kousa et al¹³ (868 N) in the RigidFix cross pin. Again, we tested 1 cross pin in a 2-pin system. Our loading rate was also much slower. For the Bone Mulch Screw, the mean yield strength (1146 N) found in this study was comparable to Kousa et al’s¹³ data (1112 N). The stiffness values in our study were different as a function of our decision to test the cross pin itself as opposed to testing the hamstring graft, the cross pin, and its fixation in the femoral bone.

Espejo-Baena et al¹⁴ compared, in porcine femurs, the biomechanical properties of the Bio-Transfix (Arthrex, Naples, Florida) and Biosteon (Stryker Endoscopy, San Jose, California) cross pins to an interference screw and to wrapping the graft around the femoral condyle. They tested these constructs by a single load until failure without any cyclic fatigue data. The strength of the cross pins (Bio-Transfix, 905 N; Biosteon, 684 N) and their stiffness values were significantly greater than the other 2 methods of fixation. They concluded that the biomechanical properties of the 2 cross-pin fixation systems were superior to the other 2 systems studied.

Ahmad et al²⁴ studied femoral fixation devices for the ACL by measuring fixation slippage. In porcine femora, the Endobutton, RigidFix, Bio-Transfix, and interference screw were subjected to cyclic loading from 50 N to 250 N for 1000 cycles. The load was held at 50 N for 45 seconds while slippage was measured at regular intervals. After cyclic fatigue, the grafts were loaded until failure. They found the graft slippage was greater in the RigidFix and interference screw constructs. The failure load of the interference screw was significantly less than the other 3 methods. The yield load of the cross pins were 737 N for the RigidFix and 746 N for the Bio-Transfix.

Our study evaluated only the cross pins and not the final construct seen in clinical practice. To study the implants in our idealized femoral tunnel, some modifications had to be made. For the RigidFix system, only 1 pin could be tested for accurate data across our cylindrical supports. The Bone Mulch Screw was detached from its proximal threaded portion so it would lie across the supports. This provides data relevant to the clinical application but differs from other studies. Specifically for the cortical allograft, its failure by brittle fracture likely may not occur in vivo or in solution.

Conclusion

The cross-pin femoral fixation with the implants tested in this study would provide adequate initial fixation for hamstring grafts. If one assumes that mechanical fixation is needed for 8 to 12 weeks until biologic fixation occurs, both polymeric implants showed gradual enough loss of mechanical properties to achieve this goal, and the other 2 implants far exceed the strength needed. Considering that 2 RigidFix pins are used clinically, the mechanical properties of either bioabsorbable cross pin appear to meet clinical demands and maintain their strength for a sufficient length of time to permit biologic fixation.

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