HIP RESURFACING
Hip resurfacing is a surgical alternative to total hip arthroplasty. This procedure was performed in the past; however, the results were inferior to that of total hip arthroplasty. More recently, newer technology has allowed for better longevity of hip resurfacing, leading to a renewed interest in this technique.
The ideal patient for hip resurfacing is a healthy man (with no history
of renal impairment) younger than the age of 55 with good bone quality. In this
cohort, resurfacing results are similar to those of total hip arthroplasty.
Resurfacing may be performed in older individuals as well as in females.
However, the results of resurfacing in these patients have been inferior to the
results with conventional total hip arthroplasty, and patients should be
counseled about this finding. Also, females of child- bearing age should not
undergo hip resurfacing at the present time. The metal ions released as the components
generate wear have an unknown effect on the unborn fetus.
TECHNIQUE
The surgical approach is similar to that of total hip arthroplasty. A
posterior or lateral approach may be used.
Once the femur is dislocated, the femoral head is sized. The acetabulum
is then exposed and prepared similar to a total hip arthroplasty. The monoblock
metal acetabular component is then impacted in place. Attention is then turned
back to the femur. Using a special jig, a guide pin is inserted into the
femoral head. Care must be taken to place the pin in slight valgus to prevent
early failure of the construct. After the pin is accurately placed, preparation
of the femur proceeds. It is sequentially reamed to remove several millimeters
of bone. Then several drill holes are placed in the femur, and the implant is
cemented in place. Once the cement cures, the hip
is reduced and checked for stability.
RESURFACING VERSUS TOTAL HIP ARTHROPLASTY
Hip resurfacing has several stated advantages over total hip
arthroplasty. Because the femoral neck is preserved, and the hip is loaded
similar to a normal hip joint, some patients report a more normal-feeling hip
compared with conventional total hip arthroplasty. Some surgeons will allow
their patients who have hip resurfacing to resume high-impact activities
(running). Also, should the femoral component fail, the conversion to a
standard total hip arthroplasty is relatively straightforward; thus, revision
surgery years down the road may theoretically be easier. Finally, there is less
risk of limb-length discrepancy as well as dislocation after hip resurfacing.
There are several disadvantages to hip resurfacing. The long-term
results for hip resurfacing are inferior to conventional total hip arthroplasty
in all groups except males younger than the age of 55. In addition, there is a
risk of femoral neck fracture with hip resurfacing. This risk can be minimized
with proper positioning of the femoral component and the avoidance of femoral
neck notching during preparation. Also, the success of resurfacing is more
dependent on surgical skill (proper component positioning) than total hip
arthroplasty.
Finally, hip resurfacing uses a metal-on-metal articulation, which in
itself has its own inherent benefits and risks.
METAL-ON-METAL ARTICULATION
Metal-on-metal articulation in hip replacement has been in use for
decades. The material has been refined over the years as technology has
improved to reduce wear and allow for longer lasting implants. Currently, a
well-functioning metal-on-metal total hip arthroplasty or resurfacing can last
for 15 years or longer.
However, many surgeons do have concerns with metal-on-metal
articulations. As metal-on metal articulations wear, cobalt and chromium
particles are generated. Elevated levels of these chemicals can be measured in
the serum of patients who have received metal-on-metal articulations. The
long-term effects of this are unclear. Several studies have shown a slightly
increased risk of hematologic cancers in patients with metal-on-metal articulations. However, the majority of studies have shown no long-term
cancer risk.
A condition unique to metal-on-metal articulation is the formation of
pseudotumors or an aseptic lymphocyte dominated vasculitis–associated lesion
(ALVAL). This occurs in approximately 1% of patients. Patients present with
pain after their replacement with no other cause (e.g., loosening, infection).
Radiographically, rapid osteolysis may be seen. These patients may require
revision due to the rapid destruction of host bone. Proper component
positioning may reduce the risk of ALVAL. An acetabular component placed in
excessive abduction is a risk factor for ALVAL. Avoiding this is
crucial in hip resurfacing.
