HAND/UPPER EXTREMITY

ORTHOPEDICS July 2011;34(7):275.

Biomechanical Evaluation of Open Suture Anchor Fixation Versus Interference Screw for Biceps Tenodesis

by Derek F. Papp, MD; Nathan W. Skelley, BS; Edward G. Sutter, MS; Jong Hun Ji, MD; Carl H. Wierks, MD; Stephen M. Belkoff, PhD; Edward G. McFarland, MD

DOI: 10.3928/01477447-20110526-04

Abstract

Biceps tenodesis provides reliable pain relief for patients with biceps tendon abnormality. Previous cadaver studies have shown that, for biceps tenodesis, an interference screw provides biomechanical strength to failure superior to that of suture anchors. This finding has led some providers to conclude that screw fixation for biceps tenodesis is superior to suture anchor fixation. The purpose of the current study was to test the hypothesis that the strength of a 2-suture-anchor technique with closing of the transverse ligament is equal to that of interference screw fixation for biceps tenodesis.

In 6 paired, fresh-frozen cadaveric shoulder specimens, we excised the soft tissue except for the biceps tendon and the transverse ligament. We used 2 different methods for biceps tenodesis: (1) suture anchor repair with closing of the transverse ligament over the repair, and (2) interference screw fixation of the biceps tendon in the bicipital groove. Each specimen was preloaded with 5 N and then stretched to failure at 5 mm/sec on a materials testing machine. The load-to-failure forces of each method of fixation were recorded and compared. Mean loads to failure for the suture anchor and interference screw repairs were 263.2 N (95% confidence interval [CI], 221.7–304.6) and 159.4 N (95% CI, 118.4–200.5), respectively. Biceps tenodesis using suture anchors and closure of the transverse ligament provided superior load to failure than did interference screw fixation. This study shows that mini-open techniques using 2 anchors is a biomechanically comparable method to interference fixation for biceps tendon tenodesis.

Drs Papp, Ji, Wierks, Belkoff, and McFarland and Messrs Skelley and Sutter are from the Division of Shoulder Surgery and the International Center for Orthopedic Advancement, the Department of Orthopedic Surgery, The Johns Hopkins University/Johns Hopkins Bayview Medical Center, Baltimore, Maryland.

Drs Papp, Ji, Wierks, and Belkoff and Messrs Skelley and Sutter have no relevant financial relationships to disclose. Dr McFarland is a consultant for DePuy Mitek, Inc. The suture anchors and interference screws used in this study were donated by DePuy Mitek, Inc.

This article was awarded a 2011 Excellence in Medical Student Research Award, given by the Johns Hopkins School of Medicine.

Correspondence should be addressed to: Edward G. McFarland, MD, c/o Elaine P. Henze, BJ, ELS, Editorial Services, Department of Orthopedic Surgery, Johns Hopkins Bayview Medical Center, 4940 Eastern Ave, #A665, Baltimore, MD 21224-2780 (ehenze1@jhmi.edu).

Posted Online: July 07, 2011

The long head of the biceps tendon continues to generate interest in clinicians who treat shoulder pain. Controversy remains regarding the function of the long head of the biceps tendon, its role as a pain generator in the shoulder, and the most effective treatment for biceps abnormalities.

First, in terms of function, theories include the following: static stabilizer of the humeral head, ¹ static barrier to superior subluxation of the humeral head, ¹ dynamic stabilizer of the humeral head in an anterior-posterior direction in the abducted arm, ¹ and stabilizer of the humeral head in the throwing athlete when the arm is in abduction and external rotation. ² Second, several biceps tendon abnormalities, including tenosynovitis, ³ painful tendinopathy, ³ partial tears of the biceps tendon, ^3,4subluxations, ^3,4 dislocation of the biceps tendon, ³ and superior labrum lesions, ⁵ have been suggested as generators of pain in the shoulder. Third, treatment for symptomatic lesions of the long head of the biceps involves biceps tenotomy or tenodesis. Biceps tenotomy (via open or arthroscopic techniques) can relieve pain and restore function. ⁶

The literature describes numerous techniques for biceps tenodesis, including fixation of the tendon to the rotator cuff interval, ⁷ to the coracoids, ⁸ to the conjoint tendon, ⁹ to the intertubercular groove, ^4,10 to the proximal humerus beneath the bicipital groove, ^11–13 and to the greater tuberosity of the lateral humeral shaft. ⁸ The 3 major methods of fixation described for biceps tenodesis are a “keyhole” technique, ¹⁴ fixation with suture anchors, ³ or fixation with interference screws. ¹⁵

Previous studies have indicated that biceps tenodesis with interference screw fixation provides greater mechanical strength than that of suture anchor fixation. ^10,16 Yet at our institution, we routinely use and have good clinical results with 2 suture anchors for fixation of the biceps tendon into the bicipital groove with repair of the transverse ligament over the top of the tendon. The purpose of our study was to test the hypothesis that the strength of a 2-suture-anchor technique with closure of the transverse ligament is equal to that of interference screw fixation alone for tenodesis of the biceps tendon.

Materials and Methods

Biomechanical testing was performed using 6 paired, fresh-frozen cadaveric upper extremities obtained from the Maryland State Anatomy Board. The average age at death of the 4 female and 2 male donors was 70 years (range, 49–84 years). The limbs were thawed in the refrigerator for 24 hours before dissection. All shoulder joints were inspected for other major abnormalities, and all biceps tendons were carefully examined for partial tearing or other abnormalities. The rotator cuff was removed, and the tendon was released from the superior glenoid tubercle and the superior labrum. The transverse ligament was released at its midpoint to create a medial and lateral flap of the ligament. The intratubercular groove was examined for osteophytes and the intratubercular portion of the tendon was examined for any abnormality.

A tenodesis of the biceps tendons was performed with the tendon secured into the bicipital groove using 1 of 2 techniques, alternating between the right and left shoulders of matched pairs. In the first technique, we used a commercially available 7×23-mm absorbable interference screw (DePuy Mitek, Inc, Raynham, Massachusetts) designed for biceps tenodesis. To fix the biceps tendon into the bicipital groove, a hole was drilled in the inferior third of the bicipital groove for the tendon to be placed. On the proximal end of the tendon, the tendon was doubled over and sutured to itself with a number-5 Ticron (Tyco, Waltham, Massachusetts) Krackow stitch. ¹⁷ This reinforced end was pulled into the tunnel using a Beath needle and a 2-0 Ticron stitch, and the interference screw was placed using the technique described by Boileau et al. ¹⁵

For the suture anchor technique of biceps tenodesis, we placed 2 absorbable suture anchors into the bicipital groove, with the inferior anchor placed in the area of the bicipital groove matching that of the interference screw noted above. The superior anchor was placed approximately 1.0 cm superior to the inferior anchor. These absorbable anchors had nonabsorbable number-2 sutures with swaged needles on each end (Panalok; DePuy Mitek, Inc.). The anchor sutures were passed through the tendon and tied, bringing the tendon into the base of the bicipital groove (Figure ). Each arm of the suture was then passed first through the tendon and then through the transverse ligament medially (Figure ) and laterally (Figure ) so that the ligament could be closed over the top of the tendon. We then reinforced that repair of the transverse ligament with 2 absorbable sutures passed through the ligament and the biceps tendon using a technique with each suture placed in a figure-8 configuration. In both techniques, the distal end of the tendon was released from the muscle and a loop was created using a number-5 braided, nonabsorbable Ticron suture with a Krackowtype stitch. ¹⁷ The entire specimen was then mounted in a ring clamp with the humerus in a vertical orientation. The distal loop was placed into a hook attached to the actuator of the materials testing machine (MTS Systems Corp, Eden Prairie, Minnesota) (Figure ). All specimens were preloaded to 5 N and then distracted at 5 mm/sec until failure of the repair occurred. The mode of failure and the load at failure were recorded. The possible modes of failure were: the device pulled out of the bone, the tendon pulled the suture out of the device (anchor), the tendon ripped out of the device (screw), or the tendon failed before the fixation device pulled out.

Figure 1:. After placing the anchors and tying the tendon down, 1 limb of the suture anchor is passed laterally through the transverse humeral ligament and tied.

Figure 2:. The second limb of the suture anchor is then passed medially through the transverse humeral ligament.

Figure 3:. The medial and lateral limbs are then tied, completing the repair of the transverse humeral ligament. The repair is reinforced with a simple absorbable suture. Figures © JHU 2011. Department of Art as Applied to Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.

Figure 4:. Specimens were tested to failure using the materials testing machine.

We analyzed the effect of repair technique on failure load using a standard linear regression with random effects to account for the paired specimens. Statistical analysis of the load to failure was performed using Stata10 (StataCorp LP, College Station, Texas). Statistical significance was set atP<.05.

Results

In all of our specimens, the tendon failed at the suture or interference screw interface with the tendon. There were no failures of the suture anchor eyelets or by pullout of the suture anchor or interference screw from the bone. Mean (95% confidence interval [CI]) failure load for the suture anchor was 263.2 N (range, 221.7–304.6 N) and was significantly greater than that for the interference screw repair 159.4 N (range, 118.4–200.5 N).

Discussion

This study shows that a technique using 2 suture anchors reinforced with 2 absorbable sutures provides a higher load to failure than that of interference screws alone. This finding is contrary to our original hypothesis and is important for the practitioner who performs biceps tenodesis because previous studies have suggested that interference screw fixation is superior to suture anchor fixation alone. ^10,16However, it is important to recognize that we performed both techniques as open, not arthroscopic, procedures. The suture anchor technique described and tested here was designed for use with a mini-open or for other open approaches to the proximal humerus.

Some of the differences between our findings and those previously reported in the literature ^10,16,18 may be the result of differences in surgical technique, such as the location of the anchors, type of anchor, and method of suture fixation to the biceps tendon. Richards and Burkhart ¹⁰ performed a similar biomechanical study using 2 metallic suture anchors and compared the results to that of an interference screw. They placed the suture anchors approximately 5 mm apart in the superior bicipital groove. In their study, the suture anchors were placed into the tendon using a simple mattress stitch.

Ozalay et al ¹⁶ used a single metallic suture anchor placed in the bone of the proximal humerus outside of the bicipital groove. The tendon was secured to the biceps tendon using a Kessler stitch, and 1 arm of the suture was passed through the suture eyelet before impacting the anchor into the bone. ¹⁰

Mazzoca et al ¹⁸ compared 4 types of biceps tenodesis techniques, and no statistical difference was noted in the load to failure for all of the techniques. In their study, they used 2 metallic and barbed suture anchors placed in the bicipital groove with the sutures secured in the tendon using a Mason-Allen technique.

Because our study was a biomechanical investigation, clinical study is needed to verify if suture anchor techniques such as this will provide satisfactory results in vivo. Some authors have suggested that the bicipital groove has too many pain fibers and have recommended tenodesis outside of the bicipital groove. ^13,19 Mazzoca et al ²⁰ studied 41 patients treated with subpectoral biceps tenodesis with interference screw fixation and found good to excellent clinical results in all. Millett et al ¹³ retrospectively studied patients treated with suture anchor fixation or interference screw fixation at the inferior aspect of the bicipital groove. They showed no statistically significant difference in the prevalence of pain at the fixation site between the interference screw (3%) and the suture anchor fixation (7%).

There are several limitations of our study. First, we tested only load to failure and did not conduct cyclical testing to replicate the type of stress the repair might experience clinically. Second, the age and bone density of the cadavers might have influenced the load to failure, but the load to failure in our study was similar to that reported in other studies. ^10,16,20 A review of the literature shows that the load to failure for interference screw fixation ranged from 233.5 N ¹⁰ to 252.4 N ²⁰ (mean, 241.7 N), and that load to failure using suture anchors for biceps tenodesis ranged from 129.0 N ¹⁶ to 164.8 N ²⁰ (mean, 143.1 N).

Conclusion

We found that a biceps tenodesis technique using 2 suture anchors and 2 absorbable sutures with a repair of the transverse ligament has a load to failure greater than that of a technique using an interference screw. Additional biomechanical study, such as cyclical testing, is needed to further compare this technique to others described in the literature. Lastly, a clinical study of this technique using suture anchors is needed to determine if it results in adequate pain relief and successful biceps tenodesis without failures.

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