The Use of Reactive-Dynamic Orthotic Ankle Joints in Different Types of KAFOs: Results of Biomechanical Tests and Patient Evaluations
Authors: Schmalz Thomas , Rauch Sophia , Drewitz Heiko , Bellmann Malte , Kannenberg Andreas 
Published: February 2025

Introduction

For patients with a complex lower-limb muscle weakness including the knee and/or hip extensors, a knee-ankle-foot orthosis (KAFO), available with different knee mechanisms, is required to guarantee safety while providing the highest possible degree of functionality. For planning the configuration of a KAFO, the orthotic ankle joint appears to be a secondary consideration. An advanced generation of orthotic ankle joints (reactive-dynamic ankle [RDA]) enables, compared with conventional components (CAJ), increased range of motion with adjustable motion resistances. However, currently, it is an open question whether the new orthotic ankle joint generation leads to additional benefits for KAFO users.

Objectives

The aim of the present study was to investigate the complex interactions between two different KAFO knee joint mechanisms (microprocessor-controlled CBrace orthosis and EMAG-Active stance-controlled orthosis) and ankle joint mechanisms representing both RDA and CAJ based on biomechanical tests and patient-reported evaluations. This comparison should help answer the question if the new ankle joint mechanism increases the patient benefits of a KAFO fitting.

Study Design

The different orthotic configurations were evaluated using a cross-sectional study design based on biomechanical tests and patient-reported evaluations.

Methods

Five patients were enrolled in the present study. All of them had been users of the microprocessor-controlled C-Brace and had experience with the stance control orthosis from previous fittings. The modular concept of the ankle joint representing the new mechanism allows for testing both RDA and CAJ functionality. Therefore, four KAFO configurations were tested in randomized order using motion analysis during level walking with normal speed, level walking with given short steps, ascending and descending ramps, and standing on level ground as well as 10-degree incline and decline. After finishing the biomechanical tests, patients were asked in a questionnaire for their subjective evaluation of the benefits of the respective orthosis.

Results

With C-Brace, the reliability of switching from stance to swing was close to 100% in all cases independent of the orthotic ankle joint condition. The reliability of switching from stance to swing with EMAG-Active was clearly enhanced with RDA for short-step level walking and ascending ramps, and high for level walking with both ankles. During level walking and ascending ramps with RDA, the mean maximum dorsiflexion was significantly increased for both KAFOs between 7° and 12°.

This was accompanied by a significant reduction of the peak external sagittal knee extension moment between 0.1 and 0.13 Nm/kg, enabling an improved swing phase initiation. During descending ramps, the C-Brace enabled a nearly natural knee flexion during stance, whereas the EMAG-Active remained in the locked state; both characteristics were not significantly influenced by either ankle joint. In the subjective evaluation with RDA, higher mean usefulness scores were found compared with CAJ for both KAFOs.

Conclusions

It can be concluded that the novel RDA joint represents an additional and beneficial option for the individual optimization of KAFOs, in particular for patients who must master varying terrains and walking conditions frequently in their daily lives.

Clinical Relevance

The use of the RDA new orthotic ankle mechanism tested in the present study results in relevant benefits, especially in gait situations in nonlevel conditions for KAFOs with different orthotic knee joint mechanisms. Therefore, this mechanism represents an additional option to optimize patient fittings with a KAFO.