What is wrong with this picture?
– Synovitis in the scapholunate ligament area weakens and eventually disrupts the ligament which results in rotary instability of the scaphoid.
– The scaphoid assumes a volar flexed position and there is secondary loss of carpal height and radial deviation of the carpals and metacarpals on the radius.
– The wrist now has shortened and the extrinsic finger muscles that cross the wrist are working at suboptimal lengths.
– The resulting imbalance of the flexor and extensor muscle-tendon units crossing the wrist can be viewed as extrinsic minus, or a relative intrinsic-positive condition.
– This is one factor in the development of intrinsic-plus deformity of the fingers.