A single digit amputation in flexor tendon zone II is a relative contraindication to replantation, since there is a high likelihood of poor functional outcome because of stiffness and immobility. Almost all patients are likely to require secondary surgery to release tendon adhesions or joint contractures. A detailed discussion with the patient regarding the likely outcome following replantation should be undertaken before proceeding with surgery. In many cases, a single digit amputation proximal to the flexor digitorum profundus insertion is best managed with a revision amputation rather than replantation. However, there may still be reasons to pursue replantation in this scenario: for example, the patient may prefer a stiff, potentially painful digit to an absent digit for social, aesthetic, or psychological reasons. In Japan, for example, a missing digit has criminal connotations. In many patients, preservation of length in the left ring finger may be preferred for wearing or receiving a wedding or engagement band. In children, zone II single-digit injuries should still be replanted where possible, as children tend to have significantly better outcomes after surgery with regard to mobility and sensation. In contrast to zone II flexor level replants, zone I flexor level replants tend to have far better outcomes even when distal interphalangeal joint motion is not preserved.1 Therefore, replantation of these is often indicated. All traumatic thumb amputations should be replanted where possible, given the importance of thumb function in opposition. The thumb remains functionally very useful even when it is stiff and relatively immobile.1–4
The two main classification systems for fingertip amputation are the Tamai1 and Sebastin and Chung2 classifications. Both the classifications are based on the level of injury and the clinical relevance of this is in relation to the anticipated difficulty of vascular repair, in particular the venous outflow. For example, in injuries distal to the lunula (Tamai zone I and Chung zone IA), direct anastomosis of venous outflow is not possible. Instead, anastomosis to the volar venous plexus may sometimes be performed; otherwise, leech therapy, nail bed bleed, or heparin therapy is required to provide adequate venous drainage. In more proximal injuries, it may be possible to repair both arteries and veins, but this is still very difficult beyond the FDP insertion. The zones of these two classification systems are shown in Figs. 85.1 and 85.2. The mechanism of injury and degree of soft-tissue damage is more relevant to the Urbaniak3 classification. This is a classification of ring avulsion injuries and does not relate to level of injury. The time since injury and the number of digits involved do not form part of any of these classification systems.
3. Urbaniak JR, Evans JP, Bright DS. Microvascular management of ring avulsion injuries. J Hand Surg Am 1981;6(1):25–30 The optimal storage temperature for an amputated digit is 4°C, which can be achieved by refrigeration of the transport container. The digit is preferably wrapped in damp gauze and placed in a bag, which may then be kept on iced water. Heavily soaked gauze may result in waterlogging of the tissues and should be avoided. It is essential to avoid the error of allowing contact between the tissues and ice, which may result in freezing and subsequent cell necrosis.1,2 In general, revascularization of amputated parts should be achieved as soon as possible. Digits are more tolerant of warm ischemia than the hand or forearm, as they contain no muscle. Warm ischemia times for digits should ideally be less than 6 hours. Cold ischemia times should be less than 24 hours. In spite of these guidance figures, successful digital replantation has been reported in several cases after up to 30 hours of cold ischemia, with one procedure after 94 hours.3 Such prolonged ischemia times are not generally recommended. Lunula Zone I Zone II FDP FDS DIP joint Fig. 85.1 Tamai’s classification of fingertip amputation. (DIP joint, distal interphalangeal joint; FDP, flexor digitorum profundus; FDS, flexor digitorum superficialis.) Lunula Zone IA Zone IB Zone IC Zone ID Root of nail bed FDP insertion FDP insertion Fig. 85.2 Chung’s classification of digital amputations.
4. Saint-Cyr M, Wong C, Buchel EW, Colohan S, Pederson WC. Free tissue transfers and replantation. Plast Reconstr Surg 2012;130(6):858e–878e
It is perfectly reasonable to proceed with a temporary vascular shunt before bony stabilization to minimize ischemia time, while careful debridement is undertaken, or a difficult bony fixation planned. This is particularly relevant where the amputated part contains a high proportion of muscle which will be less tolerant of ischemia.1 Although the most common shunt is a specifically designed PVC vascular shunt, other materials such as chest drains or pediatric feeding tubes may be used as a substitute if required. There is always a degree of edema and relative ischemia following a major replantation, in part because only the major inflow and outflow are restored and also because of the vascular response to ischemia. As such, it is prudent to decompress major nerves at their common sites of compression to minimize further insults. Fasciotomy is recommended for the same reason to decompress the forearm and intrinsic hand muscle compartments following a major replantation. Tolerable ischemia times vary according to the proportion of muscle in the amputated part and whether appropriate cooling has occurred. For an arm or forearm amputation, a maximum of 4 to 6 hours warm ischemia and a maximum of 10 to 12 hours cold ischemia are generally quoted.
When planning an upper limb replantation, the possibility of vessel and nerve gaps should be anticipated; therefore, the full arm and at least one leg should be adequately prepared for donor tissue harvest. In digital replantation, the posterior interosseous nerve can be a useful donor graft for the digital nerves with minimal donor-site disturbance. It is found in the fourth extensor compartment at the wrist. Suitable donor vessel grafts include both volar and dorsal wrist veins for digital vessels. Suitable leg grafts for larger structures in proximal replantations include the sural nerve and dorsal foot or saphenous veins. Graft harvest can proceed while other repairs are performed at the replantation site. Regional anesthesia is a useful adjunct to general anesthesia, as it improves postoperative comfort and reduces vasospasm. It can also reduce the anesthetic agent requirement, thereby reducing nausea and vomiting. Use of a tourniquet is standard practice for exploration and debridement of any upper limb wound, as it provides a clear blood-free field, making surgery more efficient and reducing blood loss. Inflation of the tourniquet should be avoided once revascularization has been performed, as stopping flow may increase thrombosis at the anastomotic site. The standard pressure used for an adult upper limb is 250 mm Hg and a safe maximum continuous time is 120 minutes. After this time, the tourniquet must be deflated, and the arm allowed to perfuse for at least 20 minutes. Where possible, a two-team approach is recommended for replantation, so one team can prepare the amputated part while the other prepares the injured digit and harvests grafts. This approach should minimize further ischemia time.1–4
The usual order for digital replant is bone first in order to set length and provide a stable functional base for further reconstruction. The tendons should be repaired second, as these will take tension off and set the length for nerve and vessel repairs. Leaving tendon repairs until after the microsurgery risks inadvertent damage to delicate nerve and vessel repairs. Repairing the nerves before the vessels is often recommended, as it keeps the operating field clear of blood for longer and ensures that following revascularization no other structural repair is required. It would still be reasonable to repair the vessels before the nerves, especially when ischemia time is already extended, and many surgeons would do so routinely, thereby leaving the nerves until last.1–4
A normal, clean digital vessel appears somewhat translucent and gray. The red-line sign along the distal neurovascular bundle may indicate damage to the vessel and is associated with a poorer prognosis. In this situation, revascularization may be futile. The “corkscrew” appearance usually indicates a traction injury, which also makes successful revascularization a challenge. A terminal thrombus may be evacuated, leaving a potentially healthy vessel end. A sausage appearance occurs when the vessel is blocked with a thrombus, which may be evacuated. Where there is doubt about the quality of the vessels further trimming should be considered and where inadequate length is an issue, a vessel graft should be used. The volar wrist is often a useful donor site for digital vessel grafts.1,2
Papaverine is a potent smooth muscle relaxant that appears to work through inhibition of phosphodiesterases and by influencing calcium channels. It may be used topically during microsurgery to dilate arteries and veins before and after anastomosis. Other agents used for this purpose include the calcium channel blocker verapamil and the local anesthetic sodium channel blocker lidocaine. Leech therapy is useful for venously congested digits, but carries a small risk of infection with Aeromonas hydrophila.1 The usual prophylaxis for this is ciprofloxacin or a third-generation cephalosporin (although one must consider the possibility of resistant organisms, which is becoming more common). Although systemic heparinization might occasionally be used where there is greater concern than usual regarding thrombosis, this has to be balanced against the risk of hemorrhage and is not routine. Systemic prostaglandin therapy has been used by some microsurgeons, but this is not commonplace.2 Oral aspirin therapy is regularly administered after replantation and may be given PR during the procedure or by mouth postoperatively, as the antiplatelet effect can reduce platelet aggregation at the anastomosis site.3–5
correct? room. The main reason for early replantation failure is arterial insufficiency (up to 60% of cases). This presents with a pale, cold finger with no bleeding on pinprick testing. Patients must be warned about the risk of both an extended initial procedure time and a potential return to the operating room following replantation. Unfortunately, digits that struggle to survive tend to have poor long-term function with atrophy, reduced sensation, and stiffness. Survival rates following digital replantation are generally well above 50% and will depend on factors such as injury mechanism, digit involved, level of injury, timing of replantation, and surgical skill. The overall survival for distal digital amputation was 86%, according to a systematic review published in 2011.1 Other published success rates range from 54 to 84%, and, as expected, the success for guillotine-type injuries is much better than for crush injuries (77 vs. 49%).2 Most patients do regain useful sensation, but this does not regularly reach normal two-point discrimination. A normal two-point discrimination is 3 mm for dynamic and 6 mm for static. A review of 293 distal replants showed two-point discrimination at less than 15 mm. In the systematic review, mean two-point discrimination was 7 mm. While cold intolerance is common and should be explained to the patient preoperatively, it will usually improve over time (2 years). A large number of patients will require secondary surgery even when the vascularity of the digit remains satisfactory.3
More than half of patients undergoing digital replantation are likely to require secondary surgery. This will be affected by the nature of the original injury and rehabilitation protocol. For example, secondary surgery is more likely in zone II flexor level replantations. The most common procedures are flexor or extensor tenolysis and/ or release of joint contractures. This is probably because newly revascularized digits are often immobilized longer than in the early postoperative phase, and subsequent stiffness soon develops as the requirements of the extensor and flexor tendon repairs and the fracture union compete in the rehabilitation regimen. Other common secondary procedures are revision fixation of a nonunion, neurolysis and/or nerve grafting, web-space release, and amputation where function remains poor.1–3