A prospective randomised study of periprosthetic femoral bone remodeling using four different bearings in hybrid total hip arthroplasty.

We performed a study to assess whether different bearing materials have an impact on femoral bone remodeling within the first four years after a hybrid total hip arthroplasty. 205 of 300 patients were available for 4 years follow-up after being randomly allocated to four prosthetic combinations: A: Zirconia ceramic head, polyethylene cup; B: Cobalt-Chrome-Molybdenum head and cup; C: Zirconia ceramic head, polyethylene moulded on the Titanium shell of the Asian cup; D: Alumina head and cup. Bone mineral density (BMD) was measured with Dual-Energy X-ray Absorptiometry in seven Gruen zones adjacent to the femoral implant. Scans were performed within one week after surgery and four years postoperatively. Clinical outcomes were monitored using the Oxford Hip Score (OHS). A high proportion of patients from group D were excluded due to re-operations (19 patients). BMD decreased significantly in all Gruen zones with the largest declines in group D. BMD changes in Gruen zones 1, 2, 3, 6, and 7 correlated with height, and body weight. Advanced age was associated with an increase in bone loss in Gruen zones 1, 2, 3, 6, and 7. A large stem size was associated with a decline in BMD in Gruen zones 1, 6, and 7.Bone remodeling after total hip arthroplasty may depend on the composition of bearing materials, but age, height, weight, and stem size are also related to changes in BMD.