Novel Hip Resurfacing System Helps Preserve Bone

The Conserve Plus Total Hip Resurfacing System contains a femoral and acetabular component configuration and is made of a metal-on-metal cobalt chromium molybdenum alloy. Among the advantages of the Conserve Plus system are conservation and preservation of bone stock, approximation of normal joint physiology and increased range of motion (ROM), improved stability, minimal morbidity, and easy revision (if necessary) since it does not violate the femoral canal. The device ranges in size from 36 mm – 56 mm on the femoral side, comparing favorably in regards to range of motion with traditional 22 mm, 28 mm, and 32 mm femoral heads. The clearance between components is size-dependent and ranges from 90 μ to 200 μ of diametral clearance, each bearing size having an optimized gap for maximum fluid film thickness.

The maximum range of motion with the Conserve Plus system is 167°, compared to 130° with traditional 28 mm heads; this range of motion decreases the likelihood of postoperative dislocation, which is the second leading cause of hip replacement failures.

The Conserve Plus Total Hip Resurfacing System is a product of Wright Medical (Arlington, TN, USA), and has been approved by the U.S. Food and Drug Administration (FDA).

"Hip resurfacing represents a valuable alternative to younger, more active patients who desire a hip reconstruction that more anatomically mimics the natural hip,” said Patrick Fisher, Sr., director of marketing for Wright's hip franchise. "We have learned that this is an option for patients who meet the criteria for hip resurfacing, and these individuals tend to be very enthusiastic and outspoken about their positive results.”

Metal-on-metal articulation devices are typically associated with cobalt-chromium-molybdenum alloy that has a high carbon content (over 0.20%). In addition, two types of processes used in manufacturing the cobalt chrome molybdenum components: casting and forging of the material. Although the chemical composition can be identical between the two materials, there is a structural difference; the grain size of the forged alloy is typically less than 10 μ, whereas the grain size for the cast material ranges from 30 μ to 1000 μ. Tests have shown less wear with cast high carbon alloy than forged alloy, although due to the limited number of samples, the difference has a low statistical reliability.

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