The Influence of Calcaneal and First Ray Osteotomies in the Contact Pressures of the Ankle Joint
Authors: Netto Cesar de Cesar , Abbasi Pooyan , Smyth Niall A. , Michnick Stuart , Casscells Nicholas , Demetracopoaulos Constantine A. , Nishikawa Danilo Ryuko , Parks Brent , Miller Stuart D. 
Published: November 2020

Category: Ankle Arthritis; Ankle; Hindfoot; Midfoot/Forefoot Introduction/Purpose: Medial displacement calcaneal osteotomies (MDCO) and first ray plantarflexion osteotomies, such as a Cotton osteotomy, are frequently used realignment procedures for hindfoot and ankle joint valgus malalignment. Multiple studies demonstrated the effects of calcaneal osteotomies on the contact pressures of the ankle joint (CPAJ), with slight medial displacement of the center of pressure and lateral unloading of the ankle joint. However, the influence of a first ray plantarflexion osteotomy on the CPAJ is yet to be determined. In this cadaveric study, we compared the effects of calcaneal and first ray osteotomies in the CPAJ. Methods: Fifteen bellow-knee cadaveric specimens were used. Tekscan 5033 sensors were placed in the ankle joint and held with cyanoacrylate. Specimens were loaded in a servohydraulic load frame. Tension loads applied to tendons: Achilles (200N), PTT (40N), peroneals combined (44N), FHL/FDL combined (35N). Specimens were tested in intact position, isolated MDCO (6 and 10mm), isolated Cotton osteotomies (4 and 8mm) and combined MDCO/Cotton osteotomies (10mm and 8mm, respectively). Specimens were then cyclically loaded from 100N-1000N at a rate of 0.5Hz for 30 cycles while CPAJ data was collected at a rate of 20Hz. Average and maximum overall pressure data were extracted as well as the center of pressure (CoP) movement in the anteroposterior (AP) and medial to lateral (ML) directions. Data was also analyzed when divided into lateral, central, and medial areas of the contact pressure map. Groups were compared by the Wilcoxon test. P-values <0.05 were considered significant. Results: We found significant (p<0.05) and progressive decrease in the average and maximum CPAJ when comparing intact ankle (1624 and 1964kPa), MDCO (1526 and 1891 kPa), Cotton osteotomy (1370 and 1642 kPa) and combined osteotomies (1292 and 1599 kPa). Cotton (4 and 8mm) and combined osteotomies showed similar contact pressures, that were significantly lower than intact specimens, emphasizing the power of first ray osteotomies in changing the contact pressures of the ankle joint. When accounting for medial, central and lateral aspects of the joint, we found that the decrease in the pressures was only significant in the central (cotton and combined osteotomies) and lateral aspects (combined osteotomy only).No significant differences were found in CoP measurements (both AP ad ML directions). Conclusion: The results of this cadaveric study demonstrate the power of Cotton osteotomies, in isolation or combined with MDCO, in decreasing the overall CPAJ, especially on its central and lateral aspects. MDCO in isolation did not differ from intact specimens. No significant changes in the center of pressure of the ankle joint were noted following any of the performed osteotomies (combined or isolated). Our findings should guide surgeons when deciding between first ray and calcaneal osteotomies as realignment procedures for hindfoot and ankle valgus deformities, when aiming to unload the lateral aspect of the ankle joint. [Figure: see text]