For the study, the scientists examined data for 537 hip resurfacing surgeries performed in the U.S. using a hip resurfacing device, called the Birmingham Hip Resurfacing implant, recently approved by the Food and Drug Administration (FDA),
They found that the majority of serious complications occurred in women of all ages and men over the age of 55.
The most common complication, and the most serious, was a fracture of the femoral neck, the slender area of bone just beneath the head of the femur.
"The ideal patients for hip resurfacing are males under the age of 55. They have the fewest, and the least serious, complications. Patients may be eager to take advantage of technological innovations, but for older individuals, a conventional hip replacement is generally more appropriate," said Dr. Craig Della Valle, lead author and a specialist in joint reconstruction at Rush University Medical Center.
Most of the patients in the study suffered from severe osteoarthritis.
Out of the 537 cases, serious complications occurred in 32 cases, including 10 cases in which the femoral neck fractured after surgery- a problem not seen with conventional hip replacements and that require additional surgery.
A total of nine fractures occurred in patients who were either female or older than 55 at the time of the implant. Eight of the fractures occurred when the surgeon was relatively inexperienced with the procedure (within the surgeon's first 10 cases).
Della Valle said that age and sex may be linked to the incidence of such fractures because of bone quality and quantity.
"Patients who are older or who are female tend to have softer bone. Also, men on average have larger bone structures, with a greater surface area for securing the implant," he said.
The researchers also identified many other serious complications, including nerve injury, joint dislocation, fracture of the proximal femur (just below the femoral neck), loosening of the metal component in the joint socket, and deep infection.
Generally, hip resurfacing is recommended for younger, more active patients because of the fear that the traditional artificial hip might wear out during their lifetime and require a second replacement, a far more complicated surgery.
"Hip resurfacing has certain advantages over the conventional total hip replacement. It preserves more bone because the head of the femur is retained. It enables the patient to return to high-impact sports because the metal components of the implant resist wear and tear and can withstand the forces associated with activities like running. Some studies have also shown that hip resurfacing carries a lower risk of dislocation because the size of the ball component is larger," said Della Valle
He added: "But despite its benefits, risks remain. Our findings suggest that we need to be cautious. This procedure is not ideal for everyone."
The study has just been published online and will appear in the January 2009 issue of Clinical Orthopaedics and Related Research.