Dislocation of primary total hip arthroplasty with 36 and 40-mm femoral heads.

Some authors suggest the use of larger (36 and 40 mm) femoral heads against highly cross-linked polyethylene acetabular liners will reduce the prevalence of early dislocation after primary total hip arthroplasty (THA). We prospectively followed 61 consecutive patients at high risk for dislocation to determine the prevalence of early dislocation after primary THA with 36 and 40 mm femoral heads. We established specific indications for the use of these larger heads in primary arthroplasty. There were 65 hips in 61 patients with a minimum followup of 1 year (mean 2 years, range 1-4 years). There were 55 36 mm heads and 10 40 mm heads. All arthroplasties were performed by the posterior approach with capsular repair. The prevalence of early dislocation was 4.6% (3 of 65). There was one patient with an anterior dislocation and two with posterior dislocation. No patient underwent reoperation for dislocation. There was no dislocation in the 10 hips that had a 40 mm head. We identified no complications related to the larger femoral heads. The use of larger femoral heads did not notably reduce the prevalence of early dislocation after primary THA in high risk patients compared to historical controls.