At the recent American Academy of Orthopaedic Surgeons annual meeting in Las Vegas, Nevada, a paper was presented at the Hip Society, which compared metal-on-metal large diameter hip replacement with metal-on-metal hip resurfacing. Patients were randomized into each group. The patient’s did not know if they received a hip resurfacing or a large head total hip. There were 96 patients reported in the study. All operations were done through the same posterior approach. The implants were from the same manufacturer. One group received the large head metal-on-metal total hip and the other group received the metal-on-metal surface replacement. Several quality of life outcome measures were utilized to compare the quality of life and activity level of the patients in each group. What was found was that there was no difference in the outcome between the two groups with regard to quality of life and activity level after the procedure. Both had excellent improvements in their quality of life and both were able to return to fairly high activity levels. Proponents of hip resurfacing point to its advantages of low dislocation rate, preservation of the top part of the femur and potential for increased activity in younger patients. Large head total head replacement possess the same advantages with the exception of preservation of the top part of the femur. While this is definitely an advantage to surface replacement, it must be balanced with the incidence of fracture underneath the surface replacement which has been reported at 1.5% in the Australian registry.
A second study at the Hip Society, from a different center, found the same results that functional outcome after hip resurfacing and large head total hip replacement are the same. These authors looked at gait speed, balance, functional tests, and clinical data at three, six, and twelve months after surgery. Both groups reached control function by six months postoperatively.
These two studies seem to diminish some of the advantage purported by advocates of surface replacement, but further study and follow-up is needed to definitively determine the true pluses and minuses of each procedure.