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Surgeon Reports Results of Hip Joint Resurfacing Using Minimally Invasive Approach

With every new surgical procedure come refinements and improvements in the technique by surgeons who have the experience and expertise to try something different. In this study, one orthopedic surgeon from the Cincinnati Orthopaedic Research Institute takes on hip joint resurfacing as his project. He worked diligently over a two-year period of time to reduce the size of the incision required for this operation until it could be considered minimally invasive. He reports the results compared with similar patients who had a total hip replacement.

Hip resurfacing is done by entering through the hip from the back (posterior direction), cutting through the hip capsule, and usually, cutting through the hip muscles in order to pop the hip out of the socket. It's necessary to dislocate the joint in order to gain access to the round head of the femur. It's the head of the femur that's shaved smooth and rounded in preparation for a metal cap that is placed over the bone. The cap is held in place with a peg that fits down into the bone.

Essentially, that's what joint resurfacing is all about. It means less loss of bone and a chance to preserve as much of the natural hip joint as possible until the inevitable total joint replacement is required. Hopefully, the conversion to a total hip replacement will be some years down the road. Younger adults who are more active and who only have arthritis in one hip are the best candidates for hip joint resurfacing.

In this study, Dr. M. L. Swank performed an equal number of total hip replacements and hip resurfacing procedures and compared the results in his patients. Over time, he was able to use a smaller and smaller incision with less and less disruption of the surrounding soft tissues. The early resurfacing surgeries used a 4.5-inch long incision. That was reduced by almost a full inch over time. The total hip replacement was still possible with a much smaller incision (two inches).

By the end of the study, Dr. Swank was able to avoid dislocating the joint by splitting the gluteus maximus (buttock) muscle and using the gluteus minimus to form a pocket. The head of the femur could be slipped into that pocket to perform the procedure. A similar approach was used to perform an equal number of total hip replacements. Although the hip was dislocated in order to cut off the femoral head and replace it, the resection was done under the skin. In the traditional, standard surgery, the head of the femur is popped out of the opening made by the incision and then a saw used to cut through the bone.

Doing it this way made it possible (in both the resurfacing and the total replacement) to access the head of the femur without cutting through all of the soft tissues. In theory, the advantage for the patient is a smaller incision, less pain afterwards, and faster recovery of strength, motion, and function. The results will show if that theory translates into actual measurable changes.

Those results were evaluated using pain, function, and complications as the main benchmarks of success. Pain was equally improved in both groups at the first post-operative evaluation point (three months). Over time, the joint resurfacing group had better overall pain scores compared with the total hip group. Likewise, less pain translated into better function for all patients. Before surgery, the patients who had a total hip replacement had the lowest scores on tests for function. So although the groups ended up with equivalent function a year after surgery, the total hip group had bigger before and after changes in function.

What about complications? There is a wide range of problems that can develop after either surgical procedure. Infections, fractures, implant loosening, hip dislocation, and poor wound healing are the most common complications. Sometimes patients report a painless squeaking during movement. That can occur with either type of implant and usually doesn't require any further treatment. In this study, there were a few problems in both groups but no trends or major complications to stand out in either group.

In summary, Dr. Swank concluded that it is possible to perform hip joint resurfacing with a minimally invasive technique. With less soft tissue damage and less torque on the femoral head, results were equal to and even improved over the tried and true total hip replacement. This is good news for younger, more active adults in need of a hip replacement but too young for that much bone loss. With very few complications and a rate that didn't exceed the one for total hip replacements, hip joint resurfacing using a minimally invasive approach is both safe and effective in the hands of an experienced surgeon.

References: Michael L. Swank, MD, and Martha R. Alkire, CNP. Minimally Invasive Hip Resurfacing Compared to Minimally Invasive Total Hip Arthroplasty. In Bulletin of the NYU Hospital for Joint Diseases. June 2009. Vol. 67. No. 2. Pp.113-115.

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