Talar Neck Malunions: Evaluation of Kinematics, Pedobarographic Changes and Patient Reported Outcome Measures
Authors: Sharma Siddhartha , Gohil Riddhi , Patel Sandeep , Dhillon Mandeep S. 
Published: December 2023

Category: Trauma; Hindfoot Introduction/Purpose: Malunion is a disabling complication of talar neck fractures and is prevalent in approximately 17% of cases. The impact of talar neck malunions (TNM) on foot biomechanics and functional outcomes is not well established. The available evidence is primarily derived from cadaveric studies which have demonstrated that TNMs result in reduced motion and significant alterations in contact characteristics of the subtalar joint. Owing to the paucity of literature on this subject, we conducted this study to evaluate the kinematic and pedobarographic changes and functional outcomes associated with TNMs. Methods: In this study, adult patients with talar neck malunions (TNM) without ankle arthrosis were prospectively enrolled over a 5-year period. The Rammelt and Zwipp classification was utilized to categorize the deformities. Demographic data and ankle and subtalar range of motion were assessed. Weight-bearing anteroposterior (AP), lateral, and long axial radiographs, as well as CT scans of both feet, were obtained. Dynamic pedobarography was performed to evaluate gait kinematics and plantar pressure distribution. Functional outcomes were evaluated using the Manchester Oxford Foot Questionnaire (MOxFQ), Visual Analog Score, and the EQ5D questionnaire. The t-test was utilized to compare the range of motion, pedobarographic and kinematic parameters between the normal and pathologic foot. Furthermore, correlation coefficients were calculated to determine the strength of the association between changes in talar neck geometry, plantar pressures, kinematics, and functional outcomes. Results: A total of 10 patients, 6 males, and 4 females, with a mean age of 32.4 years were enrolled. On the TNM side, significant increases were observed in step length and step time, while significant decreases were noted in the single limb support time and single limb support center of pressure line. Moreover, midfoot forces were significantly increased, whereas the forefoot and hindfoot forces were significantly decreased on the TNM side. A strong positive correlation was found between midfoot force and the talar torsion angle, and a moderate negative correlation was observed between hindfoot and midfoot forces and the inclination angle. A strong positive correlation was also noted between high midfoot pressures and VAS Scores, MOxFQ scores, and the EQ5D walking and usual activities domains. Conclusion: This study demonstrates that TNMs are associated with decreased single limb support time, increased step length and time, increased midfoot pressures, and decreased forefoot and hindfoot pressures. Additionally, an increase in talar neck torsion after TNM is linked with higher midfoot pressures, which can lead to higher levels of pain and poorer function. Our findings provide valuable insights into the altered foot biomechanics after TNMs, which can assist surgeons in offering optimal management strategies for these patients.