Hip replacement

Hip replacement is a surgical procedure in which the hip joint is replaced by a prosthetic implant, that is, a hip prosthesis. Hip replacement surgery can be performed as a total replacement or a hemi/semi(half) replacement. Such joint replacement orthopaedic surgery is generally conducted to relieve arthritis pain or in some hip fractures. A total hip replacement (total hip arthroplasty) consists of replacing both the acetabulum and the femoral head while hemiarthroplasty generally only replaces the femoral head. Hip replacement is one of the most common orthopaedic operations. Patient satisfaction varies widely between different techniques and implants. Approximately 58% of total hip replacements are estimated to last 25 years. The average cost of a total hip replacement in 2012 was $40,364 in the United States (about €37,300), and in the range of €7,117 to €11,091 in most European countries.

Medical uses Total hip replacement is most commonly used to treat joint failure caused by osteoarthritis. Other indications include rheumatoid arthritis, avascular necrosis, traumatic arthritis, protrusio acetabuli, certain hip fractures, benign and malignant bone tumors, arthritis associated with Paget's disease, ankylosing spondylitis and juvenile rheumatoid arthritis. The aims of the procedure are pain relief and improvement in hip function. Hip replacement is usually considered only after other therapies, such as physical therapy and pain medications, have failed.

Outcomes Hip replacement provides significantly better results than exercise training in terms of reducing pain 6 months afterwards. It is possible to play high-level sport after hip resurfacing. People who have had hip replacements generally have reduced death rates than the matched population for 10 years after surgery, but rates then increase from 11 years onwards. For this reason, hip replacement is often considered in people aged 65 to 80 when activity is being severely curtailed by hip pain. Hip resurfacing is a less invasive type of hip replacement that may be more suitable for younger patients.

Risks Risks and complications in hip replacement are similar to those associated with all joint replacements. They can include infection, dislocation, limb length inequality, loosening, impingement, osteolysis, metal sensitivity, nerve palsy, chronic pain and death. Weight loss surgery before a hip replacement does not appear to change outcomes. Edema appears around the hip in the hours or days following the surgery. This swelling is typically at its maximum 7 days after the operation, then decreases and disappears over the course of weeks. Only 5% of patients still have swelling 6 months after the operation.

Dislocation

Dislocation (the ball coming out of the socket) is one of the most common complications. Hip prosthesis dislocation mostly occurs in the first three months after insertion, mainly because of incomplete scar formation and relaxed soft tissues. The chance of this is diminished if less tissue is cut, if the cut tissue is repaired and if large diameter head balls are used. Surgeons who perform more operations tend to have fewer dislocations. Important factors which are related to dislocation are: component positioning, preservation of the gluteal muscles and restoration of leg length and femoral offset. Keeping the leg out of certain positions during the first few months after surgery further reduces risk. Dislocations occurring between three months and five years after insertion usually occur due to malposition of the components, or dysfunction of nearby muscles. Risk factors of late dislocation (after five years) mainly include:

Female sex Younger age Previous subluxation without complete dislocation Previous trauma Substantial weight loss Recent onset or progression of dementia or a neurological disorder Malposition of the cup Liner wear, particularly when it allows head movement of more than 2 mm within the cup compared to its original position Prosthesis loosening with migration

Infection Infection is one of the most common causes for revision of a total hip replacement. A 2009 study found that the incidence of infection in primary hip replacement was 1% or less in the United States. Risk factors for infection include obesity, diabetes, smoking, immunosuppressive medications or diseases, history of infection and previous hip surgery. In revision surgery, infected tissue surrounding the joint is removed, and the artificial joint replaced. This can be carried out in one- or two-stage surgery. In two-stage surgery the infected tissue and all joint replacement implants are removed in the first stage, and, after the infection is completely cleared, a new artificial joint is inserted in the second stage. In one-stage surgery infected tissue and implants are removed, and the new joint inserted, in a single procedure. Both kinds of surgery are equally effective but one-stage surgery results in faster recovery. There is also an alternative called DAIR (debridement antibiotics and implant retention) that is possible if the infection presents during the first month after primary surgery. In contrast to 1- or 2-stage revision surgery, DAIR involves replacing only the removable components while retaining the prosthesis itself. Also a thorough debridement of infected tissue is performed, antibiotics are administered and the treatment continuous for at least 6-12 weeks. The success rate of DAIR is approximately 75%, saving a lot of patients from more extensive surgery.

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