Total knee replacement restores the smooth surfaces on the end of knee bones. Conceptually, the painful arthritic surfaces are replaced with highly polished metal and plastic. Smooth caps are permanently secured to the end of femur, tibia, and kneecap with cement. The remaining normal bone, ligaments, and muscle are preserved. The operation lasts less than an hour. In the end, a virtually pain-free gliding surface is restored.
Only recently is was quite common to overhear that TKR was too painful, required too long a recovery, and was dreadful compared to hip replacement. While knee replacement remains a major operation, recent developments have improved the recovery process. In TKR, long term durability is still the overall goal, but a new emphasis has been placed on achieving better function, accelerating rehabilitation, and minimizing pain.
Progress in postoperative recuperation is credited to several technical changes in the surgery. Most obvious to patients is a major reduction in the skin incision. Depending on the size of a patient and a patient’s knee, surgeons can shrink the length of the incision by up to a third or a half of the classic incision’s length. Below the skin, well-established dissection techniques and miniaturized instrumentation have been modified to reduce intraoperative muscle and tendon trauma. Rather than divide the quadriceps muscle and tendon in half, surgeons now preserve the majority, and at times the entirety, of the muscle sleeve. Preserving the quadriceps attachment to the patella keeps the muscular forces intact.
Reducing muscle trauma in TKR has a direct clinical benefit. Clinical studies demonstrate not only a faster return of muscle function, but also a lasting improvement in range of motion. Currently, most healthy patients will leave the hospital in 2 to 3 days with only a cane. The vast majority will be independent enough to go directly home.
One major advance in biomaterials may now allow these patients to pursue work or recreation over a longer term. The bearing surface is now manufactured from enhanced materials, with either compression molded or highly crosslinked polyethylene. The stable, fixed-bearing designs continue to outperform rotating or mobile knee replacements in several major studies. Furthermore, for select patients who require even greater knee flexion for social, cultural or religious reasons, modern “High Flexion” implants will allow the knee to safely bend up to 155 degrees.
Finally, surgery these days is less painful and less frightening. Routine patients no longer require general anesthesia or ventilator assistance. Strict attention to postoperative pain management protocols have been a major success. With oral premedication, pain fibers are blocked before they can be activated. Regional nerve blocks provide safe and thorough analgesia both intraoperatively and postoperatively. Preoperative education classes not only prepare the patient and family for surgery and recovery, but also demystify the complexities of knee replacement.