- Email: [email protected]
Consequences of a Perthes-Bankart lesion in twenty cadaver shoulders
Consequences of a Perthes-Bankart lesion in twenty cadaver shoulders Nicole Pouliart, MD, PhD,a,b and Olivier Gagey, MD, PhD,c,d Brussels, Belgium, and le Kremlin-Biceˆtre and Paris, France
This study investigated whether an anteroinferior capsulolabral lesion is sufficient to allow the humeral head to dislocate and whether a limited inferior approach for creating the lesions influenced the results compared with an all-arthroscopic approach. Four ligamentous zones of the glenohumeral capsule were sequentially detached from the glenoid neck and labrum in 20 cadaver shoulders through an inferior approach. Before and after each resection step, inferior stability was tested using a sulcus test and anterior stability using a drawer test and an apprehension maneuver. Dislocation was only possible when at least 3 zones were cut. This study confirmed that superior and posterior extension of the classic anteroinferior Perthes-Bankart lesion is necessary before the capsular restraint in external rotation and abduction is overcome and dislocation occurs. Lesions other than the Perthes-Bankart need to be investigated when recurrent dislocation is treated, because this anteroinferior injury is most probably not the sole factor responsible for the instability. (J Shoulder Elbow Surg 2008;17:981-985.)
Bankart2,3 was convinced that it was the single most important cause of recurrent dislocations. Several experimental studies have shown that capsulolabral lesions may alter glenohumeral kinematics and usually result in a slight increase in anterior translation but that this lesion in itself does not seem to result in gross instability.1,5,11,13,14,16,20,21,23,28,29,39-41 Most of these studies were done in a cadaver model after the muscular envelope was removed, which may itself influence stability. In addition, instability was usually defined as an increase in translation or in mobility, which does not necessarily equate to dislocatability. In a previous study,35 we showed that arthroscopically created anteroinferior capsulolabral— Bankart—lesions were not sufficient to allow dislocation, although translation was increased. The present study in an intact shoulder model was performed to test our hypothesis that open detachment of the capsuloligamentous complex from the glenoid and labrum needs to be as extensive to obtain dislocation.
Broca and Hartmann
Twenty fresh shoulders from deceased donors, aged 81 to 103 years, were studied. Shoulders were discarded when they showed signs of previous surgery or if they did not reach 90 of glenohumeral abduction with 90 of external rotation before any dissection was done. At the end of each testing procedure, specimens were dissected further and inspected for additional lesions. When osteophytes, rotator cuff tears, biceps lesions, or other problems were observed, the results from those specimens were eliminated as well. If the cuff appeared degenerative, but still intact, the specimen was retained. All eligible shoulders underwent the testing protocol outlined in detail previously.31-35 In summary, the glenohumeral capsule was cut on the glenoid side through an axillary approach by sharply dividing it from the glenoid neck and labrum. Because the subscapularis and triceps tendons interfere with the releases, the sequential cutting sequence (Figure 1) was started in either the zone containing the anterior part of the inferior glenohumeral ligament (GHL) or in that with the middle GHL. Care was taken to divide the capsule from the glenoid neck as closely as possible to the labrum, even when this resulted in slight tangential damage to the labrum itself. In general, however, this could be avoided by continuing the incision made in the first zone under direct intraarticular
7,8
were the first to describe a subperiosteal, anteroinferior dislocation of the shoulder. Recently, this type of capsular lesion was termed an ‘‘anterior labral periosteal sleeve avulsion’’ by Neviaser.27 The other and most common type of lesion is an anteroinferior detachment of labrum and capsule, usually associated with a capsular tear or elongation. Although this pattern was originally described by Perthes,30 it is known as a Bankart lesion because
From the aDepartment of Orthopaedics and Traumatology, Universitair Ziekenhuis Brussel, bDepartment of Human Anatomy, Vrije ˆ pital Universiteit Brussel, Brussels; and cService d’orthope´die, Ho Biceˆtre, Universite´ Paris-Sud, le Kremlin-Biceˆtre, and dInstitut d’Anatomie, Paris. Reprint requests: Nicole Pouliart, Universitair Ziekenhuis Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium (E-mail: nicole. [email protected]). Copyright ª 2008 by Journal of Shoulder and Elbow Surgery Board of Trustees. 1058-2746/2008/$34.00 doi:10.1016/j.jse.2008.03.005
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FET2, Hoggan Health Industries, Biometrics EuropeBV, Almere, The Netherlands). The humerus was positioned in 0 to 30 of abduction with neutral rotation (drawer test) or in 90 of abduction with 90 of external rotation (loadand-shift test) to evaluate straight anterior and anteroinferior stability. The limitation of the applied forces was chosen from data in the literature to avoid producing lesions to the soft tissues other than those that were purposefully created. If additional tearing did occur, the specimen was discarded from the results. (This happened twice in the beginning of our protocol, especially when we created lesions on the humeral side, which is not the subject of this article.) Inferior stability was evaluated with a sulcus test in neutral rotation and 0 of abduction. The amount of anterior, medial, and inferior translation due to the applied forces was recorded with the Flock of Birds electromagnetic tracking device (Ascension Technology, Burlington, VT). These values were then used for grading on a scale of 5. This expanded scale of instability includes:
Figure 1 Schematic representation shows the capsulolabral zones that were cut along the glenoid rim and labrum. The superior zone includes superior glenohumeral (SG) ligament from the 11 to 1 o’clock position; care was taken to maintain the biceps anchor intact. The anterosuperior zone includes the middle glenohumeral (MG) ligament from the 1 to 3 o’clock position. The anteroinferior zone includes the anterior band (AB) of the inferior glenohumeral ligament from 3 to 5 o’clock. The posteroinferior zone includes the axillary pouch and posterior band (PB) of the inferior glenohumeral ligament from the 5 to 8 o’clock position. The posterior (P) capsular zone is from the 8 to 11 o’clock position.
visualization. The superior zone, with the superior GHL, could only be reached after cutting the middle zone. While rotating the humerus and reflecting the subscapularis with the attached underlying capsule, it was possible to view the superior part of the capsule and the biceps anchor. This allowed continuing the division of the capsule upward medial to the biceps tendon, so that its anchor remained intact. The superior cut was continued to the 11 o’clock position (for a right shoulder). The posteroinferior zone, with the posterior band of the inferior GHL, could only be reached after the anteroinferior zone was cut. Again, rotation, abduction, and distraction allowed good intraarticular visualization of the posteroinferior capsule with demarcation of the superior edge of the posterior part. Various combinations of adjacent zones were resected to study more extensive lesions than an anteroinferior Bankart lesion. (Table I). The specimens were mounted in a custommade jig. An axial loading force was applied through the elbow and then an anteriorly directed maximal translation force of 50 N was applied to the posterior side of the shoulder with the pusher of a handheld dynamometer (Micro-
grade 0: no translation; grade 1: increased drawer of less than 10 mm; grade 2: subluxation over the glenoid rim; grade 3: reducible dislocation, defined as spontaneous reduction of the dislocation after returning the arm to the resting position, and grade 4: locked dislocation, defined as no spontaneous reduction, reduction only with a reduction maneuver.25,31-36
Statistical analysis The sample size needed for a power of 80% with a ¼ 0.05, supposing that a difference of 1 in the amount of zones cut resulted in a mean difference of 1 grade in the dislocation scale with a standard deviation of half a grade, was estimated at 14. This estimate is only valid for differences among the number of zones resected; therefore, comparisons when grouping per sequence will not reach sufficient power because there are 5 or maximally 10 specimens per sequence. We finally used 20 specimens so that each final sequence included 5 specimens. Because the grading variables are ordered, categoric, nonparametric tests were used for statistical analysis. The Spearman r was used for correlation analysis and the Pearson c2 test was used to evaluate stratification according to the amount of the resected zones. Analysis was done with SPSS 13.0 software (SPSS Belux, Brussels, Belgium). One-way analysis of variance (ANOVA) was used to compare the results from the testing protocol in the specimens of this study, where Perthes-Bankart lesions were created through a limited open inferior approach, with those specimens from a previous study,35 where the same lesions were created arthroscopically.
RESULTS After 1 zone was cut, all 20 specimens had grade 1 instability in the load-and-shift test. With the combination of the middle and anteroinferior zone, grade 2 anteroinferior instability was observed in 10 of 15
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Table I Overview of capsulolabral sequences 1 zone resected
No. of specimens
2 zones resected
No. of specimens
3 zones resected
No. of specimens
4 zones resected
No. of specimens
Posterior zone, No.
AB-PB-MG AB-MG-SG AB-MG-PB MG-AB-SG
5 5 5 5 20
AB-PB-MG-SG AB-MG-SG-PB AB-MG-PB-SG MG-AB-SG-PB
5 5 5 5 20
2 1 0 1 4
AB
15
AB-PB AB-MG
5 10
MG Total
5 20
MG-AB
5 20
AB, Anterior band (anteroinferior zone); MG, middle glenohumeral ligament (anterosuperior zone); PB, posterior band (posteroinferior zone); SG, superior glenohumeral (superior zone).
specimens. The other 10 specimens remained at grade 1 instability. After 3 zones were cut, grade 2 subluxation developed in half of the specimens in the load-and-shift test, and the other half had a reducible dislocation (grade 3). After all 4 ligamentous zones were cut, 16 specimens had a locked dislocation, whereas 4 shoulders only had a reducible dislocation. These 4 only had a locked dislocation when the posterior capsule was also cut. In adduction and neutral rotation (drawer test), 3 specimens demonstrated a grade 2 drawer sign without any ligamentous cut. Twelve shoulders had at least grade 2 (subluxation) after 2 zones were cut and 17 after all 4 zones were cut. Without any ligamentous cut, 9 shoulders had no sulcus sign and 11 had grade 1. Only 2 shoulders still had no sulcus sign after 1 zone was cut, but 15 shoulders had a grade 2 sulcus sign after 3 zones were cut. The tested variables showed a statistically significant high to very high correlation with one another in the Spearman correlation test (Table II). The differences in the degree of instability in the load-and-shift test, in the degree of drawer sign, and in the degree of sulcus sign for the different number of zones cut were significant (Pearson c2, P < .001). One-way ANOVA revealed that the differences in the degree of instability, the degree of sulcus sign, and the degree of drawer sign resulting from lesions created through a limited open inferior approach were not statistically significantly different from the results for the same lesions created arthroscopically. This was the case for all results combined, as well as when stratifying for the number of zones cut. The open group allowed the determination that the posterior capsule and the anchorage of the inferior capsule on the long tendon of the triceps played an important role in those specimens that did not reach grade 4 instability after the classic 4 ligamentous zones were cut.
DISCUSSION The primary goal of this study was to verify that creating glenoid-sided capsuloligamentous lesions
Table II Overview of Spearman r c orrelation coefficients for correlation between the listed variables (P < .001)
Variable
No. of zones cut
Load-and-shift test Drawer sign Sulcus sign
0.943 0.577 0.711
Sulcus sign Drawer sign 0.655 0.581
0.597
through a limited open axillary approach was equivalent to creating these lesions arthroscopically. The same extent of cuts needed to be done to reach the same degree of anteroinferior instability in both models. Therefore, both models can reliably be used to simulate capsuloligamentous lesions on the glenoid side for further biomechanical studies. The results from the other 2 stability tests, the sulcus sign and anterior drawer test, illustrate that increased translation is not a good measure for instability. If one wants to evaluate the risk of a specific lesion to result in recurrent dislocation, the destabilizing effect of the lesion should preferably always be tested in the apprehension position, because this is the position at risk. From a clinical point of view, the present study confirms that an isolated anteroinferior capsulolabral lesion results in increased translation, even up to subluxation of the humeral head, but that this is not sufficient to allow the humeral head to dislocate. Experimentally, for a dislocation that reduces spontaneously (grade 3), 3 ligamentous zones had to be damaged, whereas a locked dislocation required all 4 zones to be cut. In some instances, grade 4 instability only occurred after the posterior zone was cut as well. This type of experimental study, of course, does not truly simulate acute, let alone recurrent, shoulder dislocation because capsuloligamentous stretching and elongation are not taken into account. Therefore, the results of this study should be extrapolated to the clinical situation with the necessary precautions. The limitations and advantages of the present experimental setup have extensively been discussed elsewhere.31-35 Nevertheless, the present study is corroborated by many clinical series of patients with fresh, as well as
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recurrent dislocations, where associated or extended lesions appear in a high percentage of these patients. Mizuno et al24 even found a concomitant posterior extension into the axillary region in 82% of their patients. This corresponds with the need for posterior extension of the cuts to obtain a grade 4 dislocation in some of our specimens. In a survey of several series, 8% to 46% of shoulders did not have a Bankart lesion.6,9,12,15,17,18,22,38,43,44 The extensive lesions required in our model may translate into damage to the ligaments at another level—elongation or midsubstance tears,10,17,18,43 as well as associated humeral avulsion6—or into damage of other stabilizing structures, mainly glenoid osseous defects10,17,18,43 or rotator cuff tears.4,10,17-19,26,37,42,43 Conversely, the simple reattachment of a Bankart lesion to the glenoid rim without an associated capsular shift may often not be enough to restabilize the glenohumeral joint. When obvious capsulolabral damage is observed only in the 3 to 6 o’clock glenoid position (for a right shoulder), capsular elongation should be suspected and repaired. Although our experimental protocol did not result in lesions of the biceps tendon, the higher grades of superior labrum anteroposterior lesions may form alternative lesions leading to instability. On the other hand, articular-sided partial rotator cuff tears may actually represent a lesion to the superior glenohumeral ligament and not necessarily a true cuff tear. Rotator cuff interval lesions may be another form of capsular damage that is comparable with elongation. In conclusion, this study shows that a limited open inferior approach maintains the integrity of the surrounding soft-tissue envelope in such a way that the experimental model remains as valid as when lesions are created arthroscopically. This study also indicates that an isolated, typical Perthes-Bankart lesion does not compromise the anterior capsular mechanism enough for the humeral head to dislocate anteroinferiorly. In patients with acute or recurrent dislocation, more extensive ligamentous or other lesions—be it glenoid rim fractures or rotator cuff tears—need to be present. This study again stresses the importance of looking for, and dealing with, other lesions than the most obvious one when treating unstable shoulders. REFERENCES
1. Apreleva M, Hasselman CT, Debski RE, Fu FH, Woo SL, Warner JJ. A dynamic analysis of glenohumeral motion after simulated capsulolabral injury. A cadaver model. J Bone Joint Surg Am 1998;80:474-80. 2. Bankart ASB. Recurrent or habitual dislocation of the shoulder joint. Br Med J 1923;2:1132-3. 3. Bankart ASB. The pathology and treatment of recurrent dislocation of the shoulder joint. Br J Surg 1938;26:23-9. 4. Berbig R, Weishaupt D, Prim J, Shahin O. Primary anterior shoulder dislocation and rotator cuff tears. J Shoulder Elbow Surg 1999;8: 220-5.
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5. Black KP, Schneider DJ, Yu JR, Jacobs CR. Biomechanics of the Bankart repair: the relationship between glenohumeral translation and labral fixation site. Am J Sports Med 1999;27:339-44. 6. Bokor DJ, Conboy VB, Olson C. Anterior instability of the glenohumeral joint with humeral avulsion of the glenohumeral ligament. A review of 41 cases. J Bone Joint Surg Br 1999;81:93-6. 7. Broca A, Hartmann H. Contribution a l’e´tude des luxations d’e´paule (luxations anciennes, luxations re´cidivantes). Bull Soc Anat 1890:416-23. 8. Broca A, Hartmann H. Contribution a l’e´tude des luxations d’e´paule (luxations dites incomplctes, de´collements pe´riostiques, luxations directes et luxations indirectes). Bull Soc Anat 1890:312-36. 9. Coughlin L, Rubinovich M, Johansson J, White B, Greenspoon J. Arthroscopic staple capsulorrhaphy for anterior shoulder instability. Am J Sports Med 1992;20:253-6. 10. Detrisac D, Johnson LL. Arthroscopic shoulder anatomy. Pathological and surgical implications. Thorofare, NJ: Slack; 1986. 11. Fehringer EV, Schmidt GR, Boorman RS, et al. The anteroinferior labrum helps center the humeral head on the glenoid. J Shoulder Elbow Surg 2003;12:53-8. 12. Gerber C, Terrier F, Ganz R. The Trillat procedure for recurrent anterior instability of the shoulder. J Bone Joint Surg Br 1988;70: 130-4. 13. Gohlke FE, Barthel T, Daum P. Influence of T-shift capsulorraphy on rotation and translation of the glenohumeral joint: an experimental study. J Shoulder Elbow Surg 1994;3:361-70. 14. Greis PE, Scuderi MG, Mohr A, Bachus KN, Burks RT. Glenohumeral articular contact areas and pressures following labral and osseous injury to the anteroinferior quadrant of the glenoid. J Shoulder Elbow Surg 2002;11:442-51. 15. Habermeyer P, Gleyze P, Rickert M. Evolution of lesions of the labrum-ligament complex in posttraumatic anterior shoulder instability: a prospective study. J Shoulder Elbow Surg 1999;8:66-74. 16. Harryman Dt 2d, Ballmer FP, Harris SL, Sidles JA. Arthroscopic labral repair to the glenoid rim. Arthroscopy 1994;10:20-30. 17. Hintermann B, Ga¨chter A. Arthroscopic findings after shoulder dislocation. Am J Sports Med 1995;23:545-51. 18. Hintermann B, Ga¨chter A. Theo van Rens Prize. Arthroscopic assessment of the unstable shoulder. Knee Surg Sports Traumatol Arthrosc 1994;2:64-9. 19. Hsu HC, Boardman ND 3rd, Luo ZP, An KN. Tendon-Defect and muscle-unloaded models for relating a rotator cuff tear to glenohumeral stability. J Orthop Res 2000;18:952-8. 20. Itoi E, Lee SB, Berglund LJ, Berge LL, An KN. The effect of a glenoid defect on anteroinferior stability of the shoulder after Bankart repair: a cadaveric study. J Bone Joint Surg Am 2000;82:35-46. 21. Klein AH, Harner CD, Fu FH. The Bankart lesion of the shoulder: a biomechanical analysis following repair. Knee Surg Sports Traumatol Arthrosc 1995;3:117-20. 22. Kohn D. The clinical relevance of glenoid labrum lesions. Arthroscopy 1987;3:223-30. 23. Kuhn JE, Bey MJ, Huston LJ, Blasier RB, Soslowsky LJ. Ligamentous restraints to external rotation of the humerus in the late- cocking phase of throwing. A cadaveric biomechanical investigation. Am J Sports Med 2000;28:200-5. 24. Mizuno K, Nabeshima Y, Hirohata K. Analysis of Bankart lesion in the recurrent dislocation or subluxation of the shoulder. Clin Orthop 1993;288:158-65. 25. Molina V, Pouliart N, Gagey O. Quantitation of ligament laxity in anterior shoulder instability: an experimental cadaver model. Surg Radiol Anat 2004;26:349-54. 26. Neviaser RJ, Neviaser TJ. Recurrent instability of the shoulder after age 40. J Shoulder Elbow Surg 1995;4:416-8. 27. Neviaser TJ. The anterior labroligamentous periosteal sleeve avulsion lesion: a cause of anterior instability of the shoulder. Arthroscopy 1993;9:17-21.
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28. Novotny JE, Nichols CE, Beynnon BD. Kinematics of the glenohumeral joint with Bankart lesion and repair. J Orthop Res 1998;16: 116-21. 29. O’Brien SJ, Schwartz RS, Warren RF, Torzilli PA. Capsular restraints to anterior-posterior motion of the abducted shoulder: a biomechanical study. J Shoulder Elbow Surg 1995;4:298-308. 30. Perthes G. Operationen bei habitueller Schulterluxation. Deutsch Ztschr Chir 1906;85:199-207. 31. Pouliart N, Gagey O. Significance of the latissimus dorsi for shoulder instability. II. Its influence on dislocation behavior in a sequential cutting protocol of the glenohumeral capsule. Clin Anat 2005; 18:500-9. 32. Pouliart N, Gagey O. The effect of isolated labrum resection on shoulder stability. Knee Surg Sports Traumatol Arthrosc 2006; 14:301-8. 33. Pouliart N, Gagey O. Concomitant rotator cuff and capsuloligamentous lesions of the shoulder: a cadaver study. Arthroscopy 2006;22:728-35. 34. Pouliart N, Gagey O. Simulated humeral avulsion of the glenohumeral ligaments: a new instability model. J Shoulder Elbow Surg 2006;15:728-35. 35. Pouliart N, Marmor S, Gagey O. Simulated capsulolabral lesion in cadavers: dislocation does not result from a bankart lesion only. Arthroscopy 2006;22:748-54.
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36. Richards RR, An KN, Bigliani LU. A standardized method for the assessment of shoulder function. J Shoulder Elbow Surg 1994;3: 347-52. 37. Robinson CM, Kelly M, Wakefield AE. Redislocation of the shoulder during the first six weeks after a primary anterior dislocation: risk factors and results of treatment. J Bone Joint Surg Am 2002; 84:1552-9. 38. Rowe CR, Patel D, Southmayd WW. The Bankart procedure: a long-term end-result study. J Bone Joint Surg Am 1978;60:1-16. 39. Sciaroni LN, McMahon PJ, Cheung TG, Lee TQ. Open surgical repair restores joint forces that resist glenohumeral dislocation. Clin Orthop 2002;400:58-64. 40. Speer KP, Deng X, Borrero S, Torzilli PA, Altchek DA, Warren RF. Biomechanical evaluation of a simulated Bankart lesion. J Bone Joint Surg Am 1994;76:1819-26. 41. Speer KP, Deng X, Torzilli PA, Altchek DA, Warren RF. Strategies for an anterior capsular shift of the shoulder. A biomechanical comparison. Am J Sports Med 1995;23:264-9. 42. Stayner LR, Cummings J, Andersen J, Jobe CM. Shoulder dislocations in patients older than 40 years of age. Orthop Clin North Am 2000;31:231-9. 43. Torchia ME, Caspari RB, Asselmeier MA, Beach WR, Gayari M. Arthroscopic transglenoid multiple suture repair: 2 to 8 year results in 150 shoulders. Arthroscopy 1997;13:609-19. 44. Townley C. The capsular mechanism in recurrent dislocation of the shoulder. J Bone Joint Surg Am 1950;32:370-80.
This study investigated whether an anteroinferior capsulolabral lesion is sufficient to allow the humeral head to dislocate and whether a limited inferior approach for creating the lesions influenced the results compared with an all-arthroscopic approach. Four ligamentous zones of the glenohumeral capsule were sequentially detached from the glenoid neck and labrum in 20 cadaver shoulders through an inferior approach. Before and after each resection step, inferior stability was tested using a sulcus test and anterior stability using a drawer test and an apprehension maneuver. Dislocation was only possible when at least 3 zones were cut. This study confirmed that superior and posterior extension of the classic anteroinferior Perthes-Bankart lesion is necessary before the capsular restraint in external rotation and abduction is overcome and dislocation occurs. Lesions other than the Perthes-Bankart need to be investigated when recurrent dislocation is treated, because this anteroinferior injury is most probably not the sole factor responsible for the instability. (J Shoulder Elbow Surg 2008;17:981-985.)
Bankart2,3 was convinced that it was the single most important cause of recurrent dislocations. Several experimental studies have shown that capsulolabral lesions may alter glenohumeral kinematics and usually result in a slight increase in anterior translation but that this lesion in itself does not seem to result in gross instability.1,5,11,13,14,16,20,21,23,28,29,39-41 Most of these studies were done in a cadaver model after the muscular envelope was removed, which may itself influence stability. In addition, instability was usually defined as an increase in translation or in mobility, which does not necessarily equate to dislocatability. In a previous study,35 we showed that arthroscopically created anteroinferior capsulolabral— Bankart—lesions were not sufficient to allow dislocation, although translation was increased. The present study in an intact shoulder model was performed to test our hypothesis that open detachment of the capsuloligamentous complex from the glenoid and labrum needs to be as extensive to obtain dislocation.
Broca and Hartmann
Twenty fresh shoulders from deceased donors, aged 81 to 103 years, were studied. Shoulders were discarded when they showed signs of previous surgery or if they did not reach 90 of glenohumeral abduction with 90 of external rotation before any dissection was done. At the end of each testing procedure, specimens were dissected further and inspected for additional lesions. When osteophytes, rotator cuff tears, biceps lesions, or other problems were observed, the results from those specimens were eliminated as well. If the cuff appeared degenerative, but still intact, the specimen was retained. All eligible shoulders underwent the testing protocol outlined in detail previously.31-35 In summary, the glenohumeral capsule was cut on the glenoid side through an axillary approach by sharply dividing it from the glenoid neck and labrum. Because the subscapularis and triceps tendons interfere with the releases, the sequential cutting sequence (Figure 1) was started in either the zone containing the anterior part of the inferior glenohumeral ligament (GHL) or in that with the middle GHL. Care was taken to divide the capsule from the glenoid neck as closely as possible to the labrum, even when this resulted in slight tangential damage to the labrum itself. In general, however, this could be avoided by continuing the incision made in the first zone under direct intraarticular
7,8
were the first to describe a subperiosteal, anteroinferior dislocation of the shoulder. Recently, this type of capsular lesion was termed an ‘‘anterior labral periosteal sleeve avulsion’’ by Neviaser.27 The other and most common type of lesion is an anteroinferior detachment of labrum and capsule, usually associated with a capsular tear or elongation. Although this pattern was originally described by Perthes,30 it is known as a Bankart lesion because
From the aDepartment of Orthopaedics and Traumatology, Universitair Ziekenhuis Brussel, bDepartment of Human Anatomy, Vrije ˆ pital Universiteit Brussel, Brussels; and cService d’orthope´die, Ho Biceˆtre, Universite´ Paris-Sud, le Kremlin-Biceˆtre, and dInstitut d’Anatomie, Paris. Reprint requests: Nicole Pouliart, Universitair Ziekenhuis Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium (E-mail: nicole. [email protected]). Copyright ª 2008 by Journal of Shoulder and Elbow Surgery Board of Trustees. 1058-2746/2008/$34.00 doi:10.1016/j.jse.2008.03.005
MATERIAL AND METHODS
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FET2, Hoggan Health Industries, Biometrics EuropeBV, Almere, The Netherlands). The humerus was positioned in 0 to 30 of abduction with neutral rotation (drawer test) or in 90 of abduction with 90 of external rotation (loadand-shift test) to evaluate straight anterior and anteroinferior stability. The limitation of the applied forces was chosen from data in the literature to avoid producing lesions to the soft tissues other than those that were purposefully created. If additional tearing did occur, the specimen was discarded from the results. (This happened twice in the beginning of our protocol, especially when we created lesions on the humeral side, which is not the subject of this article.) Inferior stability was evaluated with a sulcus test in neutral rotation and 0 of abduction. The amount of anterior, medial, and inferior translation due to the applied forces was recorded with the Flock of Birds electromagnetic tracking device (Ascension Technology, Burlington, VT). These values were then used for grading on a scale of 5. This expanded scale of instability includes:
Figure 1 Schematic representation shows the capsulolabral zones that were cut along the glenoid rim and labrum. The superior zone includes superior glenohumeral (SG) ligament from the 11 to 1 o’clock position; care was taken to maintain the biceps anchor intact. The anterosuperior zone includes the middle glenohumeral (MG) ligament from the 1 to 3 o’clock position. The anteroinferior zone includes the anterior band (AB) of the inferior glenohumeral ligament from 3 to 5 o’clock. The posteroinferior zone includes the axillary pouch and posterior band (PB) of the inferior glenohumeral ligament from the 5 to 8 o’clock position. The posterior (P) capsular zone is from the 8 to 11 o’clock position.
visualization. The superior zone, with the superior GHL, could only be reached after cutting the middle zone. While rotating the humerus and reflecting the subscapularis with the attached underlying capsule, it was possible to view the superior part of the capsule and the biceps anchor. This allowed continuing the division of the capsule upward medial to the biceps tendon, so that its anchor remained intact. The superior cut was continued to the 11 o’clock position (for a right shoulder). The posteroinferior zone, with the posterior band of the inferior GHL, could only be reached after the anteroinferior zone was cut. Again, rotation, abduction, and distraction allowed good intraarticular visualization of the posteroinferior capsule with demarcation of the superior edge of the posterior part. Various combinations of adjacent zones were resected to study more extensive lesions than an anteroinferior Bankart lesion. (Table I). The specimens were mounted in a custommade jig. An axial loading force was applied through the elbow and then an anteriorly directed maximal translation force of 50 N was applied to the posterior side of the shoulder with the pusher of a handheld dynamometer (Micro-
grade 0: no translation; grade 1: increased drawer of less than 10 mm; grade 2: subluxation over the glenoid rim; grade 3: reducible dislocation, defined as spontaneous reduction of the dislocation after returning the arm to the resting position, and grade 4: locked dislocation, defined as no spontaneous reduction, reduction only with a reduction maneuver.25,31-36
Statistical analysis The sample size needed for a power of 80% with a ¼ 0.05, supposing that a difference of 1 in the amount of zones cut resulted in a mean difference of 1 grade in the dislocation scale with a standard deviation of half a grade, was estimated at 14. This estimate is only valid for differences among the number of zones resected; therefore, comparisons when grouping per sequence will not reach sufficient power because there are 5 or maximally 10 specimens per sequence. We finally used 20 specimens so that each final sequence included 5 specimens. Because the grading variables are ordered, categoric, nonparametric tests were used for statistical analysis. The Spearman r was used for correlation analysis and the Pearson c2 test was used to evaluate stratification according to the amount of the resected zones. Analysis was done with SPSS 13.0 software (SPSS Belux, Brussels, Belgium). One-way analysis of variance (ANOVA) was used to compare the results from the testing protocol in the specimens of this study, where Perthes-Bankart lesions were created through a limited open inferior approach, with those specimens from a previous study,35 where the same lesions were created arthroscopically.
RESULTS After 1 zone was cut, all 20 specimens had grade 1 instability in the load-and-shift test. With the combination of the middle and anteroinferior zone, grade 2 anteroinferior instability was observed in 10 of 15
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Table I Overview of capsulolabral sequences 1 zone resected
No. of specimens
2 zones resected
No. of specimens
3 zones resected
No. of specimens
4 zones resected
No. of specimens
Posterior zone, No.
AB-PB-MG AB-MG-SG AB-MG-PB MG-AB-SG
5 5 5 5 20
AB-PB-MG-SG AB-MG-SG-PB AB-MG-PB-SG MG-AB-SG-PB
5 5 5 5 20
2 1 0 1 4
AB
15
AB-PB AB-MG
5 10
MG Total
5 20
MG-AB
5 20
AB, Anterior band (anteroinferior zone); MG, middle glenohumeral ligament (anterosuperior zone); PB, posterior band (posteroinferior zone); SG, superior glenohumeral (superior zone).
specimens. The other 10 specimens remained at grade 1 instability. After 3 zones were cut, grade 2 subluxation developed in half of the specimens in the load-and-shift test, and the other half had a reducible dislocation (grade 3). After all 4 ligamentous zones were cut, 16 specimens had a locked dislocation, whereas 4 shoulders only had a reducible dislocation. These 4 only had a locked dislocation when the posterior capsule was also cut. In adduction and neutral rotation (drawer test), 3 specimens demonstrated a grade 2 drawer sign without any ligamentous cut. Twelve shoulders had at least grade 2 (subluxation) after 2 zones were cut and 17 after all 4 zones were cut. Without any ligamentous cut, 9 shoulders had no sulcus sign and 11 had grade 1. Only 2 shoulders still had no sulcus sign after 1 zone was cut, but 15 shoulders had a grade 2 sulcus sign after 3 zones were cut. The tested variables showed a statistically significant high to very high correlation with one another in the Spearman correlation test (Table II). The differences in the degree of instability in the load-and-shift test, in the degree of drawer sign, and in the degree of sulcus sign for the different number of zones cut were significant (Pearson c2, P < .001). One-way ANOVA revealed that the differences in the degree of instability, the degree of sulcus sign, and the degree of drawer sign resulting from lesions created through a limited open inferior approach were not statistically significantly different from the results for the same lesions created arthroscopically. This was the case for all results combined, as well as when stratifying for the number of zones cut. The open group allowed the determination that the posterior capsule and the anchorage of the inferior capsule on the long tendon of the triceps played an important role in those specimens that did not reach grade 4 instability after the classic 4 ligamentous zones were cut.
DISCUSSION The primary goal of this study was to verify that creating glenoid-sided capsuloligamentous lesions
Table II Overview of Spearman r c orrelation coefficients for correlation between the listed variables (P < .001)
Variable
No. of zones cut
Load-and-shift test Drawer sign Sulcus sign
0.943 0.577 0.711
Sulcus sign Drawer sign 0.655 0.581
0.597
through a limited open axillary approach was equivalent to creating these lesions arthroscopically. The same extent of cuts needed to be done to reach the same degree of anteroinferior instability in both models. Therefore, both models can reliably be used to simulate capsuloligamentous lesions on the glenoid side for further biomechanical studies. The results from the other 2 stability tests, the sulcus sign and anterior drawer test, illustrate that increased translation is not a good measure for instability. If one wants to evaluate the risk of a specific lesion to result in recurrent dislocation, the destabilizing effect of the lesion should preferably always be tested in the apprehension position, because this is the position at risk. From a clinical point of view, the present study confirms that an isolated anteroinferior capsulolabral lesion results in increased translation, even up to subluxation of the humeral head, but that this is not sufficient to allow the humeral head to dislocate. Experimentally, for a dislocation that reduces spontaneously (grade 3), 3 ligamentous zones had to be damaged, whereas a locked dislocation required all 4 zones to be cut. In some instances, grade 4 instability only occurred after the posterior zone was cut as well. This type of experimental study, of course, does not truly simulate acute, let alone recurrent, shoulder dislocation because capsuloligamentous stretching and elongation are not taken into account. Therefore, the results of this study should be extrapolated to the clinical situation with the necessary precautions. The limitations and advantages of the present experimental setup have extensively been discussed elsewhere.31-35 Nevertheless, the present study is corroborated by many clinical series of patients with fresh, as well as
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recurrent dislocations, where associated or extended lesions appear in a high percentage of these patients. Mizuno et al24 even found a concomitant posterior extension into the axillary region in 82% of their patients. This corresponds with the need for posterior extension of the cuts to obtain a grade 4 dislocation in some of our specimens. In a survey of several series, 8% to 46% of shoulders did not have a Bankart lesion.6,9,12,15,17,18,22,38,43,44 The extensive lesions required in our model may translate into damage to the ligaments at another level—elongation or midsubstance tears,10,17,18,43 as well as associated humeral avulsion6—or into damage of other stabilizing structures, mainly glenoid osseous defects10,17,18,43 or rotator cuff tears.4,10,17-19,26,37,42,43 Conversely, the simple reattachment of a Bankart lesion to the glenoid rim without an associated capsular shift may often not be enough to restabilize the glenohumeral joint. When obvious capsulolabral damage is observed only in the 3 to 6 o’clock glenoid position (for a right shoulder), capsular elongation should be suspected and repaired. Although our experimental protocol did not result in lesions of the biceps tendon, the higher grades of superior labrum anteroposterior lesions may form alternative lesions leading to instability. On the other hand, articular-sided partial rotator cuff tears may actually represent a lesion to the superior glenohumeral ligament and not necessarily a true cuff tear. Rotator cuff interval lesions may be another form of capsular damage that is comparable with elongation. In conclusion, this study shows that a limited open inferior approach maintains the integrity of the surrounding soft-tissue envelope in such a way that the experimental model remains as valid as when lesions are created arthroscopically. This study also indicates that an isolated, typical Perthes-Bankart lesion does not compromise the anterior capsular mechanism enough for the humeral head to dislocate anteroinferiorly. In patients with acute or recurrent dislocation, more extensive ligamentous or other lesions—be it glenoid rim fractures or rotator cuff tears—need to be present. This study again stresses the importance of looking for, and dealing with, other lesions than the most obvious one when treating unstable shoulders. REFERENCES
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