Minimally invasive surgery for total hip or knee replacement has become more common, but it’s not always the right choice. There are pros and cons to this technique as well as to traditional total joint replacement (TJR).And in about 10% of cases, a second or revision surgery will be necessary.

The human body has been compared to a machine with many complex and intricate parts. Like any machine, the body’s mobile parts, its joints, wear out over time. Sophisticated technological advancements in bioengineering and in medicine have made joint replacement possible. More recently, these surgeries are less invasive than ever for the patient.

Each year in the United States, orthopaedic surgeons perform about 120,000 hip replacements and approximately 300,000 knee replacements. Ever since the first total joint replacements (TJRs) in the 1970s, the prostheses (artificial joints) and their components have become more durable, and patient satisfaction has been very high because of pain relief and improved mobility.

Anyone with advanced osteoarthritis—the leading indication for TJR—knows how excruciating the pain can be. Healthy hips and knees move easily and painlessly because of the smooth layer of cartilage that acts as a shock absorber for the joints. When cartilage becomes thin, cracked, or otherwise damaged, the joints stiffen and become painful. Bone rubs against bone. The joint lining—synovium—can also become inflamed and cause pain. The wear and tear on joints over time makes osteoarthritis common among older people, but injury, being overweight, and developmental and inflammatory conditions can lead to degenerative joint disease as well.

Dr. Calin Moucha

Although it’s tempting for patients to want a “quick fix” for their hip or knee pain, TJR shouldn’t be rushed into, believes Dr. Calin Moucha, assistant professor of orthopaedics at New Jersey Medical School and a specialist in adult joint reconstruction at University Hospital.

“There’s no such thing as a small surgery. Every one of my patients goes through a trial period of conservative measures, such as physical therapy and medication,” he says.

The medicines can include acetaminophen; traditional nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin or ibuprofen; or newer COX-2 inhibitor such as Vioxx or Bextra. However, these drugs can all have undesirable side effects: liver damage with acetaminophen and stomach bleeding with aspirin, for example.

It’s difficult to pinpoint how long a patient should try the conservative approach. Ultimately, the decision to have TJR boils down to quality of life issues.

	X-ray taken prior to total hip replacement

“When the patient has extreme pain or difficulty walking and the conservatives measures aren’t bringing relief, he or she might not be able to work, perform household tasks, or enjoy leisure activities,” says Dr. Moucha. “Exercise and medicine are only temporary measures.”

Before TJR, Dr. Moucha’s patients undergo a complete medical examination by their internist or family doctor. Then, he reviews X-rays and conducts his own evaluation that includes the patient’s gait, alignment, and spine. His recommendation may not always be TJR: in some hip cases, the pain could be originating from the spine, rather than the hip. And some patients may benefit from an osteotomy, a surgery that repositions the joint to evenly redistribute weight.

Is Minimally Invasive Surgery Always Best?

For years, TJR was performed only through a large incision. Today, with the advancements in minimally invasive surgery, specially trained orthopaedic surgeons can offer total hip and knee replacement operations that feature smaller incisions and a faster recovery time. Whether minimally invasive TJR is a better procedure than traditional surgery, however, is a matter of debate among orthopaedists.

Using total hip replacement (THR) as an example, Dr. Moucha performs two types of minimally invasive procedures. In one of the procedures, the patient is given anesthesia and positioned with the affected hip upmost. A 4- to 6-inch incision is made to access the hip (much smaller than the 9- to 12-inch incision of earlier procedures) and the hip’s damaged femoral head (the upper portion of the femur bone) is subsequently removed. The prosthesis—a cobalt-chrome stem and ball ensemble—is placed within the femur; a titanium fiber metal socket with an advanced plastic liner is affixed into the pelvis.

The prosthesis can be bonded to healthy bone using cement, which acts like grout. Or, in the uncemented procedure that Dr. Moucha generally performs, the prosthesis, made with a porous material, fuses naturally with bone. The decision to use cement or not is made on a case-by-case basis.

Total hip replacement surgery done in this manner takes between two and three hours, and the patient stays in the hospital for three or four days. Physical therapy begins in the hospital either the day of surgery or the following day, and about one-third of patients go to a rehabilitation facility for a week or two, while the rest go directly home.

Dr. Moucha was also fellowship-trained in another type of minimally invasive hip replacement procedure known as the “two-incision technique.” During this procedure, the patient is positioned on her back and is given anesthesia. A small incision (about two inches) is made in the groin and a second incision, about the same length, is made on the side of the hip. The damaged part of the hip is removed, and the prosthesis set in place with the aid of fluoroscopy.

With this type of approach, less muscle is cut and selected patients seem to return to a functional level more quickly than with other procedures. Minimally invasive total hip replacement done in this manner does seem to have some of the same benefits as other “keyhole” surgeries done for cardiac or abdominal surgeries.

“A smaller incision results in less blood loss, less trauma to the patient’s muscles, ligaments, and tendons, and a shorter recovery time for patients,” says Dr. Moucha. The patient typically stays in the hospital for one to two days and rehabilitates more quickly than with the traditional procedure, often returning to work or a regular routine in eight days.

Although minimally invasive THR has some promising benefits, Dr. Moucha does have some concerns. “There have been very few—if any—solid, evidence-based scientific studies that prove the benefits of minimally invasive total hip replacement surgery over traditional surgery,” he says. “You’re taking an established procedure—proven and with a relatively low complication rate— and making it a little more difficult with minimally invasive techniques. A smaller incision leaves the surgeon with less room to maneuver the instruments and position the prosthesis.” Also, if a surgeon has started a minimally invasive total hip replacement through a two-incision approach and experiences complications, it’s very difficult to convert to a revision procedure at that time, he says.

Another of Dr. Moucha’s concerns relates to the patient’s postoperative period. One study showed a markedly increased rate of dislocation after THR when the length of stay in the hospital was decreased by a few days.

That said, Dr. Moucha is not opposed to minimally invasive total hip replacement surgery—he simply believes that these techniques must be critically evaluated through evidence-based studies. A surgeon’s experience in performing minimally invasive joint replacement affects outcome, also.

Dr. Moucha has performed several hundred minimally invasive THRs during his fellowship training and while at University Hospital, and he agrees with several newly published reports that confirm the effect of a surgeon’s procedural volume on patient outcomes. “Surgeons must be adequately trained, and proper instruments for minimally invasive surgery must be used. Ultimately, I tell my patients that I will make as big an incision, within reason, as I need to do my job well,” he says. “One of the most important things to me is that I put in a hip replacement that will last for many years.”