Bipolar Bone Defects in Shoulders With Primary Instability: Dislocation Versus Subluxation.

BACKGROUND: In shoulders with traumatic anterior instability, a bipolar bone defect has been recognized as an important indicator of the prognosis. PURPOSE: To investigate bipolar bone defects at primary instability and compare the difference between dislocation and subluxation. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: There were 156 shoulders (156 patients) including 91 shoulders with dislocation and 65 shoulders with subluxation. Glenoid defects and Hill-Sachs lesions were classified into 5 size categories on 3-dimensional computed tomography (CT) scans and were allocated scores ranging from 0 (no defect) to 4 points (very large defect). To assess the combined size of the glenoid defect and Hill-Sachs lesion, the scores for both lesions were summed (range, 0-8 points). Patients in the dislocation and subluxation groups were compared regarding the prevalence of a glenoid defect, a bone fragment of bony Bankart lesion, a Hill-Sachs lesion, a bipolar bone defect, and an off-track Hill-Sachs lesion. Then, the combined size of the bipolar bone defects was compared between the dislocation and subluxation groups and among patients stratified by age at the time of CT scanning (<20, 20-29, and ≥30 years). RESULTS: Hill-Sachs lesions were observed more frequently in the dislocation group (75.8%) compared with the subluxation group (27.7%; P < .001), whereas the prevalence of glenoid defects was not significantly different between groups (36.3% vs 29.2%, respectively; P = .393). The combined defect size was significantly larger in the dislocation versus subluxation group (mean ± SD combined defect score, 2.1 ± 1.6 vs 0.8 ± 0.9 points, respectively; P < .001) due to a larger Hill-Sachs lesion at dislocation than subluxation (glenoid defect score, 0.5 ± 0.9 vs 0.3 ± 0.6 points [P = .112]; Hill-Sachs lesion score, 1.6 ± 1.2 vs 0.4 ± 0.7 points [P < .001]). Combined defect size was larger in older patients than younger patients in the setting of dislocation (combined defect score, <20 years, 1.6 ± 1.2 points; 20-29 years, 1.9 ± 1.5 points; ≥30 years, 3.4 ± 1.6 points; P < .001) but was not different in the setting of subluxation (0.8 ± 1.0, 0.7 ± 0.9, and 0.8 ± 0.8 points, respectively; P = .885). An off-track Hill-Sachs lesion was observed in 2 older patients with dislocation but was not observed in shoulders with subluxation. CONCLUSION: The bipolar bone defect was significantly more frequent, and the combined size was greater in shoulders with primary dislocation and in older patients (≥30 years).

Postoperative Recurrence of Instability After Arthroscopic Bankart Repair for Shoulders With Primary Instability Compared With Recurrent Instability: Influence of Bipolar Bone Defect Size.

BACKGROUND: In shoulders with traumatic anterior instability, a bipolar bone defect has recently been recognized as an important indicator of the prognosis. PURPOSE: To investigate the influence of bipolar bone defects on postoperative recurrence after arthroscopic Bankart repair performed at primary instability. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: The study group consisted of 45 patients (45 shoulders) who underwent arthroscopic Bankart repair at primary instability before recurrence and were followed for at least 2 years. The control group consisted of 95 patients (95 shoulders) with recurrent instability who underwent Bankart repair and were followed for at least 2 years. Glenoid defects and Hill-Sachs lesions were classified into 5 size categories on 3-dimensional computed tomography and were allocated scores ranging from 0 for no defect to 4 for the largest defect. The shoulders were classified according to the total score for both lesions (0-8 points). The postoperative recurrence rate was investigated for each score of bipolar bone defects and was compared between patients with primary instability and patients with recurrent instability. The same analysis was performed for the age at operation (<20 years, 20-29 years, or ≥30 years) and for the presence of an off-track Hill-Sachs lesion. RESULTS: Bipolar bone defects were smaller in shoulders with primary instability (mean ± SD defect score, 1.4 ± 1.5 points) than in those with recurrent instability (3.6 ± 1.9 points) and were larger in older patients than in younger patients at the time of primary instability. The postoperative recurrence rate was low (6.7%) in shoulders with primary instability regardless of the size of the bipolar bone defect and the patient's age, whereas the postoperative recurrence rate was high (23.2%) in shoulders with recurrent instability, especially among patients younger than 20 years with bipolar bone defects of 2 points or greater. An off-track Hill-Sachs lesion was found in only 1 patient in the oldest age group (2.2%) at primary instability, but it was found in 19 patients (20%) at recurrent instability, including 14 patients younger than 30 years. Among patients with an off-track lesion, the postoperative recurrence rate was significantly higher in patients younger than 20 years with recurrent instability (recurrence rates: <20 years, 71.4%; 20-29 years, 14.3%; ≥30 years, 0%). CONCLUSION: The recurrence rate was consistently low in patients with primary instability and was significantly influenced by bipolar bone defect size and patient age in patients with recurrent instability.

The Number of Injury Events Associated With the Critical Size of Bipolar Bone Defects in Rugby Players With Traumatic Anterior Shoulder Instability.

BACKGROUND: The size of a glenoid bone defect is responsible for reduction in shoulder stability and is correlated with the number of instability events. Biomechanical studies have suggested that it should be considered concomitantly with the Hill-Sachs lesion as "bipolar" bone defects for assessing structural degradation, but the definitive number of instability events associated with the critical size has not been investigated. PURPOSE: To (1) confirm that the number of instability events is the predictor of a critical size of bipolar bone defects and (2) demonstrate the cutoff value of the number of instability events for these defects in rugby players with traumatic anterior shoulder instability. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: One-hundred forty-four rugby players with anterior shoulder instability underwent morphologic evaluation for glenoid and Hill-Sachs lesions by computed tomography and determination of the critical (a glenoid bone defect of ≥25% or an off-track Hill-Sachs lesion) and subcritical (a glenoid bone defect of ≥13.5%) size of bipolar bone defects. In the primary analysis, the prevalence of the critical and subcritical size of bipolar bone defects was investigated. In the secondary analysis, the authors explored the predictors for these bone defects and determined the cutoff value correlating with the critical and subcritical size of bipolar bone defects by applying receiver operating characteristic curves. RESULTS: The primary analysis revealed that the prevalence of critical and subcritical size of bipolar bone defects was 20.8% and 61.8% of 144 shoulders, respectively. In the secondary analysis, multiple logistic regression analysis demonstrated that the total number of shoulder instability events and dominant shoulder were the significant factors associated with the critical and subcritical size of bipolar bone defects. The cutoff value for the number of instability events that correlated with critical bipolar bone defects was 6 for the dominant and 9 for the nondominant shoulder, whereas it was 4 for the dominant and 5 for the nondominant shoulder for subcritical bipolar bone defects. CONCLUSION: The number of shoulder instability events and the dominant shoulder were the predictors for the critical and subcritical size of bipolar bone defects for a shoulder with traumatic instability. Four injury events should herald caution when treating rugby players with shoulder instability.

Diagnosis of Engaging Bipolar Bone Defects in the Shoulder Using 2-Dimensional Computed Tomography: A Cadaveric Study.

BACKGROUND: Anatomic studies have demonstrated that bipolar glenoid and humeral bone loss have a cumulative effect on shoulder instability and that these defects may engage in functional positions depending on their size and location, potentially resulting in failure of stabilization procedures. Determining which lesions pose a risk for engagement remains challenging, with arthroscopic assessments and a 3-dimensional computed tomography (CT)-based glenoid track method being accepted approaches at this time. PURPOSE: The purpose was to investigate the interaction of humeral and glenoid bone defects on shoulder engagement in a cadaveric model. Two alternative approaches to predicting engagement were evaluated: (1) CT of the shoulder in abduction and external rotation (ABER) and (2) measurement of the glenoid lesion width and measurement of a novel parameter, the intact anterior articular angle (IAAA), on conventional 2-dimensional multiplane reformats. STUDY DESIGN: Controlled laboratory study. METHODS: Hill-Sachs and glenoid defects of varying sizes were created in 12 cadaveric upper limbs, producing 45 bipolar defect combinations. The defect characteristics were assessed using CT with the shoulder in a neutral position. ABER CT was performed with the shoulder positioned in 60° of glenohumeral abduction (corresponding to 90° of abduction relative to the trunk) and 90° of external rotation. The IAAA was measured as the cartilage arc angle anterior to the Hill-Sachs defect on the axial slice bisecting the humeral head. The performance of the ABER CT and IAAA approaches to predicting engagement were compared with the glenoid track method. RESULTS: Of the 45 defect combinations, 24 (53%) were classified as engaging using the glenoid track method. ABER CT predicted engagement accurately in 43 of 45 (96%), with a sensitivity and specificity of 92% and 100%, respectively. A logistic model based on the glenoid defect width and IAAA provided a prediction accuracy of 87%, with a sensitivity and specificity of 92% and 81%, respectively. CONCLUSION/CLINICAL RELEVANCE: Bipolar lesions at risk for engagement can be identified accurately using an ABER CT scan or by performing 2-dimensional measurements of the glenoid defect width and IAAA on conventional CT multiplane reformats. This information will be useful for surgical planning in the setting of bipolar bone defects before shoulder stabilization.

Bony defects in chronic anterior posttraumatic dislocation of the shoulder: Is there a correlation between humeral and glenoidal lesions?

BACKGROUND: The prevalence of combined humeral and glenoid defects varies between 79 and 84 % in case of chronic posttraumatic anterior shoulder instability. The main goal of this study was to evaluate the relationship between humeral and glenoid defects based on quantitative radiological criteria. METHODS: A retrospective study was performed between 2000 and 2011 including patients who underwent primary surgical shoulder stabilization for chronic posttraumatic anterior shoulder instability, with bone defects in both the glenoid and humerus and a healthy contralateral shoulder. The following measurements were taken: D/R ratio (Hill-Sachs lesion depth/humeral head radius) on an AP X-ray in internal rotation and the D1/D2 ratio [diameter of the involved glenoid articular surfaces (D1)/the healthy one (D2)] on a comparative Bernageau glenoid profile view. Measurements were taken by two observers. Correlations were determined by the Spearman correlation coefficients (r), Bland and Altman diagrams, and intra-class correlation coefficients (ICC). A sample size calculation was done. RESULTS: Thirty patients were included, 25 men/5 women, mean age 29.8 ± 11.2 years. The mean D/R was 23 ± 12 % for observer 1 and 23 ± 10 % for observer 2. The mean D1/D2 was 95 ± 4 % for observer 1 and 94 ± 6 % for observer 2. No significant correlation was found between humeral and glenoid bone defects by observer 1 (r = 0.23, p = 0.22) or observer 2 (r = 0.05, p = 0.78). Agreement of the observers for the D/R ratio was excellent (ICC = 0.89 ± 0.04, p < 0.00001) and good for the D1/D2 ratio (ICC = 0.54 ± 0.14, p = 0.006). CONCLUSION: Humeral and glenoid bone defects were not correlated. Inter-observer reliability was excellent for the D/R ratio and good for the D1/D2 ratio. LEVEL OF EVIDENCE: Nonconsecutive Patients, Diagnostic Study, Level III.