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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