Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Divergent dislocation of the elbow is defined as a specific elbow dislocation in which the distal humerus is forced between the proximal radius and ulna, resulting in separation or divergence of the proximal forearm bones. This is an uncommon injury in children, with 14 cases reported in the last 23 years. The authors report three additional cases and the findings from cadaver elbow dissections in which the injury was reproduced. The authors propose that there is only one type of divergent dislocation, resulting from indirect forces transmitted to the elbow from a fall on the outstretched hand. The injury predominantly occurs in younger children because joint laxity is a predisposing cause. Early recognition, followed by a closed reduction and a 3- to 4-week period of cast immobilization, should result in a full recovery for most children.

III.

Aims Iliopsoas impingement occurs in 4% to 30% of patients after undergoing total hip arthroplasty (THA). Despite a relatively high incidence, there are few attempts at modelling impingement between the iliopsoas and acetabular component, and no attempts at modelling this in a representative cohort of subjects. The purpose of this study was to develop a novel computational model for quantifying the impingement between the iliopsoas and acetabular component and validate its utility in a case-controlled investigation. Methods This was a retrospective cohort study of patients who underwent THA surgery that included 23 symptomatic patients diagnosed with iliopsoas tendonitis, and 23 patients not diagnosed with iliopsoas tendonitis. All patients received postoperative CT imaging, postoperative standing radiography, and had minimum six months’ follow-up. 3D models of each patient’s prosthetic and bony anatomy were generated, landmarked, and simulated in a novel iliopsoas impingement detection model in supine and standing pelvic positions. Logistic regression models were implemented to determine if the probability of pain could be significantly predicted. Receiver operating characteristic curves were generated to determine the model’s sensitivity, specificity, and area under the curve (AUC). Results Highly significant differences between the symptomatic and asymptomatic cohorts were observed for iliopsoas impingement. Logistic regression models determined that the impingement values significantly predicted the probability of groin pain. The simulation had a sensitivity of 74%, specificity of 100%, and an AUC of 0.86. Conclusion We developed a computational model that can quantify iliopsoas impingement and verified its accuracy in a case-controlled investigation. This tool has the potential to be used preoperatively, to guide decisions about optimal cup placement, and postoperatively, to assist in the diagnosis of iliopsoas tendonitis. Cite this article: Bone Jt Open 2023;4(1):3–12.

Major kinematic pattern deviations could be associated with (a) morphology of the proximal femur and potential femoral acetabular impingement problems and (b) leg length discrepancy. Gait analysis was able to quantify the kinematic deviations due to the anatomical deformities.