Isoforce: A new outrigger system for static progressive orthotic interventions of the proximal interphalangeal joint with constant force transmission—Results of a biomechanical study

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Abstract

Study Design:

Bench research—biomechanical study.

Introduction:

Static progressive orthotic devices are efficient in treating contractures. However, current outriggers are unable to keep force transmission and the force application angle (FAA) constant.

Purpose of the Study:

To evaluate the biomechanical performance of the Isoforce outrigger, a novel extension orthosis.

Methods:

A hand model was used to measure the required force at the outrigger and FAA, while simulating resolution of different contracture angles. We also tested feasibility in a small patient series.

Results:

The force required with the Isoforce device never exceeded 2.4 N, and the FAA did not change more than 6°. Corresponding figures for the reference devices exceeded 16 N and 20°. The 7 patients testing the Isoforce extension device showed an extension deficit that decreased from 40° at baseline to 25° at 6 weeks. They rated the device as very comfortable to wear.

Conclusions:

Isoforce maintains constant force transmission and FAA throughout the full range of motion, promotes the lengthening of contracted structures, and is comfortable to wear.

Level of Evidence:

Not applicable.

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