Abstract
Introduction
Most studies now use Patient Reported Outcome Measures (PROMS) as the preferred and only method for assessing ‘functional outcome’ following surgery. It is thought that these questionnaires accurately reflect the patient's pain and physical function. We hypothesised that comprehensive functional examination would therefore correlate strongly with PROMS following total knee arthroplasty (TKA).
Methods
We prospectively assessed the function of 100 consecutive knee replacement patients, pre-operatively, then at 8, 26 and 52 weeks post-operatively. PROMS employed were the Oxford Knee Score (OKS) and the Short Form-36. Additionally, leg strength (Leg Extensor Power Rig(tm)), a validated battery of timed functional tasks (Aggregated Locomotor Function, ALF) and pain scores (numerical rating scale) were also assessed. Statistical analysis was performed using the Minitab version 15 software. Level of significance was set as p = < 0.05.
Results
Seven patients were lost to follow-up, leaving 93 data sets available for analysis. All of the individual outcome measures showed statistically significant improvement between each of the assessment periods (paired sample t-test, p = < 0.05). Strong correlation was observed between the two PROMS (r = 0.74). Comparatively small correlations were identified between the PROMS and physical assessments (r = < 0.41). The pain scores correlated modestly well with the OKS (r = 0.61) but comparatively poorly with the physical assessments (r = < 0.37).
Conclusion
PROMS correlate well with pain, but less well with function following TKA. These results suggest that PROMS may not fully represent actual physical function, but rather the patient's perception of their function.
With the advancement of PROMS as the prime outcome measure of most studies, it is important to acknowledge that the assessment provided may be incomplete and, though a useful means of assessing large cohorts, their limitation in assessing functional outcome should be recognised.
