Purpose of the study: Although the association between femoroacetabular impingement and degenerative hip disease has been well established, there is no way to detect a subgroup of hips with radiographic signs of impingement which will progress to degeneration. In addition, the majority of publications on the topic have been conducted in populations of patients with an overtly degenerative hip, where the incidence of signs of impingement is higher. There has not been any study searching for the presence of signs of impingement in a symptom free population. For this reason, we searched for signs of femoroacetabular impingement in a general population and attempted to find correlations with degenerative hip disease.

Material and method: We examined 200 computed tomography (CT) series of the pelvis performed for reason other than an orthopaedic indication. Four hundred hips were thus analysed with the Amira 4.1 3D software. We measured the classical coxometric parameters, orientation of the acetabulum, alpha angle, and presence or not of a bulge at the head-neck junction. Cartilage thickness was also mapped using a precise protocol. Cartilage thickness less than 0.25mm was considered for the purpose of this study to indicate degenerative disease. All data were processed with SPPS 17.0.

Results: There were 103 men and 97 women, mean age 58 years and 59 years respectively. The mean alpha angle was 55.7. Retroversion was noted in 20% of hips and 28% exhibited an anterior bulge at the head-neck junction. The mean cartilage thickness at the anterosuperior part of the hip was 37mm. Degenerative disease was present in 28 patients (14%) whose mean cartilage thickness at the anterosuperior portion of the joint was 21 mm. There was no significant correlation between cartilage thickness and acetabular orientation, alpha angle, presence of a bulge at the head-neck junction. Only age was significantly correlated with degenerative disease r=−0.158 [p< 0.0].

Discussion: Among the parameters currently considered to be risk factors for degenerative disease of the hip joint, age alone was statistically linked with reduced cartilage thickness in our symptom-free population. This would suggest that the essential mechanism underlying degenerative disease remains to be discovered.

Conclusion: Our findings suggest we should be prudent when proposing corrective surgery for femoroacetabular impingement. Such surgery should be reserved for symptomatic patients.