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Arthroscopic Management of Posterior Instability: Evolution of Technique and Results
Arthroscopic Management of Posterior Instability: Evolution of Technique and Results Felix H. Savoie III, M.D., M. Shaun Holt, M.D., Larry D. Field, M.D., and J. Randall Ramsey, M.D.
Purpose: The purpose of this study was to evaluate the effectiveness of arthroscopic posterior shoulder reconstruction. Methods: We treated 136 shoulders in 131 patients with a diagnosis of primary posterior instability who failed 6 months of vigorous rehabilitation by operative stabilization between 1989 and 2001. Inclusion criterion was primary posterior instability that failed an extensive rehabilitative program with functional impairment and pain. Exclusion criterion was less than 12 months of follow-up and Suretac (Smith & Nephew, Andover, MA) or laser stabilization, leaving 92 shoulders in 90 patients available for the study (69 male, 21 female). Follow-up ranged from 12 to 132 months (average, 28 months). Each patient underwent diagnostic arthroscopy and surgical repair at the same time using one of several primary procedures. The procedure used was based on the pathologic entity noted at the time of surgery. Results: At an average follow-up of 28 months, 97% of the shoulders were stable and considered a success based on the Neer-Foster rating scale. Posterior pathology varied, and a reverse Bankart lesion alone was found 51% of the time, a stretched posterior capsule 67% of the time, and a combination of a reverse Bankart lesion and capsular stretching 16% of the time. The rotator interval was obviously damaged in 61% of cases. Multiple accompanying lesions were found, including anterior–superior labral tears and SLAP tears (20%), superior glenohumeral ligament injury (7%), middle glenohumeral ligament injury (38%), anteroinferior glenohumaral ligament injury (37%), and an enlarged axillary pouch (20%). Conclusions: No essential lesion is present for posterior instability. Multiple varied pathologies will be present in a shoulder presenting with posterior instability. Arthroscopic surgery allows inspection of the joint and anatomic-specific repairs based on pathology. Careful attention to all the supporting structures of the shoulder, including the rotator interval, the anterior–superior labrum, and its attached superior glenohumeral ligament, the coracohumeral ligament, the inferior glenohumeral ligament complex, and the infraspinatus, in addition to the posterior labrum and capsule, allows excellent outcomes to be achieved with arthroscopic posterior reconstruction techniques. Level of Evidence: Level IV, therapeutic case series. Key Words: Arthroscopic repair—Circle concept—Labral lesions—Labral repair—Posterior instability—Rotator interval.
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From the Tulane Institute of Sports Medicine, Department of Orthopaedic Surgery, Tulane University School of Medicine, (F.H.S.), New Orleans, Louisiana; private practice (M.S.H.), Houston, Texas; and the Upper Extremity Service, Mississippi Sports Medicine and Orthopaedic Center (L.D.F., J.R.R.), Jackson, Mississippi, U.S.A. The authors report no conflict of interest. Address correspondence and reprint requests to Felix H. Savoie III, M.D., Tulane University School of Medicine, 1430 Tulane Ave, SL-32, New Orleans, LA 70112, U.S.A. E-mail: [email protected] © 2008 by the Arthroscopy Association of North America 0749-8063/08/2404-0650$34.00/0 doi:10.1016/j.arthro.2007.11.004
osterior shoulder instability has been difficult to diagnose and even more difficult to manage. Hawkins et al.1,2 showed generally poor results with physical therapy alone. Surgical treatment has had failure rates of 30% to 50% in some series.2-8 Unlike anterior instability, there does not appear to be one essential lesion responsible for posterior instability. Additionally, many patients with multidirectional instability may have a primary posterior component, further confusing the diagnosis and management. Numerous surgical procedures to correct posterior instability have been described. Recent reports have shown good results with all arthroscopic techniques.9-11 Arthro-
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 24, No 4 (April), 2008: pp 389-396
389
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F. H. SAVOIE ET AL. TABLE 1.
Neer-Foster Rating Scale
Satisfactory No recurrence of dislocation or subluxation No pain Full activities Normal strength Within 10° of full extension and 40° of rotation compared with contralateral shoulder Unsatisfactory Failure to meet the above criteria
scopic evaluations allow for complete inspection of glenohumeral pathology, and arthroscopic techniques provide lesion-specific repair. With arthroscopy, the surgeon can assess both sides of the joint (i.e., rotator interval and anterior superior labrum) without the need for additional incisions. This report represents an evolution of our technique based on the principles of anatomic restoration of the labrum, vertical shift of the capsule, and recognition/ repair of associated anterior pathology. The purpose of this study was to examine the effectiveness of our anatomic-specific approach to arthroscopic posterior shoulder reconstruction. Our results are based on the Neer-Foster rating scale12 (Table 1).
METHODS This is a retrospective chart review of posterior shoulder reconstruction at our institution. One hundred and thirty-six shoulders in 131 patients with a diagnosis of primary posterior instability who failed 6 months of vigorous rehabilitation were treated by operative stabilization between 1989 and 2001. The inclusion criterion was clinically demonstrable primary posterior instability that failed an extensive rehabilitative program and had functional impairment and pain. The exclusion criterion was less than 12 months follow-up, or surgical management by laser (4 shoulders) or tack (5 shoulders) measures. These two groups were eliminated, leaving only those patients managed by suture techniques with or without anchors in the study. This left 92 shoulders in 90 patients available for the study. There were 69 males and 21 females. Follow-up ranged from 12 to 132 months, with an average of 28 months. Each patient underwent diagnostic arthroscopy and surgical repair at the same time using one of several primary procedures. The specific procedure used was based primarily on the pathologic entity noted at the time of surgery.
The dominant shoulder was involved in 68 patients, while the nondominant shoulder was involved in 24 patients. Two patients had bilateral symptoms (1 traumatic, 1 seizure). The average age of the patients was 26 years (range, 15 to 59 years). Forty patients reported a clear history of posterior dislocation, 30 reported pain and apprehension in a frontally flexed and adducted position, and 20 (22 shoulders) reported both pain and instability on a consistent basis. There were 40 patients with acute traumatic posterior dislocations with subsequent multiple episodes of subluxation, and 50 patients (52 shoulders) with recurrent symptomatic subluxations (no true posterior dislocation). The activity level was high school athletics in 39, college athletics in 24, recreational athletics in 18, and nonathletic in 9. Thirty-two patients were throwing athletes. Eighteen patients were workers’ compensation cases. Results were determined by the Neer-Foster rating scale and a physical examination by the junior author (S.H.) for the purpose of this study. Operative Techniques All surgeries were performed in the lateral decubitus position. Positioning: The patient is placed in a lateral decubitus position rolled 30° posteriorly. A posterior portal is used for diagnostic evaluation of the glenohumeral joint. The intra-articular abnormalities are defined and an anterior portal is established with an outside-in technique using a spinal needle. The arthroscope is placed anteriorly to evaluate the posterior aspect of the glenohumeral joint. Between 1989 and the present, arthroscopic fixation techniques for the labrum and capsule have evolved. Five primary procedures were used during this study period. These involved the use of (1) suture anchors (53 cases); (2) Suretac (Smith & Nephew, Andover, MA) fixation (5 cases); (3) suture plication (31 cases); 4) laser capsulorrhaphy (4 cases); and (5) combined capsule tendon plication by mini-open (6 patients) or arthroscopic (2 patients) technique (8 cases total). The Suretac and laser cases are not included in this patient population, and the mini-open technique used was modified during the study period to an arthroscopic technique. Therefore, these patients were included in the study. In all but 5 cases, the rotator interval was closed upon completion of the posterior procedure. These 5 cases were all within the first 3 years of the study, before we appreciated the contribution of the superior glenohumeral ligament and coracohumeral ligaments to posterior and inferior instability.
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FIGURE 1. (A) In this view from the anterior portal, the guide is placed at the 7 o’clock position posterior and inferiorly through an accessory posterior–lateral–inferior portal. The anchor is placed on the “corner” of the glenoid neck face junction. The sutures are placed through the capsule inferior to the anchor to produce a vertical shift. (B) The completed repair using a mattress suture to shift the capsule superiorly and restore the normal labral position on the face of the glenoid.
Suture Anchor Technique: The suture anchor technique is currently our preferred technique when there is any damage to the labrum and/or capsule. An accessory inferior lateral posterior portal is established. This portal is located approximately 2 cm inferior and 2 cm lateral to the normal posterior portal, or about 2 cm lateral and 2 cm inferior to the posterolateral corner of the acromion. It should traverse the interval between the infraspinatus and teres minor. The capsulolabral tissues are released from the glenoid just as in the anterior Bankart procedure (Fig 1A). The glenoid is prepared with a motorized shaver or burr to expose fresh bleeding bone. Anchors are placed along the glenoid face typically at the 7, 9, and 11 o’clock positions as needed (Fig 1A). The inferior capsule and labrum are grasped below the level of the anchor and both are pulled superiorly towards the anchor. This achieves a superior shift of the capsule and restores the capsulolabral complex tension back to normal (Fig 1B). Capsular plication sutures are added as necessary to further tension the capsule as necessary. Suture Capsulorrhaphy: The suture punch capsulorrhaphy technique was used as part of a prospective study that has previously been published.13 This technique is used when there is more extensive damage to the posterior inferior capsulolabral complex, in patients with an absent posterior capsule from previous surgery, or in patients who have posterior inferior capsule tears near the glenoid attachment of the liga-
ments (Fig 2A and B). Multiple strands of suture are inserted into the posterior inferior capsule (usually 6 to 8 strands). They are then pulled superiorly out the Neviaser portal and tied through a small incision to the fascia overlying the acromion and clavicle (Fig 2C). This achieves a large vertical shift of the posterior capsule. Combined Tendon/Capsule Plication: The miniopen technique was used in competitive power lifters when there was extensive damage to the posterior capsule and to the infraspinatus and teres minor tendons from traumatic injuries while weight lifting. This technique was adapted to arthroscopic measures near the end of the study period without a change in the results. The deltoid is split off the posterolateral acromion between the middle and posterior heads in line with its fibers to expose the tendons. Sutures are placed around the tendons and the capsule as a unit and tied. This plicates both the posterior capsule and tendons, resulting in an extremely strong repair. The arthroscopic variation avoids splitting the deltoid. Sutures are placed via a spinal needle through the lateral aspect of the teres minor and infraspinatus tendons and the lateral posterior capsule. The sutures are retrieved out the inferior medial capsule and then tied in sequence from inferior to superior. They are usually tied blindly within the bursa. This technique, which we use today, is used primarily when there is thin or absent capsule and as an adjunct to labral repairs. Once a capsulolabral re-
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FIGURE 2. (A) Arthroscopic view from anterior portal of a lax posterior capsule revealed a posterior–inferior humeral head and the wide separation of the labrum and posterior capsule. (B) The anterior superior portal view of the shallow articular cartilage defect and exposed bone of the anterior Hill-Sachs lesion associated with posterior dislocations. (C) The view of the anterior portal of a multi suture repair with extensive capsular shift of the patient in Fig 3A.
pair has been performed, a spinal needle is inserted into the posterior lateral aspect of the shoulder through the infraspinatus tendon and capsule (Fig 3A). A No. 2 Ethibond suture is threaded through it. Through the posterior portal, a suture retriever is used to penetrate the capsule slightly superior to the labral repair and then grasp the medial capsule. The threaded Ethibond is retrieved and pulled out the posterior portal. The lateral limb of the suture is retrieved blindly in the subacromial space under the deltoid and tied to the medial limb using a sliding locking knot, plicating both the capsule and the tendon (Fig 3B).
An arthroscopic rotator interval closure is added to all of the above procedures. Any other associated pathology is also repaired at the time of the index surgery. The most commonly associated finding was an avulsion of the anterior superior labrum that included the superior glenohumeral ligament (20%). Postoperative Course Patients were maintained in a gunslinger brace full-time for 3 weeks, then part-time for 3 weeks. At 3 weeks, gentle range of motion and scapular control exercises are initiated until week 6 or 8. Six to
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FIGURE 3. (A) View from the anterior portal of the posterior placation technique. A spinal needle is placed through the humeral attachment of the capsule in preparation for suture placement. A grasper is placed through the posterior portal to retrieve the suture for tying in the bursa. The suture knot from the labral repair is to the left. (B) The white, braided suture in place before tensioning and knot tying. The capsule and overlying infraspinatus tendon will both be plicated within the suture to provide stability.
8 weeks postoperatively, depending on the feel of the maturation of the repair, active rehabilitation is started. Proper scapular control is stressed during every part of the rehabilitation program. Between 8 and 10 weeks, functional rehabilitation is initiated and continued until full range of motion and normal strength is achieved. No stretching or passive range of motion is allowed until a minimum of 3 months postoperatively. Full rehabilitation usually takes 4 to 6 months. Patients are allowed to resume normal activities, including contact sports, at 6 months postoperatively. RESULTS Diagnostic Arthroscopic Findings The arthroscopic findings were documented for each patient at the time of surgery. Intra-articular pathology was varied and multiple in most cases. The posterior pathology varied between a stretched posterior capsule, a reverse Bankart lesion, or both abnormalities. A reverse Bankart lesion was found 51% of the time. A stretched posterior capsule was found 67% of the time. Both a reverse Bankart lesion and a stretched posterior capsule were found 16% of the time. Significant anterior pathology was found at the time of surgery in most cases. An anterosuperior la-
bral tear was found in 20% of cases. The rotator interval was grossly damaged to visual inspection in 61% of the patients. An associated anterior band of the inferior glenohumeral ligament injury was found in 37% of total cases. Concomitant damage to the middle glenohumeral ligament was seen 38% and the superior glenohumeral ligament without labral tearing 7% of the time. An enlarged axillary pouch was found 20% of the time. Clinical Results Patients were re-evaluated 1 to 11 years postoperatively (average, 28 months). Neer-Foster scores were used to evaluate results and are based on recurrent subluxation, recurrent dislocation, or stable shoulders. Any recurrent episodes of dislocation or subluxation were graded as failures. There were two failures out of the 92 shoulders. One patient had recurrent gross subluxation and one patient had a recurrent dislocation after resuming normal activity. Techniques initially used to repair those shoulders included 1 posterior suture anchor (1 of 53 cases), and 1 Caspari suture punch technique (1 of 31 total cases). One of the two failures did not have a rotator interval closure or other anterior procedure performed. One patient that failed did have a rotator interval closure and posterior reconstruction with the
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multiple suture punch technique. None of the 8 patients with a combined capsule and tendon plication failed. Ninety-seven percent (90 of 92) of the shoulders remained stable at final follow-up and were a success based on the Neer-Foster rating. There were four patients with clinically good results who did not have any subluxation, dislocation, or pain, but had a grade I positive load and shift test on follow-up examination in the office. This test did not produce pain. All of these were in the Caspari suture punch technique group. Three of the four did not have a rotator interval closure or other anterior procedure at the index operation. DISCUSSION Historically, posterior instability has been difficult to diagnose and to treat. In 1952, McLaughlin14 reported on posterior instability and felt that the incidence was 2% to 4% of all dislocations. Wolf and Eakin9 found the incidence to be much higher (11.6%) when the recurrent posterior subluxators and dislocators are considered together. The cause of posterior instability has been felt to be related to lax posterior inferior capsular ligaments and damage to the rotator interval.12,15,16 O’Brien et al.17 reported the importance of the inferior glenohumeral ligament complex for shoulder stability at various arm positions. Plastic deformation of the inferior glenohumeral ligament complex has been shown to occur during rapid loading in cadaveric studies.10,18 The superior glenohumeral ligament was shown to be important in preventing pathologic posterior inferior humeral translation. The posterior labrum has been implicated in posterior instability.3,4,19,20 Kim et al.11 found the most frequent lesion to be incomplete stripping of the posteroinferior aspect of the labrum in unidirectional posterior instability, and felt that it was analogous to the anterior Bankart lesion. They had success completing the lesion and repairing it with suture anchors. They also found co-existent stretching of the posterior capsule in 22 of 27 patients. In our study, we found the posterior pathology to be a reverse Bankart lesion 51% of the time, a stretched posterior capsule 67% of the time, and a combination of a reverse Bankart and a stretched capsule 16% of the time. The importance of the rotator interval in helping stabilize the shoulder from posterior inferior translation has been shown by Harryman.21 The circle concept of the shoulder has been described by several authors.5,20-30 In our series, these concepts would
seem to hold true. Wirth, Groh, and Rockwood25 restored stability in 9 of 10 shoulders with multidirectional instability/posterior instability with solely an anterior procedure. They used a superior capsular shift and rotator interval closure of the anterior capsule to restore posterior stability. This reinforces the importance of the anterior structures in posterior stability.31-33 In this study, they made no effort to correct the lax posterior capsule and relied on the concomitant tightening of the posterior capsule by the anterior procedure. The vast majority of our patients had more than one visible break in the “ring.”27-33 This varied from SLAP lesions and anterior superior labrum tears to damaged rotator intervals and even damage to the middle labrum and ligament all the way down to the anteroinferior glenohumeral ligament attachment to the anterior labrum. All of our patients had recurrent episodes of dislocation or subluxation before surgical fixation. Some of the labral injuries could have been secondary injuries from repeated dislocation/subluxation. It is also possible that the associated anterior injuries could have occurred at the time of the initial dislocation or injury and varied because of arm position at the time of force transmission through the shoulder. Overall, the success of arthroscopic posterior reconstruction at our institution is 97% based on the NeerFoster rating at an average follow-up of 28 months. The technique of posterior reconstruction has evolved at our institution. We have used several techniques to fix the posterior injury patterns. When a superior shift of the posterior capsule is achieved, it adequately tightens the posterior constraints of the shoulder regardless of technique. Careful attention must be paid to the anterior and superior aspects of the shoulder. With close observation, one can usually assess damage to the rotator interval. There may also be associated SLAP tears and other superior and middle labrum tears concomitantly. When all breaks in the ring are addressed, the result of arthroscopic fixation of posterior instability increases dramatically. We have previously reported on these techniques and the 95% satisfactory rating has been maintained.26 Although multiple methods were utilized, the principle of vertical shift of the posterior capsule to eliminate laxity, anatomic restoration of the labrum, and repair or reconstruction of all associated anterior pathology was achieved in all cases. The fact that multiple techniques were used but we still had an overall stability rate of 97% signifies the importance of the
ARTHROSCOPIC MANAGEMENT OF POSTERIOR INSTABILITY supporting structures of the shoulder. We aggressively repaired the posterior injury and any other capsular or labral tears. As experience was gained, it became easier to detect damage to the rotator interval and surrounding structures. We routinely use our widebased technique to close the rotator interval rather than a simple superior glenohumeral ligament to middle glenohumeral ligament plication, because we believe our technique more accurately mimics the study of Harryman et al.21 during arthroscopic posterior reconstruction of the shoulder. Weaknesses of this study include its retrospective nature, multiple techniques being used for the reconstruction, no observation of glenoid version, and relatively short follow-up. We also used the Neer-Foster rating scale at the start of the study to collect data and compare symptoms, and continued with it rather than switch to a more current rating scale. CONCLUSIONS Multiple and varied pathology was present in our series of posterior instability without one “essential” lesion being noted. Careful attention to all the supporting structures of the shoulder, including the rotator interval, the anterior–superior labrum and its attached superior glenohumeral ligament, the coracohumeral ligament, the inferior glenohumeral ligament complex, and the infraspinatus, in addition to the posterior labrum and capsule, allows excellent outcomes to be achieved with arthroscopic posterior reconstruction techniques. REFERENCES 1. Hawkins RJ, Kippert G, Johnston G. Recurrent posterior instability (subluxation) of the shoulder. J Bone Joint Surg Am 1984;66:169-174. 2. Hawkins RJ, McCormack RG. Posterior shoulder instability. Orthopedics 1988;11:101-107. 3. Pollock RG, Bigliani LU, Recurrent posterior shoulder instability: Diagnosis and treatment. Clin Orthop Relat Res 1993; 291:85-96. 4. Tibone JE, Ting A. Capsulorrhaphy with a staple for recurrent posterior subluxations of the shoulder. J Bone Joint Surg Am 1990;72:999-1002. 5. Schwartz E, Warren RF, O’Brien SJ, Fronek J. Posterior shoulder instability. Orthop Clin North Am 1987;18:409-419. 6. Hawkins RJ, Belle RM. Posterior instability of the shoulder. Instr Course Lect 1989;38:211-215. 7. Hurley JA, Anderson TE, Dear W, Andrish JT, Bergfeld JA, Weiker GG. Posterior shoulder instability: Surgical versus conservative results with evaluation of glenoid version. Am J Sports Med 1992;20:396-400. 8. Fronek J, Warren RF, Bowen M. Posterior subluxations of the glenohumeral joint. J Bone Joint Surg Am 1989;71:205-216.
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9. Wolf EM, Eakin CL. Arthroscopic capsular plication for posterior shoulder instability. Arthroscopy 1998;14:153-163. 10. Bigliani LU, Pollock RG, McIlveen SJ, Endrizzi DP, Flatow EL. Shift of the posterior inferior aspect of the capsule for recurrent posterior glenohumeral instability. J Bone Joint Surg Am 1995;77:1011-1020. 11. Kim SH, Ha KI, Park JH, et al. Arthroscopic posterior labral repair and capsular shift for traumatic unidirectional recurrent posterior subluxation of the shoulder. J Bone Joint Surg Am 2003;85:1479-1487. 12. Neer CS II, Foster CR. Inferior capsular shift for involuntary inferior and multidirectional instability of the shoulder. A preliminary report. J Bone Joint Surg Am 1980;62:897908. 13. McIntyre LF, Caspari RB, Savoie FHS III. The arthroscopic treatment of posterior shoulder instability: Two-year results of a multiple suture technique. Arthroscopy 1997;13:426-432. 14. Mc Laughlin H. Posterior dislocation of the shoulder. J Bone Joint Surg Am 1952;34:584-590. 15. Neer CS. Surgical repair for recurrent posterior instability. In: Neer CS, ed. Shoulder reconstruction. Philadelphia: WB Saunders; 1990. 16. Pagnani MJ, Warren RF. Stabilizers of the glenohumeral joint. J Shoulder Elbow Surg 1994;3:173-190. 17. O’Brien SJ, Neeves MC, Arnoczky SP, Roebuck SR, DiCarlo EF, Warren RF. The anatomy and histology of the inferior glenohumeral ligament complex of the shoulder. Am J Sports Med 1990;18:449-456. 18. Weber SC, Caspari RB. A biomechanical evaluation of the restraints to posterior shoulder dislocation. Arthroscopy 1989; 5:115-121. 19. Caspari RB, Geissler WB. Arthroscopic manifestations of shoulder subluxations and dislocation. Clin Orthop Relat Res 1993;291:54-66. 20. Tibone JE, Bradley JP. The treatment of posterior subluxation in athletes. Clin Orthop Relat Res 1993;291:124-137. 21. Harryman DT, Sidles JA, Harris SL, Matsen FA III. The role of the rotator interval capsule in passive motion and stability of the shoulder. J Bone Joint Surg Am 1991;74:53-66. 22. Warren RF, Kornblatt IB, Marchand R. Static factors affecting posterior shoulder instability. Orthop Trans 1984;8:89. 23. Wolf RS, Zheng I, Weichel D. The effects of thermal capsulorrhaphy and rotator interval closure on multidirectional laxity in the glenohumeral joint: A cadaveric biomechanical study. Arthroscopy 2004;20:1044-1049. 24. Plausinis D, Bravman JT, Heywood C, Kummer FJ, Kwon YW, Jazrawi, LM. Arthroscopic rotator interval closure: Effect of sutures on glenohumeral motion and anterior– posterior translation. Am J Sports Med 2006;34:1656-1661. 25. Wirth M, Groh G, Rockwood CR. Capsulorrhaphy through an anterior approach for the treatment of atraumatic posterior glenohumeral instability with multidirectional laxity of the shoulder. J Bone Joint Surg Am 1998;80:1570-1578. 26. Papendick LW, Savoie FH III. Anatomy specific repair techniques for posterior shoulder instability. J South Orthop Assoc 1995;4:169-176. 27. Wolf BR, Strickland S, Williams RJ, Allen AA, Altchek DW, Warren RF. Open posterior stabilization for recurrent posterior glenohumeral instability. J Shoulder Elbow Surg 2005;14:157164. 28. Bottoni CR, Franks BR, Moore JH, DeBerardino TM, Taylor DC, Arciero RA. Operative stabilization of posterior shoulder instability. Am J Sports Med 2005;33:996-1002. 29. Provencher MT, Bell SJ, Manzel KA, Mologne TS. Arthroscopic treatment of posterior shoulder instability: Results in 33 patients. Am J Sports Med 2005;33:1463-1471.
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30. Bradley JP, Baker CL III, Kline AJ, Armfield DR, Chhabra A. Arthroscopic capsulolabral reconstruction for posterior instability of the shoulder: A prospective study of 100 shoulders. Am J Sports Med 2006;34:1061-1071. 31. Millett PJ, Clavert P, Hatch GF III, Warner JJ. Recurrent posterior shoulder instability. J Am Acad Orthop Surg 2006; 14:464-476.
32. Yamamoto N, Itoi E, Tuoheti Y, et al. Effects of rotator interval closure on glenohumeral stability and motion: A cadaveric study. J Shoulder Elbow Surg 2006;15:750-758. 33. Provencher MT, Mologne TS, Hongo M, Zhao K, Tasto JP, An KN. Arthroscopic versus open rotator interval closure: Biomechanical evaluation of stability and motion. Arthroscopy 2007; 23:583-592.
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Purpose: The purpose of this study was to evaluate the effectiveness of arthroscopic posterior shoulder reconstruction. Methods: We treated 136 shoulders in 131 patients with a diagnosis of primary posterior instability who failed 6 months of vigorous rehabilitation by operative stabilization between 1989 and 2001. Inclusion criterion was primary posterior instability that failed an extensive rehabilitative program with functional impairment and pain. Exclusion criterion was less than 12 months of follow-up and Suretac (Smith & Nephew, Andover, MA) or laser stabilization, leaving 92 shoulders in 90 patients available for the study (69 male, 21 female). Follow-up ranged from 12 to 132 months (average, 28 months). Each patient underwent diagnostic arthroscopy and surgical repair at the same time using one of several primary procedures. The procedure used was based on the pathologic entity noted at the time of surgery. Results: At an average follow-up of 28 months, 97% of the shoulders were stable and considered a success based on the Neer-Foster rating scale. Posterior pathology varied, and a reverse Bankart lesion alone was found 51% of the time, a stretched posterior capsule 67% of the time, and a combination of a reverse Bankart lesion and capsular stretching 16% of the time. The rotator interval was obviously damaged in 61% of cases. Multiple accompanying lesions were found, including anterior–superior labral tears and SLAP tears (20%), superior glenohumeral ligament injury (7%), middle glenohumeral ligament injury (38%), anteroinferior glenohumaral ligament injury (37%), and an enlarged axillary pouch (20%). Conclusions: No essential lesion is present for posterior instability. Multiple varied pathologies will be present in a shoulder presenting with posterior instability. Arthroscopic surgery allows inspection of the joint and anatomic-specific repairs based on pathology. Careful attention to all the supporting structures of the shoulder, including the rotator interval, the anterior–superior labrum, and its attached superior glenohumeral ligament, the coracohumeral ligament, the inferior glenohumeral ligament complex, and the infraspinatus, in addition to the posterior labrum and capsule, allows excellent outcomes to be achieved with arthroscopic posterior reconstruction techniques. Level of Evidence: Level IV, therapeutic case series. Key Words: Arthroscopic repair—Circle concept—Labral lesions—Labral repair—Posterior instability—Rotator interval.
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From the Tulane Institute of Sports Medicine, Department of Orthopaedic Surgery, Tulane University School of Medicine, (F.H.S.), New Orleans, Louisiana; private practice (M.S.H.), Houston, Texas; and the Upper Extremity Service, Mississippi Sports Medicine and Orthopaedic Center (L.D.F., J.R.R.), Jackson, Mississippi, U.S.A. The authors report no conflict of interest. Address correspondence and reprint requests to Felix H. Savoie III, M.D., Tulane University School of Medicine, 1430 Tulane Ave, SL-32, New Orleans, LA 70112, U.S.A. E-mail: [email protected] © 2008 by the Arthroscopy Association of North America 0749-8063/08/2404-0650$34.00/0 doi:10.1016/j.arthro.2007.11.004
osterior shoulder instability has been difficult to diagnose and even more difficult to manage. Hawkins et al.1,2 showed generally poor results with physical therapy alone. Surgical treatment has had failure rates of 30% to 50% in some series.2-8 Unlike anterior instability, there does not appear to be one essential lesion responsible for posterior instability. Additionally, many patients with multidirectional instability may have a primary posterior component, further confusing the diagnosis and management. Numerous surgical procedures to correct posterior instability have been described. Recent reports have shown good results with all arthroscopic techniques.9-11 Arthro-
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 24, No 4 (April), 2008: pp 389-396
389
390
F. H. SAVOIE ET AL. TABLE 1.
Neer-Foster Rating Scale
Satisfactory No recurrence of dislocation or subluxation No pain Full activities Normal strength Within 10° of full extension and 40° of rotation compared with contralateral shoulder Unsatisfactory Failure to meet the above criteria
scopic evaluations allow for complete inspection of glenohumeral pathology, and arthroscopic techniques provide lesion-specific repair. With arthroscopy, the surgeon can assess both sides of the joint (i.e., rotator interval and anterior superior labrum) without the need for additional incisions. This report represents an evolution of our technique based on the principles of anatomic restoration of the labrum, vertical shift of the capsule, and recognition/ repair of associated anterior pathology. The purpose of this study was to examine the effectiveness of our anatomic-specific approach to arthroscopic posterior shoulder reconstruction. Our results are based on the Neer-Foster rating scale12 (Table 1).
METHODS This is a retrospective chart review of posterior shoulder reconstruction at our institution. One hundred and thirty-six shoulders in 131 patients with a diagnosis of primary posterior instability who failed 6 months of vigorous rehabilitation were treated by operative stabilization between 1989 and 2001. The inclusion criterion was clinically demonstrable primary posterior instability that failed an extensive rehabilitative program and had functional impairment and pain. The exclusion criterion was less than 12 months follow-up, or surgical management by laser (4 shoulders) or tack (5 shoulders) measures. These two groups were eliminated, leaving only those patients managed by suture techniques with or without anchors in the study. This left 92 shoulders in 90 patients available for the study. There were 69 males and 21 females. Follow-up ranged from 12 to 132 months, with an average of 28 months. Each patient underwent diagnostic arthroscopy and surgical repair at the same time using one of several primary procedures. The specific procedure used was based primarily on the pathologic entity noted at the time of surgery.
The dominant shoulder was involved in 68 patients, while the nondominant shoulder was involved in 24 patients. Two patients had bilateral symptoms (1 traumatic, 1 seizure). The average age of the patients was 26 years (range, 15 to 59 years). Forty patients reported a clear history of posterior dislocation, 30 reported pain and apprehension in a frontally flexed and adducted position, and 20 (22 shoulders) reported both pain and instability on a consistent basis. There were 40 patients with acute traumatic posterior dislocations with subsequent multiple episodes of subluxation, and 50 patients (52 shoulders) with recurrent symptomatic subluxations (no true posterior dislocation). The activity level was high school athletics in 39, college athletics in 24, recreational athletics in 18, and nonathletic in 9. Thirty-two patients were throwing athletes. Eighteen patients were workers’ compensation cases. Results were determined by the Neer-Foster rating scale and a physical examination by the junior author (S.H.) for the purpose of this study. Operative Techniques All surgeries were performed in the lateral decubitus position. Positioning: The patient is placed in a lateral decubitus position rolled 30° posteriorly. A posterior portal is used for diagnostic evaluation of the glenohumeral joint. The intra-articular abnormalities are defined and an anterior portal is established with an outside-in technique using a spinal needle. The arthroscope is placed anteriorly to evaluate the posterior aspect of the glenohumeral joint. Between 1989 and the present, arthroscopic fixation techniques for the labrum and capsule have evolved. Five primary procedures were used during this study period. These involved the use of (1) suture anchors (53 cases); (2) Suretac (Smith & Nephew, Andover, MA) fixation (5 cases); (3) suture plication (31 cases); 4) laser capsulorrhaphy (4 cases); and (5) combined capsule tendon plication by mini-open (6 patients) or arthroscopic (2 patients) technique (8 cases total). The Suretac and laser cases are not included in this patient population, and the mini-open technique used was modified during the study period to an arthroscopic technique. Therefore, these patients were included in the study. In all but 5 cases, the rotator interval was closed upon completion of the posterior procedure. These 5 cases were all within the first 3 years of the study, before we appreciated the contribution of the superior glenohumeral ligament and coracohumeral ligaments to posterior and inferior instability.
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FIGURE 1. (A) In this view from the anterior portal, the guide is placed at the 7 o’clock position posterior and inferiorly through an accessory posterior–lateral–inferior portal. The anchor is placed on the “corner” of the glenoid neck face junction. The sutures are placed through the capsule inferior to the anchor to produce a vertical shift. (B) The completed repair using a mattress suture to shift the capsule superiorly and restore the normal labral position on the face of the glenoid.
Suture Anchor Technique: The suture anchor technique is currently our preferred technique when there is any damage to the labrum and/or capsule. An accessory inferior lateral posterior portal is established. This portal is located approximately 2 cm inferior and 2 cm lateral to the normal posterior portal, or about 2 cm lateral and 2 cm inferior to the posterolateral corner of the acromion. It should traverse the interval between the infraspinatus and teres minor. The capsulolabral tissues are released from the glenoid just as in the anterior Bankart procedure (Fig 1A). The glenoid is prepared with a motorized shaver or burr to expose fresh bleeding bone. Anchors are placed along the glenoid face typically at the 7, 9, and 11 o’clock positions as needed (Fig 1A). The inferior capsule and labrum are grasped below the level of the anchor and both are pulled superiorly towards the anchor. This achieves a superior shift of the capsule and restores the capsulolabral complex tension back to normal (Fig 1B). Capsular plication sutures are added as necessary to further tension the capsule as necessary. Suture Capsulorrhaphy: The suture punch capsulorrhaphy technique was used as part of a prospective study that has previously been published.13 This technique is used when there is more extensive damage to the posterior inferior capsulolabral complex, in patients with an absent posterior capsule from previous surgery, or in patients who have posterior inferior capsule tears near the glenoid attachment of the liga-
ments (Fig 2A and B). Multiple strands of suture are inserted into the posterior inferior capsule (usually 6 to 8 strands). They are then pulled superiorly out the Neviaser portal and tied through a small incision to the fascia overlying the acromion and clavicle (Fig 2C). This achieves a large vertical shift of the posterior capsule. Combined Tendon/Capsule Plication: The miniopen technique was used in competitive power lifters when there was extensive damage to the posterior capsule and to the infraspinatus and teres minor tendons from traumatic injuries while weight lifting. This technique was adapted to arthroscopic measures near the end of the study period without a change in the results. The deltoid is split off the posterolateral acromion between the middle and posterior heads in line with its fibers to expose the tendons. Sutures are placed around the tendons and the capsule as a unit and tied. This plicates both the posterior capsule and tendons, resulting in an extremely strong repair. The arthroscopic variation avoids splitting the deltoid. Sutures are placed via a spinal needle through the lateral aspect of the teres minor and infraspinatus tendons and the lateral posterior capsule. The sutures are retrieved out the inferior medial capsule and then tied in sequence from inferior to superior. They are usually tied blindly within the bursa. This technique, which we use today, is used primarily when there is thin or absent capsule and as an adjunct to labral repairs. Once a capsulolabral re-
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FIGURE 2. (A) Arthroscopic view from anterior portal of a lax posterior capsule revealed a posterior–inferior humeral head and the wide separation of the labrum and posterior capsule. (B) The anterior superior portal view of the shallow articular cartilage defect and exposed bone of the anterior Hill-Sachs lesion associated with posterior dislocations. (C) The view of the anterior portal of a multi suture repair with extensive capsular shift of the patient in Fig 3A.
pair has been performed, a spinal needle is inserted into the posterior lateral aspect of the shoulder through the infraspinatus tendon and capsule (Fig 3A). A No. 2 Ethibond suture is threaded through it. Through the posterior portal, a suture retriever is used to penetrate the capsule slightly superior to the labral repair and then grasp the medial capsule. The threaded Ethibond is retrieved and pulled out the posterior portal. The lateral limb of the suture is retrieved blindly in the subacromial space under the deltoid and tied to the medial limb using a sliding locking knot, plicating both the capsule and the tendon (Fig 3B).
An arthroscopic rotator interval closure is added to all of the above procedures. Any other associated pathology is also repaired at the time of the index surgery. The most commonly associated finding was an avulsion of the anterior superior labrum that included the superior glenohumeral ligament (20%). Postoperative Course Patients were maintained in a gunslinger brace full-time for 3 weeks, then part-time for 3 weeks. At 3 weeks, gentle range of motion and scapular control exercises are initiated until week 6 or 8. Six to
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FIGURE 3. (A) View from the anterior portal of the posterior placation technique. A spinal needle is placed through the humeral attachment of the capsule in preparation for suture placement. A grasper is placed through the posterior portal to retrieve the suture for tying in the bursa. The suture knot from the labral repair is to the left. (B) The white, braided suture in place before tensioning and knot tying. The capsule and overlying infraspinatus tendon will both be plicated within the suture to provide stability.
8 weeks postoperatively, depending on the feel of the maturation of the repair, active rehabilitation is started. Proper scapular control is stressed during every part of the rehabilitation program. Between 8 and 10 weeks, functional rehabilitation is initiated and continued until full range of motion and normal strength is achieved. No stretching or passive range of motion is allowed until a minimum of 3 months postoperatively. Full rehabilitation usually takes 4 to 6 months. Patients are allowed to resume normal activities, including contact sports, at 6 months postoperatively. RESULTS Diagnostic Arthroscopic Findings The arthroscopic findings were documented for each patient at the time of surgery. Intra-articular pathology was varied and multiple in most cases. The posterior pathology varied between a stretched posterior capsule, a reverse Bankart lesion, or both abnormalities. A reverse Bankart lesion was found 51% of the time. A stretched posterior capsule was found 67% of the time. Both a reverse Bankart lesion and a stretched posterior capsule were found 16% of the time. Significant anterior pathology was found at the time of surgery in most cases. An anterosuperior la-
bral tear was found in 20% of cases. The rotator interval was grossly damaged to visual inspection in 61% of the patients. An associated anterior band of the inferior glenohumeral ligament injury was found in 37% of total cases. Concomitant damage to the middle glenohumeral ligament was seen 38% and the superior glenohumeral ligament without labral tearing 7% of the time. An enlarged axillary pouch was found 20% of the time. Clinical Results Patients were re-evaluated 1 to 11 years postoperatively (average, 28 months). Neer-Foster scores were used to evaluate results and are based on recurrent subluxation, recurrent dislocation, or stable shoulders. Any recurrent episodes of dislocation or subluxation were graded as failures. There were two failures out of the 92 shoulders. One patient had recurrent gross subluxation and one patient had a recurrent dislocation after resuming normal activity. Techniques initially used to repair those shoulders included 1 posterior suture anchor (1 of 53 cases), and 1 Caspari suture punch technique (1 of 31 total cases). One of the two failures did not have a rotator interval closure or other anterior procedure performed. One patient that failed did have a rotator interval closure and posterior reconstruction with the
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multiple suture punch technique. None of the 8 patients with a combined capsule and tendon plication failed. Ninety-seven percent (90 of 92) of the shoulders remained stable at final follow-up and were a success based on the Neer-Foster rating. There were four patients with clinically good results who did not have any subluxation, dislocation, or pain, but had a grade I positive load and shift test on follow-up examination in the office. This test did not produce pain. All of these were in the Caspari suture punch technique group. Three of the four did not have a rotator interval closure or other anterior procedure at the index operation. DISCUSSION Historically, posterior instability has been difficult to diagnose and to treat. In 1952, McLaughlin14 reported on posterior instability and felt that the incidence was 2% to 4% of all dislocations. Wolf and Eakin9 found the incidence to be much higher (11.6%) when the recurrent posterior subluxators and dislocators are considered together. The cause of posterior instability has been felt to be related to lax posterior inferior capsular ligaments and damage to the rotator interval.12,15,16 O’Brien et al.17 reported the importance of the inferior glenohumeral ligament complex for shoulder stability at various arm positions. Plastic deformation of the inferior glenohumeral ligament complex has been shown to occur during rapid loading in cadaveric studies.10,18 The superior glenohumeral ligament was shown to be important in preventing pathologic posterior inferior humeral translation. The posterior labrum has been implicated in posterior instability.3,4,19,20 Kim et al.11 found the most frequent lesion to be incomplete stripping of the posteroinferior aspect of the labrum in unidirectional posterior instability, and felt that it was analogous to the anterior Bankart lesion. They had success completing the lesion and repairing it with suture anchors. They also found co-existent stretching of the posterior capsule in 22 of 27 patients. In our study, we found the posterior pathology to be a reverse Bankart lesion 51% of the time, a stretched posterior capsule 67% of the time, and a combination of a reverse Bankart and a stretched capsule 16% of the time. The importance of the rotator interval in helping stabilize the shoulder from posterior inferior translation has been shown by Harryman.21 The circle concept of the shoulder has been described by several authors.5,20-30 In our series, these concepts would
seem to hold true. Wirth, Groh, and Rockwood25 restored stability in 9 of 10 shoulders with multidirectional instability/posterior instability with solely an anterior procedure. They used a superior capsular shift and rotator interval closure of the anterior capsule to restore posterior stability. This reinforces the importance of the anterior structures in posterior stability.31-33 In this study, they made no effort to correct the lax posterior capsule and relied on the concomitant tightening of the posterior capsule by the anterior procedure. The vast majority of our patients had more than one visible break in the “ring.”27-33 This varied from SLAP lesions and anterior superior labrum tears to damaged rotator intervals and even damage to the middle labrum and ligament all the way down to the anteroinferior glenohumeral ligament attachment to the anterior labrum. All of our patients had recurrent episodes of dislocation or subluxation before surgical fixation. Some of the labral injuries could have been secondary injuries from repeated dislocation/subluxation. It is also possible that the associated anterior injuries could have occurred at the time of the initial dislocation or injury and varied because of arm position at the time of force transmission through the shoulder. Overall, the success of arthroscopic posterior reconstruction at our institution is 97% based on the NeerFoster rating at an average follow-up of 28 months. The technique of posterior reconstruction has evolved at our institution. We have used several techniques to fix the posterior injury patterns. When a superior shift of the posterior capsule is achieved, it adequately tightens the posterior constraints of the shoulder regardless of technique. Careful attention must be paid to the anterior and superior aspects of the shoulder. With close observation, one can usually assess damage to the rotator interval. There may also be associated SLAP tears and other superior and middle labrum tears concomitantly. When all breaks in the ring are addressed, the result of arthroscopic fixation of posterior instability increases dramatically. We have previously reported on these techniques and the 95% satisfactory rating has been maintained.26 Although multiple methods were utilized, the principle of vertical shift of the posterior capsule to eliminate laxity, anatomic restoration of the labrum, and repair or reconstruction of all associated anterior pathology was achieved in all cases. The fact that multiple techniques were used but we still had an overall stability rate of 97% signifies the importance of the
ARTHROSCOPIC MANAGEMENT OF POSTERIOR INSTABILITY supporting structures of the shoulder. We aggressively repaired the posterior injury and any other capsular or labral tears. As experience was gained, it became easier to detect damage to the rotator interval and surrounding structures. We routinely use our widebased technique to close the rotator interval rather than a simple superior glenohumeral ligament to middle glenohumeral ligament plication, because we believe our technique more accurately mimics the study of Harryman et al.21 during arthroscopic posterior reconstruction of the shoulder. Weaknesses of this study include its retrospective nature, multiple techniques being used for the reconstruction, no observation of glenoid version, and relatively short follow-up. We also used the Neer-Foster rating scale at the start of the study to collect data and compare symptoms, and continued with it rather than switch to a more current rating scale. CONCLUSIONS Multiple and varied pathology was present in our series of posterior instability without one “essential” lesion being noted. Careful attention to all the supporting structures of the shoulder, including the rotator interval, the anterior–superior labrum and its attached superior glenohumeral ligament, the coracohumeral ligament, the inferior glenohumeral ligament complex, and the infraspinatus, in addition to the posterior labrum and capsule, allows excellent outcomes to be achieved with arthroscopic posterior reconstruction techniques. REFERENCES 1. Hawkins RJ, Kippert G, Johnston G. Recurrent posterior instability (subluxation) of the shoulder. J Bone Joint Surg Am 1984;66:169-174. 2. Hawkins RJ, McCormack RG. Posterior shoulder instability. Orthopedics 1988;11:101-107. 3. Pollock RG, Bigliani LU, Recurrent posterior shoulder instability: Diagnosis and treatment. Clin Orthop Relat Res 1993; 291:85-96. 4. Tibone JE, Ting A. Capsulorrhaphy with a staple for recurrent posterior subluxations of the shoulder. J Bone Joint Surg Am 1990;72:999-1002. 5. Schwartz E, Warren RF, O’Brien SJ, Fronek J. Posterior shoulder instability. Orthop Clin North Am 1987;18:409-419. 6. Hawkins RJ, Belle RM. Posterior instability of the shoulder. Instr Course Lect 1989;38:211-215. 7. Hurley JA, Anderson TE, Dear W, Andrish JT, Bergfeld JA, Weiker GG. Posterior shoulder instability: Surgical versus conservative results with evaluation of glenoid version. Am J Sports Med 1992;20:396-400. 8. Fronek J, Warren RF, Bowen M. Posterior subluxations of the glenohumeral joint. J Bone Joint Surg Am 1989;71:205-216.
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9. Wolf EM, Eakin CL. Arthroscopic capsular plication for posterior shoulder instability. Arthroscopy 1998;14:153-163. 10. Bigliani LU, Pollock RG, McIlveen SJ, Endrizzi DP, Flatow EL. Shift of the posterior inferior aspect of the capsule for recurrent posterior glenohumeral instability. J Bone Joint Surg Am 1995;77:1011-1020. 11. Kim SH, Ha KI, Park JH, et al. Arthroscopic posterior labral repair and capsular shift for traumatic unidirectional recurrent posterior subluxation of the shoulder. J Bone Joint Surg Am 2003;85:1479-1487. 12. Neer CS II, Foster CR. Inferior capsular shift for involuntary inferior and multidirectional instability of the shoulder. A preliminary report. J Bone Joint Surg Am 1980;62:897908. 13. McIntyre LF, Caspari RB, Savoie FHS III. The arthroscopic treatment of posterior shoulder instability: Two-year results of a multiple suture technique. Arthroscopy 1997;13:426-432. 14. Mc Laughlin H. Posterior dislocation of the shoulder. J Bone Joint Surg Am 1952;34:584-590. 15. Neer CS. Surgical repair for recurrent posterior instability. In: Neer CS, ed. Shoulder reconstruction. Philadelphia: WB Saunders; 1990. 16. Pagnani MJ, Warren RF. Stabilizers of the glenohumeral joint. J Shoulder Elbow Surg 1994;3:173-190. 17. O’Brien SJ, Neeves MC, Arnoczky SP, Roebuck SR, DiCarlo EF, Warren RF. The anatomy and histology of the inferior glenohumeral ligament complex of the shoulder. Am J Sports Med 1990;18:449-456. 18. Weber SC, Caspari RB. A biomechanical evaluation of the restraints to posterior shoulder dislocation. Arthroscopy 1989; 5:115-121. 19. Caspari RB, Geissler WB. Arthroscopic manifestations of shoulder subluxations and dislocation. Clin Orthop Relat Res 1993;291:54-66. 20. Tibone JE, Bradley JP. The treatment of posterior subluxation in athletes. Clin Orthop Relat Res 1993;291:124-137. 21. Harryman DT, Sidles JA, Harris SL, Matsen FA III. The role of the rotator interval capsule in passive motion and stability of the shoulder. J Bone Joint Surg Am 1991;74:53-66. 22. Warren RF, Kornblatt IB, Marchand R. Static factors affecting posterior shoulder instability. Orthop Trans 1984;8:89. 23. Wolf RS, Zheng I, Weichel D. The effects of thermal capsulorrhaphy and rotator interval closure on multidirectional laxity in the glenohumeral joint: A cadaveric biomechanical study. Arthroscopy 2004;20:1044-1049. 24. Plausinis D, Bravman JT, Heywood C, Kummer FJ, Kwon YW, Jazrawi, LM. Arthroscopic rotator interval closure: Effect of sutures on glenohumeral motion and anterior– posterior translation. Am J Sports Med 2006;34:1656-1661. 25. Wirth M, Groh G, Rockwood CR. Capsulorrhaphy through an anterior approach for the treatment of atraumatic posterior glenohumeral instability with multidirectional laxity of the shoulder. J Bone Joint Surg Am 1998;80:1570-1578. 26. Papendick LW, Savoie FH III. Anatomy specific repair techniques for posterior shoulder instability. J South Orthop Assoc 1995;4:169-176. 27. Wolf BR, Strickland S, Williams RJ, Allen AA, Altchek DW, Warren RF. Open posterior stabilization for recurrent posterior glenohumeral instability. J Shoulder Elbow Surg 2005;14:157164. 28. Bottoni CR, Franks BR, Moore JH, DeBerardino TM, Taylor DC, Arciero RA. Operative stabilization of posterior shoulder instability. Am J Sports Med 2005;33:996-1002. 29. Provencher MT, Bell SJ, Manzel KA, Mologne TS. Arthroscopic treatment of posterior shoulder instability: Results in 33 patients. Am J Sports Med 2005;33:1463-1471.
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30. Bradley JP, Baker CL III, Kline AJ, Armfield DR, Chhabra A. Arthroscopic capsulolabral reconstruction for posterior instability of the shoulder: A prospective study of 100 shoulders. Am J Sports Med 2006;34:1061-1071. 31. Millett PJ, Clavert P, Hatch GF III, Warner JJ. Recurrent posterior shoulder instability. J Am Acad Orthop Surg 2006; 14:464-476.
32. Yamamoto N, Itoi E, Tuoheti Y, et al. Effects of rotator interval closure on glenohumeral stability and motion: A cadaveric study. J Shoulder Elbow Surg 2006;15:750-758. 33. Provencher MT, Mologne TS, Hongo M, Zhao K, Tasto JP, An KN. Arthroscopic versus open rotator interval closure: Biomechanical evaluation of stability and motion. Arthroscopy 2007; 23:583-592.
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