Revision Hip Replacement Surgery Florida
Revision hip replacement surgery is when more surgery is needed on a hip joint that already has a total hip implanted. Typically, a “revision” hip replacement surgery is a more complex procedure requiring more time, expertise and special equipment. The potential complications associated with revision surgery also tend to be greater. Removing the old prosthesis can be destructive and often requires a more extensive incision and dissection. Fortunately, we now have more specialized instruments and modular prosthetic hip implant systems which are specifically designed for complex re-do surgeries with major bone deficiency. These have vastly improved our ability to reconstruct the hip and still achieve an excellent result.
There are multiple reasons why a person who already has a total hip, would require more surgery. One of the most common reasons is instability. The prosthetic ball dislocates from its intended position in the socket. Critical to reconstructing a stable hip with equal leg lengths is implanting the cup and stem in an optimal position. In my experience, the PAL (visit the Video Gallery to view the PAL video) has been essential in my ability to accomplish this consistently. The size of the femoral head, which is typically being implanted today compared to just several years ago, is larger. Larger femoral heads are more stable than smaller ones. This has been possible because on a molecular level, the quality of the plastic bearing surface has been improved. By increasing the polyethylene cross-links while eliminating oxygen free radicals, the bearing surface is made much more resistant to wear. Alternate bearing surfaces have also been developed including those made of ceramics and metal. In spite of the strategies that have been developed in recent years, instability is still a major reason why some total hips need revision.
Another common reason for revision surgery can be attributed to the bone that is supporting the prosthesis becoming deficient or absent. This can lead to the loosening or instability of components. After millions of cycles and years of use, the prosthetic ball wears into the socket. Tiny particles of debris are produced which incites an inflammatory process and stimulates the resorption of the bone that supports the implants. This condition is called osteolysis. It remains one of the biggest problems with any joint replacement in the body. Better quality plastics and alternate bearing surfaces have been developed with the hope of diminishing osteolysis. Other reasons for revision include fracture around the prosthesis or of the prosthesis, infection, and leg length inequality.
Metal on Metal Bearing
Historically, controversy existed regarding the optimal bearing for the total hip. Today, most consider a ceramic ball articulating against an improved “highly crossed linked polyethylene” socket to be the “gold standard”.
Traditionally, a metal ball attached to the stem was implanted and articulated against a plastic cup. Many different bearing have been been studied with the hope of improving longevity by improving the wear characteristics between the ball and the socket. Many patients world wide were implanted with “metal on metal” bearing. That is, a metal ball moving against a metal liner. In the lab, a construct with this bearing has the potential to produce less friction and less wear than standard metal balls on plastic. It requires “fluid film lubrication” or fluid to exist between these two surfaces acting as the lubricant. For this system to work as intended, the components must be optimally designed, the components must be optimally implanted, and a patient should not allow the joint to exceed its mechanical limits, because then fluid the develops between the two surfaced breaks down and the metal pieces rub together. Many patients with metal on metal THR world wide are now experiencing problems that require revision. The high concentrations of metal ions can destroy tissues locally and are resorbed systemically which can cause a host of problems. Because some of these patients who have these articulation which are failing remain asymptomatic until the destruction becomes extension, it is important to periodically have follow-up looking for possible problems developing. If problems are developing it is better to revise their hips sooner rather than later. I am seeing many more of these patients in my practice.
Traditionally, the metal ball attached to the femoral stem was made from a single piece of metal. Now almost all stems that are implanted world wide are modular. That is, the ball is separate from the stem. The advantage is the surgeon can more easily “fine tine” hip mechanics and leg length by choosing balls with different neck length. Because cup plastic quality is so much better than it was years ago, larger diameter balls are being implanted on the tapers of these modular stems, which has the advantage of improving stability and lessening dislocation. We are now seeing more patients present with corrosion developing between the taper and the ball. The larger head or ball sizes is one factor adding to this problem. Metal corrosion products leach from this taper-ball junction and can lead to local tissue destruction and problems systemically. They too require revision.
Modularity was taken a step farther, again with the hope of giving the surgeon more intra-operative flexibility to optimize hip mechanics, leg length and stability by also making the neck of the stem modular. Experience has shown that this class of primary hip stems have done very poorly and a large per cent have required revision. Some have even be recalled by their manufacturer.