Evaluation of Biomechanical Effects and Patient Benefits of a New Orthotic Ankle Joint in Stance Control Orthosis Fittings

Abstract

ABSTRACT Introduction A newly introduced generation of orthotic ankle joints with adjustable dorsiflexion and plantarflexion resistances and increased range of motion (ROM) has been well established in orthotic fittings of neurological patients with ankle foot orthoses. The aim of the present study was to investigate whether users of stance control orthoses (SCOs) may also benefit from this orthotic ankle joint principle using a biomechanical test design. Methods Six patients unilaterally fitted with an SCO (E-MAG Active) with the orthotic ankle joint NexGearTango (NGT; Ottobock, Duderstadt, Germany), an ankle joint representing the new principle, were enrolled in the study. The modular principle of the ankle joint allowed testing both the new functionality and the characteristics of a conventional orthotic ankle joint (CAJ; limited uncontrolled ROM). Level walking at slow, medium, and fast speed and with given short steps, ascending and descending a ramp with 10° inclination and standing (level ground as well as 10° incline and decline standing), were assessed while using NGT or CAJ, respectively. Kinematic and kinetic data were captured with an optoelectronic camera system and two force plates. Results The reliability of switching from stance to swing of the orthotic knee joint was clearly enhanced with NGT for short-step level walking and ascending ramps. For ascending ramps, a significantly increased dorsiflexion of 5° during stance and an earlier transition from decelerating to accelerating forces were found with NGT. When standing on slopes, the symmetry of weight distribution between the orthotic and unaffected limb was significantly increased with NGT. Conclusions The increased and resistance-controlled dorsiflexion of the new orthotic ankle joint principle resulted in relevant benefits in gait situations with unlevel conditions and higher demands. Therefore, this orthotic ankle joint principle may represent an additional option to optimize patient fittings with SCOs. Clinical Relevance Statement The use of the new orthotic ankle principle tested in the present study results in relevant benefits, especially in gait situations in unlevel conditions. Therefore, this principle represents an additional option to optimize patient fittings with SCOs.