Influence of Isolated and Combined Medial Displacement Calcaneal Osteotomy, Lateral Column Lengthening and Cotton Osteotomy in Three-Dimensional Foot Alignment: A Cadaveric Weightbearing CT Study

CATEGORY: Midfoot/Forefoot; Other INTRODUCTION/PURPOSE: Lateral Column Lengthening (LCL), Medial Displacement Calcaneal Osteotomy (MDCO) and Cotton Osteotomy (CO) are considered the work-horse surgical procedures for Progressive Collapsing Foot Deformity (PCFD) correction. The amount of three-dimensional correction induced by each isolated procedure cannot be established in the clinical setting since procedures are frequently performed in combination based on deformity severity and surgeon's preference. Understanding the influence of each one of the procedures, as well as their magnitudes, in the overall 3D correction of the deformity would be extremely helpful in the surgical planning of PCFD. Therefore, our simulated weightbearing cadaveric study aimed to assess the amount of 3D correction induced by different magnitudes of isolated and combined LCL, MDCO, and CO procedures, using weightbearing CT (WBCT) imaging. METHODS: In this cadaveric study 12 below-knee specimens with no deformity were used. They were mounted on a frame under 360N of axial load, while keeping conventional stance level tension to tendinous structures. Each group of four specimens underwent isolated and progressive magnitudes of MDCO (6, 10 and 14mm), LCL (6, 8 and 10mm) and CO (4, 8 and 12mm). Following isolated correction, the specimens were randomized into different amounts of combined correction, first with two procedures (only moderate correction; four specimens each combination) and then with three procedures (combined mild, moderate and large corrections; four specimens each). The 3D measurement Foot and Ankle Offset (FAO), representing the relative position between the center of the ankle joint and the weight bearing tripod of the foot, was calculated from WBCT datasets for each specimen in each one of the tested corrected conditions. Comparison between the different conditions was performed using Paired T-Test/Wilcoxon. RESULTS: All isolated performed corrective procedures (MDCO, LCL and CO) significantly influenced FAO measurements (All p- values <0.05). When applied in isolation, every 1mm increase in MDCO, LCL and CO decreased FAO values by respectively 0.8%, 0.36%, and 0.29%, highlighting the importance of the heel position in the overall 3D position of the foot. Combination of two moderate-sized procedures decreased FAO values significantly (p<0.05) and more pronouncedly, with combination of MDCO and LCL decreasing FAO by an average of 7.2%, MDCO and CO by 6.2% and LCL and CO by 3.9%, with no significant differences between the three. As expected, combination of the three procedures lead to pronounced and significant decreased of FAO values by respectively 5.2%, 8.5% and 14.2% for mild, moderate, and large corrections. The combination of the three large sized corrections was significantly higher than mild and moderate corrections (p=0.002). CONCLUSION: In this cadaveric WBCT study we assessed the influence of different magnitudes of isolated and combined MDCO, LCL and CO in foot and ankle 3D alignment. We found that all isolated procedures significantly decreased FAO measurements, with every 1mm increase in MDCO, LCL and CO decreasing FAO by respectively 0.8%, 0.36%, and 0.29%. Combination of two procedures and three procedures also lead to significant and more pronounced alignment change. The data presented in this study can serve as baseline predictive values of foot alignment correction when planning the use of MDCO, LCL and CO for surgical treatment of PCFD.