Abstract
Background:
Posterior glenohumeral dislocation is less common than anterior dislocation, and less is known about its epidemiology, functional outcome, and complications. The purposes of this study were to determine the epidemiology and demographics of posterior dislocations and to assess the risk of recurrence and the functional outcome after treatment.
Methods:
We performed a retrospective review of a prospective audit of the cases of 112 patients who sustained 120 posterior glenohumeral dislocations. Patients were treated with relocation, immobilization, and then physical therapy. Functional outcome was assessed with the Western Ontario Shoulder Instability Index (WOSI) and the limb-specific Disabilities of the Arm, Shoulder and Hand score (DASH) during the two years after the dislocation.
Results:
The prevalence of posterior dislocation was 1.1 per 100,000 population per year, with peaks in male patients between twenty and forty-nine years old, and in the elderly patients over seventy years old. Most dislocations (67%) were produced by a traumatic accident, with most of the remainder produced by seizures. Twenty patients (twenty-three shoulders) developed recurrent instability. On survival analysis, 17.7% (95% confidence interval, 10.8% to 24.6%) of the shoulders developed recurrent instability within the first year. On multivariable analysis, an age of less than forty years, dislocation during a seizure, and a large reverse Hill-Sachs lesion (>1.5 cm3) were predictive of recurrent instability. Small persistent functional deficits were detected with the WOSI and DASH at two years.
Conclusions:
The prevalence of posterior dislocation is low. The most common complication after this injury is recurrent instability, which occurs at an early stage in 17.7% of shoulders within the first year after dislocation. The risk is highest in patients who are less than forty years old, sustain the dislocation during a seizure, and have a large humeral head defect. The risk is lower for most patients who sustain the injury from a traumatic accident, especially if they are older and have a small anterior humeral head defect. There are persistent deficits of shoulder function within the first two years after the injury.
Level of Evidence:
Prognostic Level II. See Instructions to Authors for a complete description of levels of evidence.
Traumatic posterior dislocations of the glenohumeral joint occur much less commonly than anterior dislocations, and less is known about their outcome1-4. The clinical spectrum of these injuries is diverse, ranging from acute isolated traumatic dislocations, through recurrent instability, to dislocation in association with a proximal humeral fracture1. The present study is a retrospective review of a prospective audit of the subgroup of patients with acute, traumatic, isolated posterior dislocations, without an associated proximal humeral fracture. Most prior studies of this subgroup of injuries are in individual case reports or small clinical series. Owing to the diversity and rarity of the injuries, estimation of their epidemiology, long-term outcome, and functional outcome has not previously been reported in a large series of patients.
The aims of this study were to evaluate the epidemiology and demographics of acute traumatic posterior dislocation in a large, consecutive series of patients treated in a single unit over a prolonged period and to assess the functional outcome and risk of recurrence or other complications in these patients after treatment.
Inclusion Criteria
Between August 1996 and March 2008, all patients who presented with posterior shoulder dislocations were initially treated in our affiliated emergency department, which provides the only acute musculoskeletal trauma service for the local adult population. This consecutive series of patients was referred for subsequent evaluation, follow-up, and treatment in our acute shoulder injury clinic, within one week after the initial treatment.
For the purposes of this study, we included only the 112 patients (120 shoulders) who sustained first-time acute (diagnosed within four weeks after the injury) traumatic posterior glenohumeral dislocations, all confirmed by radiographs. A traumatic episode was defined as any discrete substantial injury, such as a fall, collision, or seizure. Osteochondral fractures of the humeral head (so-called reverse Hill-Sachs lesions) and glenoid rim fractures were commonly encountered, and patients with these lesions were retained in the study.
Exclusions
We excluded sixty-five patients with posterior glenohumeral dislocations that had associated fractures of the proximal part of the humerus and/or tuberosities, two patients with dislocations that had an associated humeral shaft fracture, two patients who defaulted from all follow-up after the initial shoulder relocation, and ten patients with chronic dislocations. In addition, we excluded four temporary residents with posterior dislocations who were unable to have further follow-up. Twelve patients with joint hyperlaxity were excluded because they had an atraumatic posterior dislocation.
Initial Treatment Protocol
All patients presented within the first ten days after the dislocation. The initial diagnosis was confirmed by anteroposterior and modified axial radiographs5,6. All patients initially underwent attempted closed reduction under intravenous opioid or benzodiazepine sedation. Shoulder relocation was attempted first with use of direct in-line longitudinal traction and was successful in forty shoulders (33%). If this reduction attempt failed, the humeral head impression fracture (reverse Hill-Sachs lesion) was disimpacted and cleared from the posterior glenoid lip, with use of gentle manipulation, with the arm flexed to 90°, internally rotated, and adducted7. The shoulder was then reduced by external rotation. Five patients (4%) who had shoulders that were irreducible with either of these techniques had reduction with use of these maneuvers after induction of general anesthesia with full muscle relaxation.
At the initial clinic visit, assessment of the neurovascular status of the distal extremity and routine clinical tests to assess the long head of the biceps tendon and individual components of the rotator cuff were performed8-11. Magnetic resonance imaging (MRI) was performed acutely only for patients with suspected rotator cuff tears. Generalized ligamentous laxity was assessed with use of the Beighton system, with a score of ≥4 points of a possible 9 points required for the clinical diagnosis of hyperlaxity12.
All patients were subsequently treated with immobilization in a sling for four weeks with the shoulder in a so-called gunslinger brace in neutral rotation, abduction, and flexion. Passive circumduction exercises with the arm at the side (pendulum exercises) and elbow range-of-movement exercises were permitted for twenty minutes, three times daily, with the brace removed during this period. Following brace removal at four weeks, patients were referred for a rehabilitation program under the supervision of a physiotherapist. At this stage, patients commenced active-assisted shoulder range-of-motion exercises and were allowed unrestricted range of movement. Isometric rotator cuff strengthening exercises were commenced at four weeks, progressing to isotonic exercises at eight weeks. We advised patients to continue the strengthening exercises within the first year after the injury. Physically active patients were allowed to return to general fitness training, including running, and noncontact sports at twelve weeks, but were advised to avoid competitive collision sports until sixteen weeks after the injury.
Treatment of Patients Who Developed Recurrent Instability
All patients who had a further episode of dislocation or who developed recurrent subluxation were examined with magnetic resonance arthrography and computed tomography (CT) of the affected shoulder, to delineate the nature and extent of any soft-tissue or osseous abnormality. We also examined the shoulder with the patient under anesthesia and performed diagnostic shoulder arthroscopy to delineate the cause of glenohumeral instability in medically fit patients. Patients who were medically unfit underwent relocation of the shoulder under sedation. Because of the considerable heterogeneity of the patients who developed recurrent instability, we adopted an individualized approach to the treatment of these individuals. If there were no abnormal soft-tissue or osseous abnormalities, we recommended an additional program of physical therapy for a period of six months. If discrete anatomic lesions were discovered, an anatomic operative approach was used, with repair of all soft-tissue and osseous lesions thought to be contributory to instability, on the basis of the advanced imaging and arthroscopic findings.
Outcome Assessment
The chief binary outcome measures were recurrent instability and other complications. Numeric assessments comprised the three functional assessments and the assessment of shoulder range of motion at one and two years after dislocation (for the patients in Group I whose shoulders were stable) or at the conclusion of treatment for instability for those who had a recurrence (Group II). This information was gathered and collated by a research worker. All of the clinical assessments were carried out by the senior author (C.M.R.).
The intent was to evaluate all patients during the first week after the initial dislocation and at four weeks, three months, six months, one year, and two years after the injury. At the time of each clinical follow-up, patients were directly questioned by the research worker about whether they had further dislocations, had recurrent instability symptoms, or received treatment in another center. Anteroposterior and modified axial radiographs5 were made at all visits. Functional scoring, shoulder motion, and clinical testing for signs of shoulder instability were assessed at the one and two-year review appointments for patients in Group I. Group-II patients were assessed at similar time intervals after either the operative treatment or the conclusion of the physical therapy program. After 1998, we assessed the functional outcomes using the Western Ontario Shoulder Instability Index (WOSI)13, Disabilities of the Arm, Shoulder and Hand score (DASH)14, and the Short Form-36 (SF-36)15,16. Patients were discharged from routine follow-up after the two-year assessment but were offered open future access to the clinic if needed.
We defined recurrent instability to be present when a patient either had an additional posterior dislocation confirmed by a radiograph or had developed symptoms of recurrent subluxation. Recurrent subluxation was defined as a painful "slipping" sensation of the shoulder or a recurrent "dead arm," accompanied by signs of instability on clinical testing. We tested for both anterior and posterior instability, using the apprehension, fulcrum, jerk, and load and shift tests17-21. An examination was positive for anterior or posterior instability if three of the four tests were positive in the corresponding direction. Inferior instability was present if the patient had signs of symptomatic instability on sulcus testing18,22,23. We used existing grading systems to evaluate hyperlaxity (a Beighton score of ≥4 points)12 and the size of the reverse Hill-Sachs lesion (the Bernageau grade)24,25. All patients had assessment of several candidate risk factors for recurrent instability (Table I).
In November 2009, we surveyed all patients who had been treated during the study period and had been lost to follow-up. Patients were sent a questionnaire by mail or were interviewed by telephone and were questioned about additional recurrences of instability. Any who were having ongoing problems were offered an additional clinical review. We obtained further follow-up data on ninety patients who either had been previously discharged from follow-up at two years or had moved from our catchment area. We were unable to contact seventeen patients, and five patients had died during the follow-up period and were not known to have problems related to the shoulder.
Statistical Analysis
We used local census data to assess the age and sex-specific prevalence of posterior glenohumeral dislocation during the study period. Since the development of recurrent instability was a time-dependent outcome, and the duration of patient follow-up was variable, we used survival methodology to examine the probability of recurrent instability occurring after the initial dislocation26. For patients who developed recurrent instability, the outcome was defined to be present when the shoulder redislocated for the first time or when they first developed symptoms of recurrent subluxation. Patients who did not develop recurrent instability were censored from further analysis when they were lost to follow-up, had died, or had reached the cutoff point for the end of the study in November 2009.
We used a Cox proportional hazards model of survivorship to estimate the effect of the candidate patient and injury-related risk factors (Table I) on the development of recurrent instability. All independent variables underwent statistical analysis with coding as either continuous or categorical data. We examined for potential cross-correlations between variables and used product functions to assess for possible synergistic effects of these variables via interaction terms in the regression. All variables that were predictive of recurrent instability on univariate analysis at a p value of <0.05 were included in a stepwise multivariable model (with use of forward conditional methodology) to determine the factors that were independently predictive of recurrent instability.
With use of this model, the summated products of the risk factor score and its regression coefficients for an individual patient can be used to calculate his or her prognostic index (PI). The predicted probability (St) of a recurrent instability at a given time (t) can be calculated with use of the equation: St = So(t)exp(PI), where So(t) is the baseline cumulated survival function at the time t26. In the multivariable analysis, a p value of ≤0.05 was considered significant for type-I error.
Source of Funding
No external funding was received for this investigation.
Epidemiology and Group Demographics
There were 120 acute posterior glenohumeral dislocations in 112 patients treated within our unit over the eleven and a half-year initial treatment period of the study. The median age of the patients was forty-three years (range, eighteen to eighty-six years), and seventy-nine were men (Table II). The median age of the eight patients with bilateral dislocation was thirty-two years (range, eighteen to eighty-four years). The prevalence of posterior dislocation was 1.1 per 100,000 population per year (1.2 per 100,000 per year in men and 0.6 per 100,000 per year in women) during the study period (Fig. 1). The prevalence was highest in men between twenty and forty-nine years old (Fig. 1). Seventy-two (64.3%) of the 112 patients in the overall population were in this demographic subgroup. Although there was evidence of a secondary peak of prevalence in elderly patients, with both sexes equally affected, the absolute numbers of patients treated was small, and only seventeen patients (15.2%) were over seventy years old.
The dislocations in most (seventy-five; 67%) of the 112 patients were produced by a traumatic accident—a fall from a height or a motor vehicle accident (Table II). Sports injuries were relatively uncommon, although they were more prevalent in younger patients, with a mean age of thirty-four years (range, twenty-one to forty-nine years). In thirty-five patients (31.3%), the dislocations occurred during seizures caused by epilepsy or alcohol or drug withdrawal and, more rarely, during diabetic hypoglycemic seizures. The age and sex of those who sustained a dislocation during a seizure and those who had a dislocation from a traumatic injury were similar. Only two dislocations were produced by electrocution (Table II). Twenty patients had general ligamentous hyperlaxity (a Beighton score of >4 points), and these patients sustained twenty-two shoulder primary dislocations.
Associated Injuries
There were no open dislocations or vascular injuries. Seven older patients (range, fifty-four to seventy-five years old) had a rotator cuff tear (four isolated subscapularis and three combined supraspinatus, infraspinatus, and subscapularis ruptures) on initial assessment after primary reduction, with tear confirmation on subsequent MRI scans. All patients with rotator cuff tears had improvement of their symptoms with physiotherapy treatment, although two patients with combined tears had suboptimal function and were treated by arthroscopic rotator cuff repair at three and four months after the injury.
The reverse Hill-Sachs lesion was not apparent or small (≤1.5 cm3) on radiographs of seventy shoulders and was large (>1.5 cm3) on radiographs of fifty shoulders. Posterior glenoid rim fractures were seen on radiographs of seven shoulders.
Prevalence and Risk Factors for Recurrence
Of the 120 posterior shoulder dislocations in 112 patients, twenty-three shoulders (19.2%) in twenty patients (three with bilateral instability) either sustained an additional posterior dislocation (seventeen shoulders) or developed recurrent episodes of posterior subluxation (six shoulders) by November 2009. In these patients, the overall mean time for development of recurrent instability was 7.5 months (95% confidence interval [CI], 2.2 to 12.4 months; range, one to sixty months). The median age of the twenty patients (twenty-three shoulders in twelve men and eight women) who developed recurrent instability was thirty-five years (range, eighteen to seventy-six years). The cause of the initial shoulder dislocation was a seizure for sixteen shoulders (thirteen with recurrent dislocation and three with recurrent subluxation) and was a traumatic injury for seven shoulders (four with recurrent dislocation and three with recurrent subluxation). The sixteen shoulders that initially dislocated during a seizure had recurrences only during seizures (ten shoulders) or during normal daily activity (six). The mean duration of follow-up for the patients who had not developed instability was 59.5 months (95% CI, 54.3 to 64.7 months; range, six to 112 months).
On survival analysis, 17.7% (95% CI, 10.8% to 24.6%) of the cohort developed recurrent instability within the first year after the initial dislocation. All episodes of recurrent instability within this first year developed within eight months of the original dislocation (Fig. 2). Recurrent instability developed after this eight-month mark in only two shoulders: one had the recurrence at twenty-four months and the other, at sixty months after the primary dislocation. The recurrence rates on survival analysis at two and five years after the injury were 18.6% (95% CI, 11.6% to 25.7%) and 20.6% (95% CI, 12.8% to 28.4%), respectively.
On univariate analysis, three factors were significantly associated with an increased risk of recurrent instability (p < 0.05 for all). These were an age of less than forty years at the time of the original dislocation (fifteen [30%] of the fifty patients with this risk factor had recurrence), dislocation during a seizure (sixteen [42%] of thirty-eight patients), and the presence of a reverse Hill-Sachs lesion of >1.5 cm3 (eight of sixteen patients). These variables were not cross-correlated. When these variables were entered into a multivariable analysis, they remained independently predictive of recurrence (p < 0.05). Of the twelve patients with all three risk factors, nine had recurrent instability, whereas only one (3.1%) of the thirty-two patients with no risk factors had a recurrence. Table III shows the calculated estimated risk for development of recurrent instability within two years based on the presence or absence of the three major predictor variables that were independently predictive of recurrence. The two-year follow-up period was selected as only one patient developed a recurrence after this time interval in our study.
Demographics and Treatment of Patients with Recurrent Instability
Of the twenty-two shoulder dislocations that occurred in twenty patients with clinical hyperlaxity, three developed symptoms of recurrent posteroinferior subluxation related to posteroinferior capsular laxity without labral abnormality between three and twenty-four months after the initial dislocation. These patients all had improvement in symptoms after physical therapy treatment. One patient continued to experience episodes of recurrent posteroinferior subluxation and was successfully treated with an arthroscopic posteroinferior capsular plication procedure two years after the primary dislocation.
Of the ninety-eight shoulders (in ninety-two patients) that had dislocations without hyperlaxity, twenty developed recurrent instability (seventeen had recurrent dislocation, and three had recurrent subluxations). Three patients were treated nonoperatively: two were medically frail and the other declined further treatment. Seventeen shoulders were examined with the patient under anesthesia, and magnetic resonance arthrography and arthroscopy were also performed.
In twelve of these shoulders (in ten patients, including seven men and three women, with a mean age of 38.3 years; range, eighteen to seventy-six years), the recurrent instability was attributed to a large reverse Hill-Sachs defect. Instability developed in these shoulders between two weeks and eight months after the initial dislocation; eleven had recurrent dislocation, and one had recurrent subluxation. On examination under anesthesia and on arthroscopic examination, there was early reengagement of the humeral head defect on the posterior glenoid rim in initial flexion adduction movements in all of these shoulders. Nine of these shoulders also had avulsion of the posteroinferior capsulolabral sleeve (a reverse Bankart lesion), two had small posterior glenoid rim fractures, and one had a posterior capsular tear. All had additional episodes of instability and were treated operatively. Eight had elevation and bone-grafting of the humeral head defect27, whereas four with more extensive lesions that were not amenable to elevation were treated with bone-grafting with a femoral head allograft28.
In the final five shoulders (in four patients, including three men and one woman, with a mean age of 34.5 years; range, twenty-seven to forty-four years), instability was due to posterior labral lesions. They had instability develop between two and sixty months after the initial dislocation; three had recurrent dislocation, and two had recurrent subluxation. All had extensive posterior capsulolabral tears on arthroscopic examination, and two had fractures of the posterior osseous glenoid rim. The humeral head lesions were not engaging with the posterior glenoid rim on examination with the patient under anesthesia and on arthroscopic inspection. All had further episodes of instability and were treated operatively, with an arthroscopic posterior labral repair, incorporating any posterior osseous glenoid lesion into the repair.
Other Complications
Six patients developed posttraumatic shoulder stiffness, persisting more than six weeks after the injury. All responded to a physiotherapy rehabilitation program of capsular stretching exercises. No patient had developed symptoms, signs, or radiographic changes consistent with osteonecrosis of the humeral head within the first two years after the initial dislocation.
Functional Outcomes
Some patients missed one of the follow-up assessments: a total of twelve shoulders were not assessed at one year, and fourteen were not assessed at two years. There was no significant improvement in either the functional scores or shoulder movement between the one and two-year assessments. The two-year results are therefore presented in Table IV. There were persistent deficits of shoulder movement and function in the injured shoulders of both Group I (those without instability) and Group II (those who had developed instability) at two years (Table IV). In both groups, the most marked deficits were in the shoulder-specific instability (WOSI) scores and the selective loss of internal rotation movements. Group-I patients had better mean functional scores and range of movement than the Group-II patients at two years; however, because of the cohort size, these differences were not significant (Table IV). The age and sex-controlled scores for general health on the SF-36 were similar to those of age and sex-matched controls in the eight major subcategories at one and two years after the injury.
This study confirms that the prevalence of first-time traumatic posterior dislocations of the shoulder is low at 1.1 per 100,000 population per year during the study period. In the four largest epidemiological studies performed in the last twenty years, the incidence of anterior dislocations has been reported to be between seventeen and 23.9 per 100,000 person-years29-32. This suggests that anterior glenohumeral dislocations are between 15.5 and 21.7 times more common than posterior dislocations.
In previous studies, posterior dislocations have been missed in up to 50% of patients when they initially seek medical consultation after the injury2,28,33-36. However, during the current study, in which we treated 112 patients who had the diagnosis made acutely, to our knowledge only ten patients (excluded from this study) had a delayed diagnosis. It is possible that other patients with a posterior dislocation were missed and never sought medical advice. However, it is also likely that our emergency department policy of using two trauma series orthogonal radiographs of the shoulder (anteroposterior and Velpeau or modified axial views) at the initial assessment reduced the risk of missing the posterior dislocations in the patients who presented acutely.
Both anterior and posterior glenohumeral dislocations occur more frequently in men than women, although the sex difference is less marked in posterior dislocations, for which the male-to-female ratio is 2.4:1 compared with the higher male-to-female ratio for anterior dislocations29-32. Both groups of injuries exhibit a bimodal age distribution, with a substantial peak in young men, and a smaller secondary peak of incidence in elderly individuals, with a more equal sex ratio. The overall mean age of patients who sustain a posterior dislocation is slightly higher than that reported for anterior dislocation29-32. An important difference is that a larger proportion of posterior dislocations than anterior dislocations are sustained during seizures. Posterior dislocation was produced by a seizure in 31.3% of the patients in this series and showed no significant age or sex predisposition. The predisposition to posterior dislocation in these patients is likely due to the forced sustained contractions of the internal rotator muscles of the shoulder during the seizure37.
In previous studies, the reported prevalence of simultaneous bilateral posterior dislocations was 15% (twenty-four of 164 patients with posterior dislocation in five series3,4,7,36,38), with an even higher prevalence in dislocations sustained during seizures. However, our study found a lower prevalence, with only 7.1% of dislocations overall and 11.1% of dislocations occurring during seizures being bilateral. It is possible that the perception of these injuries commonly being bilateral has been skewed by the multitude of case reports detailing the treatment of bilateral synchronous injuries.
Patients who sustain an acute anterior dislocation after a traumatic injury have an age-dependent and sex-dependent risk of developing recurrent instability, with younger male patients being at particularly high-risk39-41. In contrast, although younger patients who sustain a posterior dislocation from a traumatic injury are at increased risk of recurrence compared with older patients, the overall risk of recurrence is substantially lower than that for patients with anterior dislocation, especially if the patients with a posterior dislocation have a small osseous defect of the humeral head. In these patients, it is likely that, despite a substantial posterior capsulolabral injury, the shoulder is relatively well protected from recurrence by the protracted position of the scapula on the chest wall, such that the intact posterior glenoid acts to protect against posterior instability1,42.
A minority of patients develop recurrence after the initial posterior dislocation, although the risk is much higher in younger patients with seizure-related dislocations and large reverse Hill-Sachs lesions. In this series, nine of the twelve patients who had all three of these risk factors developed instability. Furthermore, the development of recurrence was usually an early event after the initial injury. This suggests that most of these shoulders were inherently unstable from the time of the original injury. We are currently investigating the clinical value of early counseling and are considering primary operative intervention to prevent recurrence in patients with multiple risk factors for recurrence. A much smaller proportion of shoulders have instability attributable to either hyperlaxity or the soft-tissue lesions of posterior capsulolabral avulsion, sometimes combined with a posterior glenoid rim fracture.
Our study represents a consecutive, unselected series of patients with a comparatively rare type of injury with medium-term follow-up. However, as this is a single center study, it is possible that our results may not be generalizable to other populations. Cultural and racial variations, particularly participation in different types of contact sports, may produce considerable geographic variation in both the prevalence of initial traumatic posterior dislocation and the rate of recurrence thereafter.
With the exclusion of case reports, ten previous series have considered between ten and forty-one patients with posterior dislocations2-4,7,43-48. These studies typically described satisfactory functional outcomes, with small but appreciable numbers of patients developing recurrent instability. All of these reports contained mixed patient populations with both acute and chronic dislocations and included patients with proximal humeral fracture-dislocations. It is difficult to estimate the prevalence of recurrence in these series, and comparison of our findings with these studies is not possible.
A weakness of our study was that we did not routinely perform advanced shoulder imaging on all of our patients. Previous studies with use of MRI have found a high prevalence of rotator cuff tears and other soft-tissue abnormalities, including superior labral detachments and injuries to the biceps tendon49-52. It is likely that we failed to detect a number of subclinical soft-tissue lesions and underestimated their prevalence. However, since most patients had satisfactory outcomes if they avoided instability, we do not think that routine advanced imaging is required for all patients with these injuries.
The functional outcomes assessed with use of the limb-specific DASH and WOSI scoring systems improved during follow-up and were satisfactory in the patients who were assessed at two years. Nevertheless, our study detected small but persistent defects of shoulder function at two years that were comparable with those demonstrated in a similar study of two-year outcome after acute anterior dislocation41. Patients with posterior dislocation tend to have limitations of internal rotation in contrast to patients with anterior dislocation who tend to lose external rotation. The patients who were treated operatively for recurrent instability regained a satisfactory functional outcome when reviewed at two years after the conclusion of their treatment. Although their functional scores were poorer than the larger group of patients who avoided recurrent instability, this difference was clinically unimportant on testing.
In summary, the development of posterior instability after an initial posterior glenohumeral dislocation is an early complication that is largely confined to a minority of younger patients who sustain the initial injury during a seizure and have a large reverse Hill-Sachs lesion. In contrast, the outlook for most patients who do not have these risk factors is favorable, as they tend to have a satisfactory functional outcome and a low risk of developing recurrent instability.
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