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Dislocation: A hip replacement, both standard THR and resurfacing can slip out of place. The incidence can be approximately 4% for standard THR and less for resurfacing. The causes can be due to poor soft tissue control, non-compliance to hip precautions and rarely to improper positioning of components. Treatment is usually closed reduction under anesthesia and wearing a hip brace for six to eight weeks. If dislocations become recurrent then a repeat surgical procedure may be necessary.
Loosening/Component Failure: When an implant loosens, the bond between the prosthesis and bone will become progressively weaker until the prosthesis is no longer supported by the bone, and the bone and component will function as two separate units rather than the bone and prosthesis composite functioning as one. Loosening is most commonly caused by inflammation of the bone due to metal or plastic particles. Rarely, loosening can be the result of infection or malposition of the components. The symptoms of loosening are progressively increasing pain. In the end, the only resolution of a loose component is surgical replacement of the loose component. Rarely, a joint replacement will fail because of a material failure of the component itself; i.e., fracture of the metal or plastic itself. This problem can only be corrected by surgically replacing the failed component.
Deep Wound Infection: This is not a superficial tissue infection which can usually be treated with antibiotics and occasionally debridement, but an infection around the components themselves. Luckily this is rare, but when it does happen, it needs to be aggressively treated. This involves surgically removing the components and not putting anything back in. Intravenous antibiotics are given for six to eight weeks, and if the infection has been eradicated another attempt at joint replacement can be done and be successful 80 to 90% of the time.
Femoral Neck Fracture: In spite of a successful hip resurfacing, a fracture of the femoral neck can occur. This is rare, 3% or less, but when it occurs, it is necessary to surgically implant a total hip stem and apply a large steel ball to the stem that matches the inner diameter of the implanted acetabular shell. This preserves two of the major advantages of resurfacing; a metal on metal articulating surface, and a large diameter femoral head, providing increase stability.
Epilogue: Rarely, in spite of our best efforts, at the time of surgery, technical factors make it impossible to perform a resurfacing. Also, the neck of the femur may be inadvertently damaged, dramatically increasing the risk of post-operative femoral neck fracture. In either of these situations we would revert to a resurfacing acetabulum and a THR stem with a big metal ball. As a last resort, a standard metal on metal, THR would be done.
Leg Length Discrepancy: Most people who have significant arthritis of the hip develop shortening of the affected leg due to wearing away of the cartilage and bone. Prior to the resurfacing procedure, we take measurements to determine the amount of shortening. At the time of surgery, we try to restore the leg to its proper length but it is possible to either over or undershoot by a centimeter or so. Usually, this amount is not perceptible, but if it is, a heel pad can be worn on the proper leg.