Pressure-pain threshold algometric measurement in patients with greater trochanteric pain after total hip arthroplasty

Background: The evaluation of tenderness associated with greater trochanteric pain (GTP) syndrome is amenable to bias and depends on the examiner's experience. In this study, we tested whether the use of an electronic pressure algometer enhanced the reliability of this evaluation. Patients and Methods: Pressure-pain threshold (PPT) was measured with an electronic algometer in 18 patients who developed GTP after total hip arthroplasty and in matched controls. Both groups were evaluated with visual analog scale. Results: The PPT measurements showed large interindividual variability across patients. The correspondence of the PPT measurements in asymptomatic patients was good. We found good validity for the algometer used. The PPT ratio of 0.8 (affected vs. unaffected side) can be used as a cut-off ratio. The PPT measurements at the greater trochanter (local pain) were significantly lower than at the ilio-tibial band (radiated pain). There was no correlation between PPT measurements and visual analog scales. Despite the acceptable sensitivity and specificity of pressure algometer, because of low positive predictive value and large interindividual variability, pressure algometer has a limited value as a screening test. Conclusions: The examination of tenderness associated with GTP is facilitated by the used algometer. It is the intraindividual body-side PPT differences that yield the most sensitive measurement for the assessment of deep pain. A cut-off value of 0.8 can be used for diagnostic purposes. Interindividual differences might be considerable and could mask pathologic diagnostic findings.