Active people are living longer and are able to enjoy sports and physical activities well after their “fifties.” Orthopedic surgeons are enjoying increased success at replacing human joints with better and longer lasting technologies. Space age bio-materials and computer assisted improvements are now helping patients with joint pains and arthritis live a better and more active life. Most people over 50 know a friend or relative who has had a total hip or total knee replacement. Newer technologies are predicted to improve the lifespan of modern joint replacements to 30 years and beyond. It is now possible to do these operations on younger, more active patients, and feel good about the long term prospects. Previous recommendations to avoid certain sports and labor are changing as we see patients with joint replacements doing better enjoying activities such as tennis, golf, and skiing.
One new technique in knee replacement involves the use of a computerized navigation system to plan and more accurately execute the positioning of the implants. Much like the “GPS” system in your new car, the total knee computer calculates a mathematical image of a patient’s leg after the surgeon inputs a number of specific anatomical data points. The computer screen shows an image of the knee than can move in real time. It also calculates the best position and angle to make the bone cuts so that the resulting knee replacement will be well balanced and aligned.
Orthopedic surgeons and bio-engineers believe the key to longer lasting knee implants is near “perfect” alignment to minimize wear, much like the need to maximize the alignment of the tires on your car. Presently the alignment data is transmitted form the leg to the computer by an infa-red sensor which “reads” the position of six fixed points marked on the limb using small removable pins. In the future, the pins will be replaced with permanent electrode capsules, much like implantable chips that can be placed in pets to locate them if they are lost. The chips will transmit position data to the computer, and when combined with future “smart implants” will let the surgeon know if the implants are functioning normally. Patients with chip-imbedded implants will get a check up by placing the leg under the “GPS” sensors, so the surgeon can “see” beneath the skin on his computer screen as the patient moves his knee.
Other advances involve using less invasive “tissue sparing” approaches to the hip and knee joints. The Direct Anterior Total Hip replacement procedure uses a special table that can allow placement of the hip implants without cutting any muscle. By limiting the soft tissue trauma as the implants are placed on the skeleton, the functional recovery is accelerated. As the Medical Director of the new Scottsdale Healthcare Joint Replacement Center on the Osborn campus, we have established a program that emphasizes a rapid recovery. All patients walk about 2 hours after their surgery is completed with full weight bearing unless there is an unusual circumstance. Patients have their surgery with a pumping boot on the non-operative leg to keep blood circulating at all times, and we have seen a significant decrease in clotting problems. Since patients are up walking so fast, they spend less time in bed, and have less risk of forming blood clots in their veins. The Anterior hip patients can get back to work often within one week. They have no restrictions regarding hip dislocation precautions, so they can do functional activities much faster. The Anterior hip patients have much less pain then the previously done posterior procedures which cut the gluteus and external rotator muscles in the buttocks. Larger diameter femoral heads are now routinely used to increase hip stability and range of motion. This allows patients to do more activities earlier, as the risk of hip dislocation is much less than it used to be with smaller diameter femoral heads.
New techniques in anesthesia have decreased the pain associated with knee replacement surgery. A femoral nerve block can be placed at the patients discretion in the pre-operative area which greatly decreases the immediate pain upon waking up, yet still allows early ambulation. Knee implant designs are also improving, which will significantly increase the life span of total knees. I often use a mobile bearing highly cross-linked polyethylene insert called a “rotating platform” in younger and more active patients. This allows a few degrees of twisting motion in the knees during sports such as tennis and golf, and acts as an additional shock absorber over the long term.
Partial knee replacements are done in patients with an arthritis limited to one side of the knee. These are done through a very small incision that does not violate the quadriceps muscle, and recovery is very rapid. Patients with partial knees often go home after a one night stay in the hospital, and in most cases do not need formal physical therapy to regain their knee motion. The partial knee procedure is also less stressful on elderly patients and patients with significant heart or vascular disease. The bottom line is that younger patients are now better candidates for joint replacement surgery than in the past. More patients are choosing a joint replacement to get on with the most active and productive times of their life.
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