Does a foot-drop implant improve kinetic and kinematic parameters in the foot and ankle?

ABSTRACT

INTRODUCTION: Unlike the drop foot therapy with ortheses, the therapeutic effect of an implantable peroneus nerve stimulator (iPNS) is not well described. IPNS is a dynamic therapy option which is placed directly to the motoric part of the peroneal nerve and evokes a dorsiflexion of the paralysed foot. This retrospective study evaluates the kinematics and kinetics in drop foot patients who were treated with an iPNS. MATERIALS AND METHODS: 18 subjects (mean age 51.3 years) with a chronic stroke-related drop foot were treated with an implantable peroneal nerve stimulator. After a mean follow-up from 12.5 months, kinematics and kinetics as well as spatiotemporal parameters were evaluated and compared in activated and deactivated iPNS. Therefore, a gait analysis with motion capture system (Vicon Motion System Ltd®, Oxford, UK) and Plug-in-Gait model was performed. RESULTS: The study showed significantly improved results in ankle dorsiflexion from 6.8° to 1.8° at the initial contact and from -7.3° to 0.9° during swing phase (p ≤ 0.004 and p ≤ 0.005, respectively). Likewise, we could measure improved kinetics, i.a. with a statistically significant improvement in vertical ground reaction force at loading response from 99.76 to 106.71 N/kg (p = 0.043). Enhanced spatiotemporal results in cadence, douple support, stride length, and walking speed could also be achieved, but without statistical significance (p > 0.05). CONCLUSIONS: The results show statistically significant improvement in ankle dorsiflexion and vertical ground reaction forces. These facts indicate a more gait stability and gait efficacy. Therefore, the use of an iPNS appears an encouraging therapeutic option for patients with a stroke-related drop foot.