The natural history of unexplained early poor function following total hip replacement

The majority of patients experience a significant improvement in quality of life and function after total hip replacement (THR). It has recently been shown that age and good pre-operative function are the best predictors of postoperative function. When patients fail to achieve a satisfactory outcome, a cause is often identified. Where there is no identifiable cause, advice, follow-up and management is not clear. The aim of this study was to determine the long-term outcome of patients who had early poor function, but no identifiable cause.

From a regional database, we identified 1,564 patients who underwent unilateral THR between 1998 and 2004 and who were without complication or subsequent bilateral procedure at six months. These patients were divided into two groups according to their Harris hip score (HHS) at this stage: group A consisted of 270 patients with a 'poor' result (HHS less than 70). Group B consisted of 1,294 patients with a 'good' or 'excellent' result (HHS 70 or above). The patients were reviewed at five years. One hundred and ten patients from group A and 980 from group B completed five-year follow-up without further identifiable complication.

Those with poor or fair function at six months were at an increased risk of developing an identified complication by five years including dislocation (OR 5.7, 95% CI 1.8-18.2), deep infection (OR 9.8, 95%CI 2.9-37.7) and death (OR 1.6, 95% CI 1.1-2.3). There was a greater rate of revision in group A versus group B (OR 5.7, 95% CI 2.9-11). The overall function measured by the Harris hip score significantly improved in group A, but never reached that of those with good or excellent function at six months (HHS 76.2 versus 90.3, P < 0.001).

Patients with poor function at six months, but no obvious cause, are at higher risk of developing complications by five years. This group may benefit from more regular arthroplasty review and intervention.