Total hip replacement has matured into a routine operation for the relief of hip pain and disability due to hip arthritis, giving some of the greatest quality of life increases of all medical procedures. Typically performed in older people, many get a good result from their hip replacement surgery but many do not reach their greatest potential due to lack of follow up rehabilitation in the post-operative period.
An osteoarthritic hip joint is likely to cause a degree of pain and disability for a year or more before the person comes to operation. This period of difficulty can cause influential changes in the tissues around the hip which can be relevant in the postoperative period. Pain and weakness can make us use our joints less, avoiding pushing them to the ends of their movement, a process which gradually reduces the joint's range of motion. Adaptive shortening occurs in the hip's ligaments, as the structures shorten in response to the fact that the joint is not being put through its full range any more in the normal daily pattern.
When a hip joint is not used in the normal way or through its full range the muscles which power it will lose some of their strength. The hip joint is designed to bear weight and to move the body around which involves high levels of power, provided by the largest muscles in the body, the gluteal muscles. The ability to run, walk, get up from a chair, climb stairs and go uphill is facilitated by the power of the gluteal muscles to a great extent. If these muscles weaken they can reduce a person's independence to an important degree.
The hip abductors, a smaller muscle group of the gluteal muscles, are important in controlling the side to side stability of the pelvic girdle in gait, with weakness of these muscles interfering with walking. Standing on one leg in walking we hold the opposite side of the pelvis up to avoid it dropping and make bringing through the moving leg more difficult. The hip abductor muscles do this and if weak we feel unstable in walking and tend to lurch towards the weak side, making us lean our trunk towards the other side to restore balance. This is described as a positive Trendelenberg sign.
The abnormal Trendelberg gait imposes unnatural forces on the hip and requires side flexion of the spine to hold balance on each step. The abnormal gait which results fails to strengthen the hip abductors and remedy the problem. With hip problems we tend not to extend our hips fully so the gait cycle is shortened as the hip extensor muscles fail to attain full movement and power. A restriction in hip joint movement and the presence of muscular weakness makes mobility more difficult and can make the outcome of the operation less satisfactory in the absence of rehabilitation.
Patients typically have impaired balance and coordination even before they have their joint replacement operation, with some improvement occurring as the hip's function moves more towards normal after the joint has been replaced and the mechanical function of the hip is restored towards normal. Other impairments usually include the sense of joint position sense, an important ability the lack of which compromises balance and makes falling more likely.
Physiotherapists assess a patient's hip function and ability to get through their normal daily work, looking at the deficiencies in the joint so they can plan the rehabilitation. Noting the gait of the patient will be the first thing in the assessment, moving on to checking movements of the hip, knee and spine to check for any restrictions due to joint stiffness. An abnormal gait can be habitual and the physiotherapist will analyse and correct the gait pattern towards normal.
Excessive range is not encouraged in hip replacements due to the risk of dislocation. Next the muscle power in all the surrounding muscles will be tested and then the person's balance reactions and joint position sense. Once the assessment is complete the physiotherapist will give the patient a programme including joint mobility, strengthening, and balance and gait correction. Many with hip arthroplasty do not reach their best potential due to a lack of rehabilitation care after the operation.