[Anterior femoroacetabular impingement after healed femoral neck fractures]

To describe anterior femoroacetabular Impingement (AFAI) as a cause of persistent painful loss of motion and progressive joint-destruction in patients with a healed femoral neck fracture, and to evaluate results after its surgical treatment.Eleven patients with groin pain elicited by motion and exertion following a healed femoral neck fracture were diagnosed clinically, by conventional radiographs and radial Arthro MRI with AFAI. During surgical subluxation or dislocation of the hip joint the impingement was visually verified and eliminated by re-shaping the anterior contour of the head-neck-junction.All patients presented a flat contour of the anterior head-neck-junction causing a cam-type impingement with subsequent damage of the anterior-superior acetabular cartilage adjacent to the rim. These chondral changes result from the repetitive compression and shear forces between the flattened head-neck junction and the acetabular cartilage in flexion and internal rotation. At five year follow-up a clear improvement of the symptoms was observed without any signs of progressive joint destruction.When chronic pain after a healed femoral neck fracture without necrosis of the femoral head occurs, the possibility of an AFAI caused by retrotorsion of the proximal fragment should be taken into consideration. The symptoms of AFAI can be relieved by surgical correction of the femoral head-neck-offset. The existing damage of the acetabular cartilage originated by the impingement at the time of surgery can hardly be improved. Therefore anatomical fracture reduction should be performed in order to prevent the development of osteoarthritis. Pre-existing deformities of the joint should be treated at the time of operative fracture treatment.