Metal Head for Hip Reduces Wear, Potential for ion Release

DePuy Orthopaedics Inc. has launched the aSphere M-Spec Femoral Head, a new metal hip bearing option that potentially reduces cumulative wear by 80% and associated ion release by 77% compared with conventional metal-on-metal technology.(1)

This exclusive advancement in metal bearing technology is the result of DePuy’s continued investment in state-of-the-art bearing design and manufacturing. Precision contoured aSphere heads approximate the shaping that occurs during the in vivo run-in wear phase. This advanced design incorporates a wear-resistance zone, so patients may experience a substantial decrease in metal wear debris and ion release when compared to conventional metal-on-metal designs.(2)

The aSphere head, combined with DePuy’s exclusive TrueGlide technology, facilitates a more fluid range of natural motion and up to 159 degrees range of motion. The aSphere head was cleared for marketing by the U.S. Food and Drug Administration (FDA) in December 2008, adding another advanced option to DePuy’s Pinnacle Hip Solutions bearing system. 

“In addition to improved wear and ion release, the Pinnacle System’s aSphere M-Spec Femoral Heads provide optimized head-to-shell ratios, which may enhance stability and long-term performance,” says Mark Hanes, PhD, worldwide director of research, DePuy Orthopaedics, Inc.

The aSphere head is compatible with DePuy’s complete line of advanced femoral stems to provide surgeons greater flexibility based on their preferred technique and the patient’s anatomy.

“DePuy Orthopaedics continues to advance bearing technology, design, materials and manufacturing to offer surgeons and their patients a diverse and broad portfolio that addresses their specific needs and preferences,” says David Floyd, U.S. president, DePuy Orthopaedics, Inc. “The aSphere head is the latest example of our commitment to innovation that continues to optimize our premier high stability and low wear solutions.”

All DePuy metal-on-metal bearings feature TrueGlide technology, which enhances performance with smooth, natural motion and less friction. Advanced tribology is the science behind this innovation, and the main reason for improved wear resistance over conventional technology. TrueGlide technology optimizes the diametrical clearance and surface finish of the implant, allowing the body to create a thin film of synovial fluid, enabling bearing lubrication and reducing wear. The result is a smooth, more fluid range of natural motion.

DePuy remains the leader in metal-on-metal technology offering several advantages including larger diameter bearings that improve hip range of motion and stability for higher function and a reduction in the occurrence of revision surgery. In fact, one study conducted since the device was approved in 2002 observed that an estimated 99.9% of Pinnacle Hip components remain in use.

The performance of hip replacements depends on age, weight, activity level, and other factors. There are potential risks and recovery takes time. People with conditions limiting rehabilitation should not have this surgery. Only an orthopaedic surgeon can determine if hip replacement is indicated for a patient.

¹ Data on file at DePuy Orthopaedics, Inc.  Note: Reduced wear claims are based on the results of in-vitro hip wear simulator tests, which have not been shown to quantitatively predict clinical wear performance.

² Dowson D, Hardaker C, Flett M, Isaac GH. A hip joint simulator study of the performance of metal-on-metal joints; part II: J Arthroplasty. 2004;19 (8 Suppl 3):124-130