Lumbrical Plus Finger


- See:
   - Bunnel Test for Intrinsic Tightness:
   - Lumbricals:

- Discussion:
    - this is manifested by intrinsic plus attitude in involved finger on attempted flexion: (w/ MP flexion there will be IP extension);        
    - FDP becomes an extensor of the PIP joint;
    - when FDP relaxes FDS can work w/ less antagonism and PIP can flex;
    - treatment may involve division of the lumbrical;

- Causes: (lumbrical tighter than FDP)
    - FDP Laceration or rupture Distal to the Lumbrical Origin;
            - the proximal end of the lacerated FDP tendon will retract proximally, drawing the attached lumbrical proximally as well;
            - the effect is increased tension on the radial lateral band, which causes the PIP joint to extend;
    - Amputation of the Distal Phalanx (distal to central slip insertion);
    - Excessively Long Tendon Graft:
            - when the excessively long tendon graft is inserted too loosely, the lumbrical will be able to proximally retract (to some degree) 
                   which again leads to the lumbrical plus deformity;
            - paradoxical extension:
                    - when the patient attempts to flex the fingers, the relatively tight lumbrical will cause PIP extension;
    - Tightening of Lumbrical thru Imbrication of Muscle about Tendon Graft Suture Line;
    - Lumbrical Plus Finger from Excissive FDP Tendon Lengthening:
            - common complication is a tendon graft that is too long as well as a graft whose proximal anatomosis is placed distal 
                   to the lumbrical origin;
            - this complication can be prevented by maintaining proper tension on the graft and by placing the proximal tendon graft anatomosis 
                   proximal to the origin of the lumbricals;
            - the later has the effect of not allowing the lumbricals to initiate finger extension as the FDP tendon moves into flexion



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

Last updated by Data Trace Staff on Tuesday, April 10, 2012 3:51 pm