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Mechanical Strength of Four Different Biceps Tenodesis Techniques
Mechanical Strength of Four Different Biceps Tenodesis Techniques Metin Ozalay, M.D., Sercan Akpinar, M.D., Oguz Karaeminogullari, M.D., Cenk Balcik, Ph.D., Arzu Tasci, M.Sc., Reha N. Tandogan, M.D., and Rusen Gecit, Ph.D.
Purpose: The aim of this study was to compare the biomechanical properties of 4 different biceps tenodesis techniques. Type of Study: Biomechanical experiment. Methods: Four groups of fresh sheep shoulders (28 total) with similar shape characteristics were used. Biceps tenodesis was performed using the following techniques: group 1 (n ⫽ 7), tunnel technique; group 2 (n ⫽ 7), interference screw technique; group 3 (n ⫽ 7), anchor technique; and group 4 (n ⫽ 7), keyhole technique. Each construct was loaded to failure and the groups were compared with respect to maximum load in Newtons and deflection at maximum load in millimeters. The results were statistically analyzed with 1-way analysis of variance, the Bonferroni post hoc test and the Student t test or the nonparametric Mann-Whitney U test. Results: The calculated average maximum loads were 229.2 ⫾ 44.1 N for the tunnel technique, 243.3 ⫾ 72.4 N for the interference screw, 129.0 ⫾ 16.6 N for the anchor technique, and 101.7 ⫾ 27.9 N for the keyhole technique. Statistical testing showed no statistically significant differences between groups 1 and 2, groups 3 and 4, or groups 2 and 3 with respect to maximum load and deflection at maximum load (P ⫽ .09/P ⫽ .49, P ⫽ .41/P ⫽ .79, and P ⫽ .06/P ⫽ .82 for load/deflection in the 3 comparisons, respectively). However, all other group comparisons revealed significant differences for both parameters (group 1 v group 4 [P ⬍ .01/P ⬍ .01]; group 1 v group 3[P ⬍ .01/P ⫽ .01]; and group 2 v group 4 [P ⫽ .007/P ⫽ .003]). Conclusions: The strongest construct was made with the interference screw technique, followed by the tunnel, anchor, and keyhole techniques. There were no statistically significant differences between the interference screw and tunnel techniques with respect to maximum load or deflection at maximum load. Clinical Relevance: Although it is difficult to extrapolate in vitro data to the clinical situation, the interference screw technique has better initial biomechanical properties and may produce improved clinical outcomes. Key Words: Arthroscopy—Arthroscopic biceps tenodesis— Failure load—Pull-out strength—Soft-tissue fixation—Suture anchor.
P
athology of the long head of the biceps brachii muscle (LHBB) is a well-known cause of shoulder pain.1-3 Injury to this tendon occurs with repetitive activities of pronation and supination, particularly with resistance or repetitive overhead activities.4 The 4 main etiologies for this are tendinosis or tear, medial
subluxation of the LHBB, traumatic ruptures of the LHBB, and unstable SLAP lesions.1,5-8 Until recently, there have been few surgical options for treating biceps tendon problems, but advances in arthroscopic techniques and equipment have led to new operative techniques. Biceps tenodesis is 1 treat-
From the Departments of Orthopaedics and Traumatology, Adana Medical Center (M.O., S.A.) and Ankara Medical Center (O.K., R.N.T.), and the Department of Biomedical Engineering (C.B.), Baskent University School of Medicine; and the Department of Engineering Sciences, Experimental Mechanics and Biomechanics Laboratory, Middle East Technical University (A.T., R.G.), Ankara, Turkey. Address correspondence and reprint requests to Metin Ozalay, M.D., Baskent University Hospital, Dadalog˘lu mah. 39. sok, No.6, Yüreg˘ir, 01250 Adana, Turkey. E-mail: [email protected] © 2005 by the Arthroscopy Association of North America 0749-8063/05/2108-4252$30.00/0 doi:10.1016/j.arthro.2005.05.002
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Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 21, No 8 (August), 2005: pp 992-998
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ment that has gained popularity in recent years. Biceps tenodesis can be done arthroscopically9-12 or open.5,13-18 Indications for biceps tenodesis are biceps tears involving more than 50% of the tendon, medial subluxation of the biceps tendon, and combined subscapularis tears and biceps subluxation.9 Other techniques include simple surgical release or tenotomy. Biceps tenotomy is a viable option, especially in older patients. Although it is effective in relieving pain, it leaves an objectionable muscle deformity when the biceps brachii retracts distally.3 The aim of this experimental study was to compare the mechanical properties of 4 currently used biceps tenodesis techniques in an in vitro study. METHODS Twenty-eight fresh sheep shoulders from 28 different sheep obtained at necropsy were used for the study. Ovine shoulders are anatomically similar to human shoulders.19 The diameter of the origin of the LHBB in these specimens was 7 to 8 mm. The sheep were all approximately 12 months old, and the specimens were randomly divided into 4 groups of 7 shoulders each. Four different biceps tenodesis techniques were compared with respect to biomechanical strength. Specimen Preparation In each specimen, the humerus was severed 6 cm above the elbow joint. All soft tissues were removed from the distal end and the bone was then shaped so that it fit perfectly into the set of clamps used for testing. Oblique osteotomy was performed at the base of the tuberculum majus, and all soft tissues except the tendon of the LHBB were separated from the proximal humerus. The scapula was also freed from the proximal part of the bone. The LHBB tendon was cut proximally at the level of the glenoid insertion. The tenodesis methods tested were the tunnel technique, interference screw technique, anchor technique, and keyhole technique. Tunnel Technique (Group 1, n ⴝ 7): The tunnel technique procedure used in this study was that described by Snyder4 (Fig 1). First, a No. 2 Ethibond Excel suture (Ethicon, Edinburgh, Scotland) was woven through the proximal 1 cm of the biceps tendon using a double baseball stitch, such that both ends of the suture exited at the end as lead sutures. A burr hole the same size as the biceps tendon was made in the inferior part of the biceps groove. The burr was angled inferiorly to undercut distally approximately 1.5 cm.
FIGURE 1.
The tunnel technique.
Then 2 other 1-mm holes were drilled, 1 on each side of the biceps groove and both 1.5 cm distal from the central hole. The biceps tendon lead sutures were both fed into the proximal opening of the central hole. A loop was inserted through each distal drill hole from distal to proximal direction (one after the other) to retrieve the corresponding right or left lead suture in the central hole. Traction was applied to the lead sutures so that the proximal end of the tendon was pulled into the central drill hole and down the medullary canal of the humerus. The tension was adjusted so that 1 cm of the biceps tendon was inside the central burr hole. The end of each No. 2 suture was then passed through the biceps tendon using a free needle, and the 2 ends were tied together, securing the tendon in its position within the bony trough. Interference Screw Technique (Group 2, n ⴝ 7): The diameter of the proximal end of the biceps tendon was measured using the same type of graft sizer used in knee ligament reconstructions. In all cases, the tendon diameter was 7 to 8 mm. A drill bit of the same diameter was used to drill a socket in the inferior part of the biceps groove. The tunnel length was 25 mm. The biceps tendon was whip-stitched and the ends of the suture were passed through the eyelet of transhumeral pin. The biceps tendon was then pulled into the socket using a transhumeral pin, and the tendon was fixed superiorly in the hole using an 8 ⫻ 25 mm soft titanium interference screw (Profile Screw; Depuy Orthotech Interference Screw System, Sunnyvale, CA). All interference screws were inserted according to the manufacturer’s instructions (Fig 2).
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FIGURE 3.
FIGURE 2.
The interference screw technique.
Anchor Technique (Group 3, n ⴝ 7): For this method, we used a 2.8-mm Mitek Superanchor (Mitek, Westwood, MA), which has a bullet-shaped titanium-alloy body that contains an eyelet for suture attachment, and 4 nitinol wire barbs that engage bone. The anchor site was prepared by abrading the surface of the proximal humerus with a dental burr. According to the manufacturer’s instructions, a drill hole 9.7 mm deep and 2.9 mm wide was made with the appropriate drill bit. A No. 2 Ethibond suture was first passed through the proximal end of the biceps tendon using a Kessler stitch. The suture was then threaded into the eyelet of the anchor. The anchor was inserted in the drill hole to the depth specified by the manufacturer, and 5 locking knots were tied to fix the tendon to the bone (Fig 3). Keyhole Technique (Group 4, n ⴝ 7): The keyhole technique used in this study was that described by Froimson and Oh18 (Fig 4). The proximal end of the biceps tendon was rolled into a thick ball and, using No. 2 Ethibond, was sutured together as a mass. A keyhole was made in the bicipital groove using a dental burr. The tendon was then inserted into the keyhole and pulled downward such that the tendon mass was locked in place.
The anchor technique.
assembled in the testing machine. Specially designed clamps were used to prevent slippage of the humerus and biceps tendon. The bone was fixed in a 2-mouth metal jaw and the muscle belly of the biceps was grasped by a hydraulic jaw. In activating the hydraulic jaw, the compressor operated under 8 bars of pressure. This specific jaw was used because it maintained a strong grasp on the muscle while minimizing damage or sliding of the soft tissue. During testing, the muscle tissue was moisturized continuously and the room temperature was kept at 22°C (Fig 5). Before testing, a pretension force of 5 N was applied to the muscle. Then the system was loaded with a displacement rate of 5 mm/min for assuring quasistatic loading conditions. The test speed was kept constant. During the
Biomechanical Testing Each specimen was tested using a Lloyd computercontrolled testing machine (model No. LR 50K; Lloyd, Southampton, England). A 1-kN load cell was
FIGURE 4.
The keyhole technique.
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software SPSS for Windows v 10.0 (SPSS Inc, Chicago, IL). RESULTS
FIGURE 5. The Lloyd computer-controlled testing machine with a prepared specimen.
tests, no major slippages of the test specimens from the clamps were observed. Load-deflection data were obtained using the system’s data-acquisition program. Maximum loads and yield points were determined from these data, and load-deflection curves for each group were analyzed. Maximum load (load at the time of failure) was accepted as force at pull-out (failure) in Newtons. Deflection at maximum load was defined as deformation occurred until maximum load state. The results in the 4 groups were statistically compared using 1-way analysis of variance. The means differences were determined by the Bonferroni post hoc comparison test. The homogeneity of the variances was tested by Levene’s test. The Student t test or Mann-Whitney U test was used where appropriate. All calculations were made using the
The plots of load (Newtons) versus deflection (millimeters) for each group are shown in Fig 6. The group results for maximum load (force at time of failure) are listed in Table 1, and comparison of these results in the 4 tenodesis techniques is shown in Fig 7. None of the constructs failed as a result of breakage of materials used or slippage of tissue from the fixation clamps. Group 1 (Tunnel): This method was considered to have failed when there was pull-out of the tendon from the bone tunnel or stripping of the sutures from the tendon. The tendons in all 7 shoulders pulled out, but none of the suture strands ruptured. The average maximum load at failure was 229.2 N (range, 188.8 to 299.5 N). Group 2 (Interference Screw): In these cases, the construct failed when the tendon pulled out of the bone tunnel. The mean maximum load at failure was 243.3 N (range, 122.3 to 330.2 N). Group 3 (Anchor): In all 7 shoulders, the reason for failure was suture rupture. The average maximum load was 129 N (range, 103.8 to 152 N). It was impossible to determine whether the sutures broke because of friction at the anchor eyelet or friction with bone. Group 4 (Keyhole): Failure in these shoulders resulted from pull-out of the tendon from the keyhole. The mean maximum load in this group was 101.7 N (range, 83 to 158 N). Initial comparisons among the groups using 1-way analysis of variance revealed highly statistically significant differences in maximum load, and in deflection at maximum load (P ⬍ .01 for both). The Student t test showed no statistically significant differences between groups 1 and 2 or groups 3 and 4 with respect to maximum load and deflection at maximum load (P ⫽ .09/P ⫽ .49 and P ⫽ .41/P ⫽ .79 for load/ deflection, respectively). However, between group 1 and group 3 there were significant differences for both parameters (P ⬍ .01/P ⫽ .01). The Mann-Whitney U test showed no statistically significant differences between groups 2 and 3 with respect to maximum load and deflection at maximum load (P ⫽ .06/P ⫽ .82). However, for group 1 versus group 4 and group 2 versus group 4, there were significant differences for both parameters (P ⬍ .01/P ⬍ .01 and P ⫽ .007/P ⫽ .003, respectively).
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FIGURE 6.
The plots of load versus deflection for the 4 groups.
DISCUSSION Biceps brachii pathology is a common cause of shoulder morbidity. Disorders of the biceps tendon may arise from inflammatory changes in and around the tendon, or may develop as a consequence of instability or significant injury.1,20 Over the years, there have been significant changes in the surgical treatment of the tendon of the LHBB. In the 1940s, this tendon was seen as a major source of shoulder pain and tenodesis was favored as a primary procedure.1,21,22 However, the treatment options for painful biceps tendon are still controversial today. In cases of refractory anterior shoulder pain with secondary biceps pathology, it is generally agreed that the best treatment is to remove the tendon from its anatomic position TABLE 1.
within the glenohumeral joint by either tenotomy or tenodesis.1,6,7,10 The main disadvantages of tenotomy are distal migration of the tendon of the LHBB, cosmetic deformity, and significantly impaired shoulder strength.23 In contrast to these findings, Gill et al.2 reported very good functional outcome with an arthroscopic biceps tenotomy. Osbahr et al.24 have suggested that biceps tenotomy may be a reasonable alternative to biceps tenodesis in patients with refractive and chronic bicipital pain. As the role of the LHBB becomes increasingly recognized as a component of rotator cuff pathology, indications for biceps tenodesis have expanded.25 Indications for biceps tenodesis are biceps tears involving more than 50% of the tendon, medial subluxation
Maximum Load and Reason for Failure of the 4 Tenodesis Methods
Tenodesis Type
Mean Maximum Failure Load (mean ⫾ SD)
Reason for Failure
Tunnel technique Interference screw technique Anchor technique Keyhole technique
229.2 ⫾ 44.1N 243.3 ⫾ 72.4N 129.0 ⫾ 16.6N 101.7 ⫾ 27.9N
Tendon pulled out of bone tunnel Tendon pulled out of bone tunnel All the sutures ruptured Tendon pulled out of keyhole
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FIGURE 7. Comparison of maximum load for the 4 tenodesis techniques (straight lines represent linear regression for each method; error bars indicate the standard deviation of the maximum load for each group).
of the biceps tendon, and combined subscapularis tears and biceps subluxation.9 According to Crenshaw and Kilgore,15 the indications for tenodesis are pain present for an average of approximately 5 months, bicipital tenderness, and restriction of motion. Biceps tenodesis can be performed using open or arthroscopic methods, and several techniques of both types have been described. The tunnel and keyhole techniques are usually preferred in open tenodesis,1,5,14-18 whereas screw and anchor methods are favored in arthroscopic surgery.9,10-12 In all these procedures, the strength of fixation is very important. The ideal fixation method should allow early and active full range of motion. This may be necessary for an athlete or an older patient because even a short period of immobilization may result in debilitating shoulder stiffness. In particular, athletes must be able to return to their sport as quickly and as fully functional as possible.26 Although numerous clinical studies have investigated different methods of biceps tendon tenodesis,10-12 biomechanical analysis of primary stability in these techniques has not been documented extensively. Burkhart3 compared load-to-failure results with suture anchor tenodesis involving 2 Mitek G-2 suture anchors versus 7-mm interference screw tenodesis in 12 cadaver shoulders. They found that interference screw fixation was almost twice as strong as the suture-anchor construct. Similarly, in our study, interference screw fixation was 1.9 times as strong as Superanchor fixation. Our investigation compared 4 different fixation techniques in an ovine model. Currently, there is no established animal model for in vitro testing of different biceps tenodesis techniques. We selected the ovine
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shoulder for this experiment because of the similarity in thickness between sheep and human biceps tendons. The tendon of the LHBB in sheep is shorter than that in humans, but we believe that this difference had no significant bearing on the results of our study. Sheep live approximately 10 years and have highquality bone stock. This may influence the fixation, which relies in part on a good bony bed since a 12-month-old sheep is relatively young. This could be considered a limitation to the study and it might explain the relatively large range in the failure load of the interference screw (122 to 330 N), because some of the specimens might have had a weaker bony architecture than others. Our findings showed that interference screw and bone-tunnel tenodesis techniques had the highest primary stability (average maximum load, 243.3 N and 229.2 N, respectively), whereas the keyhole provided the weakest fixation (average maximum load, 101.7 N). These results are compatible with those of other studies.3,23 Wolf et al.23 performed biceps tenodesis with a bioabsorbable interference screw and, on cyclic loading testing, the average load to failure in these specimens was 310.8 N. Burkhart3 compared suture anchor tenodesis with interference screw tenodesis and found an average load to failure of 58.22 lb for a 7-mm interference screw technique compared with 30.46 lb for a suture anchor technique using 2 Mitek G-2 suture anchors. The excellent primary strength of the tunnel and screw methods is important with respect to final outcome in biceps tenodesis. Patients who have stronger primary strength of the tenodesis may require less shoulder protection during the rehabilitation phase, and may also have lower rates of rerupture. The interference screw and tunnel methods are comparable with respect to primary stability, but the advantage of the former is that it can be easily performed arthroscopically. In contrast, the tunnel method described by Snyder4 is technically demanding and can only be done in mini-open fashion. With suture-anchor systems, clinical failure can occur because of problems with the tendon, bone, suture anchor, or suture. While anchor pull-out or suture breakage is possible,27 the weakest area is usually the suture-tendon interface, not the suture anchor device.28 We used a new-generation suture anchor in our study, and failure in all 7 of these shoulders was due to suture rupture. The sutures may have been damaged by friction at anchor eyelets or on bone edges; as mentioned, we were unable to identify the exact reasons for breakage. Meyer et al.29 also reported that
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suture material can be cut at the sharp edge of suture anchor eyelets. Keyhole tenodesis at the biceps origin was first described by Froimson and Oh18 in 1974 as a treatment for tendon rupture, biceps tendon instability, and biceps tendonitis. The authors cited a number of advantages of this method: no hardware is required; undue medial dissection is avoided; the remnant of the biceps tendon is removed, allowing good humeral head motion and preventing intra-articular derangement; and the inherent stability of the method gives the patient confidence to begin early, gentle range of motion exercise at both the shoulder and the elbow. However, of the 4 techniques we investigated, keyhole tenodesis had the lowest primary stability. Other reported disadvantages of this method are the need for a separate deltopectoral incision, greater postoperative pain, and cosmetic issues.1,5,14,16-18 To our knowledge, this is the first study that has documented the biomechanical features of keyhole tenodesis. This investigation had 2 shortcomings. First, we did not use cyclic loading and the tests were performed in single-pull load-to-failure fashion. We plan to conduct future trials with cyclic loading. Second, the study was not performed using fresh-frozen human cadaver shoulders, which would have been the preferred specimens. CONCLUSIONS Comparison of these 4 commonly used biceps tenodesis techniques shows that the tunnel and interference screw methods provide stronger fixation than the anchor and keyhole techniques. The interference screw technique can be performed arthroscopically and is good for achieving secure biceps tenodesis. The attractive features of these screws include excellent load-to-failure strength. Interference screw fixation provides strong initial fixation, and has better biomechanical properties than metallic anchors in the bicipital groove. REFERENCES 1. Sethi N, Wright R, Yamaguchi K. Disorders of the long head of the biceps tendon. J Shoulder Elbow Surg 1999;8:644-654. 2. Gill TJ, Mc Irvin E, Mair SD, Hawkins RJ. Results of biceps tenotomy for treatment of pathology of the long head of the biceps brachii. J Shoulder Elbow Surg 2001;10:247-249. 3. Barber A, Bryd JWT, Wolf EM, Burkhart SS. Current controversies: Point counterpoint. How would you treat the partially torn biceps tendon? Arthroscopy 2001;17:636-639.
4. Snyder SJ. Shoulder arthroscopy. New York: McGraw-Hill, 1994;61-76. 5. Dines D, Warren RF, Inglis AE. Surgical treatment of lesions of the long head of the biceps. Clin Orthop 1982;164:165-171. 6. Curtis AS, Snyder SJ. Evaluation and treatment of biceps tendon pathology. Orthop Clin North Am 1993;24:33-43. 7. Warren RF. Lesions of the long head of the biceps tendon. Instr Course Lect 1985;34:204-209. 8. Burkhart SS, Fox DL. SLAP lesions in association with complete tears of the long head of the biceps tendon. A report of two cases. Arthroscopy 1992;8:31-35. 9. Lo IKY, Burkhart S. Arthroscopic biceps tenodesis using a bioabsorbable interference screw. Arthroscopy 2004;20:85-95. 10. Gartsman GM, Hammerman SM. Arthroscopic biceps tenodesis: Operative technique. Arthroscopy 2000;16:550-552. 11. Klepps S, Hazrati Y, Flatow E. Arthroscopic biceps tenodesis. Arthroscopy 2002;18:1040-1045. 12. Boileau P, Krishnan SG, Coste JS, Walch G. Arthroscopic biceps tenodesis: A new technique using bioabsorbable interference screw fixation. Arthroscopy 2002;18:1002-1012. 13. Burkhead WZ, Archand MA, Zeman C, Nabermeger P, Walch G. The biceps tendon. In: Rockwood CA, Matsen FA, eds. The shoulder. Ed 2. Philadelphia: WB Saunders, 1998;1009-1063. 14. Berlemann U, Bayley I. Tenodesis of the long head of biceps brachii in the painful shoulder: improving results in the long term. J Shoulder Elbow Surg 1995;4:429-435. 15. Crenshaw AH, Kilgore WE. Surgical treatment of bicipital tenosynovitis. J Bone Joint Surg Am 1966;48:1496-1502. 16. Becker DA, Cofield RH. Tenodesis of the long head of the biceps brachii for chronic bicipital tendinitis. Long-term results. J Bone Joint Surg Am 1989;71:376-381. 17. Hitchcock HH, Bechtol CO. Painful shoulder. Observations on the role of the tendon of the long head of the biceps brachii in its causation. J Bone Joint Surg Am 1948;30:263-273. 18. Froimson AI, Oh I. Keyhole tenodesis of biceps origin at the shoulder. Clin Orthop 1975;112:245-249. 19. Gerber C, Schneeberger AG, Perren SM, Nyffeler RW. Experimental rotator cuff repair. A preliminary study. J Bone Joint Surg Am 1999;81:1281-1290. 20. Murthi AM, Vosburgh CL, Neviaser TJ. The incidence of pathologic changes of the long head of the biceps brachii. Surgical versus nonsurgical treatment. Clin Orthop 1988; 228: 233-239. 21. DePalma AF, Callery GE. Bicipital tenosynovitis. Clin Orthop 1954;3:69-85. 22. Gilcrest EL. Dislocation and elongation of the long head of the biceps brachii. An analysis of six cases. Ann Surg 1936;104: 118-138. 23. Wolf RS, Zheng N, Weichel D. Long head biceps tenotomy versus tenotomy versus tenodesis: A cadaveric biomechanical analysis. Arthroscopy 2005;21:182-185. 24. Osbahr DC, Diamond AB, Speer KP. The cosmetic appearance of the biceps muscle after long-head tenotomy versus tenodesis. Arthroscopy 2002;18:483-487. 25. Edwards TB, Walch G. Open biceps tenodesis: The interference screw technique. Tech Shoulder Elbow Surg 2003;4:195198. 26. Eakin CL, Faber KJ, Hawkins RJ, Hovis WD. Biceps tendon disorders in athletes. J Am Acad Orthop Surg 1999;7:300-310. 27. Carpenter JE, Fish DN, Huston LJ, Goldstein SA. Pull-out strength of five suture anchors. Arthroscopy 1993;9:109-113. 28. Shea KP, O’Keefe RM Jr, Fulkerson JP. Comparison of initial pull-out strength of arthroscopic suture and staple Bankart repair techniques. Arthroscopy 1992;8:179-182. 29. Meyer DC, Nyffeler RW, Fucentese SF, Gerber C. Failure of suture material at suture anchor eyelets. Arthroscopy 2002;18: 1013-1019.
Purpose: The aim of this study was to compare the biomechanical properties of 4 different biceps tenodesis techniques. Type of Study: Biomechanical experiment. Methods: Four groups of fresh sheep shoulders (28 total) with similar shape characteristics were used. Biceps tenodesis was performed using the following techniques: group 1 (n ⫽ 7), tunnel technique; group 2 (n ⫽ 7), interference screw technique; group 3 (n ⫽ 7), anchor technique; and group 4 (n ⫽ 7), keyhole technique. Each construct was loaded to failure and the groups were compared with respect to maximum load in Newtons and deflection at maximum load in millimeters. The results were statistically analyzed with 1-way analysis of variance, the Bonferroni post hoc test and the Student t test or the nonparametric Mann-Whitney U test. Results: The calculated average maximum loads were 229.2 ⫾ 44.1 N for the tunnel technique, 243.3 ⫾ 72.4 N for the interference screw, 129.0 ⫾ 16.6 N for the anchor technique, and 101.7 ⫾ 27.9 N for the keyhole technique. Statistical testing showed no statistically significant differences between groups 1 and 2, groups 3 and 4, or groups 2 and 3 with respect to maximum load and deflection at maximum load (P ⫽ .09/P ⫽ .49, P ⫽ .41/P ⫽ .79, and P ⫽ .06/P ⫽ .82 for load/deflection in the 3 comparisons, respectively). However, all other group comparisons revealed significant differences for both parameters (group 1 v group 4 [P ⬍ .01/P ⬍ .01]; group 1 v group 3[P ⬍ .01/P ⫽ .01]; and group 2 v group 4 [P ⫽ .007/P ⫽ .003]). Conclusions: The strongest construct was made with the interference screw technique, followed by the tunnel, anchor, and keyhole techniques. There were no statistically significant differences between the interference screw and tunnel techniques with respect to maximum load or deflection at maximum load. Clinical Relevance: Although it is difficult to extrapolate in vitro data to the clinical situation, the interference screw technique has better initial biomechanical properties and may produce improved clinical outcomes. Key Words: Arthroscopy—Arthroscopic biceps tenodesis— Failure load—Pull-out strength—Soft-tissue fixation—Suture anchor.
P
athology of the long head of the biceps brachii muscle (LHBB) is a well-known cause of shoulder pain.1-3 Injury to this tendon occurs with repetitive activities of pronation and supination, particularly with resistance or repetitive overhead activities.4 The 4 main etiologies for this are tendinosis or tear, medial
subluxation of the LHBB, traumatic ruptures of the LHBB, and unstable SLAP lesions.1,5-8 Until recently, there have been few surgical options for treating biceps tendon problems, but advances in arthroscopic techniques and equipment have led to new operative techniques. Biceps tenodesis is 1 treat-
From the Departments of Orthopaedics and Traumatology, Adana Medical Center (M.O., S.A.) and Ankara Medical Center (O.K., R.N.T.), and the Department of Biomedical Engineering (C.B.), Baskent University School of Medicine; and the Department of Engineering Sciences, Experimental Mechanics and Biomechanics Laboratory, Middle East Technical University (A.T., R.G.), Ankara, Turkey. Address correspondence and reprint requests to Metin Ozalay, M.D., Baskent University Hospital, Dadalog˘lu mah. 39. sok, No.6, Yüreg˘ir, 01250 Adana, Turkey. E-mail: [email protected] © 2005 by the Arthroscopy Association of North America 0749-8063/05/2108-4252$30.00/0 doi:10.1016/j.arthro.2005.05.002
992
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 21, No 8 (August), 2005: pp 992-998
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ment that has gained popularity in recent years. Biceps tenodesis can be done arthroscopically9-12 or open.5,13-18 Indications for biceps tenodesis are biceps tears involving more than 50% of the tendon, medial subluxation of the biceps tendon, and combined subscapularis tears and biceps subluxation.9 Other techniques include simple surgical release or tenotomy. Biceps tenotomy is a viable option, especially in older patients. Although it is effective in relieving pain, it leaves an objectionable muscle deformity when the biceps brachii retracts distally.3 The aim of this experimental study was to compare the mechanical properties of 4 currently used biceps tenodesis techniques in an in vitro study. METHODS Twenty-eight fresh sheep shoulders from 28 different sheep obtained at necropsy were used for the study. Ovine shoulders are anatomically similar to human shoulders.19 The diameter of the origin of the LHBB in these specimens was 7 to 8 mm. The sheep were all approximately 12 months old, and the specimens were randomly divided into 4 groups of 7 shoulders each. Four different biceps tenodesis techniques were compared with respect to biomechanical strength. Specimen Preparation In each specimen, the humerus was severed 6 cm above the elbow joint. All soft tissues were removed from the distal end and the bone was then shaped so that it fit perfectly into the set of clamps used for testing. Oblique osteotomy was performed at the base of the tuberculum majus, and all soft tissues except the tendon of the LHBB were separated from the proximal humerus. The scapula was also freed from the proximal part of the bone. The LHBB tendon was cut proximally at the level of the glenoid insertion. The tenodesis methods tested were the tunnel technique, interference screw technique, anchor technique, and keyhole technique. Tunnel Technique (Group 1, n ⴝ 7): The tunnel technique procedure used in this study was that described by Snyder4 (Fig 1). First, a No. 2 Ethibond Excel suture (Ethicon, Edinburgh, Scotland) was woven through the proximal 1 cm of the biceps tendon using a double baseball stitch, such that both ends of the suture exited at the end as lead sutures. A burr hole the same size as the biceps tendon was made in the inferior part of the biceps groove. The burr was angled inferiorly to undercut distally approximately 1.5 cm.
FIGURE 1.
The tunnel technique.
Then 2 other 1-mm holes were drilled, 1 on each side of the biceps groove and both 1.5 cm distal from the central hole. The biceps tendon lead sutures were both fed into the proximal opening of the central hole. A loop was inserted through each distal drill hole from distal to proximal direction (one after the other) to retrieve the corresponding right or left lead suture in the central hole. Traction was applied to the lead sutures so that the proximal end of the tendon was pulled into the central drill hole and down the medullary canal of the humerus. The tension was adjusted so that 1 cm of the biceps tendon was inside the central burr hole. The end of each No. 2 suture was then passed through the biceps tendon using a free needle, and the 2 ends were tied together, securing the tendon in its position within the bony trough. Interference Screw Technique (Group 2, n ⴝ 7): The diameter of the proximal end of the biceps tendon was measured using the same type of graft sizer used in knee ligament reconstructions. In all cases, the tendon diameter was 7 to 8 mm. A drill bit of the same diameter was used to drill a socket in the inferior part of the biceps groove. The tunnel length was 25 mm. The biceps tendon was whip-stitched and the ends of the suture were passed through the eyelet of transhumeral pin. The biceps tendon was then pulled into the socket using a transhumeral pin, and the tendon was fixed superiorly in the hole using an 8 ⫻ 25 mm soft titanium interference screw (Profile Screw; Depuy Orthotech Interference Screw System, Sunnyvale, CA). All interference screws were inserted according to the manufacturer’s instructions (Fig 2).
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FIGURE 3.
FIGURE 2.
The interference screw technique.
Anchor Technique (Group 3, n ⴝ 7): For this method, we used a 2.8-mm Mitek Superanchor (Mitek, Westwood, MA), which has a bullet-shaped titanium-alloy body that contains an eyelet for suture attachment, and 4 nitinol wire barbs that engage bone. The anchor site was prepared by abrading the surface of the proximal humerus with a dental burr. According to the manufacturer’s instructions, a drill hole 9.7 mm deep and 2.9 mm wide was made with the appropriate drill bit. A No. 2 Ethibond suture was first passed through the proximal end of the biceps tendon using a Kessler stitch. The suture was then threaded into the eyelet of the anchor. The anchor was inserted in the drill hole to the depth specified by the manufacturer, and 5 locking knots were tied to fix the tendon to the bone (Fig 3). Keyhole Technique (Group 4, n ⴝ 7): The keyhole technique used in this study was that described by Froimson and Oh18 (Fig 4). The proximal end of the biceps tendon was rolled into a thick ball and, using No. 2 Ethibond, was sutured together as a mass. A keyhole was made in the bicipital groove using a dental burr. The tendon was then inserted into the keyhole and pulled downward such that the tendon mass was locked in place.
The anchor technique.
assembled in the testing machine. Specially designed clamps were used to prevent slippage of the humerus and biceps tendon. The bone was fixed in a 2-mouth metal jaw and the muscle belly of the biceps was grasped by a hydraulic jaw. In activating the hydraulic jaw, the compressor operated under 8 bars of pressure. This specific jaw was used because it maintained a strong grasp on the muscle while minimizing damage or sliding of the soft tissue. During testing, the muscle tissue was moisturized continuously and the room temperature was kept at 22°C (Fig 5). Before testing, a pretension force of 5 N was applied to the muscle. Then the system was loaded with a displacement rate of 5 mm/min for assuring quasistatic loading conditions. The test speed was kept constant. During the
Biomechanical Testing Each specimen was tested using a Lloyd computercontrolled testing machine (model No. LR 50K; Lloyd, Southampton, England). A 1-kN load cell was
FIGURE 4.
The keyhole technique.
FOUR BICEPS TENODESIS TECHNIQUES
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software SPSS for Windows v 10.0 (SPSS Inc, Chicago, IL). RESULTS
FIGURE 5. The Lloyd computer-controlled testing machine with a prepared specimen.
tests, no major slippages of the test specimens from the clamps were observed. Load-deflection data were obtained using the system’s data-acquisition program. Maximum loads and yield points were determined from these data, and load-deflection curves for each group were analyzed. Maximum load (load at the time of failure) was accepted as force at pull-out (failure) in Newtons. Deflection at maximum load was defined as deformation occurred until maximum load state. The results in the 4 groups were statistically compared using 1-way analysis of variance. The means differences were determined by the Bonferroni post hoc comparison test. The homogeneity of the variances was tested by Levene’s test. The Student t test or Mann-Whitney U test was used where appropriate. All calculations were made using the
The plots of load (Newtons) versus deflection (millimeters) for each group are shown in Fig 6. The group results for maximum load (force at time of failure) are listed in Table 1, and comparison of these results in the 4 tenodesis techniques is shown in Fig 7. None of the constructs failed as a result of breakage of materials used or slippage of tissue from the fixation clamps. Group 1 (Tunnel): This method was considered to have failed when there was pull-out of the tendon from the bone tunnel or stripping of the sutures from the tendon. The tendons in all 7 shoulders pulled out, but none of the suture strands ruptured. The average maximum load at failure was 229.2 N (range, 188.8 to 299.5 N). Group 2 (Interference Screw): In these cases, the construct failed when the tendon pulled out of the bone tunnel. The mean maximum load at failure was 243.3 N (range, 122.3 to 330.2 N). Group 3 (Anchor): In all 7 shoulders, the reason for failure was suture rupture. The average maximum load was 129 N (range, 103.8 to 152 N). It was impossible to determine whether the sutures broke because of friction at the anchor eyelet or friction with bone. Group 4 (Keyhole): Failure in these shoulders resulted from pull-out of the tendon from the keyhole. The mean maximum load in this group was 101.7 N (range, 83 to 158 N). Initial comparisons among the groups using 1-way analysis of variance revealed highly statistically significant differences in maximum load, and in deflection at maximum load (P ⬍ .01 for both). The Student t test showed no statistically significant differences between groups 1 and 2 or groups 3 and 4 with respect to maximum load and deflection at maximum load (P ⫽ .09/P ⫽ .49 and P ⫽ .41/P ⫽ .79 for load/ deflection, respectively). However, between group 1 and group 3 there were significant differences for both parameters (P ⬍ .01/P ⫽ .01). The Mann-Whitney U test showed no statistically significant differences between groups 2 and 3 with respect to maximum load and deflection at maximum load (P ⫽ .06/P ⫽ .82). However, for group 1 versus group 4 and group 2 versus group 4, there were significant differences for both parameters (P ⬍ .01/P ⬍ .01 and P ⫽ .007/P ⫽ .003, respectively).
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FIGURE 6.
The plots of load versus deflection for the 4 groups.
DISCUSSION Biceps brachii pathology is a common cause of shoulder morbidity. Disorders of the biceps tendon may arise from inflammatory changes in and around the tendon, or may develop as a consequence of instability or significant injury.1,20 Over the years, there have been significant changes in the surgical treatment of the tendon of the LHBB. In the 1940s, this tendon was seen as a major source of shoulder pain and tenodesis was favored as a primary procedure.1,21,22 However, the treatment options for painful biceps tendon are still controversial today. In cases of refractory anterior shoulder pain with secondary biceps pathology, it is generally agreed that the best treatment is to remove the tendon from its anatomic position TABLE 1.
within the glenohumeral joint by either tenotomy or tenodesis.1,6,7,10 The main disadvantages of tenotomy are distal migration of the tendon of the LHBB, cosmetic deformity, and significantly impaired shoulder strength.23 In contrast to these findings, Gill et al.2 reported very good functional outcome with an arthroscopic biceps tenotomy. Osbahr et al.24 have suggested that biceps tenotomy may be a reasonable alternative to biceps tenodesis in patients with refractive and chronic bicipital pain. As the role of the LHBB becomes increasingly recognized as a component of rotator cuff pathology, indications for biceps tenodesis have expanded.25 Indications for biceps tenodesis are biceps tears involving more than 50% of the tendon, medial subluxation
Maximum Load and Reason for Failure of the 4 Tenodesis Methods
Tenodesis Type
Mean Maximum Failure Load (mean ⫾ SD)
Reason for Failure
Tunnel technique Interference screw technique Anchor technique Keyhole technique
229.2 ⫾ 44.1N 243.3 ⫾ 72.4N 129.0 ⫾ 16.6N 101.7 ⫾ 27.9N
Tendon pulled out of bone tunnel Tendon pulled out of bone tunnel All the sutures ruptured Tendon pulled out of keyhole
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FIGURE 7. Comparison of maximum load for the 4 tenodesis techniques (straight lines represent linear regression for each method; error bars indicate the standard deviation of the maximum load for each group).
of the biceps tendon, and combined subscapularis tears and biceps subluxation.9 According to Crenshaw and Kilgore,15 the indications for tenodesis are pain present for an average of approximately 5 months, bicipital tenderness, and restriction of motion. Biceps tenodesis can be performed using open or arthroscopic methods, and several techniques of both types have been described. The tunnel and keyhole techniques are usually preferred in open tenodesis,1,5,14-18 whereas screw and anchor methods are favored in arthroscopic surgery.9,10-12 In all these procedures, the strength of fixation is very important. The ideal fixation method should allow early and active full range of motion. This may be necessary for an athlete or an older patient because even a short period of immobilization may result in debilitating shoulder stiffness. In particular, athletes must be able to return to their sport as quickly and as fully functional as possible.26 Although numerous clinical studies have investigated different methods of biceps tendon tenodesis,10-12 biomechanical analysis of primary stability in these techniques has not been documented extensively. Burkhart3 compared load-to-failure results with suture anchor tenodesis involving 2 Mitek G-2 suture anchors versus 7-mm interference screw tenodesis in 12 cadaver shoulders. They found that interference screw fixation was almost twice as strong as the suture-anchor construct. Similarly, in our study, interference screw fixation was 1.9 times as strong as Superanchor fixation. Our investigation compared 4 different fixation techniques in an ovine model. Currently, there is no established animal model for in vitro testing of different biceps tenodesis techniques. We selected the ovine
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shoulder for this experiment because of the similarity in thickness between sheep and human biceps tendons. The tendon of the LHBB in sheep is shorter than that in humans, but we believe that this difference had no significant bearing on the results of our study. Sheep live approximately 10 years and have highquality bone stock. This may influence the fixation, which relies in part on a good bony bed since a 12-month-old sheep is relatively young. This could be considered a limitation to the study and it might explain the relatively large range in the failure load of the interference screw (122 to 330 N), because some of the specimens might have had a weaker bony architecture than others. Our findings showed that interference screw and bone-tunnel tenodesis techniques had the highest primary stability (average maximum load, 243.3 N and 229.2 N, respectively), whereas the keyhole provided the weakest fixation (average maximum load, 101.7 N). These results are compatible with those of other studies.3,23 Wolf et al.23 performed biceps tenodesis with a bioabsorbable interference screw and, on cyclic loading testing, the average load to failure in these specimens was 310.8 N. Burkhart3 compared suture anchor tenodesis with interference screw tenodesis and found an average load to failure of 58.22 lb for a 7-mm interference screw technique compared with 30.46 lb for a suture anchor technique using 2 Mitek G-2 suture anchors. The excellent primary strength of the tunnel and screw methods is important with respect to final outcome in biceps tenodesis. Patients who have stronger primary strength of the tenodesis may require less shoulder protection during the rehabilitation phase, and may also have lower rates of rerupture. The interference screw and tunnel methods are comparable with respect to primary stability, but the advantage of the former is that it can be easily performed arthroscopically. In contrast, the tunnel method described by Snyder4 is technically demanding and can only be done in mini-open fashion. With suture-anchor systems, clinical failure can occur because of problems with the tendon, bone, suture anchor, or suture. While anchor pull-out or suture breakage is possible,27 the weakest area is usually the suture-tendon interface, not the suture anchor device.28 We used a new-generation suture anchor in our study, and failure in all 7 of these shoulders was due to suture rupture. The sutures may have been damaged by friction at anchor eyelets or on bone edges; as mentioned, we were unable to identify the exact reasons for breakage. Meyer et al.29 also reported that
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suture material can be cut at the sharp edge of suture anchor eyelets. Keyhole tenodesis at the biceps origin was first described by Froimson and Oh18 in 1974 as a treatment for tendon rupture, biceps tendon instability, and biceps tendonitis. The authors cited a number of advantages of this method: no hardware is required; undue medial dissection is avoided; the remnant of the biceps tendon is removed, allowing good humeral head motion and preventing intra-articular derangement; and the inherent stability of the method gives the patient confidence to begin early, gentle range of motion exercise at both the shoulder and the elbow. However, of the 4 techniques we investigated, keyhole tenodesis had the lowest primary stability. Other reported disadvantages of this method are the need for a separate deltopectoral incision, greater postoperative pain, and cosmetic issues.1,5,14,16-18 To our knowledge, this is the first study that has documented the biomechanical features of keyhole tenodesis. This investigation had 2 shortcomings. First, we did not use cyclic loading and the tests were performed in single-pull load-to-failure fashion. We plan to conduct future trials with cyclic loading. Second, the study was not performed using fresh-frozen human cadaver shoulders, which would have been the preferred specimens. CONCLUSIONS Comparison of these 4 commonly used biceps tenodesis techniques shows that the tunnel and interference screw methods provide stronger fixation than the anchor and keyhole techniques. The interference screw technique can be performed arthroscopically and is good for achieving secure biceps tenodesis. The attractive features of these screws include excellent load-to-failure strength. Interference screw fixation provides strong initial fixation, and has better biomechanical properties than metallic anchors in the bicipital groove. REFERENCES 1. Sethi N, Wright R, Yamaguchi K. Disorders of the long head of the biceps tendon. J Shoulder Elbow Surg 1999;8:644-654. 2. Gill TJ, Mc Irvin E, Mair SD, Hawkins RJ. Results of biceps tenotomy for treatment of pathology of the long head of the biceps brachii. J Shoulder Elbow Surg 2001;10:247-249. 3. Barber A, Bryd JWT, Wolf EM, Burkhart SS. Current controversies: Point counterpoint. How would you treat the partially torn biceps tendon? Arthroscopy 2001;17:636-639.
4. Snyder SJ. Shoulder arthroscopy. New York: McGraw-Hill, 1994;61-76. 5. Dines D, Warren RF, Inglis AE. Surgical treatment of lesions of the long head of the biceps. Clin Orthop 1982;164:165-171. 6. Curtis AS, Snyder SJ. Evaluation and treatment of biceps tendon pathology. Orthop Clin North Am 1993;24:33-43. 7. Warren RF. Lesions of the long head of the biceps tendon. Instr Course Lect 1985;34:204-209. 8. Burkhart SS, Fox DL. SLAP lesions in association with complete tears of the long head of the biceps tendon. A report of two cases. Arthroscopy 1992;8:31-35. 9. Lo IKY, Burkhart S. Arthroscopic biceps tenodesis using a bioabsorbable interference screw. Arthroscopy 2004;20:85-95. 10. Gartsman GM, Hammerman SM. Arthroscopic biceps tenodesis: Operative technique. Arthroscopy 2000;16:550-552. 11. Klepps S, Hazrati Y, Flatow E. Arthroscopic biceps tenodesis. Arthroscopy 2002;18:1040-1045. 12. Boileau P, Krishnan SG, Coste JS, Walch G. Arthroscopic biceps tenodesis: A new technique using bioabsorbable interference screw fixation. Arthroscopy 2002;18:1002-1012. 13. Burkhead WZ, Archand MA, Zeman C, Nabermeger P, Walch G. The biceps tendon. In: Rockwood CA, Matsen FA, eds. The shoulder. Ed 2. Philadelphia: WB Saunders, 1998;1009-1063. 14. Berlemann U, Bayley I. Tenodesis of the long head of biceps brachii in the painful shoulder: improving results in the long term. J Shoulder Elbow Surg 1995;4:429-435. 15. Crenshaw AH, Kilgore WE. Surgical treatment of bicipital tenosynovitis. J Bone Joint Surg Am 1966;48:1496-1502. 16. Becker DA, Cofield RH. Tenodesis of the long head of the biceps brachii for chronic bicipital tendinitis. Long-term results. J Bone Joint Surg Am 1989;71:376-381. 17. Hitchcock HH, Bechtol CO. Painful shoulder. Observations on the role of the tendon of the long head of the biceps brachii in its causation. J Bone Joint Surg Am 1948;30:263-273. 18. Froimson AI, Oh I. Keyhole tenodesis of biceps origin at the shoulder. Clin Orthop 1975;112:245-249. 19. Gerber C, Schneeberger AG, Perren SM, Nyffeler RW. Experimental rotator cuff repair. A preliminary study. J Bone Joint Surg Am 1999;81:1281-1290. 20. Murthi AM, Vosburgh CL, Neviaser TJ. The incidence of pathologic changes of the long head of the biceps brachii. Surgical versus nonsurgical treatment. Clin Orthop 1988; 228: 233-239. 21. DePalma AF, Callery GE. Bicipital tenosynovitis. Clin Orthop 1954;3:69-85. 22. Gilcrest EL. Dislocation and elongation of the long head of the biceps brachii. An analysis of six cases. Ann Surg 1936;104: 118-138. 23. Wolf RS, Zheng N, Weichel D. Long head biceps tenotomy versus tenotomy versus tenodesis: A cadaveric biomechanical analysis. Arthroscopy 2005;21:182-185. 24. Osbahr DC, Diamond AB, Speer KP. The cosmetic appearance of the biceps muscle after long-head tenotomy versus tenodesis. Arthroscopy 2002;18:483-487. 25. Edwards TB, Walch G. Open biceps tenodesis: The interference screw technique. Tech Shoulder Elbow Surg 2003;4:195198. 26. Eakin CL, Faber KJ, Hawkins RJ, Hovis WD. Biceps tendon disorders in athletes. J Am Acad Orthop Surg 1999;7:300-310. 27. Carpenter JE, Fish DN, Huston LJ, Goldstein SA. Pull-out strength of five suture anchors. Arthroscopy 1993;9:109-113. 28. Shea KP, O’Keefe RM Jr, Fulkerson JP. Comparison of initial pull-out strength of arthroscopic suture and staple Bankart repair techniques. Arthroscopy 1992;8:179-182. 29. Meyer DC, Nyffeler RW, Fucentese SF, Gerber C. Failure of suture material at suture anchor eyelets. Arthroscopy 2002;18: 1013-1019.