Incidence of glenohumeral instability in collegiate athletics

Joint instability and osteoarthritis

Joint instability creates a clinical and economic burden in the health care system. Injuries and disorders that directly damage the joint structure or lead to joint instability are highly associated with osteoarthritis (OA). Thus, understanding the physiology of joint stability and the mechanisms of joint instability-induced OA is of clinical significance. The first section of this review discusses the structure and function of major joint tissues, including periarticular muscles, which play a significant role in joint stability. Because the knee, ankle, and shoulder joints demonstrate a high incidence of ligament injury and joint instability, the second section summarizes the mechanisms of ligament injury-associated joint instability of these joints. The final section highlights the recent advances in the understanding of the mechanical and biological mechanisms of joint instability-induced OA. These advances may lead to new opportunities for clinical intervention in the prevention and early treatment of OA.

High frequency of posterior and combined shoulder instability in young active patients

OBJECTIVE

The purpose of this study was to describe the epidemiology and demographics of surgically treated shoulder instability stratified by direction. We hypothesized that there would be an increased frequency of posterior and combined shoulder instability in our population compared with published literature. Secondarily, we assessed preoperative magnetic resonance imaging (MRI) reports to determine how accurately they detected the pathology addressed at surgery.

MATERIALS AND METHODS

A retrospective review was conducted at a single facility during a 46-month period. The study included all patients who underwent an operative intervention for shoulder instability. The instability in each case was characterized as isolated anterior, isolated posterior, or combined, according to pathologic findings confirmed at arthroscopy. The findings were retrospectively compared with official MRI reports to determine the accuracy of MRI in characterizing the clinically and operatively confirmed diagnosis.

RESULTS

A consecutive series of 231 patients (221 men, 10 women) underwent stabilization for shoulder instability over 46 months. Patients were a mean age of 26.0 years. There were 132 patients (57.1%) with isolated anterior instability, 56 (24.2%) with isolated posterior instability, and 43 (18.6%) with combined instability. Overall, MRI findings completely characterized the clinical diagnosis and arthroscopic pathology in 149 of 219 patients (68.0%).

CONCLUSION

The rate of posterior and combined instability in an active population is more common than has been previously reported, making up more than 40% of operatively treated instability, including a previously unreported incidence of 19% for combined instabilities. In addition, MRI was often incomplete or inaccurate in detecting the pathology eventually treated at surgery.

Arthroscopic Versus Open Stabilization for Anterior Shoulder Subluxations

Background:

Most of the literature on shoulder instability focuses on patients experiencing anterior glenohumeral dislocation, with little known about the treatment of anterior subluxation events.

Purpose:

To determine the outcomes of surgical stabilization of patients with anterior glenohumeral subluxations and to compare open and arthroscopic approaches.

Study Design:

Randomized controlled trial; Level of evidence, 2.

Methods:

We prospectively enrolled patients with anterior glenohumeral subluxations undergoing surgical stabilization. Patients were offered randomization between open and arthroscopic stabilization. Inclusion criteria included patients with anterior glenohumeral subluxations undergoing Bankart repair, while exclusions included the presence of glenoid or humeral bone loss, multidirectional instability, capsular tear/humeral avulsion of the glenohumeral ligament lesion, and rotator cuff tear requiring repair. Patients were randomized to an open Bankart repair through a subscapularis takedown or an arthroscopic Bankart repair, both using the same bioabsorbable suture anchors, and they were followed for a minimum of 2 years. Outcomes were evaluated with the Single Assessment Numeric Evaluation (SANE), Western Ontario Shoulder Instability Index (WOSI), American Shoulder and Elbow Surgeons Score (ASES), Simple Shoulder Test (SST), Rowe, and Tegner activity scores.

Results:

A total of 26 patients were enrolled, with 7 being lost to follow-up. Complete follow-up data were available on 19 subjects (74%): 10 in the open group and 9 in the arthroscopic group. There were no significant differences noted between the randomized groups, with a 2-year WOSI score of 320 in the open subjects and 330 in the arthroscopic subjects, and similar findings in the other scoring scales. There were no cases of dislocation following surgery. There were 3 patients with recurrent instability (subluxations only) in each group at a mean of 17 months, for an overall recurrent subluxation rate of 31%. These subjects with recurrence had lower outcome scores (WOSI, 532; SANE, 88.4). The outcomes of the 9 subjects with ≤3 subluxation events were superior to those of the 10 subjects with >3 events prior to stabilization. The patients with ≤3 events had a WOSI score of 143, compared with 470 (P = .042), and an ASES mean score of 98.8, compared with 87.1 (P = .048). Four of the 6 patients with recurrent subluxations had sustained >3 subluxations prior to stabilization.

Conclusion:

Overall, patients with Bankart lesions resulting from an anterior glenohumeral subluxation event had excellent outcomes with surgical stabilization. The overall recurrence in the 19 subjects with at least 2-year follow-up was 6 cases (31%), with no instances of dislocation in this young, active cohort. There was no significant benefit to open or arthroscopic stabilization, and we did find that stabilization of subluxation patients with ≤3 events resulted in superior outcomes compared with chronic recurrent subluxation patients with >3 events. We recommend early surgical stabilization of young athletes with Bankart lesions that result from anterior subluxation events.

Shoulder instability with concomitant bone loss in the athlete

Thorough evaluation of the athlete with persistent shoulder instability and appropriate use of imaging modalities, such as 3-dimensional computed tomography, can help quantify the severity of bony deficiency. Based on obtained imaging and examination, surgical and nonsurgical methods can be considered. In many situations both the humeral- and glenoid-sided bone loss must be addressed. Depending on the extent of bone loss, athletic demands, and surgeon experience, arthroscopic or open surgical options can provide shoulder stability and return athletes to their prior level of activity.

The Latarjet-Patte procedure for recurrent anterior shoulder instability in contact athletes

Recurrent anterior shoulder instability is common in contact athletes and the high-energy injuries seen in this group make them more prone to bone loss. Athletes with recurrent instability and associated bone loss have high failure rates when treated with a soft tissue reconstruction procedure. Therefore it is preferred to manage recurrent instability in contact athletes with the Latarjet-Patte procedure. In this article, the authors describe their technique. They have found this procedure to be safe and effective, with very low recurrence and early return to sport. A meticulous surgical technique is important to avoid intraoperative and postoperative complications.

The external rotation immobilisation does not reduce recurrence rates or improve quality of life after primary anterior shoulder dislocation: a systematic review and meta-analysis

PURPOSE

Conducting a systematic review and meta-analysis of prospective randomised controlled trials directly comparing (1) the rates of recurrence and (2) patient-based quality-of-life assessments after the external rotation (ER) or internal rotation (IR) immobilisation after primary anterior shoulder dislocation.

METHODS

PubMed, EMBASE, the Cochrane Library and ISI Web of Science were searched up to January 2013, using the Boolean operators as follows: (bankart lesion OR shoulder anterior dislocation) AND ((external rotation AND internal rotation) OR immobilisation). All prospective randomised controlled trials directly comparing recurrence rate and patient-based quality-of-life assessments between the ER and IR immobilisations were retrieved. No limitation of the language or publication year existed in our analysis.

RESULTS

Seven of 896 studies involving 663 patients were included, 338 in the ER group and 325 in the IR group. No significant difference was observed in the recurrence rate at all ages (risk ratio (RR)=0.65; 95% confidence interval, 0.41-1.03; p=0.067), at the age stratum of ≤30 years (RR=0.70; 95% confidence interval, 0.38-1.29; p=0.250) and >30 years (RR=0.86; 95% confidence interval, 0.38-1.97; p=0.722). Four trials adopted quality-of-life assessments, using the Constant-Murlay functional scoring system, the Rowe scoring system, the Western Ontario Shoulder Instability index (WOSI), the Disabilities of arm, shoulder and hand (DASH) and the American Shoulder and Elbow Surgeons evaluation form (ASES). Only one trial demonstrated borderline statistical significance (p=0.05) and probable superiority of the ER group based on the ASES. No significant difference was observed in other three trials.

CONCLUSION

Based on the results of our analysis, the ER immobilisation could not reduce the rates of recurrence after primary anterior shoulder dislocation or improve the quality of life compared with the IR immobilisation. More rigorous and adequately powered prospective randomised controlled trials with long-term follow-ups are required to elucidate a more objective outcome.

Return to play and recurrent instability after in-season anterior shoulder instability: a prospective multicenter study

BACKGROUND

There is no consensus on the optimal treatment of in-season athletes with anterior shoulder instability, and limited data are available to guide return to play.

PURPOSE

To examine the likelihood of return to sport and the recurrence of instability after an in-season anterior shoulder instability event based on the type of instability (subluxation vs dislocation). Additionally, injury factors and patient-reported outcome scores administered at the time of injury were evaluated to assess the predictability of eventual successful return to sport and time to return to sport during the competitive season.

STUDY DESIGN

Cohort study (prognosis); Level of evidence, 2.

METHODS

Over 2 academic years, 45 contact intercollegiate athletes were prospectively enrolled in a multicenter observational study to assess return to play after in-season anterior glenohumeral instability. Baseline data collection included shoulder injury characteristics and shoulder-specific patient-reported outcome scores at the time of injury. All athletes underwent an accelerated rehabilitation program without shoulder immobilization and were followed during their competitive season to assess the success of return to play and recurrent instability.

RESULTS

Thirty-three of 45 (73%) athletes returned to sport for either all or part of the season after a median 5 days lost from competition (interquartile range, 13). Twelve athletes (27%) successfully completed the season without recurrence. Twenty-one athletes (64%) returned to in-season play and had subsequent recurrent instability including 11 recurrent dislocations and 10 recurrent subluxations. Of the 33 athletes returning to in-season sport after an instability event, 67% (22/33) completed the season. Athletes with a subluxation were 5.3 times more likely (odds ratio [OR], 5.32; 95% CI, 1.00-28.07; P = .049) to return to sport during the same season when compared with those with dislocations. Logistic regression analysis suggests that the Western Ontario Shoulder Instability Index (OR, 1.05; 95% CI, 1.00-1.09; P = .037) and Simple Shoulder Test (OR, 1.03; 95% CI, 1.00-1.05; P = .044) administered after the initial instability event are predictive of the ability to return to play. Time loss from sport after a shoulder instability event was most strongly and inversely correlated with the Simple Shoulder Test (P = .007) at the time of initial injury.

CONCLUSION

In the largest prospective study evaluating shoulder instability in in-season contact athletes, 27% of athletes returned to play and completed the season without subsequent instability. While the majority of athletes who return to sport complete the season, recurrent instability events are common regardless of whether the initial injury was a subluxation or dislocation.

Gender effect on the scapular 3D posture and kinematic in healthy subjects

Populations considered for shoulder analysis are often composed of various ratios of men and women. It is consequently hypothesized that gender has no significant effect on the joint kinematic. However, the literature reports, for the shoulder, differences in the range of motion between genders. The specific influence of gender on the scapulo-thoracic kinematics has not been studied yet. The dominant shoulder of two populations of men and women composed of 11 subjects each were evaluated in three dimensions for three distinct motions: flexion in the sagittal plane, abduction in the frontal plane and gleno-humeral internal/external rotation with the arm abducted at 90°. Posture, kinematics and range of motion were studied separately. For flexion and abduction and with regard to the scapular kinematic, external rotation was significantly larger for women than men. The differences were of at least 5° at 120° of humeral elevation. Upward rotations were identical. Women also showed larger average active humero-thoracic range of motion. The mean differences were of 13°, 7°, 12° and 5° for abduction, flexion, internal rotation and external rotation, respectively. No difference was observed between the scapular resting positions of both populations. The observed differences concerning both the scapular and humeral patterns would indicate that the shoulder behaviour of men and women should not be expected to be similar.

Risk factors for anterior glenohumeral instability

BACKGROUND

While anterior glenohumeral instability has been shown to be common in young athletes, the risk factors for injury are poorly understood.

PURPOSE/HYPOTHESIS

To determine the modifiable and nonmodifiable risk factors for anterior shoulder instability in a high-risk cohort. The hypothesis was that specific baseline factors would be associated with the subsequent risk of injury.

STUDY DESIGN

Cohort study (prognosis); Level of evidence, 2.

METHODS

We conducted a prospective cohort study in which 714 young athletes were followed from June 2006 through May 2010. Baseline assessments included a subjective history of instability, physical examination by a sports medicine fellowship-trained orthopaedic surgeon, range of motion, strength with a handheld dynamometer, and bilateral noncontrast shoulder magnetic resonance imaging (MRI). A musculoskeletal radiologist measured glenoid version, glenoid height, glenoid width, glenoid index (height-to-width ratio), glenoid depth, rotator interval (RI) height, RI width, RI area, RI index, and the coracohumeral interval. Subjects were followed to document all acute anterior shoulder instability events during the 4-year follow-up period. The time to anterior shoulder instability event during the follow-up period was the primary outcome of interest. Univariate and multivariable Cox proportional hazards regression models were used to analyze the data.

RESULTS

Complete data were available for 714 subjects. During the 4-year surveillance period, there were 39 anterior instability events documented at a mean of 285 days. While we controlled for covariates, significant risk factors of physical examination were as follows: apprehension sign (hazard ratio [HR], 2.96; 95% CI, 1.48-5.90; P = .002) and relocation sign (HR, 4.83; 95% CI, 1.75-13.33; P = .002). Baseline range of motion and strength measures were not associated with subsequent injury. Significant anatomic risk factors on MRI measurement were glenoid index (HR, 8.12; 95% CI, 1.07-61.72; P = .043) and the coracohumeral interval (HR, 1.20; 95% CI, 1.08-1.34; P = .001).

CONCLUSION

This prospective cohort study revealed significant risk factors for shoulder instability in this high-risk population. Physical examination findings of apprehension and relocation were significant while controlling for history of injury. The anatomic variables of significance were not surprising-tall and thin glenoids were at higher risk compared with short and wide glenoids, and the risk of instability increased by 20% for every 1-mm increase in coracohumeral distance.

[Shoulder dislocation in athletes]

BACKGROUND

Shoulder dislocation is a common injury in athletes. Surgical and non-surgical therapy options are still the subject of controversial debate.

STUDY AIM

This article presents important considerations for decision-making and current concepts for the therapy of shoulder dislocation in athletes.

METHODS

A selective literature search was carried out in PubMed.

RESULTS

Surgical and non-surgical therapy options are described in the literature without yet defining a gold standard.

CONCLUSION

Early surgical stabilization is currently recommended in young athletes. For decision-making numerous sport and patient-related factors need to be considered. Most athletes are able to return to the pre-injury level after surgical stabilization.

The Latarjet-Patte procedure for recurrent anterior shoulder instability in contact athletes

The Latarjet-Patte procedure satisfies all of the requirements for treating recurrent anterior instability in contact athletes and is therefore their preferred management in this patient group.

Pediatric and adolescent shoulder instability

Instability of the shoulder is a common issue faced by sports medicine providers caring for pediatric and adolescent patients. A thorough history and physical examination can help distinguish traumatic instability from multidirectional or voluntary instability. A systematic understanding of the relevant imaging characteristics and individual patient disease and goals can help guide initial treatment. Given the high risk of recurrent instability, young, active patients who seek to return to competitive contact sports should consider arthroscopic stabilization after a first-time instability event. MDI should be treated initially with conservative rehabilitation. Patients who fail extensive conservative treatment may benefit from surgical stabilization. Arthroscopic techniques may now approach the results found from traditional open capsular shift procedures. Future studies should be designed to examine the outcomes in solely pediatric and adolescent populations after both conservative and operative treatment of shoulder instability.

[Stability versus mobility of the shoulder. Biomechanical aspects in athletes]

The demand profile of athletes shoulders is high. On the one hand the shoulder has to provide a maximum active range of motion that allows rapid movements of the arm and on the other hand it has to be sufficiently stabilized to decelerate rapid movements and to neutralize the resulting translational forces. Two general types of instability can be differentiated in athletes shoulders: the macroinstability typically occurring in athletes involved in contact sports and the microinstability occurring in athletes involved in overhead sports.Repetitive abduction and external rotation movements of athletes involved in overhead sports lead to adaptation of the glenohumeral joint capsule and ligaments. The anterior capsule becomes stretched while the posterior capsule develops tightness. These adaptations can result in an anterior microinstability as well as posterosuperior impingement (PSI) which implicates a pathological contact of the posterosuperior rotator cuff with the posterior glenoid and which is also associated with SLAP lesions. In contrast the shoulders of swimmers are prone to anterosuperior impingement because the arm stroke involves a forceful combined anteflexion, adduction and internal rotation of the arm.The macroinstability of contact athletes is caused by sufficient trauma and characterized by a structural lesion of capsulolabral or bony lesion. While the empirical recurrence risk of young contact athletes is already high, it can be further impaired by bony defects of the glenoid. In suspected cases, critical glenoid defects should be quantified by computed tomography (CT) scans and treated by bony augmentation of the glenoid.

Epidemiology of primary anterior shoulder dislocation requiring closed reduction in Ontario, Canada

BACKGROUND

There is a lack of high-quality population-based literature describing the epidemiology of primary anterior shoulder dislocation.

PURPOSE

To (1) calculate the incidence density rate (IDR) of primary anterior shoulder dislocation requiring closed reduction (CR; "index event") in the general population and demographic subgroups, and (2) determine the rate of and risk factors for repeat shoulder CR.

STUDY DESIGN

Cohort study (prognosis); Level of evidence, 2.

METHODS

All patients who underwent shoulder CR by a physician in Ontario between April 2002 and September 2010 were identified with administrative databases. Exclusion criteria included age <16 and >70 years, posterior dislocation, and prior shoulder dislocation or surgery. Index event IDR was calculated for all populations/subgroups, and IDR comparisons were made. Repeat shoulder CR was sought until September 2012. Risk factors for repeat shoulder CR were identified with a Prentice, Williams, and Peterson proportional hazards model.

RESULTS

There were 20,719 persons (median age, 35 years; 74.3% male) who underwent a shoulder CR after a primary anterior shoulder dislocation (23.1/100,000 person-years). The IDR was highest among young males (98.3/100,000 person-years). A total of 3940 (19%) patients underwent repeat shoulder CR after a median of 0.9 years, of which 41.7% were ≤20 years of age. Less than two-thirds of all first repeat shoulder CR events occurred within 2 years; in fact, 95% occurred within 5 years. The risk of repeat shoulder CR was lowest if the primary reduction had been performed by an orthopaedic surgeon (hazard ratio [HR], 0.76; 95% CI: 0.64, 0.90; P = .002) or was associated with a humeral tuberosity fracture (HR, 0.71; CI, 0.53, 0.95; P = .02). Older age (HR, 0.97; CI, 0.97, 0.98; P < .0001) and higher medical comorbidity score (HR, 0.92; CI, 0.87, 0.98; P = .009) were also protective. Risk was highest among males (HR, 1.26; CI, 1.16, 1.36; P < .0001) and patients from low-income neighborhoods (HR, 1.23; CI, 1.13, 1.34; P < .0001).

CONCLUSION

Young male patients have the highest incidence of primary anterior shoulder dislocation requiring CR and the greatest risk of repeat shoulder CR. Patient, provider, and injury factors all influence repeat shoulder CR risk. A comprehensive understanding of the epidemiology of primary anterior shoulder dislocation will aid management decisions and injury prevention initiatives.

The incidence of injury among male and female intercollegiate rugby players

Background:

The National Collegiate Athletic Association classifies women’s rugby as an emerging sport. Few studies have examined the injury rates in women’s collegiate rugby or compared injury rates between sexes.

Hypothesis:

Injury rates will differ between female and male intercollegiate club rugby players.

Study Design:

Descriptive epidemiological study.

Methods:

Five years of injury data were collected from the men’s and women’s rugby teams at a US service academy using the institution’s injury surveillance system. The primary outcome of interest was the incidence rate of injury during the study period per 10,000 athlete exposures. Incidence rate ratios (IRRs) were calculated using a Poisson distribution to compare the rates by sex.

Results:

During the study period, the overall incidence rate for injury was 30% higher (IRR = 1.30, 95% CI: 1.09, 1.54) among men when compared with women; however, the distribution of injuries varied by sex. The incidence rate for ACL injury among women was 5.3 times (IRR = 5.32, 95% CI: 1.33, 30.53) higher compared with that among men. Men were 2.5 times (IRR = 2.54, 95% CI: 1.03, 7.52) more likely to sustain a fracture. The rate of acromioclavicular joint injury was 2.2 times (IRR = 2.19, 95% CI: 1.03, 5.19) higher among men when compared with women. Men were 6.6 times (IRR = 6.55, 95% CI: 2.65, 20.91) more likely to have an open wound than women.

Conclusion:

There are differences in injury rates and patterns between female and male American rugby players.

Clinical Relevance:

The differences in injury patterns may reflect distinct playing styles, which could be the result of the American football background common among many of the male players.

Isometric shoulder strength reference values for physically active collegiate males and females

Background:

It is common clinical practice to assess muscle strength during examination of patients following shoulder injury or surgery. Strength comparisons are often made between the patient’s injured and uninjured shoulders, with the uninjured side used as a reference without regard to upper extremity dominance. Despite the importance of strength measurements, little is known about expected normal baselines of the uninjured shoulder. The purpose of this study was to report normative values for isometric shoulder strength for physically active college-age men and women without history of shoulder injury.

Methods:

University students—546 males (18.8 ± 1.0 years, 75.3 ± 12.2 kg) and 73 females (18.7 ± 0.9 years, 62.6 ± 7.0 kg)—underwent thorough shoulder evaluations by an orthopaedic surgeon and completed bilateral isometric strength measurements with a handheld dynamometer. Variables measured included internal rotation, external rotation, abduction, supine internal rotation and external rotation at 45°, and lower trapezius in prone flexion.

Results:

Significant differences were found between the dominant and nondominant shoulder for internal rotation, internal rotation at 45°, abduction, and prone flexion in males and in internal rotation at 45° and prone flexion for females (P ≤ 0.01).

Shoulder instability with concomitant bone loss in the athlete

Thorough evaluation of the athlete with persistent shoulder instability and appropriate use of imaging modalities, such as 3-dimensional computed tomography, can help quantify the severity of bony deficiency. Based on obtained imaging and examination, surgical and nonsurgical methods can be considered. In many situations both the humeral- and glenoid-sided bone loss must be addressed. Depending on the extent of bone loss, athletic demands, and surgeon experience, arthroscopic or open surgical options can provide shoulder stability and return athletes to their prior level of activity.

Rotator Cuff Weakness Is Not a Risk Factor for First-Time Anterior Glenohumeral Instability

Background:

Shoulder instability is a common problem in young athletes and can lead to pain and decreased ability to participate in high-level activities. Little is known about the modifiable risk factors for glenohumeral joint instability.

Hypothesis:

Isometric shoulder strength at baseline would be a modifiable risk factor associated with subsequent first-time anterior instability events.

Study Design:

Cohort study.

Methods:

Study participants were freshmen entering the United States Military Academy in June 2006. All participants completed bilateral isometric strength evaluations with a hand-held dynamometer at baseline upon entry into the study. Variables measured included internal and external rotation at 0° (IR0, ER0) and internal and external rotation at 45° of abduction (IR45, ER45). All subjects were followed for subsequent glenohumeral joint instability events until graduation in May 2010. Independent t tests were used to analyze the data.

Results:

Baseline strength data were available for 1316 shoulders with no prior history of instability, of which 26 went on to have an acute first-time anterior shoulder instability event while the individuals were at the academy. There were no significant differences in mean strength between shoulders that did not go on to develop instability (uninjured; n = 1290) and those that did develop anterior instability (injured; n = 26). The mean strength values in pounds of force for uninjured and injured shoulders, respectively, were as follows: IR0 (49.80 vs 49.29; P = .88), ER0 (35.58 vs 33.66; P = .27), IR45 (47.38 vs 46.93; P = .88), and ER45 (40.08 vs 38.98; P = .59).

Conclusion:

No association was found between isometric shoulder strength measures at baseline and subsequent first-time anterior glenohumeral joint instability within the high-risk athletic population studied in this prospective cohort.

History of shoulder instability and subsequent injury during four years of follow-up: a survival analysis

BACKGROUND

Little is known about the risk factors for glenohumeral joint instability. We hypothesized that a prior history of instability would be a significant risk factor for subsequent injury.

METHODS

We conducted a prospective cohort study over a four-year period within a high-risk group of young athletes to address the research hypothesis. Subjects were freshmen entering the U.S. Military Academy in June of 2006. Part of the baseline assessment included documenting a prior history of glenohumeral instability on entry into the study. All subjects were followed for subsequent glenohumeral joint instability events until graduation in May of 2010. The primary outcome of interest in this study was time to glenohumeral instability event during the follow-up period. We examined injury outcomes, looking for any instability, anterior instability, and posterior instability events. Cox proportional-hazards regression models were used to analyze the data.

RESULTS

Among the 714 subjects, eight shoulders were excluded from the analyses due to prior surgical stabilization, leaving 1420 shoulders, of which 126 had a self-reported prior history of instability. There were forty-six (thirty-nine anterior and seven posterior) acute instability events documented in the cohort during the follow-up period. Subjects with a prior history of instability were over five times (p < 0.001) more likely to sustain an acute (anterior or posterior) instability event during the follow-up period. Subjects with a history of instability were also 5.6 times (p < 0.001) more likely to experience a subsequent anterior instability event and 4.6 times (p = 0.068) more likely to experience a posterior instability event during follow-up. Similar results were observed in multivariable models after controlling for the influence of demographic and baseline physical examination findings.

CONCLUSIONS

Despite meeting the rigorous physical induction standards for military service, subjects with a prior history of glenohumeral joint instability were approximately five times more likely to experience a subsequent instability event, regardless of direction, within this high-risk athletic population.

Management of mid-season traumatic anterior shoulder instability in athletes

Shoulder dislocation and subluxation injuries are common in young athletes and most frequently occur during the competitive season. Controversy exists regarding optimal treatment of an athlete with an in-season shoulder dislocation, and limited data are available to guide treatment. Rehabilitation may facilitate return to sport within 3 weeks, but return is complicated by a moderate risk of recurrence. Bracing may reduce the risk of recurrence, but it restricts motion and may not be tolerated in patients who must complete certain sport-specific tasks such as throwing. Surgical management of shoulder dislocation or subluxation with arthroscopic or open Bankart repair reduces the rate of recurrence; however, the athlete is unable to participate in sport for the remainder of the competitive season. When selecting a management option, the clinician must consider the natural history of shoulder instability, pathologic changes noted on examination and imaging, sport- and position-specific demands, duration of treatment, and the athlete's motivation.

The impact of recurrent dislocation on shoulder rotator muscle balance (a prospective study of 102 male patients)

PURPOSE OF THE STUDY

We performed an isokinetic analysis of both shoulders in 102 male patients suffering from shoulder instability after several trauma-related anterior or anterior-inferior dislocations. The analysis was part of a comprehensive medical and radiological assessment (with standard X-rays and cross-sectional imaging) prior to surgery. The study's objective was to measure the strength of the patients' internal and external rotators after recurrent dislocations (by comparing injured and healthy sides) and to evaluate the dislocations' impact on the muscles on the injured side.

MATERIALS AND METHODS

The mean patient age was 24.8 (range: 16-47). We analysed the impact of instability on rotator muscle performance according to the side (dominant or non-dominant), the number of dislocations and the severity of any associated bone damage. The isokinetic analysis was performed at least one month after the last shoulder dislocation. The same operator performed all procedures. The modified Davies position was adopted, in order to record the peak torque of the internal and external rotators during concentric contractions at 60° and 180° per second. Means and standard deviations for peak torque to body weight ratios and external/internal rotator peak torque ratios were reported.

RESULTS

After several anterior or anterior-inferior shoulder dislocations, there was a non-significant difference in the external rotator/internal rotator ratio when comparing injured and healthy sides - regardless of whether the injured side was dominant or not, the number of dislocations and the severity of bone damage.

CONCLUSION

Systematic, presurgical, isokinetic testing of the shoulder does not appear to be of value in post-traumatic instability in male patients.

Physical examination findings in young athletes correlate with history of shoulder instability

The goal of this study was to evaluate physical examination findings in a healthy cohort and determine potential correlations with a history of shoulder instability. A cross-sectional analysis was performed using the baseline data for an ongoing prospective cohort study to examine the risk factors for shoulder instability. A complete history of shoulder instability events was obtained, and a blinded physical examination was performed. The cohort comprised 711 patients (627 men, 84 women) with a mean age of 18.8 years. A total of 100 patients had a history of shoulder instability. Patients with a history of instability were more likely to have increased posterior translation (P=.010), positive apprehension sign (P=.003), positive relocation sign (P=.007), and sulcus sign (P=.017).

The epidemiology of shoulder dislocations in Oslo

There are few previous studies on the incidence of shoulder dislocation in the general population. The aim of the study was to report the incidence of acute shoulder dislocations in the capital of Norway (Oslo) in 2009. Patients of all ages living in Oslo, sustaining a dislocation of the glenohumeral joint, were identified using electronic diagnosis registers, patient protocols, radiological registers of the hospitals, and the Norwegian Patient Register (NPR). The overall incidence rate was 56.3 [95% confidence interval (CI) 50.2–62.4] per 100 000 person-years, with rates of 82.2 (95% CI 71.7–92.8) and 30.9 (95% CI 24.5–37.3) in men and women, respectively. The incidence of primary dislocations was 26.2 (95% CI 22.1–30.4). The overall incidence of shoulder dislocations in Oslo was higher than previously reported incidences. The incidence of primary dislocations was also higher than that in previously reported studies for the general population but it was close to the incidence reported in Malmø, Sweden.

The female athlete

Over time, women have become more extensively involved in athletic programs. The female athlete presents a unique challenge to sports medicine in general. Although specific types of injuries are the same as in the male athlete, the female athlete is at higher risk for some of these injuries. Injuries may be sport specific, but gender-related injuries are also related to morphologic and physiologic differences between the male and female athlete. This article reviews some of the differences between the male and female athlete and focuses on a few prominent injuries or risks related specifically to the woman athlete.

Management of shoulder instability in in-season athletes

Although shoulder instability is common in young athletes, there are limited prospective data to guide treatment for competitive athletes who sustain a dislocation mid-season. The management of athletes during their competitive season requires an understanding of the natural history of shoulder instability, the specific needs of the injured athlete (eg, specific sport, player position), and the duration of treatment. Rehabilitation can enable an athlete with a shoulder dislocation to return to play within 3 weeks of injury. Bracing is an option, but it can result in restricted glenohumeral motion and thereby possibly affect performance. Surgical stabilization should be considered for the athlete with recurrent instability or inability to perform; however, this frequently results in the termination of the player's season. In this article, we review the available literature to help guide physicians treating athletes with shoulder instability.

Pathoanatomy of first-time, traumatic, anterior glenohumeral subluxation events

BACKGROUND

Relative to dislocations, glenohumeral subluxation events have received little attention in the literature, despite a high incidence in young athletes. The pathoanatomy of first-time, traumatic, anterior subluxation events has not been defined, to our knowledge.

METHODS

As part of a prospective evaluation of all cases of shoulder instability sustained during one academic year in a closed cohort of military academy cadets, a total of thirty-eight first-time, traumatic, anterior glenohumeral subluxation events were documented. Clinical subluxation events were defined as incomplete instability events that did not require a manual reduction maneuver. Twenty-seven of those events were evaluated with plain radiographs and magnetic resonance imaging within two weeks after the injury and constitute the cohort studied. Magnetic resonance imaging studies were independently evaluated by a musculoskeletal radiologist blinded to the clinical history. Arthroscopic findings were available for the fourteen patients who underwent arthroscopic surgery.

RESULTS

Of the twenty-seven patients who sustained a first-time, traumatic, anterior subluxation, twenty-two were male and five were female, and their mean age was twenty years. Plain radiographs revealed three osseous Bankart lesions and two Hill-Sachs lesions. Magnetic resonance imaging revealed a Bankart lesion in twenty-six of the twenty-seven patients and a Hill-Sachs lesion in twenty-five of the twenty-seven patients. Of the fourteen patients who underwent surgery, thirteen had a Bankart lesion noted during the procedure. Of the thirteen patients who chose nonoperative management, four experienced recurrent instability. Two of the thirteen patients left the academy for nonmedical reasons and were lost to follow-up. The remaining seven patients continued on active-duty service and had not sought care for a recurrent instability event at the time of writing.

CONCLUSIONS

First-time, traumatic, anterior subluxation events result in a high rate of labral and Hill-Sachs lesions. These findings suggest that clinical subluxation events encompass a broad spectrum of incomplete events, including complete separations of the articular surfaces with spontaneous reduction. A high index of suspicion for this injury in young athletes is warranted, and magnetic resonance imaging may reveal a high rate of pathologic changes, suggesting that a complete, transient luxation of the glenohumeral joint has occurred.

Epidemiology of shoulder dislocations presenting to emergency departments in the United States

BACKGROUND

The epidemiology of traumatic shoulder dislocations is poorly understood. The aim of the current study was to determine the incidence of shoulder dislocations presenting to hospital emergency departments in the United States and define demographic risk factors for these injuries.

METHODS

The National Electronic Injury Surveillance System, a probability sample of all injuries presenting to emergency departments in the United States, was queried for shoulder dislocations from 2002 through 2006. Patient and injury characteristics were analyzed. United States Census data were utilized to calculate incidence rates for the United States population and subgroups. Incidence rate ratios were then calculated with respect to age, sex, and race.

RESULTS

A total of 8940 shoulder dislocations were identified, resulting in an overall incidence rate in the United States of 23.9 (95% confidence interval, 20.8 to 27.0) per 100,000 person-years. The male incidence rate was 34.90 (95% confidence interval, 30.08 to 39.73) per 100,000 person-years, with an incidence rate ratio of 2.64 (95% confidence interval, 2.39 to 2.88) relative to the female incidence rate. It was found that 71.8% of the dislocations were in males. Stratified by decade, the maximum incidence rate (47.8 [95% confidence interval, 41.0 to 54.5]) occurred in those between the ages of twenty and twenty-nine years; 46.8% of all dislocations were in patients between fifteen and twenty-nine years of age. There were no significant differences based on race. Dislocations most frequently resulted from a fall (58.8%) and occurred at home (47.7%) or at sites of sports or recreation (34.5%). Overall, 48.3% of injuries occurred during sports or recreation.

CONCLUSIONS

The estimated incidence rate of shoulder dislocations in the United States is 23.9 per 100,000 person-years, which is approximately twice the previously reported value. A young age and male sex are risk factors for shoulder dislocation in the United States population.