Effectiveness of Exercise Relative Motion Orthoses for Limited Finger Joint Motion

Effectiveness of Exercise Relative Motion Orthoses for Improving Limited Proximal Phalangeal Joint Motion: A Single-Center, Single-Blinded Randomized Controlled Trial

This randomized controlled trial investigates the effectiveness of two exercise orthosis designs-the Relative Motion Flexion (RMF) and Relative Motion Extension (RME) orthoses-for improving motion in patients with proximal interphalangeal joint (PIPJ) flexion or extension deficits. A total of 148 adult patients with acute hand injuries and a minimum 10° difference between active and passive PIP joint motion will be enrolled. Participants are stratified by their primary motion deficit and randomized to either the exercise orthosis or placebo orthosis group. The orthosis is worn for 4 weeks, with follow-up assessments at weeks 6 and 8 to evaluate range of motion and patient satisfaction. All participants will continue standard hand therapy throughout the study.

The prevention and treatment of proximal interphalangeal joint (PIPJ) contractures are key goals in hand rehabilitation, often addressed with orthotic interventions. The choice of orthosis design depends on the severity and timing of the injury or disease. During the acute stage, static splinting is typically used, while more dynamic orthoses, such as static-progressive splinting, are recommended in the chronic stages to manage contractures. If a contracture already exists, hand therapists differentiate between dynamic and fixed deformities in PIPJ flexion or extension. Fixed deformities do not or hardly respond to passive mobilisation, while dynamic deformities show a difference in active and passive range of PIPJ motion - e.g. in cases of soft tissue adhesions hindering active motion.

In addition to traditional passive orthoses, which stretch the PIPJ in a fixed position during dedicated periods, exercise-based orthoses (relative motion orthoses, RM) have been developed to enhance PIPJ mobility during everyday activities. These include Relative Motion Extension (RME) and Relative Motion Flexion (RMF) orthoses, designed to improve both flexion and extension. Studies have shown that RME orthoses improve active flexion, while RMF orthoses aid in active extension, with patients reporting high satisfaction and functional benefits from using these devices in daily tasks. Furthermore, RM orthoses have been widely adopted by therapists, demonstrating benefits in improving functional hand use and promoting non-intentional exercise.

Since the use of relative motion (RM) orthoses - especially as exercise orthoses - is relatively new, few prospective studies have examined their effectiveness in improving PIPJ motion. Therefore, this study aims to compare the effectiveness of exercise RM orthoses with a placebo orthosis to identify the most beneficial treatment strategies for patients with limited PIPJ motion. The goal is to strengthen the evidence base and refining the clinical application of exercise-based orthotic interventions.

The primary objective of this study is to compare the effectiveness of two orthoses designs, the exercise RME and RMF orthosis vs. a placebo orthosis.

Secondary objectives are:

1. To evaluate if there is a clinically relevant difference in activity performance at 4 and 8 weeks after orthosis fabrication.
2. To assess if there is a statistically significant difference in patient satisfaction with (i) the orthosis and (ii) treatment outcome (satisfaction with the daily use of the hand) after 4 weeks (i and ii) and 8 weeks (ii).
3. To document adherence to orthotic intervention from baseline to 4 weeks. We strive for 37 patients per arm and a total sample size of 74 patients per study group. This results in 74 patients in the extension-group and 74 patients in the flexion-group and a total of 148 patients enrolled in this study.

Inclusion Criteria:

• PIPJ motion deficit with a minimum difference of 10° between passive and active motion
• To have an acute injury, i.e. operated on or within maximum 6 weeks of accident
• Only one hand is affected
• Adult patients over 18 years of age
• Understanding German, French or English
• Hand therapy treatment in-house at Inselspital in Bern
• Ability to give informed consent as documented by signature

Exclusion Criteria:

• Previous injuries to the hand or PIPJ (e.g., intra-articular fractures, PIPJ ligament damage) that may limit baseline joint mobility and influence responsiveness to the intervention.
• Presence of conditions such as osteoarthritis (OA) or rheumatoid arthritis (RA) that may affect PIPJ stiffness, pain, or inflammation.
• Inability to follow the procedures of the study, e.g. due to language problems, psychological disorders, dementia
• Boutonniere deformity
• Minors (below 18 years of age)