Predicting the degree of anterior stability of the shoulder after traumatic anterior shoulder dislocation or subluxation in young highly active men

Yoshitaka Tanaka, Kenji Okamura,Tomohito Imai, Masatoshi Amakao, Ryuji Koga, Shigekazu Watanabe

Department of Orthopaedic Surgery, Japan Self Defense Force, Sapporo General Hospital. Hiragishi.

Address for Correspondence:
Yoshitaka Tanaka
Department of Orthopaedic Surgery
Japan Self Defense Force, Sapporo General Hospital
Hiragishi 1-12-1-32, Toyohira-ku, Sapporo 062-8610, Japan.
Phone:  81-11-831-0162
Fax    :  81-11-831-1015
E-mail: yoshi1869@paw.hi-ho.ne.jp

Abstract:
Purpose: The anterior drawer test is used to evaluate the degree of anterior translation of the shoulder. However, it is difficult to perform it, when the patient’s relaxation is not achieved. Thus, we evaluated the findings of arthroscopy and computed tomographic arthrography in young, highly active men with traumatic anterior shoulder dislocation or subluxation to determine the objective factors that can predict the degree of anterior translation regardless of the patient’s relaxation.
Methods: A total of 65 patients 67 shoulders were enrolled in this study. On the basis of the degree of anterior translation of the shoulder, which was evaluated with the patients under anaesthesia, we divided the patients with limited shoulder movement into 2 groups: stable and unstable groups. There were 8 patients (8 shoulders) in the stable group and 57 patients (59 shoulders) in the unstable group. We compared the findings of arthroscopy and computed tomographic arthrography between the stable and unstable groups.
Results: In the univariate analysis, capsular insertion type and condition of the anterior band of the inferior glenohumeral ligament were associated with excessive anterior translation (p < 0.001). However, logistic regression analysis revealed capsular insertion type to be the strongest factor of excessive anterior translation of the shoulder (p = 0.012).
Conclusion: Evaluation of capsular insertion type on computed tomographic arthrography after shoulder subluxation or dislocation is a useful method to predict excessive anterior translation of the shoulder.

J.Orthopaedics 2009;6(3)e5

Keywords:

Shoulder; Anterior translation; Dislocation; Young men; Computed tomographic arthrography; Arthroscopy

Introduction:

Young men are prone to the risk of the recurrence of initial traumatic anterior shoulder dislocation.^{1, 2}  Anterior instability of the shoulder is usually evaluated by manual tests such as apprehension test, relocation test, and anterior drawer test.³ Anterior drawer test is considered to be useful in confirming the subluxated or dislocated shoulder, but it is difficult when the patient’s relaxation is not achieved because of shoulder pain. Therefore, it was recommended to be performed under anaesthesia (EUA)⁴, but it is difficult on outpatient basis. Other methods that can confirm the subluxated or dislocated shoulder on outpatient basis reliably equivalent to EUA are required. Some clinicians have attempted to identify the factors of the anterior stability of the shoulder from the objective findings of X-ray, magnetic resonance imaging or computed tomographic arthrography (CTA) and considered fracture of the greater tuberosity (Hill-Sachs lesion) or anterior glenoid rim (bony Bankart lesion) as a risk factor for redislocation.^2,5 

Structures such as the anterior labrum, anterior band of the inferior glenohumeral ligament (AIGHL), and rotator cuff are also considered important for the anterior stability of the shoulder.^6–11  Further, in some studies, capsular insertion type has been considered to enhance the anterior stability of the shoulder.^8,12  However, no studies appear to have investigated the factors of anterior translation of the shoulder in young men with traumatic anterior shoulder dislocation. Therefore, this study aimed to investigate the objective factors that could predict the degree of anterior translation reliably equivalent to EUA in young men with anterior shoulder dislocation or subluxation by the findings of arthroscopy and CTA.

Materials and Methods:

Between April 2000 and February 2008, we performed arthroscopic or open Bankart repair and the Bristow procedure in 91 patients (93 shoulders) with anterior shoulder dislocation or subluxation at our institution. We reviewed their information charts and surgical records, and enrolled 70 patients (72 shoulders) on the basis of the following inclusion criteria: (1) males, (2) age less than 30 years at initial dislocation or subluxation, (3) traumatic initial dislocation or subluxation, (4) no multidirectional instability, (5) no history of symptomatic shoulder before the initial injury, (6) observation of Bankart and Hill-Sachs lesions at arthroscopy, and (7) no observation of concomitant injury except bony Bankart lesion and superior labrum anterior-to-posterior (SLAP) lesion at arthroscopy. Total 21 patients (21 shoulders) were excluded from this study: 10 patients had no obvious injury at initial dislocation or subluxation or had multidirectional instability, 3 were over 30 years of age at initial dislocation or subluxation, 4 patients had posterior labrum lesions, 2 had previously undergone other shoulder surgery, and 2 patients were females. All the patients except 1 high school student were members of the Self Defense Force: this student was a rugby player. As compared to the other shoulder, the flexion, abduction, and external rotation of the injured shoulder were observed to be 10° lesser on examination of all the patients under anaesthesia. On the basis of the degree of anterior translation of the shoulder, which was evaluated with the patients under anaesthesia, we divided the patients with limited shoulder movement into 2 groups: stable and unstable groups. There were 8 patients (8 shoulders) in the stable group and 62 patients (64 shoulders) in the unstable group. The average ages at initial injury and at the time of surgical treatment were 23.7 years (15–30 years) and 24.3 years (16–31 years), respectively, in the stable group and 21.2 years (14–29 years) and 24.8 years (19–34 years), respectively, in the unstable group (Table. 1). In the stable group, 7 patients (7 shoulders) experienced primary dislocation, while the remaining 1 patient (1 shoulder) showed recurrent dislocation or subluxation. Of the 7 patients with primary shoulder dislocation or subluxation, 5 did not feel any anterior instability of the shoulder; however, they were unable to return to preinjury activities because of shoulder pain. Surgical repair was performed in the remaining 2 patients shortly (4 weeks–2 months) after the initial injury. They had negative anterior apprehension test results, and therefore, the symptoms were unclear. The patient with recurrent dislocation had been able to play rugby for 4 months after the initial dislocation without any symptoms, but he injured his shoulder again while playing rugby 6 months after the initial dislocation. In the unstable group, on the other hand, 8 patients (8 shoulders) experienced primary dislocation and 54 patients (56 shoulders), recurrent dislocation or subluxation. Six patients with primary shoulder dislocation or subluxation and all the 54 patients with recurrent dislocation or subluxation were unable to return to preinjury activities because of a sense of anterior instability. Surgical repair was performed in the remaining 2 patients with primary shoulder dislocation or subluxation shortly (6 weeks and 2 months) after the initial injury. They had positive anterior apprehension test results before surgical repair.

Based upon previously reported findings, we selected 4 variables from the arthroscopic and CTA findings and compared these variables between the stable and unstable groups. The variables were capsular insertion type, SLAP lesion, bony Bankart lesion, and condition of the AIGHL. In addition to these variables, the average ages at surgery and at initial dislocation or subluxation were also compared between the 2 groups. All the shoulders had Bankart and Hill-Sachs lesions; therefore, these findings were excluded. Rotator cuff tear was not observed in all the shoulders, and therefore, this was also excluded. It was difficult to evaluate the CTA findings in 5 patients (5 shoulders) in the unstable group, because the injected air leaked from their shoulder joints; therefore, these patients were excluded. Finally, 8 patients (8 shoulders) in the stable group and 57 patients (59 shoulders) in the unstable group were included in this study.

Evaluation of CTA findings

We performed CTA in all the patients before surgical repair. Contiguous 2-mm- or 3-mm-thick axial slices of the glenohumeral joint were obtained at 2- or 3-mm intervals with Xvision TSX-002A (Toshiba, Tokyo) after injection of 15-ml air into the joint. We examined the images for capsular insertion and bony Bankart lesion. Capsular insertion was examined at the mid-glenoid level (half-way between the superior and inferior glenoid rims) and at the inferior glenoid level (three-quarters of the distance between the superior and inferior glenoid rims), as reported by Palmer.¹⁰ These levels were determined by counting the total number of axial images through the glenoid fossa. Thus, if there were total 12 images, capsular insertion was examined at the level of images 6 and 9. Capsular insertion was assigned different types on the basis of the classification given by Moseley.⁸

Type 1 indicated a capsular insertion on the labrum (Fig.1-A), while type 2 indicated an insertion at the glenoid neck within 1 cm of the labrum base (Fig.1-B). Type 3 indicated an insertion at the glenoid neck more than 1 cm medial to the labrum base (Fig.1-C).

Fig.1-A, 1-B, and 1-C: Classification of capsular insertion

Fig.1-A: A type 1 capsule arising from the labrum.

Fig.1-B: A type 2 capsule arising from the scapular neck 1 cm medial from the  labral base.

Fig.1-C: A type 3 capsule arising from the scapular neck more than 1 cm medial from the labral base.

We defined type 1 capsular insertion when the insertion at both the mid- and inferior glenoid levels was type 1, type 2 capsular insertion when the insertion was type 2 at either the mid- or the inferior glenoid level, and type 3 capsular insertion when the insertion was type 3 at either the mid- or the inferior glenoid level.

Bony Bankart lesion was considered to be present when bony fragment of the anterior glenoid rim was observed and absent when no bony fragment was observed on any image.

Evaluation of arthroscopic findings

We evaluated the anterior translation of the shoulder on examination under anaesthesia, SLAP lesion from the patients’ surgical records, and condition of the AIGHL. These evaluations were routinely performed for all the patients before the repair of the Bankart lesion: all these evaluations were performed and recorded by 1 co-author. The degree of anterior translation was evaluated by manual anterior drawer test with the patient in supine position and with the arm in 90° of abduction and external rotation, and graded as reported by Hawkins.³ The grading was as follows: translation less than 25% of the humeral head, normal; translation up to 50% of the humeral head, grade 1; translation greater than 50% of the humeral head (subluxation of the humeral head over the glenoid rim), grade 2; and frank dislocation, grade 3. The patients with normal and grade 1 anterior translation were assigned to the stable group and those with grade 2 and grade 3 anterior translations to the unstable group.

Condition of the AIGHL was assessed as reported by Horii.¹³ The AIGHL was considered good when the ligament was clearly observed and its upper proximal end was located in the area superior to the middle-glenoid level or when the ligament could be easily raised by a probe to the area above the middle glenoid level. If the AIGHL did not satisfy this condition, it was considered poor.

SLAP lesion was considered to be present when type 2, type 3, or type 4 SLAP lesion was observed and absent when no SLAP lesion was observed.

Statistical analysis

Univariate analysis was performed to evaluate the association between anterior stability of the shoulder and the variables selected in this study. Independent t test was used to assess patient-group differences in average age at initial dislocation or subluxation and at surgery. Fisher’s exact test was used to assess the differences between categorical variables. Logistic regression analysis with removal at p ≥ 0.15 was used to identify the significant factors for anterior stability. The threshold for significance in this study was set at a p value of 0.05. Analyses were performed using SPSS version 11.5 (SPSS Inc., Chicago, Illinois).

Results :

The results of the univariate analysis of the variables with regard to anterior stability are shown in Table 2. SLAP lesion was absent in 5 shoulders and present in 3 shoulders (type 2: 2 shoulders, type 3: 1 shoulder) in the stable-group patients, while it was absent in 37 shoulders and present in 22 shoulders (type 2: 16 shoulders, type 3: 3 shoulders, type 4: 3 shoulders) in the unstable-group patients. The lesion was not associated with excessive anterior translation. Bony Bankart lesion was observed in 21 shoulders, but no large bony fragment involving greater than 20% of the glenoid fossa was observed. This lesion was also not associated with excessive anterior translation. In the stable group, 2 out of the 8 shoulders showed type 2 or type 3 capsular insertion, but in the unstable group, 57 of the 59 shoulders showed type 2 or type 3 capsular insertion. This type of insertion was significantly associated with excessive anterior translation. Similarly, condition of the AIGHL was significantly associated with excessive anterior translation.

Table 2 　Findings of CTA and arthroscopy　associated with the outcome

Age at initial injury, type 2 or type 3 capsular insertion, and poor AIGHL were entered into the logistic regression analysis: the result is shown in Table 3. Type 2 or type 3 capsular insertion was found to be the strongest factor of excessive anterior translation.

Moreover, we compared these variables between the patients with initial dislocation or subluxation of the shoulder in the stable and unstable groups (7 shoulders from each group). Logistic regression analysis could not be performed because of a small number of shoulders. However, capsular insertion type was found to be significantly associated with excessive anterior translation in the univariate analysis (p = 0.01).

Discussion :

The labrum contributes about 20 % to glenohumeral stability⁷, but only Bankart lesion is insufficient to cause anterior dislocation of the shoulder.¹⁴ In our study, each shoulder had a Bankart lesion, but the degree of anterior translation was observed to be different between the stable and unstable groups. Therefore, we considered that Bankart lesion might contribute only slightly with the degree of anterior translation. SLAP and bony Bankart lesions were also not associated with excessive anterior translation. Itoi⁵ has reported that a large bony Bankart lesion including more than 21% of the glenoid fossa caused excessive anterior translation, but no shoulder had a large bony Bankart lesion in our study.

In some reports, the AIGHL has been considered the major stabilizing restraint of anterior translation¹¹, and its high odds ratio in this study showed that it could be associated with the degree of anterior translation, though this could not be statistically proved. Age at initial dislocation did not influence the degree of anterior translation in this study. We considered the exclusion of patients with over 30 years at initial injury in this study was caused of this result.

In this study, capsular insertion type was significantly associated with excessive anterior translation. Some reports have indicated that type 2 or type 3 capsular insertion is associated with the anterior instability of the shoulder.^8,12  However, Palmer¹⁰ investigated the prediction of anterior instability of the shoulder by comparing magnetic resonance (MR) arthrography and surgical findings of stable and unstable shoulders and concluded that capsular insertion type plays no role in the prediction of shoulder instability. However, he included shoulders without dislocation or subluxation in his study. Therefore, we considered that his result did not reflect the prediction of anterior instability of the shoulders after dislocation or subluxation. We found type 2 or type 3 capsular insertion was associated with excessive anterior translation in our study, however, we did not know whether type 2 or type 3 capsular insertion was associated with anterior instability. One of the reasons for the high ratio of type 2 or type 3 capsular insertion in the unstable group was that capsular insertion was classified into type 2 or type 3 when the labrum was displaced medial to the glenoid neck, even if the capsule was inserted on the labrum. However, many shoulders with type 2 or type 3 capsular insertion in the unstable group had no labrum displacement. Therefore, we considered that the capsular insertion might be type 2 or type 3 initially before dislocation or subluxation. Singson¹² has also documented that the formation of a large anterior pouch in type 3 capsular insertion is less likely after recurrent dislocations in shoulders with strong capsular walls or with initially small or no anterior pouch. We considered that if capsular insertion was found to be type 2 or type 3 on CTA after shoulder dislocation or subluxation, the shoulder had a high possibility of excessive anterior translation which could be subluxated or dislocated even by manual stress. Therefore, surgical treatment in early stage would be suitable. Howkins³ documented excessive translation alone did not equal instability, though it was related to instability. However, in his study¹⁵, he examined the degree of anterior translation of the shoulder in 18 patients with no history of glenohumeral instability, 10 patients with recurrent anterior dislocation, and 10 patients with multidirectional instability, and he reported no shoulders with no history of glenohumeral instability had excessive anterior translation which could be subluxated or dislocated by manual stress under aneasthesia unlike the shoulders with recurrent anterior dislocation or multidirectional instability. Therefore, we considered the shoulder with excessive anterior translation which could be subluxated or dislocated by manual stress would be abnormal. On the basis of the result of this study, we considered that evaluation of capsular insertion type on CTA enabled us to predict excessive anterior translation of the shoulder and it is a useful method, especially when the anterior drawer test was difficult to perform on a patient, because he experienced pain.

This study has several limitations. First, most of the shoulders in the stable group were symptomatic. Although none of the stable-group patients felt anterior instability of the shoulder before surgical treatment, 5 of the 8 patients experienced pain when their shoulders were in 90° abduction and maximum external rotation; further, minor instability was suggested. Moreover, 1 patient had redislocation, although it had occurred due to a high-energy injury. Shoulders showing no symptoms for a long time after dislocation or subluxation should be included in the stable group, but arthroscopic evaluation of these shoulders was difficult due to the invasiveness of the procedure. Therefore, we did not include such shoulders in this study. Capsular insertion type could not evaluate anterior instability of the shoulder in this study. Second, many shoulders in this study had recurrent dislocation or subluxation, which may invite criticism. However, we consider that initial and recurrent dislocations or subluxations may be similar condition. In fact, separate analysis of initial dislocations or subluxations also suggested a correlation between capsular insertion type and anterior translation. Although the number of shoulders analysed was small, we believe that the difference between primary and recurrent dislocation or subluxation may have little effect on the result. Third, we excluded shoulders with complicated lesions other than Hill-Sachs, Bankart, bony Bankart, or SLAP lesion from this study. Therefore, the result of this study may not apply to shoulders with complicated lesions other than those mentioned above.

Conclussion:

Logistic regression analysis revealed type 2 or type 3 capsular insertion to be the strongest factor of excessive anterior translation of the shoulder. Evaluation of capsular insertion type on computed tomographic arthrography after shoulder subluxation or dislocation is a useful method to predict excessive anterior translation of the shoulder.

Reference :

1. Kralinger FS, Golser K, Wischatta R, Wambacher M, Sperner G. Predicting recurrence after primary anterior shoulder dislocation. American Journal of Sports Medicine. 2002; 30: 116-20.

2. Shimonet WT, Cofield RH. Prognosis in anterior shoulder dislocation. American Journal of Sports Medicine. 1984; 12: 19-24.

3. Hawkins RJ, Mohtadi NGH. Clinical evaluation of shoulder instability. Clinical Journal of Sport Medicine. 1991; 1: 59-64.

4. Warner JJP, Miller MD, Marks P, Fu FH. Arthroscopic Bankart repair with the  Suretac device. Part Ι: Clinical observations. Arthroscopy. 1995;11:2-13. 

5. 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. Journal Bone and Joint Surgery, American volume. 2000; 82: 35-46.

6. Lee SB, Kim KJ, O’Driscoll SW, Morrey BF, An KN. Dynamic glenohumeral stability provided by the rotator cuff muscles in the mid-range and end-range of　motion: a study in cadavera. Journal Bone and Joint Surgery, American volume. 2000; 82: 849-57.

7. Lippitt SB, Vanderhooft JE, Harris SL, Sidles JA, Harryman DT 2nd, Matsen FA 3rd. Glenohumeral stability from concavity-compression: a quantitative analysis. Journal of Shoulder and Elbow Surgery. 1993; 2: 27-35.

8. Moseley HF, Overgaard B. The anterior capsular mechanism in recurrent anterior dislocation of the shoulder. Morphological and clinical studies with special reference to the glenoid labrum and the gleno-humeral ligaments. Journal Bone and Joint Surgery, British volume. 1962; 44: 913-27.

9. Pouliart N, Gagey O. Concomitant rotator cuff and capsuloligamentous lesions of the shoulder: a cadaver study. Arthroscopy. 2006; 22: 728-35.

10. Palmer WE, Caslowitz PL. Anterior shoulder instability: diagnostic criteria determined from prospective analysis of 121 MR arthrograms. Radiology. 1995; 197: 819-25.

11.  Turkel SJ, Panio MW, Marshall JL, Girgis FG. Stabilizing mechanisms preventing anterior dislocation of the glenohumeral joint. Journal Bone and Joint Surgery, American volume. 1981; 63: 1208-17.

12. Singson RD, Feldman F, Bigliani L. CT arthrographic patterns in recurrent glenohumeral instability. American Journal of Roentgenology. 1987; 149: 749-53.

13. Horii M, Kubo T, Kurokawa M, Hirasawa Y. MRI evaluation of the inferior glenohumeral ligament. Comparison with arthroscopic findings in 81 shoulders. Acta Orthopaedica Scandinavica. 1998; 69: 163-6.

14. Speer KP, Deng X, Borrero S, Torzilli PA, Altchek DA, Warren RF. Biomechanical evaluation of a simulated Bankart lesion. Journal Bone and Joint Surgery, American volume. 1994; 76: 1819-26.

15. Hawkins RJ, Schutte JP, Janda DH, Huckell GH. Translation of the glenohumeral joint with the patient under aneathesia. Journal of Shoulder and Elbow Surgery. 1996; 5: 286-92.

This is a peer reviewed paper 

Please cite as: Yoshitaka Tanaka: Predicting the degree of anterior stability of the shoulder after traumatic anterior shoulder dislocation or subluxation in young highly active men

J.Orthopaedics 2009;6(3)e5

URL: http://www.jortho.org/2009/6/3/e5

ANNOUNCEMENTS

Arthrocon 2011


Refresher Course in Hip Arthroplasty

13th March,  2011

At Malabar Palace,
Calicut, Kerala, India

Download Registration Form

For Details
Dr Anwar Marthya,
Ph:+91 9961303044

E-Mail:
anwarmh@gmail.com

Powered by
VirtualMedOnline