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Intrinsic Weakness and Claw Hand

- Discussion:
- claw hand deformity is manifested by flattening of the transverse metacarpal arch and longitudinal arches,
with hyperextension of MCP joints and flexion of the PIP and DIP joints;
- deformity is produced by imbalance of the intrinsic & extrinsics;
- intrinsic muscles must be markedly weakened or paralyzed to produce claw deformity;
- long extensor muscles hyperextend the MCP joint, & long flexor muscles flex the PIP and DIP joints;
- weakness of the long flexors (as in high palsy) actually decreases claw fingers;
- PIP joint loses the ability to extend thru the lateral bands and must rely on the central slip;
- due to the anatomy of the saggital band, MP joint hyperextension blocks the the central slip from extending the PIP;
- hence, main force of contracted extensor mechanism is focused on saggital band, leading to further MCP hyperextension;
- tenodesis effect of extending the fingers w/ wrist flexion is lost;
- smooth flexion pattern is lost:
- normally, MP flexion initiates finger flexion, and all joint achieve full flexion nearly simultaneously;
- distal joint flexion is completed prior to initiation of MP joint flexion;
- hence, the fingers immediately come into contact w/ the palm w/ flexion;
- causes:
- combined low median and ulnar nerve lesions (may result in significant decreases in grip strength);
- brachial plexus injuries;
- spinal cord injuries
- Charcot-Marie-Tooth-Disease;

- Exam:
- w/ intrinsic weakness, the patient will demonstrate MCP hyper-extension and PIP flexion as he/see attempts to extend the digits;
- determine whether there is fixed PIP joint flexion contractures, especially in the ulnar fingers;
- w/ intrinsic weakness, PIP joint loses the ability to extend thru the lateral bands and must rely on the central slip;
- determine whether central slip is intact, by seeing if patient can extend PIP joint w/ MP joint held in flexion;

- Treatment: (Based on whether the Central Slip is Intact)
- central slip not intact:
- requires tendon transfers which pass volar to deep metacarpal transverse ligament, and are then attached to the lateral bands;
- central slip intact:
- by preventing hyper-extension of the MP joints, extrinsic extensor muscles, will be able to extend DIP and PIP joints, thus preventing the claw deformity;
- orthotics (see hand orthotics)
- dorsal knuckle bender or lumbrical bar;
- by holding the metacarpals in a slightly flexed position, the central slip can actively extend the PIP joint;
- creation of MPJ flexion contracture (may be performed by volar plate arthrplasty or tenodesis);

- Operative Correction:
- Burkhalter Transfer
- procedure of choice;
- Bunnell Transfer:
- involves FDS transfer to the lateral bands;
- interosseous & lumbricals muscles of ring finger and little fingers, substituted by the FDS of ring finger,
inorder to improve clawing and to improve flexion at the MP joint;
- first dorsal interosseous muscle substituted by ECRL & split FDS of ring finger w/
one half to first lumbrical & one half to first dorsal interosseous;
- half the tendon is passed dorsally thru the 1st interosseous, where as other half of the tendon is passed volarly to the lumbrical;
- main complication is creation of intrinsic plus hand, which preferentially extends PIP joint w/ minimal flexion of the MPJ;
- this is exacerbated by the PIP flexion lost from the FDS harvest;
- Zancolli Volar Capsulorraphy:
- performed thru a volar approach;
- goal is to create a MPJ flexion contracture, preventing claw deformity

Clinical features of paralytic claw fingers.

One in four flexor digitorum superficialis lasso for correction of the claw deformity.

Flexor digitorum superficialis tendon transfer for intrinsic replacement. Long-term results and the effect on donor fingers.

Restoration of Power Grip in Ulnar Nerve Paralysis.

Opponensplasty in intrinsic-muscle paralysis of the thumb in leprosy.

Paralytic claw hand: with special reference to paralysis in leprosy and treatment by the sublimis transfer of Stiles and Bunnell.

Patterns of movement of totally intrinsic-minus fingers based on a study of one hundred and forty-one fingers.

Movement patterns of interosseus-minus fingers.

Tendon grafting illustrated by a new operation for intrinsic paralysis of the fingers.

Abductor pollicis longus transfer for replacement of first dorsal interosseous.

Architectural design of the human intrinsic hand muscles.