The thumb is exposed during surgery using a Wagner incision. In this approach, the junction of the glabrous skin along the radial border of the thumb metacarpal marks the line of the distal incision. The incision should be curved so that at its most proximal point, it lies transversely over the FCR tendon. Skin and subcutaneous tissue flaps are raised, and branches of the radial sensory nerve should be easily identifiable and preserved. Skin retraction sutures of 3-0 silk are placed on either side of the incision. The dorsal flap is elevated, and a dorsal dissection is performed to expose the extensor mechanism on the dorsum of the thumb metacarpal. The APL insertion is exposed at the base of the thumb metacarpal, and distally the extensor pollicis brevis (EPB) and extensor pollicis longus (EPL) are identified. A subperiosteal dissection between the EPL and EPB is made approximately 1 cm distal to the insertion of the APL.

The thenar muscles are reflected off the radial aspect of the thumb metacarpal. Generally, there is an accessory slip of the APL that inserts into the thenar muscles. The accessory APL and thenar muscles can be reflected in continuity and repositioned at the end of the procedure, or the surgeon can detach the accessory APL from its insertion on the thenar muscles, to be repaired later. After this exposure, the ST and TMC joints can be exposed with gentle thumb distraction. The trapezium bone is exposed using subperiosteal dissection. It is desirable to remove the trapezium piecemeal with an osteotome, dividing the trapezium longitudinally in line with the fibers of the FCR, which lies deep to the trapezium. The trapezium can then be split transversely and the four quadrants of bone removed. The trapezium in an arthritic thumb is generally deformed with some sclerosis at the TMC joint; if a medial osteophyte is present, it should be removed completely from the surrounding joint capsule with a rongeur and/or a curet.

Once the trapezium has been removed completely, the base of the thumb metacarpal should be exposed to facilitate formation of the bone tunnel (Figure 1, A). A Carroll elevator is helpful to position the thumb metacarpal in the wound by elevating the proximal metacarpal and exposing the articular surface. The center of the articular surface is pierced with a bone awl, a small Kirschner wire (K-wire), or a drill. A second hole is made in the dorsum of the metacarpal approximately 1 cm distal to the articular surface and perpendicular to the plane of the thumbnail. These holes are expanded perpendicular to the surface of the bone so the two holes will meet in the medullary canal of the metacarpal. Using a small curet, these holes are carefully expanded so that an oblique bone tunnel results (Figure 1, B). Caution should be exercised not to fracture the bone dorsal to these bone holes because this would significantly compromise the stability of the reconstructed ligament. Once the bone tunnels are created, the APL can be harvested. Originally, this was performed through a separate incision near the musculotendinous junction; the APL can, however, be harvested with a large tendon stripper similar to those used in reconstructive knee surgery. The surgeon places the tendon stripper around the APL, taking care upon lifting the proximal skin flap that the radial sensory nerves are kept away from the tendon stripper. Then, using a rotating action while holding the tendon stripper, the APL can be divided at its musculotendinous junction. The distally based tendon is delivered into the Wagner incision. Normally, some trimming of the free end of the tendon graft is required to remove residual muscle.

The APL is then passed retrograde first through the dorsal metacarpal hole, then through the tunnel, to emerge from the articular surface hole. This can be done using a tendon-passing instrument or a small-gauge
stainless wire tied in a loop around the free end to prevent fraying the tendon as it is passed through the bone tunnel, as shown in Figures 2, A and B and 3.

The ST joint should be inspected. If there is significant wear in the distal scaphoid or proximal trapezoid, a curet should be used to expand the involved area, removing any abnormal cartilage and the subchondral bone. The base of the index metacarpal is exposed by retracting the radial flap containing the thenar muscles. The index metacarpal base should be palpated by the surgeon as well as visualized. The junction of the metaphysis is flared, whereas the diaphysis is more cylindrical in shape. At the junction of the metaphysis and diaphysis, the surgeon should create a palmar bone hole. The bone is relatively soft and will
easily accept a bone awl under manual pressure. The awl is then passed directly dorsally to create a bone tunnel, as shown in Figure 2, C. The end of the awl will be palpable subcutaneously on the dorsum of the hand. A 2-cm longitudinal incision is made over the awl, and the subcutaneous tissue is dissected to expose it.

The index metacarpal bone tunnel is expanded using handheld instruments (such as a curet or gouge) of a caliber large enough to accept the tendon graft. The tendon graft is then passed in a palmar to dorsal direction through the index metacarpal.

At this point, the efficacy of the ligament reconstruction can be assessed. With one hand, the surgeon applies tension to the tendon graft, maintaining manual tension on the free end of the APL now emerging from the dorsum of the hand. With his or her free hand, the surgeon can assess the stability of the thumb metacarpal by performing a displacement maneuver. Resistance to proximal migration should be felt when tension is placed on the free end of the APL tendon (Figure 4).

Once the efficacy of the ligament reconstruction is ascertained, the APL is fixed to the dorsum of the hand. Scissor dissection with division of some transverse fascial fibers will expose the ECRB just ulnar to the dorsal bone tunnel in the index metacarpal. The extensor carpi radialis longus inserts on the radial aspect of the index metacarpal, whereas the ECRB inserts at the radial aspect and dorsum of the third metacarpal.¹³