The purpose of this pilot study is to assess the safety and usability of the WRL HX MCP medical device, a prototypal robotic system for metacarpophalangeal joint mobilization. WRL HX MCP was developed by the Wearable Robotics Laboratory of Scuola Superiore Sant'Anna in a project funded by and in collaboration with INAIL, to fulfil the needs of patients with post-traumatic hand stiffness.

This study aims to:

1. Test the safety and reliability of the WRL HX MCP device for assisting flexion and extension movement of the stiff metacarpophalangeal joint
2. Conduct a preliminary examination of the efficacy of the device in the treatment of joint stiffness to design a subsequent RCT
3. Evaluate the performance of the device in estimating the biomechanical parameters useful for the objective treatment outcome assessment.

Ten injured workers with post-traumatic and/or post-operative index finger MCP stiffness will be enrolled in a clinical trial consisting of one to four sessions of robotic therapy with WRL HX MCP at the INAIL Rehabilitation Center in Volterra.

Pilot testing of the experimental device will include the preliminary goniometric measure of passive and active MCP range of motion (ROM), the selection of the appropriate size of exoskeleton segments to fit user's anthropometry, the robotic assessment of ROM, force and torque trajectories of MCP joint, a program of robot-assisted passive and active MCF mobilization and a final clinical and robotic reassessment of joint ROM. The session will last about 1 hour and all exercises will be administered by a trained physical therapist supported by two members of the engineering team; pain level will be assessed at baseline and after each mobilization sequence; patient feedback will be recorded about the usability of the device in term of comfort, wearability, user safety, and overall satisfaction.

For Aim 1, the Safety and Reliability of the device will be evaluated in terms of the number of adverse events and malfunctions occurring during the study session.

For Aim 2, the efficacy of robot-assisted mobilization modes will be assessed by means of the longitudinal analysis of pre- and post-treatment measurements of MCP range of motion and pain intensity level, the flexion peak torque evaluation and the final administration of an ad-hoc satisfaction questionnaire.

For aim 3, the performance of WRL HX MCP will be studied by comparing the robotic MCP angle estimation with the measurements from a motion capture system.

Inclusion Criteria:

• history of traumatic hand injury or post-traumatic hand surgery
• hand size allowing to achieve proper exoskeleton fit
• NRS pain score in the 1-5 range

Exclusion Criteria:

• cognitive or linguistic ability insufficient to understand instructions
• cardiac implanted electronic devices
• open skin at the level of the patient-device interface
• absence of contraindications for finger joints mobilisation
• current or prior history of malignancy
• pregnancy or breast feeding