CHAPTER
65

Revascularization and replantation are the reconstructions of choice for debilitating hand injuries.1 Alternatively, when the amputated and devascularized part cannot be revascularized or replanted or replantation has failed, microsurgical toe-to-hand transfer could restore the lost function and form.²

The philosophy, surgical techniques, anticipated outcomes, and necessary refinements for any of these core reconstructive procedures have been well investigated and well established in the literature since the mid-1990s.³ The ultimate goal for the surgeon performing upper extremity reconstruction using one of these techniques should be a favorable outcome and good patient and surgeon satisfaction rather than replant or toe survival alone.⁴

To fulfill this vision and maximize the functional and aesthetic rewards after replantation and toe-to-hand microsurgical transfer, and based on vast experience with replantation and toe-to-hand microsurgical transplants in our center, we try to identify those untoward results and propose pearls and tips on how to circumvent and correct unfavorable outcomes in this rewarding yet demanding field of reconstructive microsurgery.

Revascularization and replantation can now achieve a 70 to 90% success rate.5 This percentage is significantly less than that of free flap transfer,⁶ reflecting unfavorable circumstances for the surgery and also expanding the indications for more challenging indications, such as single finger amputation distal to the insertion of sublimis tendon, fingertip amputation, and ring avulsion amputations.^4,5

The surgery is complex with narrow margins for error. Thorough preparation and meticulous execution are ex tremely important to avoid any untoward outcomes. Special considerations related to the level of amputation and replantation and the mechanism of injury should be taken into account before surgery.

Planning, Decision-Making, and Preparation

The unfavorable results that result from poor planning, decision-making, and preparation will affect replant survival and functional outcome, the patient’s psychology and function, and treatment cost.⁷ Replantation should not be attempted in every occasion the surgeon deals with the amputation. In some cases, as described in this paragraph, complications may arise and the patient will endure prolonged suffering. Therefore knowing when not to replant is vital for the avoidance of unfavorable results.

When Not to Replant

A common pitfall is replanting a nonreplantable part that will eventually fail or result in a nonfunctional thumb at best (Fig. 65.1); therefore, replantation should not be attempted when all tissues are severely damaged or avulsed, multiple segmental injuries are noted (Fig. 65.2), extreme contamination is evident, or a ribbon sign or redline sign are apparent. Similarly, prolonged ischemia is a contraindication for replantation of proximal major amputations.^4–8

Fig. 65.1 (a,b) Multilevel amputation with severe damage. (c,d) Although replantation was successful, the hand has excessively poor function. (e) Osteosynthesis.

Fig 65.2 Severe multisegmental injury. Replantation is not advised in such situations.

Fig. 65.3 (a) Multisegmental injury; replantation should be avoided. (b) A pedicled groin flap was used for coverage and preparation of a secondary toe transfer. (c,d) Reasonable hand function after great toe transfer, at 22-year follow-up.

Once the part is determined to be replantable, good preparation is essential. Inadequate preparation leads to infection, nonunion, unnecessary use of vein grafts, and replant loss. Common pitfalls in preparation include inadequate débridement of all dirty and contaminated, nonviable, and nonfunctionally valuable tissues and inadequate bone shortening resulting in repair under tension or poor fracture reduction. Débridement has to be thorough and radical. As for bone shortening, it is considered adequate when skin, tendons, and veins can be repaired directly without a graft. Arteries and nerves need to be considered separately because of the long damaged segment in avulsion injuries that often needs to be grafted.4,7–10 Bone shortening is usually performed at the diaphyseal ends away from the joints and should aid in comminuted fracture reduction, converting a complex fracture type into a simpler one that is easy to reduce and fix.³²

Determining Alternatives

When replantation is not possible, spare part surgery should be.¹¹ Amputation and revision that takes into account secondary toe-to-hand transfer after adequate soft tissue coverage may be a good alternative¹² (Fig. 65.3).

To avoid nonunion and malunion, the surgeon should aim for fixation that is rigid, simple, and quick; reduces pain; and allows early mobilization.13 Management is more challenging and may necessitate corrective osteotomy, with care not to injure repaired vessels and to minimize potential tendon adhesion.

Restricted Tendon Function

Despite optimal tendon repair, tendon adhesion is not uncommon after the finger, transmetacarpal, and carpal replantations indicated in up to 13% of the cases. Other factors that contribute to limited range of motion at the time of tenolysis could be tendon rupture (as high as 20%), joint contracture necessitating capsulotomy (up to 15%) or replacement (5%), and web space contracture.¹⁴

Surgery is indicated at an average of 8 to 10 months after replantation.⁴ Tenolysis, despite the difficulty of performing it, is a worthy procedure that yields significantly better total active motion (TAM) and passive active motion (PAM) compared with pretenolysis levels.

Improvement, however, is expected to be less in zone II, in crush and avulsion injury, and in more-than-two-finger amputation.¹⁴ Tendon rupture remains the main complication of tenolysis (7%) and will necessitate a silicone rod spacer and secondary tendon graft. Therefore delayed repair with tendon graft or FDS transfer can be considered, especially in severe crush or avulsion degloving injuries.^5,8

Poor Sensory Recovery and Cold Intolerance

Digital sensibility is an important functional goal. Return of superficial pain and tactile sensibility throughout the autonomous area with disappearance of overreaction (S3 or more) has been reported in up to 61% of thumb replantation and 54% of finger replantation. The static two-point discrimination (S2PD) is comparable between direct nerve repair and nerve grafting.¹⁵

Moderate to severe cold intolerance has been reported in more than 80% of digital replantations and usually abates after a period of 2 years. It is worth noting, however, that cold intolerance is less severe and less common when the digital pulse pressure is greater than 80% of the normal side and when the replant achieves S3+ or more.¹⁵

Based on that, meticulous nerve repair by an experienced surgeon is recommended. Furthermore, in an extensive crush injury, delayed repair or secondary grafting could be a sound option.¹⁵ Although the number of repaired arteries will not affect the quality of sensory recovery, the more arteries repaired, the faster the recovery. Moreover, selection of a proximal arterial stump may provide higher digital pressure, resulting in less severe cold intolerance. Finally, sensory reeducation is expected to improve the speed and quality of recovery.¹⁵

Arterial Insufficiency

Vessel selection and preparation can minimize complications. Therefore the surgeon should select the larger artery; the ulnar digital artery for the thumb and radial two fingers and the radial digital artery for the ulnar two fingers. A healthy lumen is necessary in proximal and distal arteries, and the proximal artery must have sustained pulsatile flow. Although replants can survive on one artery, a two-artery repair will allow faster sensory recovery and reduce the incidence of cold intolerance. Vein or arterial grafts should be used liberally.^7,15

Venous Insufficiency

A few key steps can ensure an uneventful venous repair. Venous repair is usually done before the artery to minimize congestion of the digit. Dorsal veins are preferred, but sometimes volar veins can be used. Use of more than two veins is preferred and is associated with improved survival of the replant. Tight skin closure should be avoided. Veins, unlike arteries, have a fragile wall; therefore segmental injury is rare and grafts are seldom indicated.^7–10,16

Replant Loss

Failure is the most feared complication. The failure rate can be decreased by optimization of the surgical plan and performance and dedicated postoperative monitoring to ensure early detection of vascular compromise and timely intervention for improved replant survival. The salvage rate depends on the timing of take back; a 66 to 88% success rate can be achieved in early take backs.¹⁷

Replant monitoring can be achieved by clinical inspection combined with digital thermometry to increase the sensitivity and specificity of detecting failure of perfusion. Alternatively, laser Doppler with higher sensitivity and specificity for digital perfusion may be used for monitoring.¹⁸

If the replant fails despite salvage effort, amputation is performed, and the wound is managed depending on the level and extent of amputation by bone shortening and direct coverage, reserving the potential for future toe transfer or a distant pedicled flap in more extensive, proximal amputations.

The unfavorable outcome of distal replantation is replant loss. Survival at this level depends on the number of veins repaired, not arteries. Replantation was shown to achieve a more than 90% success rate when at least two veins were repaired, compared with 75% when one vein or none was repaired.16,19,20

Pearls of Wisdom

The surgeon should consider doing the artery first, because veins could be absent or difficult. The volar venous plexus is selected for zone I, and the dorsal veins are selected for zone II amputations. When there are no veins, one of the following strategies can be applied:

1. Arteriovenous shunting to the dorsal vein

2. Chemical leeches (nail bed bleeding with topical heparin application)

3. Heparin injection at the volar surface of the tip (cost-effective)

4. Medical leeches (third-generation cephalosporin or aminoglycosides are needed for prophylaxis)

5. A subdermal pocket

Vessels smaller than 0.7 mm are repaired using 11–0 suture, starting at the back wall.¹⁶ For Tamai zone I at the lunula, the transverse palmar arch or any of its branches (preferably the central branch) can be used. The bifurcation of this central branch can be further exploited for arterial and venous vascularization.²¹ At Tamai zone II, the digital arteries are used.¹⁵ Sensory repair may not be necessary but should be performed when feasible.²²

Ring Avulsion Injuries

The unfavorable outcomes of ring avulsion injuries are replant loss related to a long segment of vascular injury and skin necrosis, especially in Kay type III and IV injuries.⁷

Pearls of Wisdom

Vascular injury is best managed with vascular graft without hesitation. Although arterial grafts can be used,²³ venous grafts from the volar forearm are preferred, because they have a comparable diameter, are readily available, and could have a Y shape to enable two distal arteries based on one proximal artery.

Skin necrosis limited to the dorsal aspect of one finger can benefit from a venous flap, allowing simultaneous coverage and vascular reconstruction.²⁴ However, the survival of a large venous flap that depends on a flow-through arterialized vein may not be adequate, because the flow bypasses the flap to revascularize the distal digit but does not perfuse the flap, unlike the shunt-restriction venous flap modification.^25,26

As for extensive soft tissue loss, coverage of vital structures such as tendons and vessels will necessitate a regional flap such as the posterior interosseous flap or even a free flap.⁷ Pedicled distant flaps may prevent early mobilization and rehabilitation, leading to poor functional outcomes.

Thumb Replantation

The unfavorable outcomes of thumb replantation include a nonsensitive thumb, a short thumb, a malpositioned thumb, and replant loss.

Pearls of Wisdom

The surgeon should select the ulnar digital artery for perfusion and consider an interpositional vein graft to the radial artery at the snuff box. A sizable palmar vein can be identified in the pulp of the thumb superficial to the arteries, and it is reliable. Bone shortening should be done judiciously. Range of motion is less critical in thumb replantation compared with finger replantation as long as the position is correct. An IP arthrodesis can facilitate bone shortening and prevent a painful, stiff, and flexed IP joint (Fig. 65.4). Furthermore, a better functional outcome of the replanted thumb is expected at the distal level than at the proximal one.^{7,17,23,27,28}

Transmetacarpal Replantation

The unfavorable outcomes of transmetacarpal replantation are weak or absent intrinsic function, weak grip, poor sensory recovery, tendon adhesion, joint contracture, intrinsic tightness, and bone nonunion²⁹ (Fig. 65.5).

Pearls of Wisdom

Despite a poor outcome after this particular amputation, acceptable function can still be achieved (Fig. 65.6) if the following are considered:

• When revascularization with vein graft is needed, the venous arch from the dorsal forefoot can be used. It is important to test the venous valves with a heparinized saline flush before the venous arch is used. The first branch is designed for the thumb, which is more important than other fingers. In this arrangement if there is a problem in revascularization one of the fingers but not the thumb may be lost.

• The metacarpal bones should be evenly shortened (12 to 15 mm), which may facilitate direct repair of the retracted neurovascular bundles.

• All damaged intrinsic musculature should be excised. Correct thumb rotatory alignment should be maintained. Primary arthrodesis of the metacarpophalangeal (MCP) joint should be avoided. Early active mobilization with anticlaw splinting should be considered during rehabilitation. Secondary tendon transfer can be considered to compensate for the lost intrinsic function.

Fig. 65.4 (a) Ring avulsion amputation of the thumb. (b) After replantation with interphalangeal joint arthrodesis. (c,d) Good function was restored at 1-year follow-up.

Fig. 65.5 (a) Transmetacarpal amputation. (b,c) Poor intrinsic muscle function despite replantation success.

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