Knee implants designed for women.. Southwestern Medical Center

Orthopedic surgeons at the University of Texas Southwestern Medical Center, Dallas, are among the first to use knee implants specifically designed to fit a woman's anatomy. The implant addresses three distinct and scientifically documented shape differences in women's and men's knees.

Designed using three-dimensional computed tomography imaging, this high-flex knee more closely mimics the joints and inner workings of a woman's anatomy. 'q-his is one in a series of technical improvements in the design of knee implants that is long overdue," observes Robed Bucholz, chairman of orthopedic surgery.

During total knee replacement surgery, or adhroplasty, surfaces of the thighbone (femur), shinbone (tibia), and kneecap (patella) are replaced with a metal-and-plastic implant. Traditionally, the implants have been designed based on men's knees. For women, smaller implants were used, but size did not resolve the anatomical differences, which sometimes accounted for pain and discomfort and an "awkward" feeling. Researchers have found numerous shape differences between the average male and female knee. The new replacement addresses three gender-specific issues:

Narrower shapes. Impact size typically is based on the front-to-back measurement to allow the knee to move and flex properly. In women, however, an implant that fits from front to back can be too wide from side to side, sometimes causing it to overhang the bone.

Thinner density. Typically, the bone in the front of a woman's knee is less prominent than in a man's. After traditional implantations, some women describe a "bulky" feeling in the joint despite better function.

Tracking. A woman's femur attaches to the tibia at a slightly different angle than a man's because most women have wider hips. The angle difference between the pelvis and the knee joint affects how the kneecap tracks over the end of the femur as the knee moves through a range of motion.

Bucholz notes that about 80% of knees are replaced because patients suffer from osteoarthritis, which causes the cartilage that cushions the bones of the knee to soften and wear away. The bones then rub against one another, causing knee pain. The number of joint and knee replacement procedures performed by orthopedic surgeons is rising due, in large part, to aging baby boomers and an increasingly overweight population.

In the 1950s, the first artificial knees were little more than crude hinges; now there are a variety of knee-replacement designs that take into account age, weight, activity level, and overall health.

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