A Trial Polyethylene Carpal Component is applied
to the carpal plate, beginning with the standard
thickness
The prosthesis is reduced and range of motion
and stability are checked. The prosthesis is typically
quite stable and should demonstrate approximately
35° of flexion and 35° of extension with
modest tightness at full extension.
If the volar capsule is tight and limiting extension,
the radius may need to be shortened, but will
usually only require a couple of millimeter (avoid
excessive shortening). If a severe preoperative
flexion contracture was present, a step-cut tendon
lengthening of the flexor carpi ulnaris and occasionally
the flexor carpi radialis may be required to achieve
proper balance and motion.
When volar instability is present, the volar
capsule is inspected and if detached it is repaired
to the rim of the distal radius. If the volar
capsule is intact, a thicker polyethylene component
may be required to increase soft tissue tension
and joint stability. A mild dorsal instability
should respond to capsule closure but a thicker
polyethylene is considered for marked instability.
