Digital Replantation
Due to improvements in microsurgical technique and instruments, the spectrum of technically replantable injuries has broadened. In recent years, however, surgeons have become more critical in the evaluation of the benefits of salvaged amputations. It is essential to know not only the technical aspects of digital replantation, but also the overall benefits and outcomes for the patients, prior to proceeding. When considering when to replant and when to proceed with stump revision, the hand surgeon must consider multiple factors. The key question is very simple: Will the patient be better off if the amputated part is replanted, or would the gain be surpassed by some negative consequences of replantation? Often, the answer is not that simple. Predicted morbidity with and without replantation, success of replantation, estimated functional outcome, cost associated with replantation and rehabilitation, motivation of the patient and socioeconomic factors, such as potential job loss due to prolonged time off, are the major factors that need to be assessed and discussed with the patient before a decision is made. Some cultural differences may also exist. Patients in Far Eastern countries tend to choose replantation over stump revision, even in cases considered to have a poor functional prognosis, because of their cultural desire to keep their body whole.
Indications
Thumb amputations at any level
Multiple digit amputations
Hand amputations
Amputations distal to the flexor digitorum superficialis (FDS) tendon
Any amputation in a child
A single-digit amputation proximal to the FDS insertion is not a strong indication.1
Contraindications
The following situations are seen as contraindications.1 None of these contraindications is absolute, and they must be considered as a whole:
Significant associated injuries: The treatment of life-threatening injuries of the head, chest, or abdomen has clear priority over digital replantation.
Systemic diseases: Cardiopulmonary patients and patients with diabetic complications and other systemic diseases may not tolerate prolonged surgery.
Severely crushed or multiple injuries within the amputated part: Replantation of extensively crushed, avulsed parts and multilevel injuries may be beyond technical feasibility.
Prolonged ischemia time: The critical warm ischemia time for amputation levels containing muscle is 6 hours. If the interval is longer than 6 hours, replantation is contraindicated. Much longer warm ischemia times may be tolerated for digital amputations, as fingers do not contain muscle. Successful replantations after 33 hours of warm ischemia and 94 hours of cold ischemia have been reported. If a patient is close to the critical ischemia time, establishment of a temporary arterial shunt may be helpful to gain time.
Elderly patients: Advanced age is not a contraindication per se. The results after reconstruction, however, are poorer with advanced age, and the incidence of systemic disease is also higher.
Mentally unstable patients: It may be very difficult—sometimes impossible—to estimate the outcome after replantation of self-inflicted amputations. An emergent psychiatric evaluation may be necessary prior to decision making.
Single-digit amputations: The functional results after single-digit replantations proximal to the FDS insertion are generally unsatisfactory due to adhesions in zone 2. Children are an exception to this rule.
Examination and Imaging
A two-team approach may save time. While one team evaluates the patient and the proximal stump, the second team takes the amputated part to the operating room for inspection and may start with preparation without needing to wait for laboratory work and anesthesia.
Simple anteroposterior and lateral radiographs of both the ends of the finger are essential to evaluate the bone stumps ( Fig. 51.1 ).
Digital nerve blocks or blocks at a higher level may facilitate the examination of the proximal stump. After irrigation and removal of visible contaminants, examination of both the proximal and the distal stumps are performed under loupe magnification. Distal amputations may require the use of the operating microscope.
All tendons, nerves, arteries, and veins are identified and tagged. At least two veins should be identified. If signs of severe crushing or avulsion are present, the patient may not be a candidate for replantation.
To evaluate the feasibility of vascular anastomosis in injuries with minor crushing, a dissection of the vessels is necessary. In the presence of a length deficit, a possible site for vein-graft harvesting is identified at the volar wrist and forearm.
Skin deficits may require skin grafting. In rare cases, primary skin flaps may be necessary.
Relevant Anatomy
It is important to point out that there are some differences in the diameter of the ulnar and radial digital arteries. In the thumb, the ulnar artery is usually much larger. The index shows a similar ulnar dominance, whereas the little finger is radial-dominant. In the middle and ring fingers, both arteries are of similar size.2
Although the arteries are found on the palmar side of the fingers deep to the nerves, the veins are larger and more numerous in the dorsal subdermal layer.
Pearls
In multiple replantations, a checklist may be useful to avoid omissions. All structures are written on the operating table with an open box next to them.1 These boxes are checked in the order of their reconstruction as follows:
* Performance of venous anastomosis before arterial anastomosis may be advantageous.
Surgical Technique
Brachial plexus block has the advantage that it provides vasodilatation. For replantations of multiple digits, where a long operation time is anticipated, the operation should be performed under general anesthesia.
The groin area is routinely draped as a donor site for a skin graft. Many patients do not like to have a donor scar on the arm, as these are easily visible. Donor scars on the proximal wrist have even worse acceptance, as these are frequently perceived as sequelae of suicide attempts. After mild exsanguination of the arm, a pneumatic tourniquet is applied.
Many amputation injuries are contaminated with dirt or industrial debris ( Fig. 51.1 ). Copious irrigation is therefore essential. To reduce the spray of irrigation fluid outside the operating field, we utilize a clear sterile X-ray bag. The closed end of this readily available bag is cut open so that it becomes a tunnel with two open sides. Another good method is to use the vinyl bag as a closed system, as recommended by Chang and Jones, where three openings for the patient′s arm, the irrigation cannula, and the suction drain are closed flush.1
The dissection begins with identification of all relevant structures: After midlateral incisions on both sides of the amputated finger, both digital nerves and arteries are identified. It is easier to start in an uninjured area and trace the structures toward the injury site, except for cases where the neurovascular stumps are easily seen.
To make identification easier for later stages of the operation, the vessel ends are tagged with small-vessel clips and the nerve ends are tagged with medium-vessel clips. This simple procedure helps to avoid confusion between vessels and nerves in a bloody operating field.1
Damaged segments of arteries are trimmed back until the healthy lumen is visible. Nerves are also trimmed back to healthy fascicles as necessary. Veins are dissected in the subdermal layer of the dorsal flaps. Dissection of the veins in the amputated part may be delayed until after arterial anastomosis, as restored flow makes identification of veins easier.
The flexor and extensor tendons are identified.
Although there is no strict rule to the sequence, logistically, bony stabilization is first performed under tourniquet control, followed by the extensor and flexor tendons and then a nerve repair.
After release of the tourniquet, many surgeons prefer to repair the arteries first, as the veins are more difficult to locate. They are easier to identify when blood flow is restored after the arterial anastomosis is established.
If the veins are identified, some surgeons prefer to proceed with coaptation under tourniquet in a bloodless field prior to arterial repair.1
Bone shortening influences the length of all other structures. The purpose of bone trimming is to provide solid contact of the fragments at the fracture line and to alleviate tension during repair of vessels, nerves, and tendons. As it is not necessary to aim at absolute congruency, excessive bone shortening should be avoided.
When trimming the bone ends, a simple way of protecting the other anatomical structures from the saw blade is to use a piece of Esmarch rubber. A 10 cm piece is cut off, and a small hole is made in the center to fit tightly over the bone. The rubber protector is wrapped over the bone end, and it can be used to keep nerve, vessels, and tendons out of the saw blade′s plane.
After adequate trimming of the bone ends, osteosynthesis is performed. Similar to the principles of other fracture treatments, osteosynthesis should provide stability and compression with the least degree of soft-tissue dissection. However, due to the prolonged overall operative time and the much higher risk of adhesions with replantations compared with fractures, simpler techniques are preferred.
The more proximal the lesion, the more emphasis is on stability. Distal phalangeal amputations may be treated by an axial Kirschner wire (K-wire) alone, whereas at the metacarpophalangeal level, plate and screw fixation may be considered.
Fixation with interosseous wires in 90–90 fashion or with two parallel wires provides a fast osteosynthesis, rotational stability, and compression with minimal soft-tissue dissection ( Fig. 51.2a,b ).
Tendons are debrided as necessary and sutured. The extensor tendon may be repaired using multiple mattress sutures.
Repair of the flexor tendons deserves the utmost attention, as the final range of motion of the replanted digit depends tremendously on their function ( Fig. 51.3 ). An epitenon-first suture technique is preferred, as this technique provides both a higher mechanical strength and less forcible manipulation of the tendon ends than the core suture (modified Kessler)-first method, and it is easier to avoid bunching at the suture site and fraying of the margins.3
The margins are first sutured with 6.0 Prolene running suture. Then a small slit is made at the proximal tendon end, where a modified Kessler suture is placed with a 3.0 polyester suture. The suture is tied in the proximal tendon end, which avoids the separation of the suture line by the bulky knot. With early postoperative therapy planned, a horizontal mattress core suture should be added to complete a four-strand repair.
The nerves are repaired primarily with 9.0 nylon. Two epineurial sutures are sufficient if the coaptation is performed tension-free ( Fig. 51.4 ). Nerve defects are reconstructed with autologous nerve grafts. The posterior interosseous nerve, sural nerve, and medial antebrachial cutaneous nerves are well suited as donors. The medial antebrachial cutaneous nerve is easily found ~4 cm distal to the medial epicondyle in the subcutaneous layer.
Nerve defects shorter than 2 cm may also be reconstructed with nerve allografts, autologous vein grafts, or synthetic conduits. Chiu and Strauch have shown that nerve reconstructions with vein grafts have a satisfactory sensory function in small defects, with results comparable to the results after autologous nerve grafts.4
Arterial anastomosis should be attempted only if high-pressure “spurting” blood flow is established from the proximal vessels. Repair of an artery with weak flow is bound to fail. If the arterial flow remains weak, damaged portions of arteries must be resected until healthy intima is visible under high-power magnification.
If flow does not recover even in the presence of undamaged intima, one of the following will improve the flow: (a) relief of external compression of the artery, (b) warming of the hand and the operating room, (c) correction of hypovolemia, (d) elevation of the patient′s blood pressure. If all these measures are unsuccessful, simply waiting may help.
The intima may be damaged over a long segment in avulsion injuries, which must be resected and reconstructed with a reversed interpositional vein graft. The volar forearm is an ideal donor area for vein grafts.
When replanting the thumb, it is much easier and safer to primarily perform an end-to-side interposition vein graft between the ulnar digital artery and radial artery in the anatomic snuffbox rather than a direct end-to-end repair of the ulnar digital artery of the thumb in a contorted position. Moreover, the first (distal, thumb artery to vein) anastomosis may be performed independently on the back table without interference with dissection of the proximal stump.
At least one vein needs to be repaired for each arterial anastomosis.5 If the reconstructed arteries outnumber the repaired veins, venous congestion is likely. To be on the safe side, an attempt should be made to repair two veins for each artery ( Fig. 51.5 ).
Skin closure is the last part of the operation ( Figs. 51.6 , 51.7, and 51.8a,b ). All injured and devitalized skin is débrided. Skin of questionable viability should be removed. Liberal use of skin grafts is recommended, taking into account that the hand will swell after surgery. Postoperative tension will cause compression and subsequent thrombosis of the veins. If necessary, skin grafts may also be placed on vessels and nerves. Unmeshed skin is cosmetically superior. Multiple slits created in the grafts will allow drainage. Several silicone drains are inserted under the skin flaps and led out between the skin sutures.
The first layer of dressing consists of bacitracin with paraffin or Xeroform gauze. Care is taken not to apply any dressings circumferentially, as postoperative swelling may constrict the fingers. The second layer is a bulky gauze dressing. The finger tip is left uncovered. A palmar short arm splint is loosely applied to immobilize and protect the replantation. The utmost care is taken not to constrict the hand with any of the applied layers.
Pitfalls
Although reports suggest that several hours of cold ischemia time may be tolerated prior to replantation of digits (due to the lack of muscle tissue in the digits), it is generally preferred to limit ischemia time to 6 hours.
Successful replantation requires a coordinated effort of multiple disciplines (anesthesia, surgery, surgical assistants, around-the-clock nursing, etc.) and should not be performed if these necessities are not available and coordinated.
Venous congestion is the most common cause of failed replantation. Refrain from a tight wound closure and restrictive circumferential bandages.
Have a low threshold for vessel and nerve grafting. Often after these traumatic injuries, the amount of shortening of the vessels and nerves to healthy tissues makes primary repair impossible. Overstretching the ends of nerves and vessels so they meet is likely to result in failure.
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