Image from: http://www.bjc-houston.com/hip/
The answer may lie in the materials the surgeons select.
A study in the Journal of the American Medical Association (JAMA Internal Medicine) has found that women are more likely than men to need follow-up surgery after receiving a total hip replacement (THR).
Few applications are as demanding as medical implants. They must withstand a highly corrosive environment. That can be achieved with common alloy steels. The hard part is that biomaterials must also integrate with biological tissue.
That task is much harder to accomplish. Relatively few materials are accepted biologically. Fewer still are able to also support the mechanical loading a hip joint requires.
About 400,000 THRs are performed each year in America with an average recipient age of 66. Overall, the likelihood of corrective surgery is 29% higher in women than in men. This gender-specific trend raises an important question, “Why are women back on the operating table more often?”
The difference in medical success between men and women may be related to implant materials and design. Of the 35,140 procedures studied, women were more likely than men to receive an implant with a smaller femoral head and a metal-on-UHMWPE configuration. Men were more likely to receive a larger femoral head and a metal-on-metal implant.
To understand the impact of materials on premature deterioration, engineers need to consider i) the amount of stress-shielding a material imposes and ii) the surface condition of the implant. Stress-shielding is a problem that reduces bone growth. It occurs when the implant absorbs impact energy instead of transferring it the bone.
As for surface conditioning, rough surfaces have proven to provide an important scaffolding structure to aid bone ingrowth. A second surface consideration is smoothness - smoother surfaces minimize wear on bearing surfaces like the femoral head.
Replacing biological systems is complex, and as noted in the study, materials science has a role to play to reduce the likelihood of a second trip to the hip surgeon.