Purpose: To determine the incidence of anterior femoroacetabular impingement (AFAI) as a cause of idiopathic coxarthrosis in young adults.

Materials and methods: We carried out a retrospective study of 196 patients with total hip replacement (THR), selecting patients under 55 (51 cases, 26.02%). We recorded epidemiological, clinical and radiological data prior to the implantation of the THR. In all cases we used cementless stems and cups. The statistical analysis was done with SPSS software v10.0.

Results: The mean age was 50.7 (29–55). There was a predominance of men (31 cases, 61%) over women (20 cases, 39%). The mean BMI was 30.1 kg/m2 (20–42). The mean time with pain before hip arthroplasty was 8 years (2–20 years). Among the possible causes of the origin of coxarthrosis we found sequelae of acetabular fractures, hip growth dysplasias, rheumatoid arthritis, sequelae of Perthes disease and AFAI. 70.6% presented a “hump” in the head-neck junction on the axial projection, which appeared at the onset of symptoms; 10% presented frank deformity of the femoral head and 8% had protrusion of the head toward the acetabulum. The patients with AFAI presented less mean flexion (78.5°) and internal rotation (2.9°) (p< 0.05), and the predominant type of pain was inguinal irradiating to the thigh or greater trochanter (p< 0.05). The mean time from onset of symptoms to implantation of THR was less in this group (7.4 years) as compared to the rest (10.4 years) (p< 0.05).

Discussion: Murray (Br. J. Radiol 38:810–24, 1965) and Harris (CORR 213:20.23, 1986) had already mentioned AFAI as a predisposing factor in the degeneration of the coxofemoral joint. In recent years its importance has increased as the resection of the femoral hump in the initial degenerative stages has became more widespread (Tönnis 0 and I). This osteoplasty can be performed by hip arthroscopy (small humps), with dislocation of the femoral head (as described by R. Ganz) or by a very small anterior approach without dislocation of the femoral head as proposed by Ribas-Vilarubias (2004). Leunig (2005) speaks of an AFAI incidence of 15% in the general population and Tanzer (CORR 429:170-77, 2004) discovered “humps” in the femoral head-neck junction in 68–100% of patients with THR. Our study gives similar results, placing the incidence at 70.6% in patients under the age of 55 who have had a THR.

Conclusions: We think the incidence of femoroacetabular impingement is high and that this syndrome plays an important role in the onset of degeneration of the coxofemoral joint in young adults. These findings suggest the advisability of early surgery to attempt to delay the rapid progression toward primary arthroplasty at an early age.