No single conceptual development has had an impact on the field of hand surgery as profound as the advent of microsurgical techniques. The ability to repair blood vessels that could not be seen without visual assistance led to an accelerated phase of discovery and innovation that continues to this day. The availability of microsurgical techniques has expanded the extent and type of injuries that can be considered correctable and have made operations for these corrections relatively commonplace.
After the coaptation of blood vessels was first performed by Dr. Alexis Carrell in 1902, modifications followed in techniques for suturing and instrumentation and their applications. The great pioneers of microsurgery developed instrumentation and other techniques that allowed the anastomosis of blood vessels. After the techniques were deemed feasible experimentally, their initial applications were in treatment of the traumatized hand, with replantation being one of the earliest milestones.
In 1962, Malt and McKhann performed the first replantation of a completely severed arm in a 12-year-old boy in Boston. In 1963, Chen and colleagues performed the first successful replantation of an amputated hand in Shanghai, China. In 1968, the first replantation of an individual digit, a thumb, was achieved by Drs. Komatsu and Tamai in Japan. As centers became increasingly more familiar with the technique and as experience around the globe expanded, replantations of increasing complexity were performed. This has led us to the current day, in which the initial procedures for replantation have been adapted, refined, and extended and include repair of distal tip amputations, ectopic banking of amputated parts, and, ultimately, vascularized composite allotransplantation.
General Considerations in Replantation
Epidemiology
Few studies have evaluated the impact of amputations and replantations on society. A study from Sweden determined the incidence to be 1.9 per 100,000 person-years (males 3.3, females 0.5). Eighty-six percent occurred in males and 9% in children (age 0 to 14 years). The majority occur in males 45 to 54 years of age. Factory workers (26%) and carpenters (14%) were most commonly injured. A large national database study of upper extremity amputation and replantation cases in the United States demonstrated that the patients undergoing replantation were younger (average age 36 years) than those suffering amputation but not undergoing replantation (average age 44 years). Replantation was most often performed in teaching hospitals and larger urban hospitals.
Emergency Management
The patient sustaining an upper extremity amputation should be rapidly and efficiently transported to a specialty center capable of replantation. The patient’s candidacy for replantation should be determined after he or she has been assessed in the emergency department. The field trauma care of such a patient should follow the principles of global trauma management. It may be easy to overlook more urgent basic trauma protocols in the setting of the distracting, and sometimes dramatic, appearance of extremity amputations. The ABCs of trauma management should never be neglected.
Specific management of the amputated parts should include collection of all amputated parts in the field, regardless of the degree of contamination or quality of tissue. These parts should be wrapped in a sponge saturated with saline, placed in a plastic bag, and subsequently placed in a bag of ice or on a bed of ice. The goal is to cool the part but avoid freezing of the tissue. The bag should be labeled with the patient’s demographic information and transported with the patient to the hospital setting. The amputated stump should be treated with pressure dressings and elevation to control bleeding. Tourniquets should be avoided as well as attempts at ligation of blood vessels in the field, if possible.
In the emergency department, the amputated parts and the amputated stump should be evaluated for the purposes of operative planning and decision making. The patient’s limb and amputated parts should be evaluated radiographically. Tetanus prophylaxis should be provided.
Patient Selection
Very few indications or contraindications for replantation are absolute. The most compelling indications for replantation include thumb amputations at any level ( Figure 42.1 ), multiple-digit amputations ( Figure 42.2 ), any amputation in the pediatric population, and amputations through the wrist, forearm, and elbow. Contraindications for replantation include medical instability that would make lengthy surgical intervention excessively risky. Relative contraindications include single-digit amputations through zone 2 of the flexor tendon sheath, multilevel segmental amputations, and ring finger avulsion amputations. These are felt to be relative contraindications because the procedures are difficult to perform and satisfactory functional results are difficult to achieve. Reports of series of patients in these categories have been published demonstrating surprisingly good results, with authors questioning whether these conditions should be considered relative contraindications.
A relative indication for replantation is a single digit distal to the flexor digitorum superficialis insertion. Although the functional loss from such an amputation in a digit other than the thumb is not great, surgical replantation of such an amputated digit can be performed quite speedily and the functional outcomes are good. Lack of involvement of the proximal interphalangeal joint and preservation of the flexor digitorum superficialis insertion will likely provide good proximal interphalangeal motion and an overall satisfying functional result even without significant return of distal interphalangeal flexion. For this reason, amputations at this level are felt to have a more favorable prognosis than those through zone 2 ( Figure 42.3 ).
Special consideration should be given to major replantation cases. Good functional outcomes can be achieved with replantation through the midpalm, wrist, and forearm. The more proximal the amputation, however, the less promising will be the result because of the amount of nerve regeneration needed to achieve protective sensation and the potential for stiffness of the elbow joint; also, myonecrosis may occur in proximal replantation cases with a prolonged ischemia time.
The length of the ischemia time is a much less critical issue in digit-level amputations because muscle sensitive to ischemia is not present. At the level of the midpalm or wrist, the intrinsic muscles may be débrided if injured. If they are uninjured and are left intact despite a prolonged ischemia time, the resultant fibrosis and dysfunction may be manageable. In more proximal injuries, however, the muscle burden of an amputation through the proximal forearm or transhumeral level is quite significant. In these cases, the ischemia time becomes paramount.
Digit replantation is considered feasible if the warm ischemia time is limited to 6 to 12 hours. With a well-preserved, cooled part, cold ischemia can likely be tolerated for up to 24 hours after digital amputation prior to replantation. Sporadic cases of delayed digit replantation have been reported after 33 hours and 94 hours of warm and cold ischemia, respectively. Successful hand replantation has been reported in one case after 54 hours of cold ischemia. The limits of tolerated ischemia time in distal amputations are thus poorly defined. Indeed, Lin and colleagues studied ischemia time in 31 cases of hand and finger replantation that exceeded 24 hours and found no correlation between ischemia time and postoperative outcome.
In amputations involving the forearm, even 2 to 3 hours of warm ischemia time can result in substantial muscle necrosis, which can produce a coagulopathy after reperfusion. Venous outflow from the reperfused extremity contains toxic compounds such as oxygen-free radicals that can cause tissue damage and vasospasm. In these cases, cooling the amputated part (to 4° C) can dramatically prolong the time between injury and successful replantation. Cooling must be performed to the appropriate level because excessive cooling below 4° C can cause formation of intracellular crystals that can cause tissue damage similar to frostbite.
Properly cooled parts have been replanted up to 36 hours after the time of injury; however, the survival rate of an amputated part decreases with the delay to replantation.
It is these considerations of muscle burden, ischemia time, distance of required nerve regeneration, and degree of skeletal injury, as well as the mechanism of injury, that need to be considered in every case of major replantation.
Technical Considerations in Preparing for Replantation
Whether at the digit level or transhumeral level, replantation is best performed with a team effort. The efficiency, speed, and quality of replantation are enhanced using a team approach. Two teams enable simultaneous work on the amputation stump and the amputated parts. In lengthy cases (such as multiple-digit amputations), the team model allows surgeons to work in shifts; each shift of well-rested surgeons works with a fresh perspective and relieves the fatigued surgeons on the shift before them.
This approach should be used as soon as the decision to operate has been made. The amputated parts should be brought to the operating room so that débridement, dissection, and preparation can begin before the patient arrives in the operating room. This will minimize the patient’s anesthesia time and allow the surgical team to assess the quality of the part and thus the likelihood of replantation or technical requirements.
Intraoperative Technique
Preparation of the Amputated Part
The amputated parts are treated with a surgical prep solution and placed on a back table with full sterile technique. Midaxial incisions are made on both the radial and ulnar sides of the digit. The volar and dorsal skin flaps are elevated. The neurovascular bundles are dissected in the radial and ulnar sides and assessed for their quality, caliber, and length. The flexor tendon is prepared with a locking 3-0 suture, with the loose ends protruding through the severed end of the tendon. The extensor tendon is elevated but is not affixed with sutures. The bone is shortened generously to enable primary nerve coaptation. Osseous shortening is preferentially performed from the level of the amputated part so that failure of the replantation would not result in excessive shortening of the amputation stump. If the shortening of the bony structure requires resection back to the adjacent joint, the joint is prepared for arthrodesis by removal of the cartilage and subchondral bone and preparation for a cup-and-cone relationship between the amputated part and the stump.
Anticipated osseous fixation is prepared. This is usually performed with longitudinal nonparallel Kirschner wires driven from proximal to distal in an antegrade fashion through the tip of the digit and then recessed to the level of the proposed osteosynthesis site. Pin balls are applied to the Kirschner wires and protrude through the tip of the digit so that they do not constitute a hazard to the surgeon during the remainder of the operation. The pin balls will later be removed, and the pins driven retrograde to achieve fixation.
We usually remove the nail plate at the time of digit preparation and discard it. This can be helpful if the digit demonstrates venous insufficiency following operation and requires heparin pledget application in the nail bed or leech application. This will avoid the need for nail removal at the bedside in an awake postoperative patient.
An attempt is made to separate the nerves and arteries as minimally as necessary for assessment and preparation. Preserving surrounding subcutaneous tissue may minimize desiccation thoughout the case.
The vessels need to be assessed with a microscope to evaluate the intima in the lumen. Avulsive injuries will often cause significant dissection of the vessel wall layers or fracturing of the intima near the zone of injury ( Figure 42.4 ). This will require resection of the distal vessel until a normal vessel is observed. If a single arterial reconstruction is being performed, the distal vessel of better quality will be used. This can be performed in a crossover fashion to the contralateral digital artery if length and caliber facilitate it. Additionally, the second distal artery could be considered as a source of venous outflow if no dorsal veins are available, so this vessel should be preserved in the field, and both vessels should be dissected in preparation for replantation.
In the dorsal subcutaneous fat, the veins are assessed. This is also performed with the least amount of initial dissection of the veins possible. The quality and number of available veins are assessed under the microscope.
Preparation of the digit can sometimes be difficult if the surgeon does not have an assistant available. Placement of the longitudinal Kirschner wires can facilitate unassisted dissection. The nonparallel Kirschner wires protruding through the tip of the digit can be held stable with a surgical clamp to prohibit pronation/supination of the part during dissection.
Preparation of the Hand
Information about the osseous level of shortening is shared by the surgical teams. If arthrodesis of either the proximal interphalangeal or distal interphalangeal joint will be performed, the amputation stump is fashioned into a convex cone configuration in preparation for the arthrodesis. If extraarticular fixation is planned, the bone may be prepared so that it is aligned to simplify reduction. The simplest configuration is a transverse osteosynthesis site so that fixation and rotational alignment can most easily be achieved.
The proximal tendon is prepared by retrieving it through the fibroosseous sheath, resecting the edge back to a healthy transverse tenotomy, and preparing it with a 3-0 locking suture similar to the preparation of the distal flexor tendon.
The dorsal extensor tendon is elevated and prepared but does not require presuturing for preparation. The radial and ulnar neurovascular bundles are assessed via radial and ulnar midaxial incisions, and the dorsal skin is elevated with subcutaneous fat for preparation of the veins. A microscope is brought into the field at this point to assess the vessels. Considerations about the quality of the proximal vessels are the same as those described for the distal part. Ultimately, the quality of the proximal artery will be determined by the spurt test, which is performed after the tourniquet is released.
The digital nerves are resected back to a healthy fascicular pattern with great care taken to attempt to achieve primary nerve coaptation after osseous shortening.
Dorsally, the veins are assessed. The proximal veins are usually easier to find and prepare than the distal veins because of their larger caliber. If additional length is needed for vein coaptation, side branches may be ligated to elongate and transpose veins to reach the anastomosis site ( Figure 42.5 ).
It should be noted that the preparation of the amputated part is typically done under tourniquet control. For this reason, all of these processes in preparation of the amputation stump and ultimate replantation should be done as efficiently and rapidly as possible. The surgeon needs to assess, prepare, and plan each sequential phase with a premium placed on speed and a constant awareness of the duration of tourniquet time that has elapsed.
Replantation
Different surgeons favor significant variations in digital replantation technique. There is not a consensus about the “correct” way to perform replantation because there are benefits with many different strategies. Several common concepts are seen in all of the techniques, however.
If multiple digits have been amputated, it is always more efficient to perform the replantations sequentially. For example, the osseous structures in all digits may be addressed and replanted prior to moving forward with the tendinous structures. In this way, structures that are best repaired during tourniquet control can be repaired rapidly digit by digit and structures that are more easily addressed with tourniquet release can also be repaired digit by digit.
Structures that require microscopic procedures are generally repaired last so that the delicate repairs are not damaged by the more disruptive tendon or bone repairs.
The tourniquet time also influences the sequence of events because some procedures may require tourniquet control and others are easily performed without the benefit of a tourniquet.
In our center, we perform digital replantations in the following sequence:
Under tourniquet control we perform osseous fixation, extensor tendon repairs, flexor tendon repairs, digital nerve repairs under the microscope, and dorsal vein repairs under the microscope if time permits.
After tourniquet release we perform any remaining dorsal vein repairs that have not been performed under tourniquet control, arterial repairs under the microscope after adequate inflow has been ensured, and loose approximation of skin.
There are many reported variations in the sequence of the structures repaired in digital replantation. Some surgeons prefer to repair all dorsal structures (extensor tendon and veins) first, followed by all volar structures (flexor tendons, digital nerves, and arteries), for the benefit of positioning efficiency. Other surgeons will purposefully plan the vein repairs last in an effort to achieve arterial inflow first. Surgeons who advocate this technique have reported the benefit of arterial inflow in assessing and locating dorsal veins with the engorgement of venous return. Lastly, some surgeons have advocated repairing flexor tendons before extensor tendons because they feel they are better able to reproduce the position of the replanted digit within the cascade of the hand.
A particular note should be made of the sequence of events for major replantation. When a significant muscle burden exists in the amputated part, the degree of urgency in achieving perfusion is significantly more acute than with a digital replantation. In this case, most surgeons would advocate moving toward arterial repair as quickly as possible. In our center, if we feel that the part was managed with appropriate cooling and has been brought to the operating room with a very short ischemia time, we will perform osseous fixation first in an efficient and rapid manner and then move toward arterial reconstruction. However, if either ischemia time or temperature has been compromised and we feel that there is extreme urgency in achieving revascularization, we will elect to use an artificial arterial shunt. Shunts rapidly achieve distal perfusion by cannulating both the proximal and distal ends of the vessel(s) requiring repair ( Figure 42.6 ). In this setting, a catheter is placed both proximally and distally and is secured, usually with insufflation of balloon cuffs. This can be further secured with an exterior suture ligation of the vessel on top of the shunt to achieve a watertight seal. After arterial inflow is established, the extent of venous bleeding is assessed. A second shunt may be used in the venous system so as to minimize the amount of blood loss. If the muscle burden of the amputated part is significant, the anesthesiologist must be prepared to address this with appropriate hydration and fluid cardiovascular monitoring.
