Femoral stems with exchangeable necks are a recent development in hip arthroplasty. They are proposed to be better in restoring offset and leg length while not compromising the fixation in the femoral canal. Few studies have been published on the clinical and functional outcome of modular neck hip system.

The Australian Joint registry data was analysed to evaluate the outcome after modular neck hip arthroplasties with the diagnosis of primary osteoarthritis. Only prostheses with data for more than 50 patients were studied. The indications for revision were identified. A comparison of outcomes with conventional hip arthroplasties was done.

The analysis confirmed that femoral stems with exchangeable necks have a significantly higher risk of revision compared to all other primary total conventional hip replacement (adj HR=2.13; 95% CI (1.88, 2.42), p<0.001). With the exception of three, all femoral stems with exchangeable necks have a higher rate of revision compared to primary total conventional hip replacement. The three exceptions have a short follow up. There is an increased incidence of revision for loosening and dislocation.

The recent registry data suggests that with end point being revision, the outcome of exchangeable neck hips are worse than conventional hips in patients with primary osteoarthritis of hip.