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Arthritis Q and A on Minimally Invasive Hip Replacement Surgery

Is minimally invasive hip replacement surgery all that it’s cracked up to be? Simon Mears, M.D., chief of total joint arthroplasty and trauma at the Johns Hopkins Bayview Medical Center, explains the advantages.

Q. What are the benefits of minimally invasive hip replacement surgery?

A. Patients must understand that although the term “minimally invasive” sounds attractive, the surgery is still the same as the standard procedure, only it is performed through smaller incisions. In fact, recent research has found little difference in patient recovery when the length of the incision was studied. The surgery still entails cutting bone, removing damaged hip parts, and affixing the implant to the thighbone and hip.

There are several possible advantages when a hip is replaced with minimally invasive technique. These factors include:

• A smaller incision. Typical incisions are now 3 to 4 inches, on average, compared to 9 inches with traditional surgery. In some cases, surgeons can perform the surgery through two 1.5-inch incisions. The socket portion of the prosthesis is placed through an incision in the front of the leg, while the ball portion of the prosthesis is placed—with x-ray guidance—through an equally small incision in the buttock. Instead of cutting through muscles and tendons to reach the hip, the surgeon will part between them with small instruments and his fingers.

Current studies are investigating the exact amount of muscle damage after a minimally invasive procedure. Some authors have suggested that by making smaller incisions more muscle damage actually occurs because the surgeon cannot completely visualize the muscles and tendon.

• Less pain. With a smaller incision and no need to cut through muscle and tendon, post-operative pain levels are thought to be significantly reduced. The pain of the procedure has been altered by the use of newer anesthetic methods. This includes the use of new peripheral nerve blocks and indwelling nerve catheters. These techniques can numb the specific nerves that go to the hip during and after surgery. This allows for the use of less pain medicine and anesthetic, preventing common side effects such as postoperative nausea and vomiting. Researchers are trying to differentiate whether reduced pain after surgery is due to better anesthesia or if the approach itself causes less surgical pain.

• Lower blood clot risk. Although this has not yet been proven with a study, I find that when using the two-incision approach I do not have to twist the patients’ leg during surgery as I do in a traditional hip replacement. This seems to reduce the 24 risk of blood clot development, although it will require tens of thousands of patients to prove this. Patients are encouraged to get out of bed the day of surgery, which limits the immobility that may increase the risk for blood clots.

• Surgical confidence. Since an x-ray machine is used for prosthesis placement during a two-incision minimally invasive hip procedure, I am confident that the stem and cup are properly placed and affixed to the bone.

• Quicker hospital discharge. Some highly experienced surgeons now perform the procedure as an outpatient surgery. Patients leave the hospital 12 hours after their surgery as long as they can get out of bed by themselves, rise from a chair, walk 100 feet, and walk up and down stairs.

In general, younger healthy patients will be discharged within 48 hours. Patients use a cane but are quickly weaned from this. Contrast this with a conventional procedure, where hospitalization is usually four days and additional rehabilitation is needed over the course of the next few weeks.

• Fewer restrictions. After conventional hip replacement, patients are usually instructed to avoid certain motions to prevent the risk of hip dislocation. High on the list are the recommendations not to bend the hip past 90 degrees or cross the legs when seated. To prevent pain and possible dislocation, patients are also given a special restrictive pillow to place between their legs at night. Following surgery with the two-incision approach, the hip now has good innate stability and the chance of dislocation is much less likely. Therefore, I do not put any restrictions on motion or recommend the use of a pillow for my patients.