CURRENT CONTROVERSIES IN TOTAL HIP ARTHOPLASTY
Figure 1
APPROACH
Figure 2
MINIMALLY INVASIVE SURGERY (MIS)
“MIS” has been a trend in arthroplasty for several years. For some surgeons, MIS means minimizing deep tissue dissection and avoiding any violation of neuromuscular planes (see anterior approach above). For others it is performing surgery through the smallest possible incision. Theoretically, minimizing soft tissue trauma may result in a faster recovery. Opponents of MIS complain that there is a greater incidence of nerve injury and component malposition. Thus far, the literature does not support any lasting benefit to smaller incisions in THA.
METAL-ON-METAL
Until recently, metal-on-metal (MoM) hips were gaining widespread popularity for their low wear rates. The ability to implant larger femoral heads also promised improved stability and lower dislocation rates. Over the last few years, MoM has been the bearing couple in one out of every three implanted hips. In 2010 concerns arose regarding adverse local tissue reactions (ALTR) to microscopic metal wear debris. Findings included pain, instability, local pseudotumor, bone and soft tissue destruction. Although the true incidence of ALTR is unknown, new-onset pain, limp, swelling or instability should raise concern and prompt referral to an arthroplasty surgeon. Radiographs, ultrasound and metal-subtraction MRI can all aid diagnosis. Following serum cobalt and chromium levels may also be helpful, but these are frequently elevated even in well-functioning hips. It is worth noting that the vast majority of patients with MoM THA continue to do very well.
RESURFACING
Figure 3
SURGEON VOLUME
Most total hips are implanted by orthopedists with a volume of less than 30 such cases annually. Recent outcomes data has reaffirmed that surgeons who perform greater than 50 to 100 hip replacements per year have significantly improved outcomes, including decreased revision rates, infection, dislocation and length of hospital stay. Practice makes perfect.