Selecting, assessing and interpreting measures of function for patients with severe hip pathology: The need for caution

Introduction: It is not always possible to use a combination of patient-reported outcome measures (PROMs), performance tests and clinician-administrated measures to assess physical function prior to hip surgery. We hypothesised that there would be low correlations between these three types of measure and that they would be associated with different patients' characteristics.

Materials and methods: We conducted a cross-sectional analysis of the preoperative information of 125 participants listed for hip replacement. The WOMAC-function subscale, Harris Hip Score (HHS) and walk, step and balance tests were assessed by questionnaire or during a clinic visit. Participant's socio-demographics and medical characteristics were also collected. Correlations between functional measures were investigated with correlation coefficients. Regression models were used to test the association between the patient's characteristics and each of the three types of functional measures.

Results: None of the correlations between the PROM, clinician-administrated measure and performance tests were very high (<0.90). Associations between patient's characteristics and functional scores varied by type of measure. Psychological status was associated with the PROM (P-value<0.0001) but not with the other measures. Age was associated with the performance test measures (P-value ranging from ≤0.01 to <0.0001) but not with the PROM. The clinician-administered measure was not associated with age or psychological status.

Discussion: Substantial discrepancies exist when assessing hip function using a PROM, functional test or a clinician-administered test. Moreover, these assessment methods are influenced differently by patient's characteristics. Clinicians should supplement their pre-surgery assessment of function with patient-reported measure to include the patient's perspective.

Level of evidence: III, observational cross-sectional study.