The Hip Joint
How to Recognize a Failing Hip Replacement
The major causes of failure in hip replacement are: dislocation of the joint, loosening of the stem and cup, and failure of the stem. Dislocation of the prosthesis can occur immediately after surgery if you move your leg into a prohibited position. It is therefore necessary to avoid extremes of internal rotation, forward flexion, and adduction for about 12 weeks until a thick capsule forms around the artificial joint. If you dislocate, you will need to be put under deep anaesthesia so your hip muscles can relax sufficiently to allow the artificial hip joint to be reduced. Care should be taken to avoid dislocation as the sciatic nerve, which supplies large leg muscles, is in danger of damage when your hip dislocates.
Loosening of the stem component is a late complication that most often occurs 5-10 years after total hip replacement. It can be confirmed with X-rays. Risk factors for this include age (less than 50 years -- such people usually being more active), weight (more than 80 kilograms), and a high level of physical activity at any age. Mild trauma can fracture the femur around a prosthesis stem, especially if the bone is osteoporotic.
The main long-term threat to hip replacements appears to be polyethylene and metallic wear debris from the interacting surfaces of the components. This debris can cause inflammation in adjacent tissues that results in bone loss which, in turn, leads to prosthesis loosening. Up to 35% of retrieved modular prostheses exhibit corrosion or other evidence of damage. Fracture, dislocation, malpositioning of components, infection around the implant, poor cementing technique, and certain stem designs can also contribute to loosening of the stem component.
Thigh pain is the primary symptom of stem loosening, especially during walking. This pain often radiates to the knee.
Loosening of previous generation actabular components increases markedly after 12-15 years of function. Obesity and strenuous activities can contribute to failure of the acetabular component. Loosening of the acetabular cup is often signaled by pain in the groin region upon going from a sitting to a standing position.
Revision surgery, to correct a loose implant, is generally more difficult and takes longer to perform than the initial hip replacement.