Overview
Boutonnière injuries involve damage to the central slip of the extensor tendon over the proximal interphalangeal (PIP) joint (zone III) of the finger. These injuries disrupt the balance of the extensor mechanism, leading to volar displacement of the lateral bands and progressive development of Boutonnière deformity, characterized by PIP joint flexion and distal interphalangeal (DIP) joint hyperextension. Due to the gradual onset and closed nature of the injury, diagnosis is often delayed, and untreated cases may result in joint contractures, reduced range of motion (ROM), pain, and functional limitations.
Treatment is typically conservative and requires prolonged immobilization and splinting, often followed by dynamic orthoses such as Capener splints. However, evidence supporting current treatment strategies is limited and clinical outcomes are variable. Recently, the Relative Motion Flexion (RMF) orthosis has been introduced as an alternative approach aimed at restoring extensor mechanism balance. Existing evidence is limited to small or heterogeneous studies, highlighting the need for further evaluation.
This pilot study aims to assess the feasibility and preliminary effects of RMF orthosis treatment in patients with Boutonnière injuries. The primary objective is to evaluate changes in finger range of motion (ROM) and to estimate variability and within-subject correlations to inform sample size calculations for a future randomized controlled trial. Additional feasibility outcomes include recruitment rate, adherence to treatment, and practicality of measurement procedures.
Secondary objectives include evaluating pain, grip strength, functional hand limitations in daily activities, and patient-reported tolerability and comfort of the orthosis.
The study will be conducted as a prospective longitudinal cohort pilot study with repeated within-subject measurements at baseline, 3 months, and 12 months. A total of 25 adult patients with acute or subacute closed zone III extensor tendon injuries will be recruited consecutively at the Hand Surgery Rehabilitation Unit, Skåne University Hospital, Malmö.
Inclusion criteria include age ≥18 years, positive pencil test, and confirmed central slip injury. Exclusion criteria include open injuries, significant joint contractures (\>20°), chronic injuries (\>1 year), previous surgery or trauma in the same finger, concomitant fractures or tendon/nerve injuries, inflammatory arthropathies, and severe cognitive or psychiatric conditions or substance abuse.
All participants will receive treatment with an RMF orthosis according to a structured protocol consisting of 6 weeks of continuous use followed by 6 weeks of intermittent daytime and nighttime use. No separate control group will be included; analyses will be based on within-subject comparisons over time.
Primary outcome is ROM measured at the MCP, PIP, and DIP joints using a goniometer. Secondary outcomes include pain (Numeric Rating Scale), grip strength (Jamar dynamometer), hand function (QuickDASH), adherence and tolerability questionnaires, and recruitment rate.
Data will be analyzed using descriptive statistics and nonparametric longitudinal methods, including Friedman tests and Wilcoxon signed-rank tests for paired comparisons across time points.
The study will be conducted in accordance with the Declaration of Helsinki, with ethical approval sought from the Swedish Ethical Review Authority. All participants will provide informed consent, and data will be pseudonymized in accordance with GDPR. The study poses minimal risk, and participants will be monitored throughout treatment with adjustments made as needed.
This pilot study will generate essential data on treatment variability, feasibility, and preliminary outcomes of RMF orthosis use. The results will inform the design of a future randomized controlled trial and may contribute to improved evidence-based management of Boutonnière injuries, potentially leading to better functional outcomes and more efficient rehabilitation strategies.
Description
Boutonnière injuries involve disruption of the central slip of the extensor tendon over the proximal interphalangeal (PIP) joint (zone III) of the finger. This leads to imbalance in the extensor mechanism, with volar displacement of the lateral bands and progressive development of Boutonnière deformity, characterized by PIP flexion and compensatory DIP hyperextension. Due to the often gradual onset and closed injury mechanism, diagnosis is frequently delayed. If untreated, the condition may result in stiffness, joint contractures, pain, reduced range of motion (ROM), and long-term functional impairment.
Current conservative treatment typically consists of prolonged immobilization of the PIP joint in extension, followed by dynamic orthotic management. Although widely used, evidence supporting existing treatment strategies is limited and outcomes are variable. Treatment is often demanding for patients due to prolonged splinting and restricted hand function during rehabilitation.
The Relative Motion Flexion (RMF) orthosis has been introduced as an alternative treatment strategy aimed at restoring balance within the extensor mechanism while allowing greater functional use of the hand during rehabilitation. However, current evidence is limited to small case series, heterogeneous cohorts, and studies with methodological limitations. Further prospective evaluation is therefore needed.
This study is designed as a prospective longitudinal pilot cohort study with repeated within-subject measurements. The primary purpose is to evaluate feasibility and to generate parameters required for planning a future randomized controlled trial, including estimates of variability in range of motion outcomes and within-subject correlations over time.
The study will also explore preliminary effects of RMF orthosis treatment on finger range of motion, as well as secondary outcomes including pain, grip strength, functional hand limitations, and patient-reported tolerability and adherence.
A total of 25 adult patients with acute or subacute closed central slip injuries (zone III) will be recruited consecutively at the Hand Surgery Rehabilitation Unit, Skåne University Hospital, Malmö, Sweden.
Participants will be treated with an RMF orthosis according to a structured rehabilitation protocol consisting of 6 weeks of continuous use followed by 6 weeks of intermittent use during daytime and nighttime. Treatment is delivered as part of routine rehabilitation follow-up, with adjustments made as clinically indicated.
Outcomes will be assessed at baseline, 3 months, and 12 months after treatment initiation. Primary outcome is range of motion (ROM) measured at the MCP, PIP, and DIP joints using a goniometer. Secondary outcomes include pain intensity (Numeric Rating Scale), grip strength (Jamar dynamometer), hand function (QuickDASH), and a study-specific questionnaire assessing adherence and tolerability. Recruitment rate will be recorded as number of eligible patients included per month.
As a pilot study, no control group is included. Analyses will focus on within-subject changes over time and estimation of parameters needed for sample size calculation in a future randomized controlled trial. Data will be analyzed using descriptive statistics and nonparametric longitudinal methods, including Friedman tests and Wilcoxon signed-rank tests for paired comparisons across time points.
The study will be conducted in accordance with the Declaration of Helsinki. Ethical approval will be sought from the Swedish Ethical Review Authority (Etikprövningsmyndigheten). Written informed consent will be obtained from all participants. All data will be pseudonymized and handled in accordance with applicable data protection regulations (GDPR). The study involves minimal risk, and participants will be monitored throughout the rehabilitation period.
This pilot study will provide essential feasibility data and preliminary clinical outcomes for RMF orthosis treatment. The results will inform the design of a future randomized controlled trial and may contribute to improved evidence-based management of Boutonnière injuries, with the potential to enhance functional recovery and optimize rehabilitation strategies.
Eligibility
Inclusion Criteria:
- persons with acute and subacute closed injurt to the central slip/extensor tendon zon 3
- positive pencil test
Exclusion Criteria:
- open injury or infection
- joint contracture \>20
- trauma \>1 year ago
- previous trauma or surgery in the same finger
- simultaneous crush injury
- concomitant fracture and/or digital nerve injury and/or flexor tendon injury
- rheumatoid arthritis
- drug abuse, sever cognitive impairment, or severe psychological disorder
