Medical Device Daily Contributing Writer

Methodist North Hospital (Memphis, Tennessee) hosted a live surgical webcast featuring a total knee replacement, with an incision measuring just 5-inch in length. Michael Lynch, MD, performed the surgery, with Bret Sokoloff, MD, narrating. Both orthopedic surgeons are with Memphis Orthopaedic Group.

The Methodist Total Joint center includes a specialized team of nurses for operating rooms, recovery and postoperative care as well as dedicated physical therapists. The center does only total joint procedures.

Each year in the U.S., about 200,000 people undergo total knee replacement surgery. While knee replacement has been around a long time, recent major advancements have greatly improved the outcomes.

The healthy knee joint is formed by the top of the shinbone called the tibia and the bottom of the thighbone, or femur. The kneecap is called the patella. Cartilage provides padding between the bones and helps assure an effortless, gliding movement of the joint. A special membrane, called the synovial membrane, produces a lubricant that contributes to the smooth movement of the knee.

When healthy, the knee is a remarkable mechanism. When arthritis intrudes, however, the knee is unable to effectively cushion the body from impact and stress. As the cartilage surface on the ends of the bones is worn away, the normal mechanics of the knee joint are altered. The knee becomes inflamed and irritated, and the damaged cartilage, inflamed tissues, and exposed bone causes pain. The result is erosion of the joint and pain that can gradually hamper one's quality of life, reducing independence and making it hard – or impossible – for the patient to do the things he wants to do.

Solokoff cited common symptoms of severe arthritis of the knee joint. “These symptoms include: swelling of the joint, knee pain, bow-legged or knock-kneed deformity, loss of motion and the feeling of the knee 'giving way.'”

Total knee replacement surgery almost always reduces joint pain. Most knee replacements last 20 years and many will last even longer. Knee replacement surgery not only allows individuals to eradicate knee pain from their daily lives; it provides them with years of easier movement and improves the quality of their daily lives.

Sokoloff took his first e-mail question. “How soon are patients back on their feet?” He replied: “Once over the recovery process, there's about six weeks to the first plateau and then about three months to golf, tennis, etc. It takes about 12 to 18 months until the operative knee is as good as the other normal knee.”

The patient was a 62-year-old woman with degenerative arthritis of the left knee. She had had a total knee replacement done on her right leg several years ago with unqualified success. Lynch showed X-rays of the left knee demonstrating wearing of the compartment and the loss of articulating cartilage.

The patient received a spinal anesthetic, then Lynch positioned a pneumatic tourniquet around the top of her operative knee. The tourniquet was inflated to control any heavy bleeding. He then prepped and draped the knee in the traditional manner. A 5-inch incision was made.

From the Internet audience: “What type of anesthetic do you usually use?” Sokoloff answered, “We prefer epidurals, not general anesthetics. We supplement with a nerve block which lasts for a day after surgery. The patients also get a pain pump. Epidurals are better than general anesthesia in terms of blood loss and there is a reduced risk of blood clots postoperatively.”

Lynch cut through the fat of the knee to the kneecap, controlling the small bleeders with electrocautery to reduce postoperative bleeding. Moving down along the side of the kneecap, he separated the quadriceps muscle for a short distance then turned the kneecap to the outside. The back of the kneecap could be seen as Lynch entered the knee joint. The inner side of the tibia could be seen and he then flexed the knee to show the pathology in the joint.

The end of the femur showed fibrillated (soft and mushy appearing) and bare bone. There was no cartilage left to protect the bone-to-bone interface. Some of the bone around the cruciate ligaments was removed. Lynch explained, “The prosthesis will substitute for the cruciate ligament. This surgical approach is better in that it retains the cruciates. It is eminently satisfactory.”

Both menisci were removed, then Lynch drilled a hole in the tibia to put in the alignment rods. The alignment rods are used to guide the jig used to make desired cuts in the bone to align the prosthesis. A saw was used along the gig, then he checked the alignment of the cut and found it straight. “This means she will be neither bowlegged nor knock-kneed,” Lynch said.

After cleaning off the soft parts of the exposed tibia, he sized the prosthesis – a Genesis II from Smith & Nephew Orthopaedics (Memphis, Tennessee). It is specifically tailored to the size of the patient's normal bone. Lynch chose a size 3, one of the smallest sizes. “We are ready to accept the base plate here on the tibia, now we move to the femur [thigh bone] side of the knee,” Sokoloff said.

Again, Lynch used guide rods and jigs to make cuts for insertion of the prosthesis. Sokoloff noted, “This prosthesis has an interesting feature. It lets the kneecap track properly after surgery. Dr. Lynch is making a slightly deeper cut in the femur here. This is in order to get to stronger bone on this outer arthritic condoyle. As he removes the distal end of the femur you can see there is no osteoporosis in this section. It is good solid bone.”

Lynch then made further cuts to shape the femur properly for acceptance of the prosthesis. The back edge of the femur was removed and a trial prosthesis was inserted in both the tibia and femoral components of the knee joint. He then placed a polyethylene interface between the two. The joint was flexed and moved side to side to check for stability and alignment.

“I'm satisfied with this alignment,” Lynch said. “Now we will insert the actual prosthesis, but first we'll clean up the back of the kneecap where we will place a plastic button. We use this caliper to measure thickness of the kneecap. The prosthetic button will restore the depth of the cap to within a millimeter of its current thickness,” he said. Then he reamed the back of the kneecap, resurfacing it. A trial button was placed. No painful areas of bone were left to rub against each other.

From the audience: “What is the life expectancy of the prosthesis?” Sokoloff answered, “It depends on the individual's weight, their general health and certainly on the alignment of the device. Most last 15 to 25 years.”

A team member began to mix the cement Lynch would use to secure the prosthetic components. Simultaneously, Lynch washed the boney areas thoroughly with Betadine solution to remove fat from the marrow to allow the cement to set better. The “cement” was actually a cold-curing acrylic polymer – methyl methacrylate. The tibial, the femoral and then the kneecap components were cemented into place. The prosthesis was of cobalt chrome, and the plastic kneecap and spacer were highly cross-liked polyethylene.

The wound was closed in a typical manner. Lynch flexed the knee and moved it side to side, demonstrating a 120- to 130-degree bend of the knee with full extension. As he dressed the wound, he concluded, “Our patients stay a remarkably short time due to improved techniques for pain management. And they are usually dismissed home, not to rehabilitation. All will have physical therapy for some weeks.”