ANKLE ARTHRODESIS, BIOMECHANICAL ANALYSIS

Abstract

Introduction: Ankle arthrodesis is still a surgical technique, which implies compensations with a higher range of motion from the neighbouring joints (knee-tarsus). The aim of this study is to compare and analyze the functional results of large outcome ankle arthrodesis through both kinetic and kinematical motion study and plantar support study.

Material and Methods: We studied 19 patients (17 males and 2 females) with post-traumatic ankle arthrodesis (15 right side and 4 left side) with a minimum follow up of three years (3–9 years). No other lower extremity pathologies were associated. Average age was 37 years (23–56 y.o) and average weight 84,5 kg (54–117 Kg).

We performed physical (including body mass index, BMI), functional and image examination (X-Rays and CT scan). In order to objectify the results we used SF-36, AOFAS scale (max 90 points) and Mazur scale (max 97 points). Kinetic parameters of motion with two force plates (Kistler, Switzerland) and pedography (Emed, Novel, Munich, Germany) were obtained. Kinematic data were obtained with a 3-D video analysis system (Clima system, STT, San Sebastian, Spain). A statistical descriptive study was performed to know the grade of patients’ satisfaction and to analyze the range of motion (ROM) and reaction force of the limbs. Both sides were compared.

Results: results obtained with Mazur scale were 49,26 points (14 – 83), 49,89 points AOFAS scale (22 – 84), 85,79 points SF-36 (85 – 109). Pain score (VAS) was 4.1 points. BMI over 30 points was found six patients. Image analysis of all patients showed an adequate fracture consolidation and a correct ankle position. Kinematical study expressed a lower ROM in the fusion ankle than in the healthy one, basically due to the neighbouring joints movement compensation. Regarding motion parameters we only found differences at the anterior-posterior force switch direction point (41,67% of the healthy foot step and 50,37% in the fusion foot step). Support time was greater in fusion ankle than in healthy one. Midfoot and centre forefoot pressures resulted greater in fusion feet.

Conclusion: Patients with ankle arthrodesis presented often overweight. They show a good subjective outcome in the quality life scales and few mechanical alterations despite of the low score of the ankle and pain specific rating scales.