The theoretical benefits of increasing the head size in the articulation is a reduced rate of dislocation, one of the more common and debilitating complications of hip surgery. By increasing the femoral head size, the surgeon increases the ratio of the diameter of the head to the neck of the prosthesis. This reduces the chance that the femoral component will “impinge” on the bone or the rim of the acetabular component.
The theoretical benefits of using a slightly larger head in the bearing surface should be considered against the fact that in some bearing surfaces, particularly polyethylene, an increased size of femoral head can result in a slightly increased rate of wear.
The decision with regard to the best bearing surface for any patient should be taken and tailored according to the patient’s age and activity profile both in terms of social and occupational activities. This should all be discussed with the surgeon at the time that any decision is taken to proceed towards hip replacement.
It is essential, with whatever bearing surface is used, that the implants are in perfect position and the hip is well ‘balanced’ in terms of soft tissue tension. Virtually any bearing surface will show accelerated wear, and likely an increased dislocation rate, if the implants are not well aligned. Similarly, accelerated wear can be associated with abnormal or excessive activity on the part of the patient. What is thought to be an ‘acceptable’ activity level after surgery, including the expected safe range of movement, should be discussed with the surgeon before the procedure is planned and undertaken.
In summary it is important, in my opinion, that any surgeon that carries out a number of hip replacements should have experience and understanding of all of the various bearing surface options to allow the patient and surgeon in consultation to make a sound evidence-based decision in each and every circumstance.