“It used to be we only had three sizes for knee replacements, essentially small, medium, and large. Now we have at least ten different sizes,” says David Mayman, orthopedic surgeon at the Hospital for Special Surgery. Mayman says a gender-specific knee really isn’t important, but admits he would like to see manufacturers working on slimmer and wider versions of the sizes he has now. “It would be like having a 7 narrow or 7 wide shoe, instead of just a size 7 for all women,” he explains.
Getting hip
“Walking, and the differences between a woman’s pelvis and a man’s, are more of a gender concern when it comes to hip implants rather than a knee issue,” Sculco says. That’s why, Mayman adds, “We’re very particular about measuring the side of the femur [the thigh bone] in a female hip implant.” That is what will ultimately affect the leg’s range of motion and flexibility.
Unless one is totally rebuilding the hip (which is not the most common procedure), a hip replacement refers to smoothing out the top of the femur (which is shaped like a ball) and the socket—a hole at the bottom of the pelvis—so that they fit together.
Fitting a hip used to literally require cement, but Mulliken says this isn’t necessarily true anymore. “We now have ways to make the bone grow right into the implant and that makes the replacement much more stable. But we still need cement in knees,” he adds.
That doesn’t mean cement is obsolete. “If the bone is of poor quality, perhaps due to osteoporosis, the bone may not grow,” Sculco says. “So we’ll cement the implant anyway to ensure it stays in place,” A good surgeon can determine the bone quality via x-ray or when actually looking at it during surgery. A bone test called a DEXA scan done beforehand is another aide.
Other advances
There have been advances beyond the actual bone replacements. “We’ve seen the incision for a hip replacement, for example, go from up to 12 inches to only about 3 or 4 inches. That makes recovery easier and people lose less blood,” Sculco says. Mulliken agrees, saying, “Twenty years ago, a total knee replacement averaged three hours; now it’s 45 minutes.”
Sculco says he feels the biggest advance in allowing older adults to have joint replacements relates to anesthesia. “Older patients didn’t do well with general anesthesia,” he says. “Now we use an epidural, sedating the patient lightly. The patient is more alert so there’s less confusion afterward. There are fewer breathing problems.”
This kind of anesthetic is also a big reason for less blood loss and shorter time spent in surgery. Computer technology allows surgeons to be more precise in joint placement. “It’s like having a computer guidance system. It helps me find the ideal placement 95% of the time versus 80% of the time when I had to do it with just my own vision,” Mayman says.
“Pain management is another big advance. After surgery, we control patients’ pain much better,” Sculco says. Besides leading to less mental fogginess, pain management “is a big key to success in getting someone out of bed the same day instead of in four days,” he adds.
Whether you’re seeking a hip or knee replacement, bring all of your concerns and goals to your orthopedic surgeon. That is ultimately the person to help you determine the implants and procedures most likely to meet your expectations.