The goals of hip replacement include the relief of pain secondary to various forms of arthritis, restoration of function, providing a stable hip with a functional range of motion and as close as possible normalizing leg length. These goals are met by first obtaining stable fixation of the acetabular (cup) and femoral (stem) components to the bone. This is accomplished by appropriate surgical technique and use of reliable implants. Stable range of motion depends on many factors including, component related factors and patient related factors. Restoration of leg length is a function of the size of the implant used, the soft tissue tension around the hip joint, a level pelvis and relatively straight spine. When patients note a difference in length after surgery there ere are several factors that come into play. These include, normalization of length from a previously shortened hip that was due to loss of the joint surface, soft tissue tightness about the hip that can cause contractures in one direction or another, and ongoing or acquired pelvic obliquity that can tip the pelvis in one direction thereby causing an apparent leg length difference, when the true difference is in fact minimal. One of the common initiators of concerns about leg length is attempts at measuring the leg length with the patient lying down. This is often very inaccurate and can lead to inappropriate concerns about length.
Patients undergoing hip replacement should work first and foremost on healing their soft tissue, restoring their function, and if concerns about length are present, discussing them with their doctor and reviewing the possible etiologies including, pelvic obliquity, soft tissue contracture, and true skeletal length differences. A collaborative effort to discuss and resolve these issues often leads to a very satisfactory outcome.
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