CAN PAIN BE USED TO SELECT PATIENTS FOR RADIOGRAPHIC FOLLOW UP AFTER TOTAL HIP REPLACEMENT

Abstract

The best follow up strategy after hip replacement (THR) is unclear. There are conflicting demands to obtain early diagnosis of loosening, and to minimise clinic visits. It would be desirable to achieve follow up with a validated symptom questionnaire alone, but it is unclear how frequently THRs are asymptomatic during early loosening.

This study examined the relationship between patient reported symptoms after THR using two measures (Oxford Hip Questionnaire (OHQ) and Visual Analogue Scale (VAS)), and the classification of the patients AP x ray of the hip as having definite loosening, possible loosening, or a sound implant. We examined data from 325 patients who had undergone a standard Charnley THR for osteoarthritis. Patients had a mean follow-up of 85 months (range 24–144). X rays were examined by a single Consultant Orthopaedic surgeon, and classified as satisfactory, possible loosening or definite loosening.

As expected, the large majority of patients had a satisfactory appearance on x-ray at all-time points. 12 patients were classified as having definite loosening on the basis of the available x-rays. 8 of these were subsequently listed for revision surgery at review. 20 patients were noted to have evidence of possible loosening. Examination of the Oxford hip questionnaire and VAS data demonstrated a strong relationship between OHQ value and the VAS result for pain (r = 0.78, p < 0.001, Spearman rank correlation). Data were analysed separately (using ROC curves) to determine whether the OHQ or VAS was a satisfactory method of selecting patients who fell into “definite loosening” or “definite or possible loosening” groups. Neither OHQ or VAS were sensitive or specific for definite or possible loosening.

We conclude that x rays are required for early detection of loosening, and that follow up by OHQ or VAS alone is insufficient for this purpose.