Traumatic hip dislocation: early MRI findings

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Abstract
Objective of this study was to present the spectrum of early magnetic resonance imaging (MRI) findings following traumatic dislocation of the femoral head, and to identify any associated injuries that may have therapeutic or prognostic significance and be better delineated by MRI than by conventional radiography. Prospective MRI of both hips was performed on 18 patients (14 male, 4 female; age range 14–54 years; average age 30.5 years) within 5 weeks of a traumatic femoral head dislocation. The interval between the time of injury and the imaging studies ranged from 2 to 35 days (average 13.2 days). Posterior dislocation was present in 14 patients and anterior dislocation in 4 patients. In the majority of cases, we performed axial T1, coronal T1, and coronal T2* (MPGR) sequences. Images were retrospectively evaluated by consensus of three radiologists for possible abnormalities of the bone and cartilage, joint space, and soft tissues. Because all patients were treated with closed reduction, surgical correlation was not obtained. All patients had a joint effusion or hemarthrosis. Of the 14 patients with posterior dislocation, isolated femoral head contusions (trabecular microfractures) were identified in 6 patients. Four patients had small femoral head fractures, and one had an osteochondral defect. Acetabular lip fractures were seen in six patients, and one patient had a labral tear. Four patients had intra-articular loose bodies and one had ligamentum teres entrapment. Twelve patients had iliofemoral ligament injury. All patients had muscle injury involving the gluteal region and medial fascial compartment, and 13 patients had anterior fascial compartment muscle injury. Seven patients with posterior dislocation had posterior fascial compartment injury. Of the four patients with anterior dislocation, two had bony contusion, two had cortical infraction, one had a labral tear, and all four had an iliofemoral ligament injury. All four patients in this group had muscle injury of the gluteal region and of the anterior and medial fascial compartments. MRI can effectively identify and quantify the muscle injury and joint effusion that invariably accompany traumatic hip dislocations. It is also useful for demonstrating trabecular bone contusion (trabecular injury) and iliofemoral ligament injury, which occur commonly with acute hip dislocation.