Metacarpal Shaft Frx   


- Discussion:
    - displacement of metacarpal shaft fractures is prevented by intermetacarpal ligaments and intrinsic muscles;
    - the border metacarpals (thumb, index, and little) are not supported as well as the ring and long metacarpals and are therefore more likely to displace;
    - effect of shortening:
           - in short oblique fractures, the average shortening is about 5 mm;
                 - obstacles to further shortening is the deep intermetacarpal ligament and interosseous muscles;
           - for each 2 mm increment of shortening, there was a corresponding 7 deg extensor lag at the MCP joint;
           - reference:
                 - Metacarpal shaft fractures: the effect of shortening on the extensor tendon mechanism.
    - types of metacarpal shaft fractures:
           - spiral fractures
           - oblique fractures involving two metacarpals
                 - oblique frxs have tendency to telescope, producing rotational deformity & caused by proximal pull of intrinsic muscles;
           - transverse frxs of long & ring fingers are usually stable after reduction since they are splinted by boder metacarpals;
           - comminuted fractures or frx with a segmental loss of bone;


- X-Rays:
    - 30 deg pronated lateral: for index and long metacarpals;
    - 30 supinated lateral: for ring and little metacarpals;


- Non Operative Treatment:
    - provide an adequate local anesthetic block to allow digital reduction;
    - reduction:
          - easy to reduce but difficult to maintain;
          - flex of the MP joint to gain control of distal fragment & then push metacarpal head dorsally (& metacarpal shaft volarly) to achieve reduction;
          - rotational deformities are best treated by buddy taping the injured finger to another;
    - functional assessment:
          - the injured finger is observed for its ability to fully flex and extend;
          - fracture shortening will lead to an extensor lag;
          - if adequate MCP extension is not achieved, then surgical fixation should be considered;


- Indications for Surgical Treatment:
    - displaced or shortened fractures require fixation inorder to maintain the set relationship of the finger flexors and extensors;
    - spiral and oblique fractures tend to rotate (esp when involving two metacarpals) which is difficult to control w/ casting;
    - apex dorsal angulation in the index, long, and ring will cause a cosmetic deformity, since it disrupts the normal transverse palmar arch;
    - inability for the MCP joint to fully extend (after an anesthetic block) is another indication for surgery;

- Operative Treatment of Shaft Frx


- Complications:
    - extrinsic tendon tightness:
           - may result from crushing injuries to the hand;
           - test extrinsic tightness by test PIP flexion while the MP joints are held flexed;
                   - w/ extrinsic tightness, there will be more PIP flexion w/ the MP's held extended;
                   - w/ the PIP joints fully flexed, the MP joints will move into extension;
           - this requires aggressive hand therapy, and if no improvement is found, then extensor tendon tenolysis and dorsal joint capsulotomy is required;
           - in some cases a Littler Release may be appropriate:
                   - a portion extrinsic tendon is excised over the proximal phalax;
                   - extrinsic tendon will then extend the MP joint, and the intrinsic tendons will then extend the PIP joint;
    - intrinsic tendon tightness:
           - may result from crushing injuries to the hand;
           - in contrast to extrinsic tendon tightness, when the MP joint is extended, flexion of the  PIP joints is limited



Year Book: Functional Treatment of Metacarpal Fractures: 100 Randomized Cases With or Without Fixation.

Metacarpal shaft fractures: the effect of shortening on the extensor tendon mechanism.



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

Last updated by Data Trace Staff on Thursday, October 4, 2012 1:59 pm