Smith & Nephew Launches New Hip in U.S.

British orthopedic device company Smith & Nephew plc has launched its Polarstem cementless stem for total hip replacement in the United States. Available outside the United States since 2002, the implant is one of the company’s most popular stems globally and features a unique geometry and surface texture. Polarstem earned 510(k) clearance from the U.S. Food and Drug Administration in October of last year.

According to Smith & Nephew, the Polarstem implant offers several design features that assist with muscle sparing approaches for U.S. surgeons who use the direct anterior approach for total hip replacement. For example, the proximal portion of the stem is wider to help reduce the possibility of movement downward into the bone. The distal portion of the stem is shorter and features a narrower tip, making it easier to implant through the smaller incision used in the direct anterior approach. Lastly, the stem features an advanced surface texture of titanium plasma and a hydroxyapatite layer.

“The Polarstem implant has advantages over similar style stems that are currently on the market. The wider proximal fit and fill, as well as the reduced distal body of the stem has allowed a better patient fit for my patients with little to no limitations in regards to bone type or femoral morphologies,” said Jason Lang, M.D., associate professor of orthopedic surgery at Wake Forest University, Winston-Salem, N.C.

“Simply based on its excellent mid-term follow up data of 99.5 percent survivorship at 5.6 years and the design advantages it offers for minimally invasive and direct anterior surgeons, the Polarstem implant stands apart from other hip stems,” said Gaurav Agarwal, president of orthopaedic reconstruction for Smith & Nephew’s Advanced Surgical Devices Division. “However, when you add the wear-reducing advantages of our proprietary Verilast technology, the final construct truly becomes an optimal hip replacement option.”

Verilast technology is a low-friction bearing couple combining Oxinium oxidized zirconium, a patented ceramicized metal alloy for the femoral head, and a cross-linked polyethylene (XLPE) cup liner for the acetabulum. During lab testing, Verilast technology demonstrated 67 percent less wear than the combination of cobalt chrome and XLPE. In the 2013 Australian National Joint Registry, total hips utilizing the combination of ceramicized metal on XLPE was shown to have higher survivorship rates of any total hip construct utilizing other bearing combinations.

With the direct anterior approach, an incision is made on the front of the hip rather than the side or back. As a result, the surgeon can follow the natural spaces between the hip joint’s muscles and tendons, thereby minimizing the damage to the surrounding soft tissues. Because there is less soft tissue that needs to heal, patients undergoing direct anterior hip surgery reported less postoperative pain.

Additionally, because the gluteal muscles and other natural stabilizers are left undisturbed during the direct anterior approach, it is possible for patients to regain mobility more quickly and ultimately go home from the hospital sooner.