High incidence of femoroacetabular impingement deformity in bi-column acetabular fractures.

Introduction: Dynamic interaction of cam and pincer deformities can result in pathological contact forces in femoroacetabular impingement (FAI) syndrome. Similar deformities were noted during acetabular fracture reconstruction. We hypothesise that the prevalence of FAI deformity is higher in patients sustaining acetabular fractures than in a control group.

Methods: This retrospective radiographic study compared the parameters that define FAI deformity in 100 patients consecutively admitted to a trauma unit with an acetabular fracture and a control group of 100 patients with lateral compression pelvic fracture without acetabular injury. Both underwent identical clinical imaging. Centre-edge angles (CEA) and alpha angles were used to define patients with pincer, cam, or mixed FAI deformity.

Results: There were significantly more patients with FAI deformity in the acetabular fracture group than in the control group (71% vs. 18%, p < 0.0001). There were considerably more fractures involving both anterior and posterior acetabular columns in patients with 'pincer' sockets (p = 0.02, OR = 2.95, 95% CI, 1.12-7.78).

Conclusions: There is a high prevalence of cam and pincer deformities in patients with acetabular fractures, particularly bi-column fractures.