RESUMO
INTRODUCTION: The purpose of this study was to assess the natural history of bone bruise and bone mineral density (BMD) after traumatic hip dislocations and conservatively treated acetabular fractures. Our hypothesis was that poor bone quality can influence degree of bone bruise and, in time, cause degenerative changes. MATERIALS AND METHODS: Eight consecutive patients with traumatic hip dislocations and five patients with conservatively treated fractures in the femoral head and/or acetabulum were included. Magnetic resonance imaging (MRI) was obtained after 1, 17, 42, 82 and 97 weeks. Dual-emission X-ray absorptiometry (DXA) measurements were made after 10 days and 2 years. Sizes of bone bruise lesions were measured and classified. At the 2-year follow-up, Harris hip score (HHS) was calculated and signs of radiological osteoarthritis (OA) registered. RESULTS: The bone bruise changes were small and all changes resolved within 42 weeks in all, except for three patients; one with a small Pipkin fracture had segmental avascular necrosis (AVN) of the femoral head, one had persisting1-3mm small spots of bone bruises in the femoral head and the third had <1cm lesions in both the femoral head and the acetabulum. The lesions were bigger in the femoral head in the hip dislocations and more pronounced in the acetabulum in the fractured acetabuli. We found no significant changes in BMD in four regions of interest (ROIs) after 2 years. No patients developed OA, and all had excellent HHS except for the one patient with AVN. CONCLUSION: The post-traumatic bone bruise changes in the dislocated hips and the fractured acetabuli were small and transient compared to findings of other authors examining traumatised knees. The patients had excellent function and no OA after 2 years if they did not develop AVN. In our small sample of relatively young patients with normal age-adjusted BMD, no post-traumatic osteopenia was observed. This might differ in the elderly with poorer bone quality; further studies are needed to assess that.
