KNEE

ORTHOPEDICS July 2011;34(7):524.

Arthroscopic Medial Retinacular Imbrication for the Treatment of Recurrent Patellar Instability: A Simple and All-Inside Technique

by Hu Xu, MD; Chunli Zhang, MD; Guoxian Pei, MD; Qinsheng Zhu, MD; Yisheng Han, MD

Abstract

Proximal soft tissue realignment is the main surgical intervention for recurrent patellar instability. In recent years, all-inside arthroscopic procedures or mini-open surgeries have replaced traditional surgeries, which have more associated morbidity and poor cosmetic results. This article describes a simple and all-inside arthroscopic technique for the operative treatment of recurrent patellar instability. Using 2 epidural needles in several steps and no accessory portals required, the medial patellar retinaculum is imbricated to the desired tension. The combination of lateral release and medial retinacular placation obviously improves the patellar tracking compared with preoperatively.

Drs Xu, Zhang, Pei, Zhu, and Han are from the Department of Orthopedics, Xijing Hospital, Fourth Military Medical University, Xi’an, People’s Republic of China.

Drs Xu, Zhang, Pei, Zhu, and Han have no relevant financial relationships to disclose.

Correspondence should be addressed to: Hu Xu, MD, Department of Orthopedics, Xijing Hospital, Fourth Military Medical University, Xi’an, 710032, People’s Republic of China (xuhutiger1997@yahoo.com.cn).

Although >100 different surgical methods have been described for the treatment of recurrent patellar instability, the best choice remains controversial. Since various procedures in a number of studies have been proved effective, no gold standard surgery has been defined yet. Most surgeries typically involve 2 basic techniques: proximal soft tissue realignment and distal bony realignment. Proximal realignment generally is addressed by a combination of lateral retinacular release and imbrications of medial retinaculum. Traditional open surgical management ordinarily leads to poor cosmetic results; therefore, total arthroscopic techniques and arthroscopy-assisted mini-open medial reefing for the medial soft tissue realignment have been reported in recent years. ^1,2 However, most arthroscopic methods for medial retinacular plication either require special instruments or have relatively complicated procedures.

Almazán et al ³ introduced an arthroscopic technique for the repair of the shoulder rotator interval. Using 2 spinal cannular needles with several steps, the defect of the rotator cuff interval lesion could be repaired without accessory portals. Combining Almazán et al’s ³ method with previously reported knee arthroscopic techniques, we developed a simple and all-inside procedure for the treatment of recurrent patellar instability.

Surgical Technique

Surgery is performed with the patient under general or spinal anesthesia. The patient is positioned supine on the operating table with an inflated tourniquet applied to the operative extremity. The leg is sterilely prepped and draped in routine fashion. Using the standard inferolateral and inferomedial portals, routine diagnostic arthroscopy is performed to observe the lesion of menisci and cartilage, traumatic loose bodies (chondral or osteochondral fragments), and rupture of the anterior and posterior cruciate ligaments. Corresponding treatments including partial meniscectomy, chondroplasty, and removal of loose bodies are performed.

Particular attention should be paid to check the relationship of the patellar ridge with the femoral trochlear groove through range of motion of the knee and assessing patellar tracking from both inferolateral and inferomedial portals. Lateral tilt and overhang of the lateral patellar facet can be observed. The extent of laxity of the medial patellar capsuloligmentous complex and tightness of the lateral patellar retinaculum can be evaluated.

Two spinal needles (17F Weiss or Tuohy) are used for reefing the patellar medial retinaculum. A suture retriever is prepared by a needle and a suture loop with 1 end passed through the cannula of the needle (Figures ). A spinal needle is inserted into knee joint at the medial patellar edge, and under arthroscope the needle is retreated for 1 or 2 cm to make a proper suture loop for another needle passing (Figures ). At a medial 2 or 3 cm from the first needle on the skin, another needle is pierced into the joint posteromedially to make the inner exit as far away the medial edge of patella as possible. Within the joint, under arthroscopic view, 2 suture retriever loops are crossed (Figures ) and 1 end of the suture loop is pulled by a forceps to open the loop into a free suture (Figures ). After removal of 2 needles from the joint and leaving 2 sutures, the suture loop is pulled to deliver 1 end of the free suture out of joint to complete 1 stitch (Figures ). This procedure is repeated 3 or 4 times so that the stitches evenly spread from the superior pole to the inferior pole of the patella (Figure ). Using a giant needle subcutaneously passing through the 2 eyelets of 1 stitch on the skin, the end of suture at patella edge is brought to the far medial eyelet (Figures ).

Figure 1:. Two spinal needles, each with a suture loop, were inserted into the joint on the medial side of the patella (A). Under arthroscopic control, 2 suture retriever loops were crossed (B) and 1 suture end was pulled (C, arrow) to open the loop to a free suture (D). After removal of the needles, pulling 2 ends of a suture loop (E, arrow) brought another suture out of the joint (E, F) to complete a stitch. Bold arrow: bruise of medial patellofemoral ligament. The procedure was repeated several times so that the stitches (arrowheads) evenly spread from the superior to the inferior pole of the patella (G). Abbreviations: FC, femoral condyle; P, patella.

Figure 2:. A giant needle passing through the inlet and outlet of the stitch subcutaneously (A, arrow) led the suture end at medial patellar edge out from the far medial eyelet (A, B). Abbreviations: IM, inferomedial portal; P, patella.

The camera is switched from the inferolateral portal to the inferomedial portal to get a better view of the lateral retinaculum. In most patients with recurrent patellar instability, after debridement of the lateral synovium of the patella by a 4.5-mm Linvatec soft tissue shaver (Largo, Florida), a radiofrequency device is inserted in the joint through the inferolateral portal to perform lateral retinaculum release. A full-thickness retinaculum cut is made from the superior pole of the patella to the inferior pole at 1 cm lateral to the patella.

The assistant manually tightens the sutures at medial side of the patella, and patellar tracking is evaluated again from full extension to 90° of flexion under arthroscope. After medial plication and lateral release, the new relationship of the patellar ridge with the femoral sulcus can be observed. Furthermore, it is found that lateral tilt and overhang of lateral patellar facet are vanished or improved. At the same time, it also can be found that the patella is pulled medially from apparent view. Based on re-evaluation of patellar congruency in the trochlea and tracking, we regulate the tension of medial retinaculum imbrication to avoid internal tilt in case of excessive medialization of the patella.

Then the fluid of the joint is drained and the sutures tightened and knotted 1 by 1 when the assistant pushes the patella medially and maintains the tension according to the reevaluation under arthroscope (Figure ). After this procedure, we check the joint under arthroscope again to make sure patellar tracking is satisfied, and then bury the knots subcutaneously (Figure ).

Figure 3:. After re-evaluation of patellar tracking, the sutures were tightened and knotted with the knots buried subcutaneously (A, arrowheads). The medial reefing (arrowhead) was checked again under arthroscope (B). Bold arrow: bruise of medial patellofemoral ligament. Abbreviations: FC, femoral condyle; IL, inferolateral portal; IM, inferomedial portal; P, patella.

Postoperatively, as a part of standard rehabilitation program, quadriceps contractions and straight-leg raises are encouraged immediately after anesthesia fades. After 2 weeks, the patient is allowed to partially bear weight with crutch support and brace protection. Full weight bearing is allowed at 4 weeks. The brace is unlocked to enable patients to begin range of motion exercises not beyond 60° and 90° every 2 weeks. At 4 weeks, the patient is allowed to increase knee flexion as tolerated.

Results

To date, 17 patients with recurrent patellar instability have been treated by this all-inside arthroscopic technique. Traumatic chondral or osteochondral fragments were found in 4 cases, and 3 of them underwent chondroplasty. In 2 cases, lesion of the menisci was found and corresponding partial meniscectomy was performed. No anterior and posterior cruciate ligament rapture was found. No operational complications such as intra-articular infection or iatrogenic injury were observed. Mean operative time was 48.4±6.7 minutes (range, 39–61 minutes), whereas average time for medial imbrication was 23.2±4.9 minutes (range, 17–35 minutes). Furthermore, in the latest 5 cases performed in the past 12 months, medial reefing was performed in <20 minutes.

Postoperatively, 3 patients have been followed for >2 years, 7 patients for 1 year, and 5 patients for <1 year. Two patients were lost to follow-up. No recurrence of patellar subluxation or luxation has been found. On physical examination, all patients had a normal patella tracking and good stability in response to manual translation of the patella. One patient who failed to follow standard rehabilitation program had significant loss of range of motion (from 5° to 95°) 7 months postoperatively.

Discussion

For the treatment of patellar dislocation, many open procedures, including soft tissue realignment and bony procedures such as Elmslie-Trillat, ⁴ Roux-Goldthwait, ⁴ Hauser, ⁵ Insall proximal realignment, ⁶and combined realignment procedures, ⁷ have been popularized in the past. Although these traditional operations have proven to result in successful clinical outcomes to a varying extent, they generally accompany apparent morbidity and poor cosmetic results. Nevertheless, the recent progress of knee arthroscopy provides the possibility of minimally invasive procedures for proximal realignment of the patella.

Our technique does not require special instruments, complicated surgical skills, or accessory portals. The procedure is simple and easy for surgeons to perform. Halbrecht ⁸ reported an all-inside technique for proximal patella realignment under arthroscopy. Using 1 epidural needle toward 2 different directions subcutaneously, the medial retinaculum and capsule were penetrated twice so that the suture was introduced to create a loop for knotting. Compared to our technique, the disadvantages of Halbrecht’s ⁸method are: (1) it requires an accessory superolateral portal; (2) the second stab through the retinaculum by epidural needle subcutaneously is difficult to precisely control the position of the outlet and the span of a stitch; and (3) it takes more time and more complicated skills to knot 4 or 5 times in the joint under arthroscope rather than freehand knotting outside the joint.

In 2002, Haspl et al ⁹ developed another all-inside method with some instruments including a working cannula and Transporter Suture Retriever (Acufex, Mansfield, Massachusetts). In their method, an accessory superomedial portal was needed, and 4 or 5 arthroscopic knots were formed and slid down through the extra-articular cannula. Compared to our technique, their procedure is relatively complicated, and the span of the stitch is limited since the inlet and the outlet are perforated from a cannula through the same superomedial portal.

In 2007, Ali and Bhatti ¹ reported a technique to reef the medial retinaculum with a long and prebent 16-gauge Tuohy needle, meniscal suture needle, and artery forceps, which created a subcutaneous plane to retrieve sutures. Their method is not simpler than Haspl et al’s ⁹ since 4 portals (inferolateral, inferomedial, superolateral, and midmedial parapatellar) are needed. According to Ali and Bhatti, ¹ the inlets of the stitches are not close to the medial edge of the patella, mainly as a result of the difficulty of bending a metal 16-gauge Tuohy needle precisely for perforating the capsule twice in aimed positions.

In 2006, Schöttle et al ¹⁰ reported a similar technique, with 2 differences compared to our method: (1) the first needle is pierced through the periosteum of the medial patellar facet, which may lead to avulsion of the insertion on the periosteum as a result of the high tension of knotting in medial imbrication; and (2) an eyelet is advanced through the subcutaneous tissue and is pressed against the skin, where a second epidural needle is inserted through the eyelet into the joint. It may be not easy for a needle to pass through the subcutaneous eyelet precisely.

Although some studies show the clinical success of isolated lateral retinacular release for the treatment of recurrent patellar dislocation, ¹¹ a recent systematic review combining the results of 14 studies concludes that compared with lateral release and medial soft tissue realignment, lateral release alone yields significantly inferior long-term results with respect to symptoms of recurrent lateral patellar instability. ¹² In our technique, we performed both lateral release and medial retinacular imbrication for patients, and no recurrence of patellar subluxation or luxation has been found. After full-thickness lateral release, the patella could be pushed medially by an assistant and medial plication performed. In 2010, Dodson et al ¹³ performed plication first and then released the lateral retinaculum. However, based on clinical experience, we believe that the initial lateral release would provide suitable conditions to further medial plication and knotting the sutures with desired tension. Furthermore, it is incorrect to knot the sutures as tightly as possible in medial reefing. An in vitro study has implied that proximal soft tissue realignment may result in significantly medialized and internally tilted patellar movement. ¹⁴ We suggest that the knotting should be adjusted to appropriate tension according the re-evaluation of patellar tracking under arthroscope.

Our technique is performed in patients with recurrent patellar instability combined with acute injury of the medial patellofemoral ligament body (Figures , , ), since imbrication provides a tension-free condition for ligament healing.

Indications for our technique include recurrent patellar instability resulting from laxity of the medial retinaculum, injury of the medial patellofemoral ligament body, and cases without serious trochlear dysplasia, patella alta, and a considerably high Q angle. However, for the treatment of most severe osseous abnormalities, such as significantly high Q angle, serious patella alta, or trochlear dysplasia, distal bony realignment procedures should be initially considered rather than our technique. Moreover, theoretically our technique is unsuitable for some special types of patellar instability even with a normal Q angle. For example, in cases of avulsion of the medial patellofemoral ligament from the patellar side, ligament reattachment on the medial patellar facet or the reconstruction of the medial patellofemoral ligament is a better choice. ^13,15 In another unpublished study by our medical group, we used anchors for the treatment of patellar instability combined with avulsion of the medial patellofemoral ligament.

Conclusion

The advantages of our technique include simple steps, no special instruments, no accessory portals, and ease of manipulation for arthroscopists. The pitfalls include the limitation that it cannot be performed when the medial patellofemoral ligament has been avulsed off the femoral or patellar side, and that the sharp tip of the spinal needles may cut off the sutures when they pierce into the joint.

For further information:

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KNEE

ORTHOPEDICS July 2011;34(7):251.

Do Microfractures Improve High Tibial Osteotomy Outcome?

by Walter Pascale, MD; Simone Luraghi, MD; Laura Perico, MD; Valerio Pascale, MD

Abstract

The aim of this study was to determine if microfractures improve the outcome of high tibial osteotomy in patients with medial compartmental osteoarthritis in genu varum. Forty patients presenting with Outerbridge grade III and IV chondropathies on the femoral and/or the tibial joint surface underwent high tibial osteotomy with Puddu plates (Arthrex, Inc, Naples, Florida) for primary medial compartment osteoarthritis in genu varum at our institution. Patients were randomly assigned to either the high tibial osteotomy plus microfractures group (A; n=20) or the high tibial osteotomy alone group (B; n=20). Final assessment was conducted 5 years postoperatively, including clinical response measured by the International Knee Documentation Committee (IKDC), Lysholm score, and patient satisfaction score. All patients were blinded to the treatment received and followed the same rehabilitation protocol. A statistically significant improvement between pre- and postoperative values was observed for Lysholm and IKDC scores in both groups, without any statistically significant difference between them. Regarding the satisfaction score, there were no differences between the 2 groups in terms of preoperative self-assessment ( P>.05), whereas postoperative subjective satisfaction at 5-year follow-up was significantly higher in group A than in group B ( P=.0036).

Our study results provide further evidence that medial tibial osteotomy is an effective surgical option for treating a varus knee associated with medial degenerative arthritis in patients wishing to continue accustomed levels of physical activity. In particular, patient satisfaction was higher among those who underwent the combined treatment involving high tibial osteotomy to correct femorotibial angle and microfractures.

Drs Pascale (Walter), Luraghi, Perico, and Pascale (Valerio) are from IRCCS Galeazzi Orthopaedic Institute, and Dr Pascale (Valerio) is also from Clinica Ortopedica e Traumatologica, Università degli Studi di Milano, IRCCS Galeazzi Orthopaedic Institute, Milan, Italy.

Drs Pascale (Walter), Luraghi, Perico, and Pascale (Valerio) have no relevant financial relationships to disclose.

Correspondence should be addressed to: Walter Pascale, MD, IRCCS Galeazzi Orthopaedic Institute, Via R. Galeazzi 4, 20161 Milano, Italy (pascalew@tiscali.it).

Posted Online: July 07, 2011

Treatment of unicompartmental knee osteoarthritis continues to raise discussion. As initially described by Jackson et al, ¹ the causes of knee joint cartilage degeneration have been primarily attributed to medial deviation of the functional axis of the knee, tibial and femoral bone deformities, and malalignment and disorientation due to primary laxity of the collateral ligaments. ² High tibial osteotomy is a treatment of choice, particularly in patients wishing to continue to practice high levels of physical activity. Unicompartmental prosthesis is a more definitive treatment than high tibial osteotomy and is indicated in patients affected by wider cartilage degeneration or in older patients. ³

First described by Jackson and Waugh ⁴ in 1982, high tibial osteotomy attracted attention following publication of long-term results in a study by Coventry et al. ⁵ Debeyre and Artigou ⁶ outlined the technique of open wedge medial tibial osteotomy. With the introduction of the Puddu plate (Arthrex, Inc, Naples, Florida) into clinical practice in the late 1990s, which simplified the technique, high tibial osteotomy has reached wider acceptance. However, controversy exists about the use of high tibial osteotomy in association with microfractures to stimulate cartilage regeneration. ^7,8

Johnson ⁹ reported that microfracture is a suitable treatment for knee cartilage lesions, providing repair of the lesions by the formation of fibrocartilage. Although favorable results have been reported in patients with slight deviation of the functional axis, the long-term outcome remains unclear. ^10,11 In their studies, Bergenudd et al ¹² and Odenbring et al ¹³ found that high tibial osteotomy can lead to long-term clinical improvement in cases of knee cartilage lesions.

The aim of this study was to assess patient satisfaction and functional outcome after high tibial osteotomy in combination with microfractures in patients with medial osteoarthritis in genu varum.

Materials and Methods

The study population comprised 40 patients who underwent high tibial osteotomy with Puddu plates for primary medial compartment osteoarthritis in genu varum at our institution between 2002 and 2003. Inclusion criteria were chondropathies present on the femoral and/or the tibial joint surface, multiple Outerbridge grade III and IV lesions, femorotibial deviation between 7° and 10°, age between 40 and 70 years, body mass index (BMI) <32 kg/m ². The work was approved by our institution’s ethical committee. All patients gave their consent to be included in the study.

Group A patients were treated with high tibial osteotomy plus microfractures (20 knees in 20 patients), while group B patients received high tibial osteotomy alone (20 knees in 20 patients). All 40 patients were randomly assigned to either group by an external researcher not involved in the study using a randomization block. All procedures were performed by the same surgeon (W.P.), and the patients were blinded to treatment received. Imaging studies, including anteroposterior (AP), lateral, and tangential knee and long-leg radiographs and magnetic resonance imaging (MRI) were performed for each patient (Figure ). The radiologist also was blinded to the study conditions. The patients received a 30-day course of prophylactic deep venous thrombosis treatment and a short-term course of prophylactic antibiotic therapy.

Figure 1:. AP radiograph of a high tibial osteotomy procedure.

Knee joint cartilage was evaluated arthroscopically by the same surgeon preoperatively according to Outerbridge’s criteria: grade 0=normal; grade I=softening and slight fibrillation of the surface; grade II=generally smooth joint surface but with unevenness, fragmentation, fissuring, and fibrillation over an area <1.5 cm; grade III=white fibrous tissue, fragmentation, fissuring, and fibrillation over an area >1.5 cm; grade IV=subchondral bone exposure and eburnation over almost all the joint surface. ¹⁴

Symptoms were evaluated by the International Knee Documentation Committee (IKDC) and Lysholm scales preoperatively and at 6 months, 1 year, 2 years, and 5 years postoperatively. This study presents the 5-year follow-up data. Lysholm scores were considered: >64=not sufficient; 65–83=sufficient; 84–94=good; 95–100=excellent. Patient satisfaction was measured according to a satisfaction scale (score 1–10).

Surgical Technique

High tibial osteotomy was performed by wedge interlocking osteotomy and fixation with a Puddu plate. Prior to osteotomy, the degree of joint degeneration was measured arthroscopically. In group A, abrasion arthroplasty was performed using a steel abrader to a depth of approximately 1 mm; microfractures were created by drilling holes in the perimeter and the central area of the damaged cartilage to a depth of approximately 1 mm until bleeding of the subchondral bone occurred. This procedure was performed on the tibial plateau and femoral condyle in all patients except for 3 patients in group A who did not present with chondropathy of the tibial plateau and who received microfractures of the femoral condyle only. Group B patients underwent high tibial osteotomy only.

Starting from postoperative day 2, the physiotherapy regimen comprised physiotherapist-assisted continuous passive motion exercises, approximately 4 hours daily for 2 weeks, as well as isometric gymnastic and passive and active kinesis for approximately 2 hours daily for 2 weeks (Figure ). ^15,16 The work load was adjusted at 6 to 8 weeks, before full weight bearing was permitted.

Figure 2:. After 2 weeks of the rehabilitation program, patients were able to actively reach 90° of flexion.

Analysis of variance (ANOVA) was performed on continuous data; the chi-square test was used to analyze the categorical scores. Statistical significance was set at P<.05.

Using an alpha value of 0.05 and a power of 80%, the power calculations were derived from an estimated difference of 8 points in postoperative Lysholm score between the 2 groups. The sample size resulted in 20 patients for each group.

Results

The clinical characteristics of the patients are summarized in Table . Group A comprised 13 men and 7 women, and group B comprised 15 men and 5 women. Average patient age at surgery was 50±4.6 years (range, 44–64 years) in group A and 49.7±5.8 years (range, 43–67 years) in group B ( P<.05).

Table 1. Patient Clinical Characteristics

Eleven patients in group A and 13 patients in group B were affected by Outer-bridge grade III lesions, whereas all other patients, 9 in group A and 7 in group B, presented with grade IV cartilage lesions. All patients presented with femoral and tibial eburnation, with the exception of 3 patients in group A and 2 patients in group B who did not have tibial eburnation. Three patients in group A and 2 in group B had received arthroscopic debridement; the remaining patients, 17 in group A and 18 in group B, had undergone conservative treatment for 1 year. All patients were affected by multiple lesions, differing in size and in Outerbridge grade, but no cases involved the entire tibial plateau or condyle. A significant difference between pre- and postoperative values in terms of femorotibial angle correction was present in each group (178.5±1.5 and 184.5±0.9 for group A, respectively; 178.2±1.6 and184.6±0.9 for group B, respectively; all P<.05), but no statistically significant differences between the 2 groups were observed (P<.05).

The same trend was observed for the Lysholm and IKDC scores preoperatively and 5 years postoperatively: analysis showed a statistically significant improvement in postoperative Lysholm scores in both groups compared to the preoperative scores ( P<.05), but there was no statistically significant difference in pre- and postoperative scores between the 2 groups ( P>.05) (Table ). Preoperative IKDC score was D in 70% and 75% of patients in group A and B, respectively ( P>.05). Postoperative IKDC score significantly increased in both groups: 16 patients in the combined treatment group (80%) and 17 patients treated with high tibial osteotomy alone (85%) scored A, whereas the others scored B, with no significant differences between the 2 groups ( P>.05).

Table 2. Mean Pre- and Postoperative Lysholm and Satisfaction Scores

Regarding the satisfaction score, there were no differences between the 2 groups in terms of preoperative self-assessment ( P>.05), whereas postoperative subjective satisfaction at 5-year follow-up was significantly higher in group A than in group B ( P=.0036). The inverse correlation between BMI and postoperative Lysholm score ( r=-0.049; P=.001) was statistically significant only in group B patients. Furthermore, a negative correlation emerged between age and lesion grade according to Outerbridge’s criteria in group B patients: with increasing age, the lesion grade decreased (grades III and IV at an average age of 51.8 and 46.9 years, respectively; P=.014).

Postoperative Lysholm score was sufficient in 65% and good in 35% of group A patients, whereas in group B it was insufficient in 5%, sufficient in 60%, and good in 35% of patients. The patients who scored highest on the Lysholm scale were those with the highest preoperative lesion grade.

Magnetic resonance imaging assessment 5 years postoperatively disclosed regeneration of cartilage tissue on the femoral and tibial bones. In 3 cases of residual pain and articular stiffness in the operated knee, an arthroscopic second look of the joint observed good formation of a covering tissue (Figure ).

Figure 3:. Arthroscopic second look after 1 year with microfracture treatment of a medial femoral condyle.

At 1-year follow-up, 1 patient was excluded from the study because of failure to return for examination. At 5-year follow-up, 2 patients (5%) were noted to have 3° undercorrection in genu varum that produced arthroscopically and clinically insufficient healing. For this reason and because of persistent pain, both received total knee arthroplasty (TKA). Deep venous thrombosis in 1 patient (2.5%) resolved with medical and compression therapy and did not affect the final analysis of the results.

Discussion

Our study results provide further evidence that medial tibial osteotomy is an effective surgical option for treating a varus knee associated with medial degenerative arthritis in patients wishing to continue accustomed levels of physical activity. In particular, patient satisfaction was higher among those who underwent the combined treatment involving high tibial osteotomy to correct femorotibial angle and microfractures. Furthermore, an inverse correlation emerged between BMI values, Lysholm and IKDC scores, patient age, and degree of correction.

In this study population, a second intervention was necessary in only 2 cases where correction of the mechanical axis failed to restore normal valgus and serious pain persisted at 5-year follow-up. The 2 patients subsequently underwent TKA.

Published data suggest that abrasion-microfractures fail to completely resolve knee joint damage in patients with medial compartment arthritis associated with severe genu varum. ^17–19 Indeed, symptoms may later return, even after initial good results at 1-year postoperatively. For this reason, as described by Shaw and Moulton, ²⁰ high tibial osteotomy associated with microfractures is a valid attempt to correct the primary cause of arthritis. As demonstrated in a study by Puddu et al, ²¹ medial tibial osteotomy is able to produce a clear improvement in clinical and subjective symptoms. Given the subjective nature of pain symptoms, our results show that the combined treatment achieved greater postoperative patient satisfaction, although the clinical results in the 2 treatment groups were objectively definitely comparable. This was probably due to the fibrocartilage formation that abrasion and microfracture are able to promote by stimulating the incoming of subchondral bone marrow blood to the surgical site. Fibrocartilage formation leads to enhanced restoration of physiological knee joint equilibrium, thus reducing pain and increasing patient satisfaction.

Six years postoperatively, we performed arthroscopic reintervention for a medial meniscal lesion in 3 patients. In these patients we were able to observe the new regenerated cartilaginous tissue on the area treated by microfractures. In 2 of these patients, the new formed tissue completely covered the chondral lesion, both approximately 1 cm ², at femoral condyle level in 1 case and on the tibial plateau in the other. In the third patient, where the lesion size was approximately 3 cm ², the new regenerated cartilaginous tissue just partially covered the tibial area. However, despite the results obtained by the second look arthroscopy in 3 of our patients showing no differences between condyles and tibial plateau, our surgical experience allowed us to observe that normally the use of microfractures in combination with osteotomy yields better subjective results in the femoral condyle than in the tibial plateau.

Even if it is known that chondral lesions microfractures could not result in exhaustive and durable results, in particular in lesions >1 cm ², this technique is still the most used treatment for isolated cartilage lesions. When patients present an axial deviation, the outcome could ameliorate combining microfractures with high tibial osteotomy. However, when high tibial osteotomy is not practical, as in normal morphotype patients, alternative treatments could be used for larger cartilage lesions according to patient age, activity level, and general joint conditions. ²² This evidence induced us to use microfractures in patients with focal chondral lesions, whereas for larger lesions, and in cases of correct indications, we performed high tibial osteotomy or a uniprosthesis.

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HIP

ORTHOPEDICS June 2011;34(6):127.

In Vivo Assessment of Total Hip Femoral Head Separation from the Acetabular Cup During 4 Common Daily Activities

by Thomas J. Blumenfeld, MD; Diana A. Glaser, PhD; William L. Bargar, MD; Glen D. Langston, BS; Mohamed R. Mahfouz, PhD; Richard D. Komistek, PhD

Abstract

In vivo video fluoroscopies of well-functioning total hip arthroplasties (THA) have shown that femoral head separation from the medial articular bearing surface occurs during gait. Other activities may cause the same phenomenon. We examined this while patients performed the following 4 activities of daily living: pivoting to each side in stance, shoe tying, sitting down, and standing up. Ten healthy patients (5 men, 5 women, average age 66 years) all 1 year or more after cementless THA performed for degenerative arthritis, with Harris Hip Scores =90, were studied. Each patient performed the activities of daily living while data was captured using video fluoroscopy. Based on previously reported criteria, femoral head separation (the femoral head sliding lateral to the acetabular liner) was determined to be reliably predicted if the distance between the femoral head and acetabular cup was =0.5. Results showed that the greatest femoral head separation occurred during the pivoting activity (mean, 1.53 mm; range, 0.00–3.34 mm; SD, 1.05 mm). The separation values identified during pivoting occurred at the extremes of internal or external rotation for all patients. The other 3 activities showed lower separation distances. Separation during the pivoting activity exceeded the reported separations occurring during walking. This finding was seen in a small group of patients, and the data should be interpreted with caution. We conclude from this study that the evaluation of gait alone may not be sufficient to accurately assess femoral head separation occurring during activities of daily living for healthy, active patients.

Drs Blumenfeld and Bargar are from Sutter General Hospital, University of California Davis and Dr Glaser is from Rady Children’s Hospital of San Diego, California; Mr Langston is from Wright Medical Technology, Inc, Arlington, and Drs Mahfouz and Komistek are from the University of Tennessee, Knoxville, Tennessee.

Dr Blumenfeld is a consultant for DePuy. Drs Glaser, Mahfouz, and Komistek and Mr Langston have no relevant financial relationships to disclose. Dr Bargar is a consultant for Curexo.

Funding for the data acquisition and analysis was obtained from DePuy, a Johnson & Johnson Company. The funding allowed for obtaining data on 10 patients.

Correspondence should be addressed to: Thomas J. Blumenfeld, MD, 1020 29th St, Sacramento, CA 95616 (tblumenfeld@jointsurgeons.com).

Posted Online: June 14, 2011

The postoperative outcomes of total hip arthroplasty (THA) patients have been broadly studied through the use of patient questionnaires, ¹ instrumented implants, ² and kinetic and kinematic evaluations. ^3–7The majority of these studies have focused on the evaluation of implant performance during gait since walking is the predominant weight-bearing activity occurring in the daily lives of most individuals. The performance of hip prostheses during other common activities of daily living may be important to analyze. Other activities may lead to higher femoral head separations (the femoral head sliding lateral to the acetabular liner) than present during gait; therefore, a variety of movements must be studied to gain a full understanding of the conditions occurring at the prosthetic hip joint.

In vitro methods have been developed to test the long-term endurance of implants, taking into account a variety of activities of daily living. ⁸ These studies, which are of value for preclinical evaluations, do not analyze the performance of implants in a true in vivo environment. Therefore, in vivo analysis of hip joint prostheses is required in an attempt to understand and define prosthetic functioning. Instrumented implants have been used to analyze hip contact forces under in vivo conditions during various activities of daily living. ^9–11 Hodge et al ¹² showed that while the observed force on the implant during the ascension of stairs was higher than during walking, it was not as high as rising from a chair. In contrast, a separate telemetric study revealed no substantial difference between the peak resultant force (2.6× body weight) during gait and ascension of stairs. ¹⁰

Previous in vivo studies have determined that femoral head sliding within the acetabular cup does occur in THA patients, and that the magnitudes of femoral head separation are higher for abduction/adduction activities than for gait. ^4,13 The subsequent impact following femoral head separation from the liner leads to increased loading conditions at the bearing surface interface, especially superolaterally, which may lead to increased wear at the bearing surfaces of the implants. ^4,6,13–15 To date, no studies exist focusing on the fluoroscopic evaluation of in vivo hip kinematics and femoral head separation for a variety of activities of daily living.

The objective of the present pilot study was to obtain and evaluate the in vivo femoral head separations of 10 well-functioning THA patients while performing a variety of common activities of daily living not yet studied in detail: pivoting, tying a shoe, standing up and sitting down, both performed with and without the aid of handrails.

Materials and Methods

Patients

Ten patients implanted with a well functioning THA were examined. Five men and 5 women were analyzed under in vivo, weight-bearing conditions using video fluoroscopy. All patients received a similar cementless total hip prosthesis with a Summit femoral stem, a Pinnacle acetabular cup, a metal 36-mm diameter femoral head, and a Marathon cross-linked polyethylene liner (all implants Depuy, Johnson and Johnson Company, Warsaw, Indiana). All surgeries were performed by 2 of the authors (T.J.B., W.L.B.), both using a similar posterolateral approach with repair of the capsule and short external rotators. The average patient age was 66.1 years (range, 53–77 years). Body Mass Index values revealed 3 patients in the normal range (Body Mass Index, <25) and 7 patients in the overweight or obese category. The patient demographics overlapped the age and Body Mass Index distribution of the typical THA population. All patients were diagnosed with degenerative arthritis, 2 patients had acetabular dysplasia, and 1 patient had a stage 1 protrusio deformity.

Only THA patients with excellent clinical results (Harris Hip Scores >90 points (mean, 96 points; range, 90–100 points) presenting no functional deficits, an absence of generalized inflammation, and negligible chronic pain were included in the study. ¹⁶ Each patient was implanted with a unilateral THA and could independently abduct their operated hip against gravity without difficulty. None of the patients walked with a detectable limp. No patient sustained a hip dislocation or reported hip subluxation. Radiographic measurements of limb length were obtained on all patients. None had shortening of the analyzed limb in comparison to the unoperated side. The femoral offset was restored, and the acetabular component was oriented within the safe zone position for all THA patients. ¹⁷ The average duration of postoperative follow-up at the time of analysis was 13.1 months (10.3–20.5 months).

Activities

Each patient performed 4 different activities to evaluate the femoral head separation: pivot, shoe tie, sit-down and stand-up (both with and without handrails). The pivot activity was defined as turning of the upper body while leaving both feet firmly planted on the ground starting in the most internally-rotated position possible (upper body twisted toward the side with the hip implant) and then turning the upper body to the most externally-rotated position possible (upper body twisted away from the side with the hip implant). The shoe tie exercise consisted of a patient bending the upper body forward while sitting in a chair, from an erect seated position to a position nearly parallel to the floor while reaching between the knees (simulating the act of tying a shoelace). Sit-down exercises were executed by having a patient slowly sit in a chair (seat height 18 in) with arms from an upright position. Stand-up was then the opposite; the patient rose from sitting in a chair to an erect, standing position. Patients were allowed to hold the arms of the chair for stability if they wished.

Data Collection

Preliminary screening questionnaires were used for evaluation of the Harris Hip Score. Two cameras were used in conjunction with a single-plane fluoroscopy unit to capture the in vivo weight-bearing movement of the implants in the hip joint and the corresponding leg during each activity. The activity to be performed was modeled for the patient by 2 of the authors (T.J.B., W.L.B.). The patient was allowed to perform several trials of the activity prior to data acquisition. For all activities, patients were asked to keep equal weight on their limbs; validation of this via use of a force plate was not performed. Data was obtained from a single repetition of the activity for each patient. Patient data-sets were processed and interpreted using a 3-dimensional ^18,19 registration process alongside MATLAB (The MathWorks, Inc, Massachusetts), programs authored by the Center for Musculoskeletal Research. ¹⁹ For each patient, fluoroscopic video frames were digitized to specific time intervals according to the requirements for analysis of each activity, which ranged from 4 frames needed for shoe tie, sit-down, and stand-up to 5 frames needed for the pivot exercise. Both femoral and pelvic 3D translational and rotational kinematics were gathered for analysis. Based on the transformation matrices obtained for each individual body, relative motions of the femur and pelvis were calculated and then used to determine the distance between the center of the femoral head and the acetabular cup components. Application of this measurement allowed a diagnosis concerning whether or not sliding of the femoral head from the acetabular cup (separation) had occurred (Figure ). ^4,5

Figure 1:. Demonstration of the Overlay Method and of the Diagnosis of Separation (the Distance Between the Center of the Femoral Head and the Acetabular Component Is Denoted as Hip Joint Separation when >0.5 mm).

Error Analysis

An error analysis was previously published and confirmed the precision of the 3-dimensional model-fitting process. ^13,19 An error value of 0.5 mm was determined to be the threshold; therefore, femoral head sliding was reliably predicted if the distance between the femoral head and acetabular cup was >0.5 mm.

Results

Values representing the separation of the femoral component from the acetabular cup have been calculated for each activity and reported in millimeters. In the present study, we found that the separation values differed for the 4 activities (Figure ). The highest average hip separation was observed during the pivot activity with a mean of 1.53 mm (range, 0.00–3.34 mm; SD, 1.05 mm). Corresponding lowest separation values occurred while performing the stand-up activity, with an average of 0.69 mm (range, 0.00–1.60 mml; SD, 0.46 mm).

Figure 2:. Quartile Boxplot of Separation Results from 4 Activities.

Using a threshold of separation significance of 0.5 mm, observations of significant separation occurred in 9 of 10 (90%) patients during the pivot and sit-down exercises, which represented the highest incidence in the study. Conversely, the stand-up exercise showed only 6 of 10 (60%) patients having a separation >0.5 mm (Figure ). High hip separation incidence persisted during pivot when analyzing separation at a threshold of 1.0 mm (60%); considerably less incidence was found in shoe tie and sit down and was nearly absent in stand up (Figure ).

Figure 3:. Incidence of Separation >0.5 mm per Activity. For the Pivot Activity (PI, Blue) and Sit down Activity (SDOWN, Green), 9 of 10 Patients Exhibited Separation Greater than 0.5 mm. For the Shoe Tie Activity (SHOE, Red), 8 of 10 Patients Exhibited Separation >0.5 mm. For the Stand up Activity (SUP, Purple), 6 of 10 Patients Exhibited Separation >0.5 mm.

Figure 4:. Incidence of Separation >1.0 mm per Activity. For the Pivot Activity (PI, Blue), 6 of 10 Patients Exhibited Separation >1.0 mm. For the Shoe Tie Activity (SHOE, Red), 4 of 10 Patients Exhibited Separation >1.0 mm. For the Sit down Activity (SDOWN, Green), 3 of 10 Patients Exhibited Separation >1.0 mm. For the Stand up Activity (SUP, Purple), 1 of 10 Patients Exhibited Separation >1.0 mm.

Distinct trends were observed for each activity by evaluating the calculated separation values during the execution of the motion. In our analysis of the pivot activity, maximal separation occurred during internal rotation of the hip in 80% of patients. The highest separation values were seen at the extreme of rotation, while little or no separation occurred in the neutral position. For 2 of the 10 patients, lower separation values were identified as the hip rotated externally through the prescribed motion.

All 10 patients showed the greatest separation in the latter half of the shoe tie activity, during which the upper body is most bent forward. For the sit-down exercise, half of the patients (5/10) demonstrated maximal separation during the first half of the movement, and the other patients exhibited maximums during the latter half of the motion. Overall, a trend of decreasing separation values started from the beginning (standing) to the end (sitting) of the movement. For the stand-up exercise, half of the patients (5/10) demonstrated maximal separation during the first half of the activity, while the other patients exhibited maximums during the latter half of the motion. Contrary to the sit-down exercise, the opposing trend of increasing separation was apparent throughout the motion (from sitting to standing).

Discussion

Past fluoroscopic studies on THA separation are limited and have focused primarily on analysis during gait or abduction/adduction. ^4,14 Using in vivo fluoroscopic analysis to evaluate other motions commonly encountered during a typical day has not yet been performed. Kinematics obtained from video fluoroscopy has been found to be consistently accurate to within 0.5 mm. ^18,19 This process has been successfully used to analyze many different joints and implant systems in vivo. ^5,20–22

Previously, separation was found to occur in gait and abduction/adduction activities. ^6,13,14,18 Further analyses were necessary to determine if separation occurred during other activities of daily living and if the type of activity affected the incidence and magnitude of hip separation. We found a high incidence and magnitude of separation for the activities analyzed in the present study. In observed cases of separation between the femoral head and acetabular cup, contact area between the 2 components is reduced. In this case, a separation of the femoral head from the medial articular surface leads to a smaller superolateral region of contact. Therefore, the femoral head may pivot on the peripheral rim of the liner when separation values are extreme. This lessens the articular contact area, causing higher exerted pressures on the articular surfaces, potentially leading to increased wear of the components.

In comparison with the past studies, our findings during the pivot activity exceed the common separations encountered in walking. Average separation during pivot was 1.5 mm higher than the previously reported 1.2 mm of separation encountered during gait. ¹⁴ Lombardi reported a separation incidence of 100%, similar to the 90% observed for the pivot motion. ¹⁴ When comparing the pivot separations to separations previously reported for abduction/adduction analysis, the pivot exercise demonstrated lower overall separation values. Separation averages for abduction/adduction are reported as 2.4 and 3.3 mm, respectively, higher than the 1.5 mm observed for pivot motions within this study. ^13,14 We believe that the separations seen during the pivot activity are important, as discussed below.

The other activities, shoe tie, sit down, and stand up, all exhibited lower separation values than the pivot motion. When comparing these 3 activities to previously reported gait separation, the magnitudes and incidences of separation are considerably lower. From these results, we can conclude that examination of shoe tie, sit down, and stand up is not as important as the consideration of pivot, gait, and abduction/adduction activities when focusing on the extremes of hip joint activity during daily usage.

This study has 4 significant limitations:

1. We examined a small group of patients, and all patients had well-functioning THAs. Our results should not be used as normative values until a larger group of patients are studied. More importantly, our results may not apply in patients with hip instability or abductor weakness; we would suspect that the separations in these conditions would be higher.

2. Other kinematic features, such as the amplitude and direction of angular rotation of the femoral head within the acetabular cup, were not studied.

3. We have chosen to report our findings relative to previously reported studies on femoral head separation, and the patient populations may not be comparable.

4. The separations seen during pivoting demonstrated in this study, occurring during 2-legged stance, may not represent those occurring in conjunction with gait.

We conclude from this study that the evaluation of gait alone may not be sufficient to accurately assess the range of separation values encountered in daily life for healthy, active patients. Of the investigated activities presented herein, separation value averages for the pivot motion were greater than those found previously for gait. As selected patients are now being allowed to run after THA, if the separations we have demonstrated with pivoting exist at the higher velocities encountered with running, the bearing separation and subsequent joint relocation forces may be detrimental to implant longevity. The upper boundaries of separation values in hip arthroplasty in both well-functioning and poorly-functioning THAs require further investigation.

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