Review Question - QID 217486

The use of dual-mobility bearings in total hip arthroplasty (THA) in patients under the age of 55 is associated with a lower rate of instability and dislocation.

Conversion to THA from a previous hip surgery poses unique challenges to surgeons. This patient, in particular, appears to have had a surgical dislocation of a hip as evidenced by the greater trochanteric to less trochanteric screw, and blade plate after osteotomy. The exposure required for these cases is similar to that of a true THA revision case, and care must be taken to preserve the soft tissues and place hardware components in the appropriate positions to avoid post-operative complications, such as dislocation. Fortunately, dual-mobility constructs have provided an alternative bearing surface that has protection against hip dislocation in the short to mid-term.

Rowan et al conducted an age-matched retrospective review of their institution comparing patients under the age of 55 who had dual-mobility (DM) and fixed-bearing (FB) total hip arthroplasties. They had equivalent mean age and follow-up at 48.5 years and 3.3 years, respectively. Their data showed a decreased dislocation rate with DM compared to FB, with no dislocations (true dislocations or intraprosthetic dislocations) in the DM group and 7 (5.1%) in the FB group. There were equivalent Harris Hip Scores and other patient-reported outcomes, including the WOMAC and UCLA activity scores.

Stockton et al looked at the rate of re-operation and conversion to total hip arthroplasty in 792 younger patients initially treated with open reduction internal fixation (ORIF) of femoral neck fractures. They found that nearly 33% underwent some sort of re-operation at a median of 16 months, with most of them being hardware removal. They also found that approximately 1 in 7 undergoes a conversion of ORIF to THA at a median of 2 years. They conclude that these findings should be considered when discussing treatment options with patients who have femoral neck fractures.

Giacomo et al conducted a meta-analysis on the use of DM in the revision arthroplasty setting. They looked at 7 studies with nearly 1800 patients and ~50% split of DM versus FB revision THAs. They found a statistically significant reduction in dislocation rates and rates of aseptic loosening, but no difference in infection. They concluded that in short to mid-term follow-up, DM bearings appear to be superior compared to FB in reducing dislocation.

Figures A and B are the AP and lateral radiographs of a right hip with significant degenerative joint disease and femoral head AVN with collapse.

INCORRECT ANSWERS:
Answer 1: There is no evidence that DM bearings result in lower HHS compared to FB THA.
Answer 2: Rates of aseptic loosening have not been shown to be increased in DM THA compared to FB THA.
Answer 3: There is no difference in rates of postoperative infection when comparing DM THA and FB THA.
Answer 5: There is no difference in mean operative times when comparing DM THA and FB THA.