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Patients with Perthes Disease May Benefit from Metal-on-Metal Hip Resurfacing

Legg-Calve Perthes disease, a disease where the femoral head, or the top of the thigh bone, softens and breaks down, occurs most often in children between 4 and 8 years old, but leaves damage in the hip that results in problems in adulthood.

Total hip arthroplasties, or replacements, (THAs) use the femur (thigh bone) to help stabilize the implant. However, this can be difficult if the part of the bone has been damaged by Perthes disease. For this reason, the authors of this study wanted to see if total hip resurfacing, a procedure that only replaces part of the hip, and reshapes and caps the head of the femur instead, would be a better option for these patients.

Hip resurfacing is being done more often among people under 55 years old who need hip replacements. The advantages include they are harder to dislocate and they don't require as much word done on the remaining bone as a full replacement. This gives surgeons more to work with if additional hip surgeries are needed as the patients get older.

The records of 18 patients were examined for this study. One patient had both hips resurfaced, for a total of 19 hips to be reviewed. Following the surgery, all patients were allowed to stand and participate in physiotherapy, although weight bearing was only at 50 percent until 6 weeks after the surgery. Hip progress was assessed before surgery and then at 6 weeks, 6 months, and 1 year after the procedure, and annually thereafter. The physicians used the Harris hip score (0 to 100, with 100 being the best), and x-rays. Patients did self-evaluations with the Short Form-12 Health Survey that assessed the mental component and physical summary, also at the time of the doctor assessments. In order to compare the treatment group with others who had THAs, the authors did a literature search to identify similar patients and to review their outcomes.

The results of the hip resurfacing were positive. Before the surgery, the Harris hip score ranged from 16 to 68. Although 1 patient did not do well, for the rest of the patients, this score rose to 53 to 98 following surgery. The patient who did not do well went on to have a THA. The researchers found that the patients' range of motion of the hip improved from 70 degrees to 140 degrees before surgery to 115 degrees to 140 degrees after surgery.

One of the problems experienced by these patients is the shortening of one leg. The average shorter leg was shorter by 11.3 millimeters before the surgery. This improved to 6.7 mm after the surgery.

The authors concluded that although there was no true control group due to the unavailability of such a group, the study's findings indicated that through the follow-up period, the hip resurfacing was a success for this patient group. They pointed out that due to the possible increased damage to the femur among patients who had Perthes disease, this approach allows for a stronger result than a THA.

References: Harold S. Boyd, MD, et al. Resurfacing for Perthes Disease. In Clinical Orthopaedics and Related Research. December 2007. Vol. 465. Pp. 80-85.

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