TOTAL HIP REPLACEMENT

Hip joint is the joint between the thigh bone (femur) and the pelvis. The hip joint is a “ball and socket joint” similar to the shoulder joint allowing movements in all directions. While the main function of the shoulder is mobility, the hip has to be mobile as well as stable. So the hip joint is more congruous (the ball is seated deeper in the cup compared to the shoulder) and also supported by strong ligaments.  The articulating parts are the femoral head (ball) and the acetabulum (socket). The articulating surfaces are covered with a special lining known as articular cartilage.

Arthritis develops when the lining (articular cartilage) gets damaged due to various reasons including ‘wear and tear’ (osteoarthritis) as well as inflammatory conditions like rheumatoid arthritis. In addition arthritis in the hips can also develop secondary to a number of problems including mechanical problems like impingement syndrome, sequelae of child hood hip disorders like Perthe’s disease, problems with the blood supply (avascualr necrosis) as well as following trauma to the hip joint. The hip becomes painful. The initial management is non-operative including painkillers, anti-inflammatories, physiotherapy, activity modification, using a walking stick etc.

When the pain due to knee arthritis increases and is not controlled by conservative measures, then it would be appropriate to consider surgical options which essentially means some form of hip replacement which would depend on the age and activity level of the patient.

Total hip replacement is considered to be one of the most successful operation of the 20th century. In this operation, the surgeon changes the ball and socket joint of the hip joint to an artificial joint. Sir John Charnley pioneered the development of hip replacement in the 1960’s. In the Charnley total hip replacement, both the acetabular component and the femoral component were cemented and the articular surface was a metal on plastic combination. The ball in the Charnley hip replacement is about 22 mm.

Since then more and more younger patients are being offered hip replacements and studies have shown that conventional hip replacements do not last long in young and active patients. In addition, the 22 mm ball also affords less stability of the hip replacement with risk of dislocation and dislocation rate of 5% has been quoted in studies.

With improvement in material science, further developments have been made to improve the longevity of the hip replacements particularly in young and active patients. Various implant devices have been introduced including different types of cemented devices and un-cemented devices as well as different bearing surfaces including cross-linked poly, ceramics and metal on metal devices. These are called as “alternative bearings” compared to “conventional bearings”. Each has certain characteristic features, advantages and disadvantages and one might suit an individual person better than the others. For more information – please see the section on “bearing options in young and active”.

In addition to the potential increased durability, the modern bearings also allow a bigger size ball to be used instead of the 22 mm ball used in Charnley total hip replacement. The bigger the ball of the hip replacement, the better the stability of the hip joint.

A study in which Mr.Ganapathi was involved found that over £500000 were spent (on a conservative estimate) in treating 100 patients with hip dislocations. In addition to the financial burden, the study also found that even after further revision surgery, the function and outcome score of the patients who had dislocation were inferior to those who did not have a dislocation. Recent studies have shown that the risk of dislocation could be reduced by larger size femoral head (ball of the hip joint). With the availability of modern material for bearing surfaces, it is possible to use a relatively larger ball than conventional total hip replacement (see does size matter?).

Although, total hip replacement is a very successful procedure, like any major operation it has certain risks (although rare) including that of infection, bleeding, damage to the neurovascular structures, thrombo embolism (clots in the legs which can go to the lungs), dislocations, limb length discrepancy, periprosthetic fractures, anaesthetic complications etc., (see section on complication). The complication rate will be somewhat higher if the hip replacement is more complex (see revision hip replacement) and also when hip replacement is done for certain hip fractures. The complication rate to some extent will also depend on the individual patient’s medical status and Mr. Ganapathi will in some cases send you for an anaesthetic opinion before deciding on surgical treatment.