March 2017 No. 44
Leaving the DIP Joint Free when Treating a Boutonnière Injury
The customary treatment for a closed boutonnière injury is immobilization of the proximal interphalangeal (PIP) joint in full extension with the DIP joint free to allow distal interphalangeal (DIP) joint flexion.
There are two reasons DIP joint flexion is important:
- DIP joint flexion increases the tension in the lateral bands [in blue], bringing them to their most dorsal position. The loss of central slip integrity which creates a boutonniere deformity leads to several biomechanical faults including volar translation of the lateral bands. It is important the lateral bands are positioned in the most dorsal position possible during healing of the central slip.
- DIP joint flexion maximizes the length of the oblique retinacular ligament (ORL) [in pink]. If the boutonnière deformity persists, the ORL adaptively shortens, impeding normal finger mechanics.
When a patient presents with non-acute boutonnière deformity with an associated PIP joint flexion contracture, serial casting to regain PIP joint extension is required before the PIP joint can be immobilized in full extension for the treatment of the boutonnière injury.
Often therapists assume the DIP joint must also be left free during the period of serial casting. It is important to note that the two reasons for DIP flexion stated above can be achieved only when the PIP joint is in full extension. DIP flexion cannot create either elongation of the ORL or dorsal movement of the lateral bands unless the PIP joint is simultaneously fully extended.
In the author’s opinion it is actually desirable to include the DIP joint in the serial cast. By wrapping the casting material around the middle and distal phalanges, one can slowly bring the DIP joint out of a hyperextended position (if applicable). Whether or not the DIP joint rests in hyperextension, the inclusion of the DIP joint lengthens the distal lever arm of the PIP joint serial casting construct which greatly enhances mechanical advantage. It is extremely difficult to apply a cast that precisely holds the PIP joint in its maximum extension and still allow full flexion of the DIP joint. The shorter the finger, the greater is this challenge. Allowing DIP joint flexion when working to extend the PIP joint with casting usually sacrifices full extension of the PIP joint.
If your boutonnière patient presents with an associated PIP joint flexion contracture, the following serial cast sequence is recommended:
- Apply casting material circumferentially around the middle and distal phalanges, serially positioning the DIP joint toward a neutral position (if applicable) and allow the material to become firm.
- Then apply casting material circumferentially around the proximal phalanx and the already applied cast on the two distal phalanges to position the PIP joint serially toward zero degrees.
For shorter fingers where the length of the proximal phalanx does not give adequate purchase for positioning of the PIP joint, a modified technique can be used as suggested in the Journal of Hand Therapy or in our HandLab video course, The Obstinate PIP Joint.
Thanks to Emily Altman PT, DPT, CHT for editorial comments.
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Disclaimer: HandLab Clinical Pearls are intended to be an informal sharing of practical clinical ideas; not formal evidence-based conclusions of fact.