63 Nonunion following Digital Replant
63.1 Patient History Leading to the Specific Problem
A 25-year-old man presented to the emergency room having sustained a machinery crush injury that resulted in total amputation of all the fingers in his dominant right hand (▶Fig. 63.1). Only the amputated part of the middle finger was found replantable and it was heterotopically replanted over the index finger stump. Bone fixation was by a K-wire. The wound healed well and the K-wire was removed at 6 weeks. The index replant survived, but despite adequate immobilization, he developed a nonunion at the replant site. He has a normal thumb. The nonunion in the only available finger in his dominant right hand was very painful and disabling.
63.2 Anatomic Description of the Patient’s Current Status
Six months after an index finger replantation, the patient presents with instability at the replant site. The instability prevented him from using the finger for any pinch or grip activities (▶Fig. 63.2). All the interphalangeal (IP) joints are stiff in straight position, and 40 degrees of active flexion is possible at the metacarpophalangeal (MCP) joint. The thumb is unable to meet the index finger tip. On attempting thumb–index side pinch, due to the instability at the nonunion site, he is not able to generate any pinch or grip strength.
In the type of injury sustained by the patient, the aim is for the salvage of maximum functional units. Only one digit was replantable. Since the MCP joint was intact and skin cover was adequate, it was decided to replant it over the index finger stump. The rest of the finger stumps had raw areas that needed flap cover to salvage the base of the proximal phalanges of the middle and little fingers, which would enhance function if toe transfers were done at a future date. The patient was not willing for the option of toe transfers at all and so replantation over the stump of the index and closure of the amputation stumps of other fingers was done. When only one finger is replanted, we prefer to do it in the index position since it is more comfortable for pinch activities and the strength generated. A little finger placement will provide a wider span of the grip, but our patients have found more satisfaction with index placement. In replantation surgery, primary bone union is a determinant for successful functional outcome.
Fig. 63.2 (a, b) The successfully replanted index finger is dysfunctional because of the nonunion of the middle phalanx.
63.3 Recommended Solution to the Problem
Secondary procedures following replantation are complex procedures. There is a potential risk of losing the replant due to inadvertent injury to the vessels, since most replants are dependent on the repaired blood supply for a long time. So prevention of nonunion is important. This is achieved by adequate bone shortening to ensure viable bone ends, good soft-tissue cover, adequate fixation, and primary wound healing. In this patient, on viewing the X-ray it is possible that the articular surface of the middle phalanx was not adequately nibbled to present a good cancellous bone stock. Single K-wires do not provide rigid fixation adequate enough for bone union. In this situation, we need to gain access to the nonunion site without damaging the repaired vessels, freshen up the nonunion site to viable bone ends, and achieve bone union. An angulation of 30-degree flexion at the site was planned, so that the thumb–index tip pinch is possible.
63.4 Recommended Solution to the Problem.
• Access to the nonunion site has to be achieved without injuring the vessels repaired during replantation.
• The nonunion ends have to be freshened up to reveal viable cancellous bone ends.
• While fixing up the bone, it has to be fixed in an angle to obtain good functional outcome, in this instance, a good thumb–index pinch.
• Fixation techniques that do not require too much dissection are to be used to prevent inadvertent injury to the vessels and achieve primary wound healing.
The notes and the intraoperative photographs taken are studied to have an idea of the course of the repaired vessels (▶Fig. 63.3). Post replant, the vessels do not always lie in their anatomical pathway. A handheld Doppler was used to mark the signals of the digital arteries. In this patient, we could get continuous signals only from the ulnar-side digital artery. The area to be protected from injury was determined. The surgery was done under brachial block with upper arm tourniquet. A 2.5-cm longitudinal incision was made in the midline on the dorsum centered at the level of the replant. The incision was deepened to beneath the tendon, dissection was made just over the bone, and the two bone ends were freed. The surface of the proximal bone end was transversely freshened. We planned for a 30-degree flexion at the replant site and a little radial tilt so that the index finger tip should easily meet the thumb tip. We find it easy to do all the adjustment needed to achieve this position by appropriate shaping of the bony surface at one end. We chose to do this at the distal surface since it presented a broader surface. A single K-wire was obliquely driven distally and then keeping the replanted part in 30-degree flexion and about 10-degree radial deviation, the K-wire was driven in a retrograde manner into the proximal phalanx to achieve fixation. It was done in a single attempt and the fixation was stable. Adequate contact of good bone surface was confirmed. Tourniquet was released and the finger viability was confirmed. Hemostasis was achieved and skin closed with 6–0 nylon sutures.