We prospectively evaluated the degree of absolute agreement between measurements of lateral center-edge angle (LCEA) on plain radiography (XR) and computed tomography (CT) in a consecutive cohort of 205 patients (410 hips) undergoing hip arthroscopy. Preoperative measurements of the LCEA were performed bilaterally utilizing standardized anteroposterior radiographs and coronal reformatted CT scans. Demographic variables including age, gender, height, weight, BMI and clinical diagnosis were recorded for all patients. Overall, measured values of the LCEA were 2.1° larger on CT compared with XR (32.9° versus 30.8°, P < 0.001). Subgroup analysis revealed the highest mean difference in hips with acetabular dysplasia and concomitant cam-type femoroacetabular impingement (FAI) [mean difference (CT–XR) 5.5°, 95% confidence interval (CI) 3.7°–7.3°, P = 0.011], followed by hips with isolated acetabular dysplasia (mean difference [CT–XR] 4.9°, 95% CI 2.7°–7.0°, P < 0.001). In contrast, 119 (29.0%) of the hips demonstrated larger measurements of the LCEA on 25 XR relative to CT. Of these hips, 20 (16.8%) had pincer-FAI and 25 had cam-FAI (21.0%), representing a significantly higher proportion compared with all other clinical subgroups (P = 0.045 and 0.036, respectively). Our study demonstrates measured values of the LCEA are consistently inflated on CT relative to XR for a wide variety of hip pathologies, highlighting the need for standardization and validation of CT-based measurements to improve the quality of clinical decision making.Level of Evidence: Diagnostic Level II.

Surgical interventions in the ankle are becoming more prevalent with increasing athletic demands and emerging focus on techniques for prevention of joint injury. Knowledge of the surgical techniques, imaging appearances, and complications in the postoperative ankle is necessary for the accurate diagnosis of postoperative complications and for optimal patient care.

MRI plays a critical role in the evaluation of osteomyelitis. However, MRI findings of osteomyelitis are not entirely specific and may mimic infiltrative tumors. We describe a case of extraosseous extruded medullary fat with a tiny transcortical tract caused by acute osteomyelitis, diagnosed by MRI and confirmed with intraoperative findings and pathology. Identification of extruded medullary fat is a specific MRI finding that aids in the differentiation of acute osteomyelitis from infiltrative tumor thereby preventing unnecessary biopsy and facilitating prompt diagnosis and initiation of appropriate treatment.

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Post-transplantation lymphoproliferative disorder (PTLD) encompasses a broad category of lymphoid and plasmacytic proliferations that occur following solid organ and/or allogeneic stem cell transplantation. PTLD manifests in the setting of chronic immunosuppression and is thought to be associated with the Epstein Barr Virus, although Epstein Barr Virus infection or reactivation is not required for the process to occur. Pathologic correlation is necessary for diagnosis with B-cell lymphocytes the most commonly isolated cellular etiology. There is a broad range of clinical and imaging presentations of PTLD with intestinal and nodal involvement being the most common. Imaging plays an integral part in the diagnosis and management of PTLD, as it is utilized in the initial diagnosis and staging, guiding biopsy of lesions, and gauging treatment response. Presenting symptoms of PTLD are often vague and nonspecific and depend on the organ systems affected. Musculoskeletal involvement is especially rare, with only a few cases described in the literature. We present a case with multifocal osseous manifestations of PTLD occurring years after a renal living donor transplant.