Preoperative Assessment and Management
Proper selection of candidates for replantation is very important. While all attempts at reconstruction should be made, at times, the condition of the patient or the part may preclude successful replantation.
Careful planning, meticulous operative technique, and patient intraoperative decision-making are critical. One should adhere to the outlined sequence of steps for replantation.
A well-vascularized replant with good soft-tissue cover permits early range of motion to prevent tendon adhesions.
Replantation in the upper extremity may be associated with a relatively high complication rate because of malunion/nonunion, joint stiffness, tendon adhesions, muscle contractures, poor sensory return, and cold intolerance.
A replantation center provides comprehensive care for these complex injuries. Within the replantation center, close communication between the surgeon and hand therapist is essential.
Microsurgical techniques have made the salvage of devascularized digits, hands, and upper extremities possible. Trauma can result in either complete amputation or devascularization of parts. Replantation is the reattachment of a completely amputated part by restoration of arterial inflow and venous outflow, whereas revascularization is the restoration of arterial inflow, venous outflow, or both to an incompletely amputated part, no matter how small the point of attachment. This chapter focuses on the management of replantation; however, the principles presented also apply to revascularization.
The first successful replantation of an upper arm amputation was performed in 1962 by Malt and McKhann, and the first successful replantation of an amputated thumb was performed in 1968 by Komatsu and Tamai. Since then, replantation teams have been organized in major hospitals, and microsurgical techniques have become an integral part of the training of orthopedic and plastic hand surgeons. The techniques of replantation in the upper extremity have been extrapolated to successful replantation of other parts of the body, including the lower limb, the scalp, the ear, portions of the lip and nose, and the penis and have led directly to the evolution of elective microsurgical free tissue transfer.
Although success rates in microsurgery have risen, hand surgeons will need to critically evaluate the outcomes of replantation and revascularization. In some instances, a successful replantation or revascularization may lead to stiffness, insensibility, and pain, causing more dysfunction than immediate completion of the amputation. The purpose of this chapter is to outline principles in preoperative assessment and management, surgical technique, and postoperative therapy that will optimize overall hand function after traumatic amputation.
Preoperative Assessment and Management
Regional Replantation Centers: A Team Approach
Traumatic amputations and other severe hand injuries are best treated in a regional replantation center because of the availability of multiple hand microsurgeons and familiarity with preoperative, intraoperative, and postoperative protocols and clinical pathways. Integral members of the replantation team include transfer coordinators, emergency department physicians, hand surgeons, anesthesiologists, critical care nurses, and hand therapists. In addition, interventional radiologists, intensive care specialists, psychologists, and social workers may play important roles. Because of the possibility of long operating times and tedious surgery, several microsurgeons should be available to receive patients and perform these complex and technically demanding procedures.
Transfer to a Replantation Service
Once the surgeon has decided, usually by telephone, that the patient and the amputated part are suitable for potential replantation, an established order of procedures is undertaken ( Box 96-1 ). In many instances, it is difficult to assess the true severity of injury without direct examination. It is the policy of dedicated replantation centers to accept all possible candidates for evaluation of possible replantation.
Name, age, hand dominance, occupation
Mechanism of injury
Time of injury
Referring doctor and hospital
Via ambulance or helicopter
Instructions to transferring facility
Ensure that patient is stable for transfer
Apply pressure dressing to extremity
Update tetanus prophylaxis
Administer cefazolin intravenously
Wrap part in wet sterile gauze, place in sealed plastic bag in container of ice and water
Send radiographs with patient
Upon arrival in emergency department
Type and screen
Check complete blood count and pertinent laboratory test results
Obtain operative consent for replantation/revascularization, completion amputation, transfusions, and possible vein, nerve, and skin grafts
In operating room
General anesthesia or axillary block
Warming blanket on operating table
Aspirin suppository 325 mg per rectum
Foley, intermittent pneumatic leg compression devices to prevent deep venous thrombosis
Preparation of amputated part on back table: tagging of nerves, veins, and arteries
The referring physician should ensure that hemorrhage from the amputation stump has been stopped by application of a pressure dressing and elevation. Ligation of vascular structures is usually not necessary and is discouraged. In cases of severe hemorrhage, fluid resuscitation is instituted. Tetanus prophylaxis is updated, and intravenous antibiotics are infused. The amputated part is then wrapped in sterile gauze moistened with saline solution, sealed in a plastic bag, and placed in a container of water and ice at a temperature of 4°C. The surgeon should also advise the referring physician as to the urgency of transfer of the patient and amputated part either by ambulance or, for major replantations, by helicopter. Radiographs of the part and the extremity are sent with the patient to save critical time in the receiving hospital.
Evaluation for Replantation Surgery
All transferred patients are received in the emergency department to be screened for other injuries. A rapid physical examination is performed to exclude any associated injuries. It is critical that life-threatening concomitant injuries such as intracranial bleeding, cervical spine injury, and pneumothorax are ruled out. A member of the replantation team should obtain a careful history from the patient, including age, hand dominance, occupation, and preexisting systemic illness. Most important, a detailed description of the mechanism of injury usually allows the surgeon to determine whether the amputation was caused by a sharp transection or a crushing or avulsion mechanism. Radiographs of the amputated part and the proximal extremity should be obtained if they have not already been sent with the patient. It is important to exclude any associated fractures in the limb proximal to the level of amputation. Routine investigations include a chest radiograph, electrocardiogram, complete blood count, and electrolyte panel. Blood typing and cross-matching may be necessary for major limb replantations.
Replantation Decision Making
In general, any patient with a complete or partial amputation involving the upper extremity is a candidate for replantation or revascularization, but ideal candidates have sustained sharp, guillotine-type injuries of the thumb, multiple digits, hand, wrist, or forearm, and these wounds are only minimally contaminated ( Box 96-2 ). However, the decision to proceed with replantation of an amputated part can be made only by an experienced microsurgeon or hand surgeon. Because the patient and family may expect a miraculous result, it is important that the physician referring such a patient to a replantation center explain that the patient is being referred for evaluation by an experienced microsurgeon to determine whether replantation is possible rather than raising their hopes unrealistically. When faced with a difficult decision regarding replantation, the surgeon should consider whether the function of the hand can be improved by replantation, compared with closing the amputation stump and fitting the patient with a prosthesis in the future. All patients undergoing possible replantation or revascularization must give consent for possible completion amputation.
Single digit in children
Contraindications to replantation may be either absolute or relative ( Boxes 96-3 and 96-4 ).
Significant associated injuries
Multiple injuries within the amputated part
Prolonged warm ischemia time
Significant associated injuries. Digital amputations are rarely associated with other major injuries, but major amputations of the arm are commonly associated with head, chest, and abdominal injuries. These may be life-threatening and may preclude replantation of the upper extremity amputation.
Multiple injuries within the amputated part. Extensive damage along the digital arteries from a crush or avulsion mechanism may preclude replantation. If there is extensive crushing or degloving of the amputated part ( Fig. 96-1 ) or if there are segmental amputations at multiple levels in the amputated extremity ( Fig. 96-2 ), this will usually contraindicate replantation. Clinical inspection of the amputated part may be correlated with radiographs, which may reveal fractures at multiple levels.
Systemic illness. Finally, elderly patients with a history of a myocardial infarction, heart failure, chronic obstructive pulmonary disease, or poorly controlled insulin-dependent diabetes may not be candidates for prolonged surgery and anesthesia.
Patient’s age. Elderly patients may have significant systemic disease, but more important, the recovery of tendon and nerve function in the replanted digit is usually much poorer compared with a younger patient; there is also the added risk of producing stiffness in the interphalangeal (IP) joints of adjacent uninjured fingers. Arteriosclerosis is relatively rare in the arteries of the upper extremity but can occasionally complicate the anastomoses of the radial and ulnar arteries during replantation at the wrist level in an elderly patient. Conversely, many elderly patients are quite active, and their hand function is critical to their activities of daily living (ADL) and hobbies.
Replantation in young children may be more technically demanding because of the small caliber of the vessels and increased vasospasm, but every effort should be made to replant a digit in a child because the digit will continue to grow. In addition, the results of the tendon and nerve repairs are much better than those in an adult.
Avulsion injuries. With avulsion injuries, there is usually extensive damage to the digital arteries and digital nerves both proximal and distal to the level of amputation. Experimentally, injury to the digital artery has been shown to extend as far as 4 cm from the site of transection by electron microscopy compared with 0.8 cm under the operating microscope. Avulsion amputations of the digits resulting from rodeo or water-skiing injuries are fairly obvious on clinical inspection, with long segments of the digital nerves or flexor and extensor tendons attached to the amputated digit. In contrast, the digital arteries are usually avulsed distally from within the digit, sometimes all the way to the trifurcation of the digital artery at the level of the distal interphalangeal (DIP) joint. Replantation will be successful only if a normal-appearing lumen of the distal digital artery can be found before the digital artery trifurcates and requires the use of interposition vein grafts or transposition of a neurovascular bundle from an adjacent digit.
The most extreme example of an avulsion injury is the so-called ring avulsion injury. These injuries may range from circumferential lacerations at the level of the proximal phalanx with thrombosis or transection of the dorsal veins and both digital arteries to complete degloving of the soft tissue envelope of the digit or amputation of the digit through the DIP joint ( Fig. 96-3 ). The simplest classification of ring avulsion injuries by Urbaniak and colleagues consists of three categories ( Box 96-5 ). This classification was subsequently expanded by Kay and colleagues into four categories ( Box 96-6 ).
Class I Adequate circulation
Class II Inadequate circulation
Class III Complete degloving or complete amputation
Class I Circulation adequate, with or without skeletal injury
Class IIa Arterial circulation inadequate, no skeletal injury
Class IIv Venous circulation inadequate, no skeletal injury
Class IIIa Arterial circulation inadequate, with fracture or joint injury
Class IIIv Venous circulation inadequate, with fracture or joint injury
Class IV Complete amputation
Arterial revascularization requiring interposition vein grafts usually is necessary for class IIa and IIIa injuries, whereas class IIv and IIIv injuries require venous anastomoses. Class IV complete degloving or complete amputations require a full replantation procedure. Approximately 75% of class II, III, and IV ring avulsion injuries can be successfully salvaged by revascularization or replantation.
Prolonged warm ischemia time. Muscle is the one tissue most susceptible to ischemia and begins to undergo irreversible changes after 6 hours at room temperature. Because a proximal forearm or upper arm amputation contains significant muscle mass, it is vitally important that such amputations be cooled as quickly as possible and, if necessary, reperfused through arterial shunts to reduce the warm and cold ischemia times and allow successful replantation. Because the digits do not contain any muscle, they have a much longer ischemic tolerance. With multiple digital amputations, successful replantations after 33 hours of warm ischemia and after 94 hours of cold ischemia have been reported. A hand amputation was successfully replanted after 54 hours of cold ischemia. However, these represent extreme anecdotal cases, and every effort should be made to streamline transfer and preparation of patients.
Massive contamination. Radical surgical debridement precedes any major upper extremity replantation, but occasionally massive contamination in farm injuries or by impregnation of all tissues by oil or grease in industrial injuries may prevent complete debridement and therefore preclude replantation because of the risk of infection and overwhelming sepsis.
Psychological problems. Self-inflicted amputations, usually of the hand or wrist, may precede a later successful suicide attempt. These patients definitely require an emergency psychiatric evaluation before any decision regarding replantation is made.
Single-digit amputations. Although a single-digit amputation should always be replanted in children, replantation of a single digit in an adult remains controversial. Even though viability can be restored after amputation proximal to the proximal interphalangeal (PIP) joint, digital motion is compromised because of the adhesions associated with flexor tendon repairs in zone II, resulting in less than satisfactory flexion at the PIP and DIP joints. Replantation of an index finger amputation proximal to the PIP joint in an adult is almost universally unrewarding because the brain excludes the index finger and substitutes the middle finger for thumb–middle finger pinch. Similarly, replantation of a single middle finger, ring finger, or small finger may interfere with the motion of the other two fingers because of the common origin of the flexor digitorum profundus (FDP) tendons. However, replantation of a single digit amputation through the middle phalanx distal to the insertion of the flexor digitorum sublimis (FDS) tendon or through the distal phalanx may provide excellent sensory return and full flexion at the PIP joint is maintained.
Preparation of the Amputated Part
If the surgeon decides that the patient and the amputated part fulfill the criteria for replantation, the amputated part and radiographs are taken to the operating room so that the amputated part can be prepared while the patient is still being made ready for anesthesia and surgery. The amputated part is cleaned with routine bactericidal solution and placed on a small operating table. If there is gross contamination, the part can be irrigated with sterile saline solution. All the structures in the amputated part are then identified and tagged, initially under loupe magnification and later under the operating microscope.
In an amputated digit, two midlateral incisions are made so that anterior and posterior skin flaps can be mobilized to provide access to the radial and ulnar neurovascular bundles. For ring avulsion injuries, a single dorsal midline incision may sometimes be used. For arm and forearm amputations, the incisions are not placed directly overlying the nerves and arteries because it is likely that primary closure will not be possible, and it is better not to place skin grafts directly over the repaired arteries and nerves. The incisions in the amputated part and in the amputation stump can be staggered so that the flaps can be transposed in a Z -plasty fashion during final closure. Contused skin margins and any contaminated subcutaneous tissue are sharply debrided.
In major forearm and upper arm amputations, it is difficult to determine how much of the muscle will eventually remain viable. Obviously contused, lacerated, or contaminated muscle must be sharply debrided. Irrigation with heparinized Ringer’s lactate solution through a catheter inserted in one of the inflow arteries can be used to determine which portions of the muscles will remain viable once arterial inflow is restored. Any muscle that does not “weep” the Ringer’s lactate solution should be radically excised because it will not be perfused after the arterial and venous anastomoses have been completed. Carpal tunnel release and fasciotomies are usually required in upper arm and forearm amputations. These incisions are designed over the anterior and posterior forearm muscle compartments and over the second and fourth metacarpals to provide access to the intrinsic muscle compartments.
Tagging of the Neurovascular Structures
Under loupe magnification or the operating microscope, the two digital arteries and the radial and ulnar digital nerves are identified through the midlateral incisions and traced in a distal-to-proximal direction to identify the digital nerves and arteries at the level of the amputation. With avulsion amputations, there may be tortuosity of the digital arteries; these should then be traced, if necessary, as far distally as the DIP joint until the arterial lumen appears normal under the operating microscope when cut with microdissecting scissors. In some avulsion injuries, the digital artery cannot be found at the level of the amputation and has been avulsed from distally within the digit. The distal end of the digital artery will need to be found to allow successful replantation, but it will obviously require interposition vein grafts. The two digital arteries and two digital nerves are identified with vascular clips to allow easier identification later in the procedure. We recommend tagging the nerve ends with medium-sized hemaclips and the arteries with small-sized hemaclips to differentiate these structures before coaptation or anastomosis. The digital nerves are cut 1 to 2 mm distal to the level of the amputation until a normal-appearing fascicular pattern is seen. Similarly, the digital arteries are cut with the microdissecting scissors and the vessel lumen dilated with a vessel dilator. Serial sectioning is continued distally until a normal-appearing lumen of the digital artery is seen under the operating microscope. It is critical that damaged vessels be excised until normal intima is encountered, even if interposition vein grafts will be required. Failure to go beyond the zone of injury and to resort to vein grafting is a common pitfall in replantation surgery.
The dorsal skin flap is elevated distally in the plane between the subcutaneous tissues and the underlying extensor tendons to visualize the dorsal veins within the subcutaneous tissues. The dorsal skin is then elevated for 1 to 2 mm from the level of the amputation to identify two or three veins, which are also tagged with small hemaclips.
In upper arm and forearm amputations, the brachial, radial, and ulnar arteries, together with the median, ulnar, and radial nerves and several large subcutaneous veins, need to be similarly identified and tagged.
Preparation of Flexor and Extensor Tendons
The extensor tendon in the amputated digit does not usually retract and can be gently elevated from the underlying periosteum for a distance of 5 mm distal to the amputation. If the tendon end is ragged, it can be transected sharply with a scalpel. The FDP and FDS tendons may be apparent at the level of the amputation or may be found more distally in the digit, depending on the position of the hand at the time of amputation. The flexor tendon sheath will need to be incised to identify the two flexor tendons, but care should be taken to preserve at least 50% of the A2 and A4 pulleys to prevent postoperative bowstringing. The ends of the two flexor tendons should be cut sharply with a scalpel to debride any ragged or contaminated tissue. A core suture of 3-0 or 4-0 braided nylon may be placed into the FDP tendon before bony fixation of the amputated part because it may become more difficult to place this core suture later in the replantation sequence.
Bone Shortening and Fixation
Bone shortening is an integral component of replantation surgery in all upper extremity amputations because it potentially allows primary nerve repair and end-to-end vessel anastomoses. Depending on the level of amputation, the surgeon needs to decide whether bone shortening should be performed on the amputated part only, on the amputation stump only, or in both places. However, it is important to maintain the mobility of the metacarpophalangeal (MCP), PIP, and DIP joints and the insertion of the flexor and extensor tendons.
The periosteum on the amputated bone is elevated away from the bone end. A small hole is made in a piece of Esmarch’s bandage or surgical glove, and the bone end is placed through this hole to protect the soft tissues during bony resection. The bone is then cut transversely using a power saw. In forearm amputations, the radius and ulna may need to be shortened 2.5 to 5 cm, and in upper arm amputations, the humerus may need to be shortened 4 to 8 cm to allow primary nerve and muscle repair.
Rigid internal fixation is the technique of choice in replantation surgery, primarily to allow early protected motion of the adjacent joints. Although K-wire fixation is a rapid and simple technique, more rigid fixation will allow earlier and more aggressive postoperative therapy. For replantations through the phalanges, 90-90 intraosseous wiring is used. In addition to 90-90 fixation ( Fig. 96-4 ), longitudinal K-wires or plates can be used for transmetacarpal amputations. One should limit periosteal stripping in these cases, so wiring is usually preferred over plating. Rigid fixation of the radius and ulna requires 3.5-mm dynamic compression plates; 4.5-mm dynamic compression plates are necessary for rigid fixation of the humerus ( Fig. 96-5 ). These plates or intraosseous wires may be applied to the bone within the amputated part before fixation of the part to the amputation stump.
If the amputation passes through a joint, primary arthrodesis accomplishes both bony shortening and bony fixation. This is especially indicated in amputations of the thumb at the level of the MCP joint and amputations of the hand at the level of the radiocarpal joint. However, for amputations of the digit through the MCP joints, an alternative option is immediate placement of a silicone elastomer implant for arthroplasty to preserve motion at this joint.
Finally, hemostasis is achieved in the amputated part by bipolar coagulation because this is sometimes difficult to achieve once revascularization has been performed. Hemostasis is particularly important in transmetacarpal amputations, in which branches of the deep metacarpal arteries may bleed profusely, and also in forearm amputations. The amputated part is now ready for replantation and is wrapped in gauze moistened with ice-cold saline solution until the patient is ready.
Preparation of the Amputation Stump
The patient is usually placed under general anesthesia. A urinary catheter must be inserted because of the length of the procedure. In addition, we routinely use stockings and intermittent compression devices on the legs to prevent deep venous thrombosis. The patient is covered with a heating blanket to maintain body temperature. A padded tourniquet is applied around the upper arm for preparation of the amputation stump for all amputations except those through the humerus itself. Debridement, identification, and tagging of all structures are performed exactly as described previously to prepare the amputated part. The flexor tendons may have retracted more proximally and, after retrieval, can be held out to a suitable length by transfixion with a 25-gauge needle. A similar core suture of 3-0 or 4-0 braided nylon can be placed in the proximal stump of the FDP tendon before replantation. After identification of the digital arteries, they can be mobilized more proximally into the palm. The ends of the digital arteries are then sharply cut with microdissecting scissors and the vessel lumen dilated with vessel dilators. The arteries are serially sectioned until a normal-appearing intima is seen under the operating microscope.
After debridement, identification, and tagging of all structures, the tourniquet is deflated to assess the force of arterial inflow. Distal traction is applied to each proper or common digital artery using a microforceps; if there is a good “spurt” test result, each digital artery is occluded with a single-vessel clamp. If there is poor inflow through the proximal arteries, this may be caused by vasospasm or more proximal compression of the ulnar artery in Guyon’s canal. The digital arteries can be bathed with papaverine to relieve any vasospasm. In transmetacarpal amputations, the ulnar artery may be released through Guyon’s canal to expose the entire superficial palmar arch. Finally, hemostasis is achieved in the proximal stump, especially in transmetacarpal amputations and in forearm and upper arm amputations.
Technique of Replantation
Although the following section describes the standard technique for replantation, revascularization procedures follow portions of this algorithm depending on the extent of injury. We advise using a sterile pen to compile a list of injured components. This provides a checklist for repair and, in multiple digit injuries, allows accurate recording of the injury and repair for decision making in postoperative therapy.
Once the surgeon has established that there is good proximal arterial inflow and sufficient time (20 minutes) has elapsed since the previous tourniquet deflation, the tourniquet is reinflated to facilitate bony fixation and repair of the flexor and extensor tendons and digital nerves.
A definite sequence of repair during digital replantation has been advocated:
Extensor tendon repair
Flexor tendon repairs
However, the sequence of repair is now more related to the individual surgeon’s preference. It is logical to perform the bony fixation, flexor and extensor tendon repairs, and the digital nerve repairs under the tourniquet and then complete the replantation with the digital artery anastomoses and dorsal vein anastomoses. Alternatively, we sometimes perform the venous anastomoses before releasing the tourniquet and performing the arterial anastomoses so that the venous anastomoses (extremely tedious) are done in a bloodless field. In cases of multiple digit amputations, we usually proceed with a structure-by-structure approach (fix all bones, then all tendons and so on) rather than a finger-by-finger approach.
The distal amputated part is aligned with the proximal stump, and rigid internal fixation is completed using compression plates for the humerus, radius, and ulna; longitudinal K-wires, 90-90 intraosseous wiring, or minicompression plates for the metacarpals; and 90-90 intraosseous wiring for the phalanges. For amputations through the MCP joint of the thumb or through the radiocarpal joint at the wrist, primary arthrodesis is performed using similar techniques. Rigid fixation allows earlier postoperative therapy.
If possible, the dorsal periosteum should be repaired using 5-0 absorbable suture. This probably enhances bony union but more importantly may prevent extensor tendon adhesions at the site of bony fixation.
Extensor Tendon Repair
The extensor tendon is then repaired using 4-0 nonabsorbable interrupted mattress or figure-of-8 sutures.
Flexor Tendon Repair
The hand is then turned over, and the volar periosteum is repaired with 5-0 absorbable sutures. Both FDP and FDS tendons are repaired if possible. The flat FDS tendon is repaired with interrupted mattress or modified Kessler sutures of 4-0 braided nylon. The two core sutures previously placed into the proximal and distal stumps of the FDP tendon are then tied and the tendon repair completed with a running circumferential suture using 6-0 monofilament suture. In both flexor tendons, a second horizontal mattress suture with 3-0 or 4-0 braided nylon is used to achieve a four-strand core repair that will allow early active motion. The same meticulous technique should be used for repair of the flexor tendons in a replant as in a primary zone II flexor tendon repair to provide the best possible circumstances for independent gliding of the flexor tendons after replantation.
The microscope is then brought into position, and the proximal and distal digital nerves are coapted by an epineurial repair using 9-0 or 10-0 nylon sutures. In more proximal amputations at the wrist, forearm, or upper arm level, a group fascicular repair of the median, ulnar, and radial nerves is performed, again using 9-0 nylon sutures. Obviously, the median, ulnar, and radial nerve repair should be performed without any tension at the site of repair, and this is usually possible because of the previous bony shortening.
If the usual tourniquet time of 120 minutes has not been exceeded during bony fixation, extensor and flexor tendon repair, and the nerve repair, the venous anastomoses can be started under the tourniquet. Otherwise, the tourniquet is deflated, and the arterial and venous anastomoses are performed with the tourniquet down. The adventitia is removed from the ends of the digital arteries, and the lumen is dilated with vessel dilators. If the digital arteries can be approximated under minimal tension using a double-approximator clamp, direct end-to-end anastomoses can be performed using interrupted 9-0 or 10-0 nylon sutures. If tension is excessive or if there is a definite segmental gap between the proximal and distal ends of the artery, interposition vein grafts will be necessary. In digital replantations, both digital arteries should be repaired, if possible, but most digits can be successfully replanted by anastomosis of only one digital artery. In the forearm, both the radial and ulnar arteries should be repaired.
Two or three dorsal veins in each digit are anastomosed end-to-end using standard microsurgical techniques, usually using 10-0 nylon sutures. If there is any tension whatsoever on the venous anastomoses when the proximal and distal stumps of the vein are introduced into the approximator clamp, interposition vein grafts should be considered. For transmetacarpal amputations and amputations at the level of the wrist, at least three or four dorsal veins should be anastomosed, approximately two veins for each artery. The advantage of performing the venous anastomoses before anastomoses of the digital arteries is that it reduces blood loss and avoids performing the venous anastomoses in a pool of blood once arterial inflow has been restored.
However, the arterial anastomoses may need to be performed before the venous anastomoses in the following circumstances:
When there has been a long ischemic interval
In very distal amputations in which restoration of arterial inflow into the digit sometimes allows easier identification of the very distal veins
In upper arm and proximal forearm replantations where there is a significant mass of devascularized muscle, in which case the arterial anastomoses must always be performed first and the patient allowed to bleed from the open veins in the distal part for a short time before completing the venous anastomoses. (Otherwise, if the venous anastomoses were completed first, the acidotic, hyperkalemic venous blood returning to the systemic circulation from the reperfused ischemic muscle may result in cardiac arrest.)
Interposition vein grafts may be required in three circumstances:
When bony shortening cannot be performed to preserve a functional joint
In avulsion or crush injuries in which there is an extensive zone of injury along the artery
In thumb amputations in which the ulnar digital artery is usually the dominant arterial blood supply to the thumb, it is necessary to hypersupinate the hand to perform an end-to-end anastomosis of the ulnar digital artery of the thumb. It is much easier to anastomose an interposition vein graft to the larger ulnar digital artery while the amputated thumb is on the back table ( Fig. 96-6 ). The interposition vein graft can then be anastomosed to the princeps pollicis artery on the dorsum of the first webspace, which is a much more convenient position both for the surgeons and the operating microscope.