Distal Digital Replantation
The anatomic and functional characteristics of the fingertip are unique. Distal replantation is the replantation at or distal to the distal interphalangeal joint (DIPJ). It is the ideal technique to restore the original tissue, with good cosmetic and functional results. It can preserve the nail, maintain the digit length, has no donor-site morbidity, and avoids the complications of other methods of soft-tissue coverage, such as painful neuroma, stump hypersensitivity, and hook nail deformity.
Historically, distal replantation was controversial because of the technical difficulties, low survival rate, perioperative morbidity, and high costs of surgery and rehabilitation. However, recent studies have showed persistently high survival rates, minimal complications, good functional outcomes, and high patient satisfaction. Distal replantation is currently regarded as the primary treatment method for distal tip amputations and is routine practice in some centers. Restoration of digital length and the presence of a nail may be desirable for certain occupations, such as musicians. In many Asian cultures, the importance of body integrity is strong.
There is no absolute indication for distal replantation. All viable options should be discussed with the patient and the family, with pros and cons balanced. The decision depends on
The expected chance of survival of the replanted fingertip
The ability of the patient to endure the possible perioperative complications both physically and psychologically
The demand and desire of the patient
Ideal candidates are children with a sharp cut amputation. They have more elastic and easily repaired arterial walls, better survival rates without vein anastomosis, and excellent sensory recovery even without nerve repair ( Fig. 52.1a,b ).
Young patients who are nonsmokers with a sharp cut amputation are also are ideal candidates ( Fig. 52.2a,b ).
Heavily contaminated and crushed parts ( Fig. 52.3 )
Patients with other serious injuries or medical diseases
Peripheral vascular disease, such as vasculitis, Raynaud disease, or chronic renal failure
Mentally unstable patients who are not able to comply with the postoperative care
Prolonged warm ischemic time
However, there is no absolute contraindication to a distal replantation.
Successful replantation has been observed following avulsion and crush injuries. Vein grafts can salvage the fingertip with vascular defects and intimal tears. The determination as to whether the fingertip is replantable can be made only after inspection using the operating microscope ( Fig. 52.4a,b ).
Preexisting diseases may preclude the patient′s withstanding a long operative period and prolonged blood loss, but distal replantation can be performed under plexus anesthesia (PA), local anesthesia (LA) ( Fig. 52.5 ), forearm intravenous local anesthesia (FIRA), or intravenous local anesthesia (IVLA). The operative time is usually 3–4 hours. Perioperative anticoagulation is not mandatory, especially in a clean-cut amputation with healthy vessels ( Fig. 52.6a,b ) and in children. Bleeding can be minimized with use of a tourniquet, venous anastomosis, and good hemostasis;
Successful hand replantation has been achieved after 54 hours of cold ischemia.1 Prolonged ischemia time is not an absolute contraindication, though the success rate drops. The replanted fingertip is small with no muscle tissue. Replantation after a prolonged period of ischemia would not carry the systemic risk that accompanies a more proximal replantation.
Radiographs of the hand and the amputated fingertip should be obtained, to plan for the bone fixation method or need for fusion. A highly comminuted fracture in the amputated part that is not amenable to internal fixation may constitute a contraindication for replantation.
Distal replantation is the ideal method to restore a fingertip.
High success rates and patient satisfaction are usually obtained.
Thorough understanding of the vascular anatomy and strict adherence to every surgical detail are important for good results.
The trauma to the finger at the incidence of injury most likely determines the feasibility of replantations and patency of anastomosis. Whether the fingertip is replantable or not can be determined only under the operating microscope, and the decision should be realistic.
Understanding the unique vascular anatomy of the distal phalanx and the pulp helps to develop confidence in locating the ultrafine vessels for anastomosis.
Venous anastomosis should be attempted at least once, as this decreases venous engorgement and makes postoperative care less intensive. It is mandatory if more than one artery is being anastomosed.
Frequent monitoring of the replanted finger is of paramount importance in offering punctual remedial actions (e.g., gentle massage, bloodletting, adjustment of hand position, and anticoagulation status). A bloodletting procedure may also be needed even if the veins are anastomosed.
The small distal part requires little energy to survive. Usually one arterial anastomosis is enough. The operative risk and complications are low. Patient satisfaction is very high. The cosmetic and functional outcomes cannot be replaced by any other means.
The level of injury is classified into 4 zones according to Ishikawa et al2: zone 1 for amputations distal to the midpoint of the nail; zone 2 for amputations between the nail base and midpoint of the nail; amputations between the DIPJ and the nail base were divided into zones 3 and 4.
A thorough understanding of the neurovascular anatomy of the fingertip is essential. We performed a cadaver study on the vascular anatomy in 32 fingers and 8 thumbs.
Radial and ulnar digital arteries run distally in the finger along with the digital nerves, which lie medial and volar to the digital arteries ( Fig. 52.7 ).
The diameter of the radial and ulnar digital arteries is similar in the middle finger, but in the other fingers the caliber of the two digital arteries varies. The dominant digital artery is the one that is adjacent to the middle finger (i.e., the ulnar digital artery of the index and the radial digital artery of the ring and little fingers) ( Fig. 52.7 ).
At the distal phalanx, ~ 5 mm distal to the distal finger crease, the digital artery turns toward the midline, crossing dorsal to the digital nerve, anastomoses with the contralateral digital artery, and forms an arcade in the pulp just distal to the insertion of the flexor digitorum profundus tendon, at the mid-distal phalanx ( Fig. 52.8 ).
The diameter of the pulp arcade is ~ 0.4–0.8 mm. The arcade gives off at least two distal branches with diameters of 0.2 to 0.5 mm ( Fig. 52.9 ).
Just distal to the distal finger crease, a branch bifurcates from the digital artery, turning distally and dorsally, to form a nail-matrix arcade on the dorsum of the nail matrix.
Two branches from the pulp arcade turn dorsally, forming two nail-bed arcades.
The two nail-bed arcades and the nail-matrix arcade provide the dorsal arterial supply of the distal phalanx.
Terminal branches of the volar arteries run over the distal phalanx tuft to anastomose with the terminal branches from the distal nail-bed arcades.