An evaluation of retrospective outcome scores in elective foot and ankle surgery

Patient reported outcome measures are becoming more popular in their use. Retrospective scoring is not yet a validated method of data collection but one that could greatly decrease the complexity of research projects. We aim to compare preoperative and retrospective scores in order to assess their correlation and accuracy.

36 patients underwent elective foot and ankle surgery. All patients were scored preoperatively using the SF-12 (including both the physical and mental subsets) and FFI. Patients then recorded both PROMs at the 3-month follow up (av. 139 days). Results were then analyzed for statistical significance.

36 patients (av. age 54.6): completed both sets of questionnaires. There were 15 hindfoot and 21 forefoot procedures. No retrospective scores were identical. The mean percentage difference between the preoperative scores was -7.9% (-17.3 to 1.6%, 95% CI) for Physical Component of SF12, -3.2% (-10.3 to 3.9%, 95% CI) for mental component of SF12 and 40.7% (25.3 to 56.1%, 95% CI) for FFI. This retrospective accuracy was statistically significant (p<0.001). When the scores were plotted against each other, the outcome measurements showed positive correlations (Physical SF 12 p=0.48, Mental SF 12 p=0.80 and FFI p=0.81). With both PROMs mean percentage differences combined, patients undergoing hindfoot procedures (3.5%; -5.0 to 12.1%, 95% CI) were more accurate with retrospective scoring than their forefoot counterparts (17.5%; 5.0 to 30.0%, 95% CI). This was not statistically significant (p=0.07). Using regression analysis, we found no significant statistical difference in the retrospective accuracy when compared against both time to retrospective scoring and the outcome measure at 3 months post operatively.

Retrospective scoring appears to lack accuracy when compared to prospective methods. However, our data shows the SF12 is recalled more accurately than the FFI (p<0.001) and both the mental and physical components are recalled to within 10% of the pre-operative score. These results show patients tend to recall their symptoms at a worse level preoperatively than originally described, especially those with forefoot problems.