Risk Factors For Shoulder Instability Research Articles

Increased Glenoid Retroversion Is Associated With Increased Rotator Cuff Strength in the Shoulder

Background: The rotator cuff muscles are critical secondary stabilizers in the shoulder. Increased glenoid retroversion and rotator cuff strength have been associated with the risk of posterior shoulder instability; however, the effect of increased glenoid retroversion on rotator cuff strength remains unclear. Purpose/Hypothesis: The purpose was to examine the association between glenoid version and rotator cuff strength in the shoulder in a young and healthy population with no history of shoulder instability. The hypothesis was that increased glenoid retroversion would be associated with increases in rotator cuff muscle strength. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A prospective cohort study was conducted over a 4-year period within a high-risk population to identify the risk factors for shoulder instability. Analyzed participants included 574 freshmen entering a United States service academy. Baseline data collected upon entry into the study included magnetic resonance imaging measurements of glenoid version. Rotator cuff strength was also assessed at baseline using a handheld dynamometer. Internal and external rotation strength were assessed with the glenohumeral joint positioned in neutral and in 45° of abduction. The current study represents an analysis of the baseline data from this cohort. Results: The mean age, height, and weight of participants was 18.77 ± 0.97 years, 176.81 ± 8.48 cm, and 73.80 ± 12.45 kg, respectively. The mean glenoid version at baseline was 7.79°± 4.85° of retroversion. Univariate linear regression analyses demonstrated that increased glenoid retroversion was associated with increased internal and external rotation strength of the rotator cuff in neutral and 45° of abduction (P < .001). Similar results were observed in multivariable models controlling for important confounding variables. Conclusion: The results of this study demonstrate that as glenoid retroversion increases, internal and external rotation strength of the rotator cuff also increase in a young and healthy athletic population. These compensatory changes may contribute to increased glenohumeral dynamic stability in the presence of worse static stability with increasing retroversion.

Risk factors for anterior shoulder instability: a matched case-control study

Anatomic skeletal features of the shoulder play important roles in anterior shoulder dislocation. However, studies on the effect of the humeral structure are few. This case-control study aimed to analyze the risk factors of anterior shoulder instability, including glenoid and humeral factors. Anterior shoulder instability was found in 64 of 10,035 individuals who underwent magnetic resonance imaging. Propensity score matching was used to select controls matched for age, sex, height, and weight. We analyzed the glenoid and humeral structural data using conditional logistic regression analysis and identified cutoff points using receiver operating characteristic curve analysis. Significant differences were found between the control and dislocation groups in the depth-to-width ratio (0.119 ± 0.034 vs. 0.105 ± 0.037, P = .021), height-to-width ratio (1.51 ± 0.13 vs. 1.67 ± 0.16, P < .001), humeral head diameter-to-glenoid fossa diameter ratio (1.56 ± 0.11 vs. 1.64 ± 0.20, P < .001), and humeral containing angle (67.3° ± 5.9° vs. 60.4° ± 5.9°, P < .001). The humeral containing angle (odds ratio, 0.95; P = .024) and the glenoid height-to-width ratio (odds ratio, 7.88; P = .002), adjusted for the depth-to-width ratio and diameter ratio, were associated with anterior shoulder instability. The cutoff point for the humeral containing angle was 64° and for the height-to-width ratio was 1.60. This study revealed significant risk factors for shoulder instability in the Chinese Han population. The humeral containing angle and the glenoid height-to-width ratio were risk factors for anterior shoulder instability.

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.

Risk Factors for Anterior Glenohumeral Instability

Objectives:While anterior glenohumeral instability has been shown to be common in young athletes, the risk factors for injury are poorly understood. The elucidation of risk factors is critical to help develop prevention strategies. We hypothesized that specific modifiable and non-modifiable factors at baseline would be associated with the subsequent risk of injury in a cohort of young athletes.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-trained orthopaedic surgeon, range-of-motion, strength with a hand-held dynamometer, and bilateral noncontrast shoulder 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 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:We obtained complete data on 714 subjects. During our 4 year surveillance period, there were 38 anterior instability events documented. While controlling for covariates, significant risk factors of physical exam were: apprehension sign HR=2.96 (1.48, 5.90, p=0.002) and relocation sign HR=4.83 (1.75, 13.33, p=0.002). 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 (1.07, 61.72) p=0.043 and the coracohumeral interval HR=1.20 (1.08, 1.34, p=0.001).Conclusion:This prospective cohort study revealed significant risk factors for shoulder instability in this high-risk population. While modifiable risk factors such as strength and range-of-motion were not associated with subsequent instability, some non-modifiable risk factors were. That the exam findings of apprehension and relocation were significant while controlling for prior history of injury suggests that patients may be unaware of prior instability episodes. The anatomic variables of significance are also not surprising - tall and thin glenoids were at higher risk compared to short and wide glenoids; and the risk of instability increased by 20% for every 1mm increase in coracohumeral distance.

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).

Increased Generalized Joint Hypermobility Is Related To History Of Glenohumeral Joint Instability.

BACKGROUND: Little is known about the relationship between gender, race, generalized joint hypermobility and glenohumeral joint instability. PURPOSE: The purpose of this study was to describe the patterns of generalized joint hypermobility within a young, physically active cohort, and to examine the relationship between gender, race, generalized joint hypermobility scores, and history of glenohumeral joint instability within this population. METHODS: A cross-sectional analysis was performed to examine the relationship between gender, race, generalized joint hypermobility, and history of glenohumeral joint instability using baseline data collected on 714 subjects as part of a larger prospective cohort study to evaluate the risk factors for shoulder instability. A multivariate logistic regression model was constructed to evaluate the relationship between measures of generalized joint hypermobility and history of glenohumeral joint instability while controlling for gender and race. RESULTS: Logistic regression analysis revealed a significant relationship between generalized joint hypermobility and history of glenohumeral joint instability (C2 = 5.16, df = 1, P = 0.023). Subjects with a total Beighton Scale score ≥2 were nearly two and a half times as likely (OR = 2.48, 95% CI = 1.19-5.20, P = 0.016) to have experienced glenohumeral joint instability prior to arrival at the United States Military Academy when controlling for gender and race. A significant relationship was observed between gender and measures of generalized joint hypermobility. Females had significantly higher total Beighton Scale scores than males. Gender (C2 = 0.196, df = 1, P = 0.658) and race (C2 = 0.714, df = 1, P = 0.410) were not related to history of glenohumeral joint instability. CONCLUSIONS: This investigation provides preliminary evidence in support of the relationship between generalized joint hypermobility and glenohumeral joint instability while controlling for the influence of gender and race. Further prospective research is needed to confirm this relationship.