Resurfacing arthroplasty of the hip

Hip resurfacing is an attractive concept as it preserves proximal femoral bone stock, optimises stress transfer to the proximal femur and offers inherent stability and optimal range of movement (1).

Technology (2):

• metal on metal (MoM) hip resurfacing arthroplasty involves removal of the diseased or damaged surfaces of the head of the femur and the acetabulum. The femoral head is fitted with a metal surface and the acetabulum is lined with a metal cup to form a pair of metal bearings
• MoM hip resurfacing devices are considered by some surgeons to be harder wearing than conventional THRs. Having no polythene component, MoM devices cannot be subject to the loosening due to polythene degradation that affect conventional THRs. MoM devices are therefore potentially less likely to fail for these reasons than conventional THRs
• if failure does occur, revision to conventional THR remains an option and is considered to be easier to perform under most circumstances and to provide better outcomes than revision of a primary THR, as less femoral bone is removed during the original procedure
• there is however a concern with these devices concerning the possibility of metal degradation products being absorbed into the body. The implications of this are presently unknown

Potential advantages of hip resurfacing include (1):

• initial preservation of proximal femoral bone stock
• more normal loading of femur eliminating proximal femoral stress shielding
• easier and more durable revision of femoral component if required
• reduced risk of leg lengthening/shortening
• reduced risk of dislocation Improved range of movement
• improved function/activity level
• low wear bearing reducing risk of peri-prosthetic osteolysis

Potential disadvantages include:

• no long-term outcome data
• no published controlled studies
• technically more demanding
• new modes of failure - femoral head collapse, femoral neck fracture

Contraindications to hip resurfacing include (2):

• avascular necrosis, acetabular rim deficiencies, osteoporosis, inflammatory arthritis
• systemic conditions e.g. renal failure, metal allergy
• note that patients with osteoarthritis secondary to minor developmental dysplasia of the hip (DDH) can be treated satisfactorily with hip resurfacing. However, the deformities associated with more severe forms of DDH are difficult to address with surface arthroplasty

NICE have stated that:

• MoM hip resurfacing arthroplasty is recommended as one option for people with advanced hip disease who would otherwise receive and are likely to outlive a conventional primary total hip replacement (2)
  • also recommended that surgeons take into account activity levels of potential recipients and bear in mind that the current evidence for the clinical and cost effectiveness of MoM hip resurfacing arthroplasty is principally in individuals less than 65 years of age
• prostheses for total hip replacement and resurfacing arthroplasty are recommended as treatment options for people with end-stage arthritis of the hip only if the prostheses have rates (or projected rates) of revision of 5% or less at 10 years (3)

Reference:

1. Roberts P et al. Resurfacing arthroplasty of the hip. Curr. Ortho. 2005;19: 263-279
2. NICE (June 2002).Metal on metal hip resurfacing arthroplasty
3. NICE (February 2014). Total hip replacement and resurfacing arthroplasty for endstage arthritis of the hip