Hip Resurfacing vs Total Hip Replacement
Hip resurfacing surgery is a kind of hip replacement in which only the ball of the diseased hip is cut and replaced with a prosthetic implant. The socket is replaced in a similar fashion to a total hip replacement.
The hip joint is a large weight-bearing ball and socket joint. The ball (head of the femur) of the joint is formed by the upper part of the thighbone (femur). The ball is attached to the body of the thighbone through a bony neck. The ball rotates inside a bony socket formed by the pelvic bone (acetabulum).
The surface of the head of the femur and the acetabulum are covered with articular cartilage. The articular cartilage along with the bone is gradually destroyed in osteoarthritis. The destruction of the bone and cartilage leads to pain and disability. Hip replacement surgery is offered when all other nonsurgical treatments have been tried without relief. The non-surgical options include pain medications, therapy, cortisone injection, etc.
Hip Resurfacing Surgery
During a hip resurfacing surgery, the patient usually sleeps through the procedure while being under general anesthesia. Spinal anesthesia may also be used where the patient remains awake but is numb waist down. The surgeon gives a skin incision usually from the back.
The surgeon separates/cuts various tissues to reach the diseased joint. The surgeon then proceeds to cut the head of the femur. The head of the femur is removed and the acetabulum is prepared. The preparation of the acetabulum involves serially reaming the acetabulum surface to remove the diseased cartilage and the bone.
A metallic cobalt-chromium alloy prosthetic acetabulum shell may be press-fit or cemented in the socket. The surgeon then prepares the neck of the femur by contouring its shape.
A prosthetic metal alloy head of the femur is then capped over the contoured neck of the femur. The prosthetic joint is then relocated and checked for stability. The incision is closed in layered and a rehabilitation process is started.
The hip resurfacing previously was done by the use of a metallic head of the femur over a plastic (polyethylene) cup. The metal over poly design faced high rates of accelerated wear and failure. The newer hip resurfacing is only done with a metal-on-metal design.
Hip Resurfacing Vs Total Hip Replacement
While patients with hip arthritis who may need replacement surgery are usually candidates for total hip replacement, not all patients are candidates for hip resurfacing. The candidates for hip resurfacing usually are:
- Young patients under 60 years of age, as younger patients have a higher chances of requiring a second surgery (revision hip replacement) secondary to wear and tear. The patients in the younger age group are also more active with a more physically demanding lifestyle.
- The hip resurfacing requires boney strength of the femur as the neck of the femur bears the stress of the implanted prosthetic head. Therefore, postmenopausal women, patients with metabolic disease, patients with short stature are not ideal candidates for hip resurfacing surgery.
- Patients with a deformed upper thigh bone who may need a hip replacement surgery may benefit from a hip resurfacing procedure.
- Patients with a deformed acetabulum or patients with significant leg length discrepancy are not good candidates for hip replacement surgery.
- Patients with chronic kidney disease are also not good candidates for hip resurfacing as the metal ions accumulate in the body
Although relatively a newer procedure as compared to a total hip replacement, hip resurfacing offers several advantages as compared to a traditional total hip replacement.
- The bone stock is relatively preserved in hip resurfacing as compared to total hip replacement. The preservation of bone is helpful in young patients who might need revision surgery due to activity-related wear and tear.
- Hip resurfacing avoids possible complications of implant migration and stress shielding. Stress shielding of the femoral stem in traditional implants may lead to unrelenting thigh pain and loosening.
- Hip resurfacing allows the surgeon to implant a larger diameter head of the femur. The implant diameter in hip resurfacing is almost similar to the natural head of the femur. A larger head of the femur is less likely to dislocate.
Hip replacement dislocation occurs when the prosthetic head of the femur pops out of the socket. A large diameter head has to travel a greater distance before it can dislocate therefore allows a larger safe range of motion.
- Hip resurfacing also leads to a more accurate restoration of the leg length after the surgery. There is less chance of a leg length discrepancy occurring as a result of replacement surgery.
The hip resurfacing may however be associated with a number of unique complications.
- There is a small chance of a fracture occurring in the immediate postoperative period. The break in the bone occurs commonly in the femoral neck that may require the conversion of hip resurfacing to a total hip replacement.
- The surgery may require greater exposure that may warrant more cutting/separating of the tissues. Greater cutting and manipulation of the soft tissues may increase the chances of heterotrophic calcification. In heterotrophic calcification, there is an abnormal formation of bone tissue in the muscles surrounding the joint.
- If a leg length inequality exists before the surgery due to arthritis, the difference may not be corrected in a hip resurfacing surgery.
- Since the hip resurfacing surgery involves a metal-on-metal design, cobalt and chromium metal ions concentration increases in the blood. Although, no side effects of the increased metal ions have been seen they may potentially cause adverse effects in a long term.
The metal ions may also increase substantially in patients with prior kidney disease as the ions may not be eliminated from the body.
- Some patients may be allergic to metal ions that may cause inflammation around the implant and subsequent loosening.
Hip resurfacing is a relatively new technique compared to the highly successful total hip replacement. Hip resurfacing offers several advantages over total hip replacement but the majority of the patients may not be candidates for hip resurfacing.
Further, long-term safety and results of hip resurfacing have not been adequately studied compared to a total hip replacement. Speak with your orthopedic joint replacement surgeon regarding which type of surgery may be best suited in your case.