Correlation of Clinical Evaluation and Radiographic Hindfoot Alignment in Stage II Adult-Acquired Flatfoot Deformity.

Background: Previous work has demonstrated that the amount of radiographic hindfoot correction required at the time of adult-acquired flatfoot deformity (AAFD) operative treatment can be predicted by the amount of radiographic deformity present before surgery. Successful outcomes after reconstruction are closely correlated with hindfoot valgus correction. However, it is not clear if differences exist between clinical and radiographic assessment of hindfoot valgus. The purpose of this study was to evaluate the correlation between radiographic and clinical evaluation of hindfoot alignment in patients with stage II AAFD.
Methods: Twenty-nine patients (30 feet) with stage II AAFD, 17 men and 12 women, mean age of 51 (range, 20-71) years, were prospectively recruited. In a controlled and standardized fashion, bilateral weightbearing radiographic hindfoot alignment views were taken. Radiographic parameters were measured by 2 blinded and independent readers: hindfoot alignment angle (HAA) and hindfoot moment arm (HMA). Clinical photographs of hindfoot alignment were taken in 3 different vertical camera angulations (0, 20, and 40 degrees). Pictures were assessed by the same readers for standing tibiocalcaneal angle (STCA) and resting calcaneal stance position (RCSP). Intra- and interobserver reliability were assessed by Pearson/Spearman's and intraclass correlation coefficient (ICC), respectively. Relationship between clinical and radiographic hindfoot alignment was evaluated by a linear regression model. Comparison between the different angles (RCSP, STCA, and HAA) was performed using the Wilcoxon rank-sum test. P values of less than .05 were considered significant.
Results: We found overall almost perfect intraobserver (range, 0.91-0.99) and interobserver reliability (range, 0.74-0.98) for all measures. Mean value and confidence interval (CI) for RCSP and STCA were 10.8 degrees (CI, 10.1-11.5) and 12.6 degrees (CI, 11.7-13.4), respectively. The position of the camera did not influence readings of clinical alignment ( P > .05). The mean HMA was 18.7 mm (CI, 16.3-21.1 mm), and the mean HAA was 23.5 degrees (CI, 21.1-26.0). Clinical and radiographic hindfoot alignment were found to significantly correlate ( P < .05). However, the radiographic HAA demonstrated increased valgus compared to both clinical alignment measurements, with a mean difference of 12.8 degrees from the RCSP (CI, 11.0-14.5, P < .0001) and 11.0 degrees from the STCA (CI, 9.2-12.8, P < .0001).
Conclusion: We found significant correlation between radiographic and clinical hindfoot alignment in patients with stage II AAFD. However, radiographic measurements of HAA demonstrated significantly more pronounced valgus alignment than the clinical evaluation. The results of our study suggest that clinical evaluation of hindfoot alignment in patients with AAFD potentially underestimates the bony valgus deformity. One should consider these findings when using clinical evaluation in the treatment algorithm of flatfoot patients.
Level of Evidence: Level II, prospective comparative study.