Clinical Trial Comparing Volar, Dorsal, and Custom Thermoplastic Splinting in the Treatment of Acute Mallet Finger
Condition: Mallet Finger
Study type: Interventional
Phase: Phase 3

Summary: 
      In most cases of acute mallet finger, or avulsion of the extensor digitorum communis terminal
      tendon from the distal phalanx, splinting is the treatment strategy employed. The type of
      splint used to treat these injuries continues to be controversial. Custom splints have
      recently been advocated though no strong comparative evidence is available.

      The primary objective of this investigation was to show superiority of the custom
      thermoplastic splint over both the dorsal and volar non-custom splints. The null hypothesis
      was that a radiographic lag difference greater than 5 degrees would not be observed between
      groups. The primary outcome measure is the residual extensor lag difference (compared to the
      contralateral equivalent digit) at 12 weeks post-splinting.
    

Detailed description: 
      In most cases of acute mallet finger, or avulsion of the extensor digitorum communis terminal
      tendon from the distal phalanx, splinting is the treatment strategy employed. These are
      considered Doyle I injuries- closed injuries with or without a small (<20%) avulsion
      fragment. Absolute and relative indications for surgical intervention include an open injury,
      or a bony mallet involving greater than 20% of the articular surface of the distal phalanx
      with volar subluxation of the distal phalanx relative to the proximal phalanx. The type of
      splint used to treat Doyle I mallet injuries continues to be controversial. Custom splints
      have recently been advocated though no strong comparative evidence is available.

      Objectives. The primary objective of this investigation was to show superiority of the custom
      thermoplastic splint over both the dorsal and volar non-custom splints. The null hypothesis
      was that a radiographic lag difference greater than 5 degrees would not be observed between
      groups. The primary outcome measure is the residual extensor lag difference (compared to the
      contralateral equivalent digit) at 12 weeks post-splinting. Week-12 was chosen as a
      compromise between minimizing drop-out and the most distant timepoint reasonably obtainable.

      A novel outcome lag measurement was developed for this study, using the contralateral normal
      digit as an internal control for establishing residual extensor lag. The residual extensor
      lag difference was calculated with a single radiograph obtained with the beam directed
      laterally at the affected digit and the contralateral equivalent digit (Figure 2). For
      example, if the injured mallet finger was the right index finger, a single lateral radiograph
      of the right and left index fingers on the same film was obtained. The patient was instructed
      to maximally extend the both digits. This allowed for accurate determination of extensor lag
      and comparison with the unaffected side . Adequacy of the lateral view was assessed by
      considering the superimposition of the phalangeal condyles of the affected digit. If they
      were not not superimposed, the radiograph was repeated.

      A pilot study was performed to establish the most reliable technique for measuring residual
      lag radiographically. Three measurement techniques were trialled by individuals with three
      levels of training: resident, fellow, and consultant staff. A clearly defined technique was
      employed using digital images only (Inteleviewer, Intelerad, Montreal, Canada). The
      radiograph was enlarged on the viewing monitor so that the middle and distal phalanges
      maximally filled the screen. The techniques used bisecting lines for the middle and distal
      phalanges referencing either the volar cortex, dorsal cortex, or longitudinal axis of the
      phalanges (Figure 3). Twenty-six lateral finger radiographs were blinded and assessed, and
      then repeat measurements were obtained three weeks later. Inter-item correlation matrices and
      intraobserver Pearson's correlations showed extremely high correlation values ranging from
      0.993 to 0.999 for the longitudinal axis technique. This pilot study established the
      longitudinal axis technique as the most reliable in measuring residual radiographic lag.

      Several secondary objectives were investigated. These included correlations between residual
      lag and other factors, including patient age, Michigan Hand Outcome Questionnaire scores
      (MHQ) and the development of complications; incidence of complications in each splinting
      group; comparing radiographic to clinical extensor lag differences; and evaluating the course
      of residual lag after splinting has been discontinued. Exploratory analyses were performed as
      hypothesis generators only, including sub-group analysis.
    

Intervention name(s): Volar aluminum splint; Dorsal aluminum splint; Custom thermoplastic
Intervention type(s): Device; Device; Device
Intervention description(s): Alumafoam strip with padding removed, placed on the VOLAR aspect of the digit spanning the middle and distal phalanges only.; Alumafoam strip with padding removed, placed on the DORSAL aspect of the digit spanning the middle and distal phalanges only.; Customized thermoplastic splint with circumferential contact proximal to the joint and volar contact distal to the joint. This is a similar design to the original Stack splint, except that it is custom molded.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Treatment