Pathology of Boutonniere Injuries


- See:
        - Rheumatoid Boutonniere
        - Thumb Boutonnere Injuries

- Mechanism of Injury:
    - rupture of central slip directly from its bony insertion commonly results from closed blunt trauma (w/ or w/o fracture);
    - rheumatoid Arthritis
    - volar PIP dislocation

- Pathology:
    - lesion results from disruption of extensor central slip along w/ disrupiton of triangluar ligament (the later of which can occur either at the time of injury, or can occur w/ chronic attenuation;)
    - w/ central slip disruption, PIP joint may initially be capable of weak finger extension if the triangular ligament remains intact;
            - active extension is possible, since the triangular ligment holds holds the lateral bands in an anatomic position;

- Disrupted Triangular Ligament:
    - patients will not be able to actively extend PIP joint, but will be able to actively hold the PIP in extension, if it is first passively extended;
          - this occurs because the lateral bands will relocate into their native position w/ PIP extension, allowing pt to hold finger in extension;
    - if it is unclear whether the central slip is disrupted, then test PIP joint extension w/ the wrist and MP joints held in flexion;
          - this should relax the lateral bands;

- Triangular Ligament Intact:
    - the intrinsic contributions to the central slip are disrupted, and therefore the intrinsics transmit their actions to the DIP, causing hyper-extension;
    - later on, the triangular ligament will slowly attenuate, allowing the deforming forces of the volarly positioned intrinsics and transverse retinacular ligament, to pull the lateral bands into a volar direction, below axis of PIP joint;
            - subsequently, the lateral bands will act as flexors of the PIP joint, as well as acting as extensors of the DIP joint;
            - forced active extension hastens this process;
            - this accenuates the PIP flexion & DIP extension deformities;
    - in chronic cases, there is contrature of the transverse retinacular ligament, which converts a dynamic deformity to a fixed PIP contracture;

- MP Joint:
    - may show a hyperextension deformity, since w/o the normal insertion of the extensor slip to the PIP joint, all of the force is concentrated on the MP joint



Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Monday, September 24, 2012 11:34 am