Hip resurfacing is often seen as a modern alternative to the more conventional total hip replacement, but new data from a study led by Rush University Medical Center in Chicago, USA, suggest that a patient's age and gender are key to the operation's success. The study will be published in the December issue of the Springer journal Clinical Orthopaedics and Related Research.
In a review of over 500 surgeries performed in the United States using a hip resurfacing device recently approved by the Food and Drug Administration (FDA), the researchers 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.
In hip resurfacing, the femoral head remains, but its surface is reshaped to accept a rounded cap with a short stem that sits in the femur. A thin metal cup is pressed into the hip socket. Both components are made entirely of cobalt chrome, a metal.
"The ideal patients for hip resurfacing are males under the age of 55. They have the fewest, and the least serious, complications," said Dr. Craig Della Valle, lead author and a specialist in joint reconstruction. "Patients may be eager to take advantage of technological innovations, but for older individuals, a conventional hip replacement is generally more appropriate."
The researchers analyzed data for the first 537 hip resurfacing surgeries performed in the United States after the Birmingham Hip Resurfacing implant, manufactured by Smith & Nephew, was approved by the FDA in October 2006. The majority of the patients suffered from severe osteoarthritis. All 89 orthopedic surgeons involved in the procedures had undergone training required by the FDA before conducting their first cases. Their level of experience with hip surgery varied. Some were joint replacement specialists; others were general orthopedic surgeons.
Serious complications occurred in 32 of the 537 cases, including 10 cases in which the femoral neck fractured after surgery, a problem not seen with conventional hip replacements. Such fractures require additional surgery. Nine of the fractures in the study 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).
"Patients who are older or who are female tend to have softer bone," Della Valle said. "Also, men on average have larger bone structures, with a greater surface area for securing the implant."
Hip resurfacing is generally recommended for younger, more active patients out of concern 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," said Della Valle. "It preserves more bone because the head of the femur is retained. But despite its benefits, risks remain. Our findings suggest that we need to be cautious. This procedure is not ideal for everyone."
Reference
Della Valle CJ et al (2008). Initial American Experience with Hip Resurfacing Following FDA Approval. Clinical Orthopaedics and Related Research. DOI 10.1007/s11999-008-0563-2
The full-text article is available to journalists as a pdf.
Journal
Clinical Orthopaedics and Related Research