Hip resurfacing arthroplasty is a type of hip replacement that replaces the arthritic surface of the joint but removes far less bone than the traditional total hip replacement. Because the hip resurfacing removes less bone, it may be preferable for younger patients who are expected to need a second, or revision, hip replacement surgery as they grow older and wear out the original artificial hip replacement.
Usually the patient’s natural hip socket is left alone, or sometimes a thin plastic liner is put inside the socket to smooth out the surface. Most of the time, the round head of the femur gets the resurfacing. Special instruments are used to shape the bone of the femoral head so that a new metal cap can fit snugly on top of the bone. The cap is placed over the smoothed head like a tooth capped by the dentist. The cap is held in place with a small peg that fits down into the bone. The patient must have enough healthy bone to support the cap.
A recent study from the Joint Replacement Institute at St. Vincent Medical Center in Los Angeles, California was designed to compare the results between joint replacement and joint resurfacing. They wanted to look at patient characteristics called demographics such as age, gender, general health, height, weight, and so on. A second measure used in the comparison was the preoperative clinical condition of the patient: joint range-of-motion, strength, and function. And then, of course, the results or final outcomes from the surgery were compared. Patients were followed for two to four years to give an idea of what were the mid-term (intermediate) results.
The patients having hip joint resurfacing were more often men, an average of three inches taller and 10 to 20 pounds lighter, and had arthritis only in one hip compared with the total hip replacement group. The hip resurfacing patients were in better overall, general health compared with the total hip replacement group. And patients in the resurfacing group were younger than the other group by a good 10 years.
In order to keep all things as equal as possible, the patients in both groups attended physical therapy and followed the same rehab program. Activities were not restricted in any way. Patients were told to do whatever they felt up to. According to the results of tests performed on patients in both groups, the hip resurfacing group got better faster, had less pain right away, and reported higher activity levels compared to the total hip replacement group.
A closer look at the two groups showed that the total hip group gained more motion because their loss of motion before the surgery was so much greater than the hip resurfacing group. In the end, the two groups had the same hip motion in all directions. And although the hip resurfacing group got faster pain relief, they didn’t always get complete pain relief. More of the resurfacing patients still reported pain during the follow-up period. The total hip replacement patients were more likely to be pain-free at the two- and four-year follow-up visit. But that might also be because they were older and less active.
It’s natural to see the better results for hip resurfacing and think, Ah ha! That’s the better operation to have! But, in fact, the results of this study support the continued careful selection of patients to have this procedure. The good results may be more likely attributed to patient characteristics than to differences between joint resurfacing versus joint replacement. Younger, more active, healthier patients received the hip resurfacing and that seems to be reflected in the results as well. Statistical differences in joint motion and risk of dislocation weren’t observed between the two groups.