Smith & Nephew Touts Results of Hip Resurfacing Study

Not every company exhibiting at this year’s meeting of the American Academy of Orthopaedic Surgeons had a new product to debut. Some, like Smith & Nephew plc, showcased existing devices but cleverly timed the release of clinical study results to coincide with the event.

Among the products showcased at the London-based firm’s ostentatious orange-and-black booth during the show (which runs through Feb. 11 in San Francisco, Calif.) was the Polarcup Dual Mobility Hip System, a device designed specifically to address the challenges of treating patients—in both primary and revision cases—who are susceptible to dislocation and need enhanced stability.

The Polarcup System, according to Smith & Nephew, allows surgeons to implant a smaller, constrained femoral component within a larger, anatomically sized polyethylene head, this providing greater stability by increasing range of motion and jump distance. “The stability philosophy is widely used in the European market where surgeons have extensive experience with dual mobility in elderly and less active patients,” said John Soto, senior vice president for Smith & Nephew’s Global Hip Franchise.

The Polarcup System complements the company’s Birmingham Hip Resurfacing (BHR) System, which took center stage on the second full day of the meeting when Smith & Nephew announced the results of a new clinical study for the device. Conducted at the request of the U.S. Food and Drug Administration, the study followed the progress of 400 United Kingdom-based BHR patients and found that 99 percent either were satisfied or extremely satisfied with their procedure after 10 years.

“These results further exemplify why the BHR Hip is unlike any other metal-on-metal implant,” Soto said. “Not only does the BHR Hip offer all the advantages of hip resurfacing, including bone-conservation, greater range of motion and decreased risk of dislocation, but it does so while maintaining implant survivorship rates that are on par with, or in some patient populations even better than, traditional total hip replacement which has long been considered the most successful orthopedic surgical procedure for relieving chronic pain.”

In addition to patient satisfaction, the 10-year BHR data showed:

• The Oswestry Modified Harris Hip Score (OMHHS) averaged 92.5 points;
• The implant survival rate according to the Kaplan-Meier analysis was 95.9 percent, exceeding the 10-year implant survivorship threshold of 90 percent that was established by the National Institute for Health and Clinical Science; and
• A radiographic success rate of 99.7 percent.

The study results, Smith & Nephew executives claim, prove the BHR Hip is better than its competitors’ products, particularly those that have been recalled. The company attributes the success of its BHR Hip to the device’s metallurgy and design geometry. The BHR Hip, according to Smith & Nephew, has a metallurgy history that dates back more than 30 years and includes first-generation metal-on-metal materials. In particular, the BHR Hip is made using an “as cast” process that maintains the quantity and quality of carbides in the metal, thereby creating a material with high wear resistance.

Additionally, the BHR Hip’s design geometry replicates the natural hip’s ability to pull the body’s own joint fluids into the space between the ball and socket. Much like the lubricating barrier in a healthy hip, BHR’s geometry creates a natural fluid layer between the femoral head and the cup so the two metal surfaces glide smoothly during physical activity. Without this lubrication, higher metal wear occurs and the likelihood of premature failure increases.

The 10-year study sample was comprised of patients who received implants by primary investigator and BHR design surgeon Derek McMinn, M.D., F.R.C.S., of The McMinn Centre in Birmingham, England. The study included 258 males and 142 females who underwent either unilateral or bilateral hip replacements and were about 53 years old on average (the age range stretched from 23 to 84).

While the BHR implant closely matches the size of a patient’s natural femoral head (hip ball), it substantially is larger than the femoral head of a traditional total hip replacement implant. This increased size translates to greater stability in the new joint, and it decreases the chance of dislocation of the implant after surgery, Smith & Nephew executives noted. Dislocation is a leading cause of implant failure after total hip replacement.

Total hip replacement involves the removal of the entire femoral head and neck. The BHR technique, however, leaves the head and neck untouched. It is this neck length and angle that determines the natural length of a patient’s leg after surgery; since it is not removed and replaced with an artificial device during the resurfacing procedure, there is a greater likelihood of maintaining accurate leg length, the company claimed.