3-D CT is the most reliable imaging modality when quantifying glenoid bone loss.

BACKGROUND: Posttraumatic anterior shoulder instability is associated with anterior glenoid bone loss, contributing to recurrence. Accurate preoperative quantification of bone loss is paramount to avoid failure of a soft tissue stabilization procedure as bone reconstruction is recommended for glenoid defects greater than 20% to 27%. QUESTIONS/PURPOSES: We determined whether radiography, MRI, or CT was most reliable to quantify glenoid bone loss in recurrent anterior shoulder instability. METHODS: Seven intact fresh-frozen human cadaveric shoulders were imaged with radiography, MRI, CT, and three-dimensional (3-D) CT. Three sequential anterior glenoid defects then were created, measured, and the shoulders reimaged after each defect. Defect sizes were less than 12%, 12% to 25%, and 25% to 40%. The gold standard measurement was determined by comparing measurements taken on the cadaver by two surgeons using digital calipers with the measurements determined by using electronic digital calipers on the 3-D CT. This measurement was used for comparison of all estimations by the evaluators. Twelve independent blinded evaluators reviewed the 112 image sets and estimated the percent of glenoid bone loss. Images were scrambled and rereviewed by the same observers 2 months later to determine intraobserver reliability. We determined reliability with kappa values. RESULTS: Kappa values between predicted bone loss versus true loss (determined by our gold standard measurements) across all 12 raters for each modality were: 3-D CT, 0.50; CT, 0.40; MRI, 0.27; and radiographs, 0.15. Interobserver agreement (kappa) values were: 3-D CT, 0.54; CT, 0.47; MRI, 0.31; and radiographs, 0.15. The intraobserver agreement (kappa) values were: 3-D CT, 0.59; CT, 0.64; MRI, 0.51; and radiographs, 0.45. CONCLUSIONS: Three-dimensional CT was the most reliable imaging modality for predicting glenoid bone loss. Regular CT was the second most reliable and reproducible modality.

Comparison of various imaging techniques to quantify glenoid bone loss in shoulder instability.

INTRODUCTION: The purpose of this study was to determine the most accurate imaging modality to quantify glenoid bone loss in recurrent anterior shoulder instability. This will allow the best preoperative prediction for patients needing a bone graft. MATERIALS AND METHODS: Seven fresh frozen shoulder cadavers were imaged with radiographs, magnetic resonance imaging (MRI), computed tomography (CT), and 3-dimensional CT (3-D CT). Native shoulders were imaged, and 3 sequential anterior-inferior glenoid defects were created, measured, and reimaged. Defect sizes were <12.5%, 12.5% to 27%, and >27%. Four blinded evaluators (2 musculoskeletal radiologists, 2 shoulder fellowship-trained surgeons) reviewed the 112 image sets and estimated the percentage of glenoid bone loss. Images were scrambled and re-reviewed by the same observers 2 months later to determine intraobserver reliability. RESULTS: Pearson correlation coefficients between predicted vs true bone loss across all 4 raters were 0.875 (3-D CT), 0.831 (CT), 0.693 (MRI), and 0.457 (x-ray imaging). Prediction errors (PE) were (mean ± SD in percentages) 3-D CT (-3.3 ± -6.6), CT (-3.7 ± -8.0), MRI (-2.75 ± -10.6), and x-ray images (-6.9 ± -13.1). Mean PE values were not significantly different among 3-D CT, CT, and MRI; however, the PE SDs were similar among the 4 evaluators for 3-D CT and lower than all other imaging techniques. Prediction based on x-ray images had the largest PE and SD. Covariance parameters revealed large variances for shoulders for MRI and x-ray imaging. The intraobserver intraclass correlation coefficients were 0.947 (3-D CT), 0.927 (CT), 0.837 (MRI), and 0.726 (x-ray image). CONCLUSIONS: The most accurate imaging modality in predicting glenoid bone loss among the 4 blinded independent evaluators was 3-D CT.

Benign subcutaneous emphysema of the upper extremity.

Benign subcutaneous emphysema is a rare clinical entity, documented by only a small collection of case reports. The presence of crepitus on physical examination and subcutaneous gas on radiographs is concerning for necrotizing fasciitis. Necrotizing fasciitis is a dangerous and deadly infection accounting for 500 to 1000 cases annually in the United States, with mortality rates of up to 76%. Delay in surgical treatment is related to increased morbidity and mortality; therefore, a high clinical suspicion should be maintained in patients with subcutaneous emphysema and/or crepitus. It is critical to recognize that no laboratory result or radiologic finding should delay surgical intervention if a high clinical suspicion for necrotizing fasciitis exists. However, not all subcutaneous emphysema represents a life-threatening infection. This article presents a case of benign subcutaneous emphysema treated with close observation and prophylactic antibiotics. Patients with necrotizing fasciitis typically appear ill and have the triad of swelling, erythema, and disproportionate pain. Patients who are not systemically ill and have minimal pain, no significant inflammatory changes at the site of crepitus, and stable hemodynamic parameters can be treated conservatively, with the caveat that close clinical monitoring is essential to avoid the unnecessary morbidity and mortality that can result from delaying intervention in the case of necrotizing fasciitis.