Metal on Metal Hip resurfacing for the Younger Patient
Conventional total hip replacement surgery is an excellent choice for elderly patients with various forms of arthritis. It is however now widely accepted that hip resurfacing may be more suitable for younger more active patients. High quality implants, improved surgical techniques and the use of more wear resistant surfaces have all increased the likelihood of hip resurfacing being more satisfactory for the young patient.
The total hip replacement requires the removal of the femoral head and the insertion of a hip stem down the shaft of the femur. Hip resurfacing on the other hand preserves the femoral head and the femoral neck. During surgery only a few centimetres of the bone around the femoral head will be removed to shape it so the implant will fit tightly inside the resurfacing implant. The surgeon will also prepare the acetabulum for the metal cup which will form the socket portion of the ball and socket joint.
Metal on metal implants have been found to reduce the production of wear debris which is associated with early loosening of the prosthesis.
INDICATIONS FOR HIP RESURFACING
- Age – Most patients over the age of 65 are generally good candidates for total hip replacements. Younger patients may be considered for hip resurfacing.
- Activity levels – Patients with high activity levels associated with their occupation or sport may be considered suitable for hip resurfacing.
- Bone Quality – Osteoporosis is a relative contraindication to hip resurfacing and predisposes to the risk of femoral neck fracture following resurfacing. Bone loss and deformity may also preclude hip resurfacing.
- Destructive Arthritis – Severe bone destruction, such as that seen in some forms of inflammatory arthritis or after prolonged use of anti-inflammatory drugs in osteoarthritis may preclude hip resurfacing.
- Patient Factor – The patient must understand that hip resurfacing is as yet unproven in the long term and be prepared to accept the known and unknown risks of the procedure which can be discussed fully with the surgeon. The patient should be willing to be followed up long term.
WHAT YOU CAN EXPECT
- Most patients are discharged from hospital within 5-7 days either walking with elbow crutches or sticks.
- At 6 weeks most patients can start driving, return to work and are capable of walking up to 1 mile/day.
- At 8 weeks most patients are capable of walking up to 2 miles/day.
- At 6 months most patients can return to sport.
- There is a slight risk of developing either an infection in the joint or a DVT post operatively but this is true of most major orthopaedic surgery.
- There is a slight risk of dislocating after hip surgery but this is extremely rare due to the larger size of the femoral implant (“ball”)
- If bone quality is poor there is a risk of the femur fracturing close to the prosthesis.
- It is possible that wear products from the metal surfaces could be absorbed and cause harmful effects. No cases of such have been reported but further research is required to determine the likelihood and consequences of this possibility.
- The hip resurfacing procedure has not been proven long term, longevity and long term effects of wear debris are unknown.
It must be expected that failures will occur and if these are due to a failure of the femoral part, either from fracture or bone collapse, then revision to a total hip replacement will be necessary. However, a study of the hip resurfacing done throughout the UK in the last four years has revealed only about 1% of patients have required a revision operation so far. If a revision is necessary it will present much less of a problem than revising a total hip replacement because the femoral canal has not been encroached before.
DISADVANTAGES OF HIP RESURFACING
As the bone of the femur is retained it is possible that it could fracture following surgery during the early post-operative period if too much weight is put on the leg. This is why crutches are used for 3 to 4 weeks post-operatively to protect the amount of weight the leg has the bear. With the correct rehabilitation the risk of fracture is less than 2%.