Paial Claw hand is due to:

The metacarpophalangeal joints become hyperextended because of the paralysis of the lumbrical and interosseous muscles, which normally flex these joints. Because the first and second lumbricals are not paralyzed (they are supplied by the median nerve), the hyperextension of the metacarpophalangeal joints is most prominent in the fouh and fifth fingers. The interphalangeal joints are flexed, owing again to the paralysis of the lumbrical and interosseous muscles, which normally extend these joints through the extensor expansion. The flexion deformity at the interphalangeal joints of the fouh and fifth fingers is obvious because the first and second lumbrical muscles of the index and middle fingers are not paralyzed. In long-standing cases the hand will show hollowing between the metacarpal bones caused by wasting of the dorsal interosseous muscles True/complete claw hand involving all the fingers is produced by a combined lesion of ulnar and median nerve