The Efficacy of Surgical Treatment in the Correction of Adult Acquired Flatfoot Deformity: A Three- dimensional Biometric Weightbearing Computed Tomography Evaluation

Abstract

Category: Hindfoot; Ankle; Midfoot/Forefoot Introduction/Purpose: Multiple surgical techniques are used in the correction of Adult Acquired Flatfoot Deformity (AAFD). Assessment of the efficacy of a surgical treatment in the correction of the deformity is usually performed by clinical evaluation and conventional radiographic imaging. Weightbearing CT (WBCT) allows a more reliable and multiplanar evaluation of AAFD. The Foot and Ankle Offset (FAO) is a WBCT biometric semi-automatic measurement that gauges the relative positioning between the foot tripod and the center of the ankle joint. This study aimed to investigate the efficacy of surgical treatment in correcting AAFD, comparing preoperative and postoperative FAO measurements. We hypothesized that surgical treatment would provide significant correction of the deformity, centering the tripod of the foot underneath the ankle joint. Methods: In this prospective comparative study, 21 adult patients (22 feet) with flexible AAFD were included, mean age 55 (range, 23-81) years, 13 females and eight males. Patients underwent preoperative and postoperative standing WBCT examination. Three-dimensional coordinates (X, Y and Z planes) of the foot tripod (weightbearing point of the first and fifth metatarsals and calcaneal tuberosity) and center of the ankle (apex of the talar dome) were harvested by two independent and blinded observers. The FAO was automatically calculated from the harvested 3D coordinates by dedicated software. Data regarding the surgical technique used was recorded. Patient Reported Outcomes (PROs) were collected preoperatively and postoperatively at a mean follow-up of 22 (range, 8-36) months. Pre and postoperative FAO measurements were compared by paired T-tests. Multivariate analysis was used to assess the influence of surgical procedures in the amount of FAO correction. P-values of less than 0.05 were considered significant. Results: We found excellent intra (0.98) and interobserver reliability (0.96) for FAO measurements. The mean preoperative FAO was 10.4 (95% CI, 8.5 to 12.1). There was a significant correction of the deformity postoperatively (p<0.0001), with a mean postoperative FAO of 1.4 (CI, -0.1 to 2.9), and mean improvement of 8.9 (95% CI, 6.6 to 11.2). Average increase in PROs was (p<0.05): physical function (8; CI, 4 to 12), pain interference (10.3; CI, 4.8 to 15.9), pain intensity (5.3; CI, -10:20.6), mental health (4.2; CI, 0.2:8.2), physical health (4.3; CI, 0.9 to 9.8), and depression (10.4; CI, -0.6 to 21.4). The mean number of surgical procedures performed was 8 (range, 2-12). Spring ligament reconstruction was the only technique that influenced the amount of FAO correction (P<0.001). Conclusion: To the author’s knowledge, this is the first study to assess the amount of surgical correction of AAFD using standing WBCT images and semiautomatic 3D measurements. We found that surgical treatment provided a significant and pronounced amount of correction in the FAO, with the foot tripod more centered underneath the ankle joint. We also found a significant improvement in the PROMIS after an average postoperative follow-up of 22 months. Among multiple different surgical procedures performed, reconstruction of the spring ligament was the only technique that significantly influenced the amount of FAO correction. Longer-term follow-up studies are needed. Figure 1.