The type of injury is the most important factor in determining the survival rate and functional outcome [6, 7]. Clean-cut guillotine type amputations have a very high success rate (99.5 %) and should be attempted, whereas extensively crushed and avulsion amputations have poor survival rate (crush amputations 33.3 %, avulsion amputations 78.6 %) and must be approached with caution.

Avulsion injuries associated with the “red-line sign” or the “ribbon sign” are poor prognostic indicators for replantation since they denote severe traction injuries to the neurovascular bundle. The red-line sign consists of small hematomas seen in the skin along the course of the neurovascular bundle caused by disruption of small branches to the skin. This in turn leads to intimal tears to the digital vessels and often makes replantation unsuccessful due to non-reflow from intimal injuries or disruption of skin-feeding branches from the digital artery. The ribbon sign is indicative of severe traction and torsion to a vessel resulting in a vessel that resembles a ribbon that has been stretched and curled on a gift-wrapping. If ribboning has occurred proximal to the trifurcation of the digital artery, which occurs at the distal interphalangeal joint, vein grafting proximal and distal to the zone can salvage the finger. However, involvement of the trifurcation bilaterally cannot be bypassed with a vein graft and is essentially a non-replantable injury.

Although level of injury has no bearing to the survival rate of replants, it does affect functional outcomes [7]. Good functional results are achieved with replantation of fingers with amputations distal to the FDS insertion, or at the palm, wrist, and distal forearm. Less functional recovery is expected with replants within zone 2 of the fingers since they result in stiffness and weakened grip strength that provide little or no functional benefit and often result in significant delays in return to work.

All thumbs should get first priority in replantation regardless of level of amputation or mechanism of injury [8]. This is because thumbs are responsible for 40 % of the hand function and important for prehensile abilities. In fact in multi-digit amputations, if the thumb cannot be replanted, the least damaged finger should be replanted in the place of the thumb [9]. If the thumb is intact or replantable, the ring and small finger should be replanted to restore grip. Next the index and/or middle finger is replanted to restore pinch grip. See Table 5.3.

Digits lack muscle and hence are more tolerant to ischemia than other body part amputations. The permitted duration of warm ischemia is up to 12 h (compared to 6 h for a major limb). Cooling can prolong the ischemia time to up to 24 h. Reports of successful replantation after longer ischemia times have been reported for up to 94 h of cold ischemia [10].

Any amputation at any level and any mechanism of injury in children is an indication for replantation. Children have a tremendous recuperative ability with a good functional result. Similarly all healthy young adults with minimal comorbidities are good candidates for replants. Elderly patients may have significant cardiovascular and respiratory comorbidities that preclude a long operation. Furthermore, diseases that affect small vessels such as atherosclerosis, connective tissue disorders, autoimmune diseases, and diabetes mellitus can directly affect replantation success rates [11]. Joint stiffness, poor nerve regeneration, peripheral vascular disease, and coordination problems with poor recuperative abilities are additional inhibitory factors for good functional outcomes in elderly digital replants. That said, functional results are not entirely dependent on patient age and amputation level [12], and elderly replant candidates should be treated on a case-by-case basis. Replantation success rates are 2.3 times higher in female compared to male patients [6]. This however probably reflects the severity of injuries sustained by male patients. Alcohol does not affect replantation success rates [6]; however, personal habits such as smoking and caffeine consumption can affect microvascular patency. Nonsmokers have an 11.8 times greater rate of replant survival than smokers [6]. This is attributed to the vasoconstrictive properties of nicotine. Patients should be strongly advised to quit smoking completely after replantation. Some authors recommend no smoking be permitted within the very vicinity of a fresh replant [6].

Once the decision has been made to proceed with replantation, the surgeon needs to have the mind-set that he/she is going to do the best to make it a successful outcome. Any lingering doubts about whether the effort is worthwhile or a half-hearted effort of going to the operating room just to take a look is doomed to failure and will make the surgeon entertain an easier amputation option. The goal of the surgery is to do emergently what would be difficult or impossible to do later. The use of “spare parts” from a non-salvageable finger for salvage of another finger is a prime example of this principle. Another guiding principle is the “one-stage treatment with early mobilization” [15]. This advocates a stable fixation, tension-free vascular repair, and skin closure, so as to allow rehabilitation as early as the first week following surgery to minimize tendon adhesions and joint stiffness.

Shortening of the bone within reason is done to reduce the risk of septic nonunion and to allow primary tension-free repair of vessels, nerves, tendons, and skin. As a rule it is better to trim more of the bone of the amputated part rather than the proximal stump so as to preserve length on the proximal stump in case the replant fails. All structures should be repaired primarily and tension-free if possible. When this is impossible, nerve or tendon grafts should be employed. If tissue loss is too great and neither of these options are available, plans for staged reconstruction (i.e., tendon transfers) should be considered. The usual sequence of repair of structures is: bone shortening and stabilization, extensor and flexor tendon repair, arterial anastomosis, venous anastomosis, nerve coaptation, and skin coverage [16]. See Table 5.4.

Once in the operating room, the patient is placed on the operating table with proper pressure point padding. Warming blankets are placed and the ambient temperature of the operating room is kept warm to prevent hypothermia and vasospasm during the procedure. A urinary catheter is placed for accurate fluid status assessment and in preparation for a long procedure. An axillary block is placed with an indwelling catheter for intraoperative and postoperative pain control. A two-team approach is usually best, with one team preparing the proximal segment and the other the amputated segment. For multiple digit replants, it is better to take a structure-by-structure approach rather than one digit at a time. A tally sheet of injured and repaired structures helps decrease the incidence of errors and frustrations (Fig. 5.3).

Preparation of the amputated part can be initiated on a back table under sterile conditions in the operating room long before the patient is brought to the operating room and while the patient is being anesthetized. We recommend stabilizing the segment on a tongue depressor as shown in Fig. 5.4, to facilitate dissection under the microscope. If the part is grossly contaminated, it is irrigated with copious normal saline and foreign bodies removed. The neurovascular structures are exposed with bilateral mid-axial incisions (Fig. 5.5). Dorsal incisions may be needed to expose dorsal veins. The digital vessels and nerves are dissected and tagged with 9-0 nylon sutures or microclips. Digital vessels are assessed for signs of intimal damage (e.g., telescope, cobwebs, ribbon sign, terminal thrombosis). The lumen is irrigated with heparinized saline. The edges are freshened and need for vein grafts is assessed. If the need for a vein graft is indicated, harvesting a vein graft before bone fixation will help minimize warm ischemia time (Fig. 5.6). Half modified Kessler sutures (also known as the Tajima suture technique) are placed on the extensor and flexor tendons [17]. Bone shortening of up to 5–10 mm may be needed for tension-free vessel and nerve repair and is best performed with an oscillating saw. Excessive shortening is to be avoided, since most replants require vein grafts for tensionless repair unless the amputation is clean and sharp [18]. If the amputation destroys a substantial portion of the joint, the articular surface is removed to prepare for joint fusion. Retrograde K-wires or intraosseous wires are then placed through the bone on the amputated part.