Thumb Carpometacarpal Joint Fusion

Indications

Mild to moderate painful thumb carpometacarpal (CMC) joint arthritis recalcitrant to nonoperative management. Arthritis must be limited to the trapeziometacarpal joint without involvement of the scaphotrapeziotrapezoid joint.

Technique

Plan longitudinal dorsal incision from midshaft of thumb to scaphotrapeziotrapezoid joint. Incise skin and bluntly dissect through the subcutaneous tissue. Protect sensory branches of the radial and lateral antebrachial sensory nerves. Isolate first [abductor pollicis longus (APL) and extensor pollicis brevis (EPB)] and third [extensor pollicis longus (EPL)] extensor compartments (Fig. 68-1).
Identify radial artery and its venae comitantes. Vessels course deep to the first compartment and at the level of the scaphotrapeziotrapezoid joint. Retract the vessels in a proximal direction.
Retract the abductor pollicis longus tendon in a radial direction and the extensor pollicis brevis tendon in a radial direction. Identify the CMC joint and perform a longitudinal arthrotomy beginning at base of thumb metacarpal and ending over trapezium (Fig. 68-2).
Elevate capsule in a radial and ulnar direction until entire base of thumb metacarpal and trapezium is exposed. Cut trapezium parallel to joint surface using a fine-bladed microsagittal saw (Fig. 68-3). Remove a slice of bone that includes articular surface and subchondral bone.
Cut thumb metacarpal base to place thumb in the intended position of fusion. Standard position is 45 degrees to the coronal and sagittal planes of the palm. This requires a wedge resection with an apex along the ulnar side of the thumb. Remove enough bone to include the articular surface and subchondral bone.
Position thumb with the resected surfaces in apposition. Check thumb alignment. Modify thumb metacarpal cut if necessary. Obtain provisional fixation via percutaneous 0.045 in. wire inserted across CMC joint (Fig. 68-4).
Obtain rigid fixation with 2.0 mm or 2.4 mm minicondylar plate (Fig. 68-5). Cut plate to appropriate length to provide four to five screws into metacarpal. Contour plate so that it lies along the metacarpal and trapezium. Begin with fixation in the trapezium. Drill a hole to accommodate the blade portion of plate. Measure depth of hole and cut blade to correct length. Insert blade into hole and tap into position. Check alignment of plate and secure plate to metacarpal using bicortical fixation.
Place screw into trapezium and additional screws into metacarpal. Verify position of internal fixation using fluoroscopy. If the fixation is rigid remove the wire. If the fixation is marginal leave the pin in place.
Close subcutaneous tissue and skin with absorbable suture. Apply bulky compressive dressing and thumb spica splint with interphalangeal joint free.