Introduction
This chapter discusses soft-tissue cover of defects of the skin and subcutaneous tissue in the thumb and fingers. The distal parts are called the fingertip and thumb tip , which are defined as the structures distal to the flexor digitorum superficialis tendon (FDS) in the finger or the interphalangeal (IP) joint of the thumb. The thumb tip is usually discussed separately from the fingertip, as the thumb and fingers are distinct anatomically and functionally. Although this chapter will discuss soft-tissue cover for the entire thumb and fingers, most of the text concerns fingertips and thumb tips, as these injuries are more often seen.
Treatment goals and functional impacts
The major concerns in determining the treatment of soft-tissue defects of the thumb and fingers are the size of any tissue defect, the level and obliquity of any amputation, and whether the injury is a clean-cut or a crush injury. The essential goals of repair of the thumb and fingertips are (1) maintaining sufficient length, (2) restoring sensation, and (3) restoring appearance. An additional and lesser goal is to restore active range of motion of the digit at the distal joint.
The length and appearance of the digits are fundamental concerns, constituting about 50% of the goal of repair or reconstruction ( Table 22.1 ). With respect to appearance, preserving the nail complex is very important. Sensibility constitutes another 40% of the goal and is the most important single factor in thumb or fingertip repair and reconstruction. By contrast, active range of motion of the finger distal interphalangeal (DIP) joint and the thumb IP joint are less important, constituting the other 10% of the goal of repair and reconstruction (see Table 22.1 ). Although important to the finer motor function of the digits, active motion of the DIP and IP joints contributes only 15% of total digital motion, with normally functioning finger proximal interphalangeal (PIP) and thumb metacarpophalangeal (MCP) joints.
| Structures | Percentage Goal (%) | Reasons |
|---|---|---|
| Length and appearance | 50 | Length is the basis of hand action |
| Appearance of the tip affects overall perception of the hand | ||
| Sensibility/sensation | 40 | Sensation is particularly important and necessary for all digital tips |
| DIP joint motion (finger) or IP joint motion (thumb) | 10 | Less important compared with sensation and length/appearance |
| Responsible for only 15% of finger/thumb motion, although important to finer motor function. |
* The percentage goals can be applied to repair of the entire thumb or finger, but the PIP motion should be an additional major goal. For finger or thumb tips, the length and appearance weigh 50% of the goals, and the length of the tips alone weighs 20% in its importance (see Table 22.2 ).
The relative importance of each structure to function at the thumb tip and fingertip is shown in ( Table 22.2 ). Small decreases in either the length or sensation may not be a great concern for the patients. A shortening of less than 0.5 cm, a mild decrease in sensation rather than significant loss of the sensation, and a loss of DIP joint motion of about 20 degrees usually cause little functional or cosmetic impairment. Optimal repairs attempt (1) to maintain the length, with the intention of limiting shortening to less than 0.5 to 1 cm; (2) to recover sensation to grade 3+ (S3+), or more, with static two-point discrimination (2PD) less than 5 or 6 mm; and (3) to restore active finger DIP or thumb IP motion of 40 to 50 degrees.
| Structures/Function | Importance (%) |
|---|---|
| Pulp sensation | 40 |
| Pulp and nail cosmetics | 30 |
| Length | 20 |
| DIP (or thumb IP) motion | 10 |
Anatomy and injury types
Anatomical considerations
The distal phalanx is the backbone of the thumb tip and fingertip. However, the very distal tip includes only the soft tissues of the pulp and the distal edge of the nail. The arterial supply of the thumb tip or fingertip consists of a network of multiple small branches of the terminal branches of the digital arteries ( Fig. 22.1 ). The digital arteries run along the sides of the distal digital skeleton, with a diameter of 1 to 1.5 mm, which is sufficient for microsurgical anastomosis. They terminate in this arterial network around the DIP or IP joints and the proximal half of the distal phalanx, and suture of this network beyond the middle of the distal phalanx is difficult. The main draining veins of the digital tips run as a network on the dorsum of the digit.
The digital arteries do not have venae comitantes, but there is a venous plexus in the subcutaneous tissue surrounding each artery. Therefore any island flap based on a digital artery must include 2 to 4 mm of subcutaneous tissues around the artery to allow venous return through this venous plexus. The flexor tendons terminate on the palmar aspect of the distal phalanx, and the digital nerves split into multiple terminal branches at the level of the DIP joint, forming a transverse arch in the palmar subcutaneous tissue of the pulp ( Fig. 22.2 ). These branches are small and, thus, difficult, or impossible, to repair surgically.
Types of injuries
Thumb tip and fingertip amputations can be transverse or oblique. The resultant defects of the latter can slope antero-posteriorly or laterally. The injury can be classified in terms of its severity, as a “clean cut” or “crush” injury or by the tissues involved. So the injury can be a pulp tissue injury or loss, a fracture, nail and nail bed damage, a complete amputation, or a combination of any of these. Nail injuries are a common part of the overall injury in many instances.
Designating a pulp defect as a pulp defect with nail defect, a bony defect, or loss proximal to the germinal matrix as different types of injury is unnecessary, as directly stating the tissues involved is simpler. For documenting details of the injury level or orientation in a chart or report, the authors propose a zone division and classification of fingertip injury, which unifies existing tendon zoning with orientation of tissue loss and tissues involved ( Fig. 22.3 ).
Treatment of thumb or finger tip defects and amputations
Thorough washing and debridement are the first step in dealing with these injuries. Nonviable tissues should be debrided and the circulation of the remaining distal tissues assessed. Surgical repair follows only after wound cleaning and debridement. The choice of the most suitable repair technique varies according to numerous factors, such as the location and size of the defect, the tissues involved, and the age, general condition and needs of the patient.
Decision making on repair options: Self-regeneration, replantation, or repair surgery
Replantation versus composite graft or other options.
Replantation of a clean and tidy proximally amputated thumb or finger is clinically routine. However, replantation of the thumb tip or fingertip is subject to the decision of individual surgeons. The very distal tip can be replanted or sutured back directly as a composite graft. Although technically possible, and replantation around the DIP joint is indeed a routine in many established hand units, and indicated when the patient has a strong wish to have this surgery, such replantation bears a greater risk of failure than other reconstructions. The functional gain is also sometimes limited. As the sensation of the replanted tip may not be good, the function may not be much different from that of a slightly shortened finger or thumb with normal sensation distally.
The amputated tips, especially distal to the DIP joint, can be sutured back to the proximal stump of the digit without blood vessel repair as a composite tissue graft. This procedure avoids lengthy surgery. The more distal the amputation, the sooner the reattachment, and the younger the patient, the greater the chance of survival. This is a method popularly used in children. In children, microvascular repairs in the tips are difficult, but the composite graft in general has a 50%, or more, chance of survival. Moimen and Elliot reported that in children aged 1 to 14 years among 18 digital tips replaced within 5 hours, 11 (61%) of 18 digital tips survived completely, 4 partially survived and 3 failed; among 32 digital tips replaced after 5 hours, 22 survived partially and 10 failed completely.
In adults, a composite graft of the tip is less likely to survive, so composite grafting is not often used. If the patient strongly wishes to have the distal part attached, but the surgeons consider microvascular repair not feasible, the amputated tip can be sutured back directly, which often ends with partial or total soft-tissue necrosis, needing debridement. Therefore a distal amputation or a defect in adults is commonly repaired using other methods. Nevertheless if the amputated distal part is small and not possible for replantation, composite grafting is a valid option, which avoids the inevitable shortening if surviving.
Self-regeneration.
Of particular note, a pulp defect or a digit tip amputation with loss of length of less than 1 or 2 cm may heal without any surgery; a larger defect may also heal without surgery, but often surgery is done to reduce healing time ( Box 22.1 ). , The amputation wound or a defect area is covered with moist antiseptic dressings for 2 to 3 weeks for a small defect, or 4 to 6 weeks for a larger defect including a defect with bony exposure. Such a cover allows soft-tissue regeneration and ingrowth to fill the defect in soft tissue and to cover the exposed phalanx, and then reepithelialization will follow. If there is bone exposure at the tip, many colleagues nibble back the bone a little to allow soft-tissue cover of the bone at the expense of slight digital shortening. This avoids healing with the bone immediately under the skin, leading to tip tenderness. Alternatively, a small V-Y flap can be harvested through two incisions distal to the DIP joint to cover the exposed bone and the flap loosely sutured to the dorsal aspect of the finger, so avoiding bone shortening and allowing faster healing.
- 1.
Covering the defect with moist antiseptic dressings without surgical repair to allow self-regeneration for a defect less than 1–2 cm 2
- 2.
The above method can be used for a defect of 2–3 cm long, but this requires a longer regeneration time, so advancement flaps to cover the defect fully, or partly then allowing the rest of the defect to self-regenerate, is the commonly used treatment.
- 3.
Consider a pedicled or free vascularized flap transfer if the defect is extensive (longer than 3 cm), which can be from the wrist, dorsum of the hand, or foot, or a venous flap from the forearm.
- 4.
Dermal substitutes can be used for extensive defects of the dorsum of the finger or thumb, including the nail area.
- 5.
Dermal substitutes can also be used for reconstruction of thumb and finger volar defects but may not restore the normal bulk of the volar subcutaneous tissues.
If the patient is willing to wait for 1 or 1.5 months, self-regeneration, without flap reconstruction, is an acceptable option of treatment for any localized loss of skin alone at a digit tip of 1 to 2 cm long ( Fig. 22.4 ). Acceptable appearance can be expected after such digit tip regeneration. Tissue regeneration can also be used to heal a small area of skin and subcutaneous tissue loss with exposed tendon. Self-regeneration also works for larger defects more proximally in the digits, but these take longer to heal and may heal with more scarring.
Any moist dressing that does not contain desiccant chemicals can create the appropriate environment for self-regeneration ( Fig. 22.5 ), as it is the regenerative potential of the digit tip that works to cover the defect rather than any particular dressing initiating this process. Even ordinary gauze can be used for the cover to achieve similar outcomes provided that the dressing is changed daily and an antiseptic ointment is used to keep the wound site moist and free of infection. The exact antiseptic ointment used varies according to local preference and availability.
Dermal substitutes serve the same purpose as moist dressings in maintaining an in vivo culture chamber for tissue regeneration and require less frequent wound care and dressing changes. The repair process is also by self-regeneration under the dermal substitute. The dermal substitute degrades and falls off weeks later when the tissues underneath have regenerated. For a defect of 1 to 1.5 cm, most surgeons consider a dermal substitute to be unnecessary as moist dressings will work as efficiently for these small defects. A defect of the nail bed or on the dorsum of the digit may benefit more from dermal substitute cover than a pulp defect, as subcutaneous tissue is thin dorsally and the dorsal wounds dry easily under simple dressings despite attempts to maintain a moist environment under the dressing.
Flap transfers in the digit.
We would like to underline the importance of defect size in the selection of the most appropriate flaps. While small fingertip defects (<1 or 1.5 cm 2 ) are usually left to heal by self-regeneration with the aid of moist dressings, avoiding surgical treatment, larger pulp losses (longer than 1.5–2 cm 2 ) of fingers usually require flap reconstruction ( Box 22.2 ), for which an advancement homodigital flap, such as a V-Y flap, is used to cover the entire wound, or a part of the wound, allowing uncovered parts to heal through self-regeneration. For many patients who do not wish to have longer healing time, we routinely use advancement homodigital flaps to reconstruct digital tips with exposed bone, particularly for reconstruction of oblique pulp defects. These procedures are simple to carry out and carry their own appropriate innervation (see Box 22.2 ).
- 1.
Thumb tip or fingertips need good sensation to function,
- 2.
Skin grafting should be avoided in the thumb tip or fingertip distal to the interphalangeal/distal interphalangeal joints.
- 3.
Self-regeneration in the distal tip restores close to normal sensation.
- 4.
Neurovascular pedicled homodigital flaps (e.g., Neurovascular Atasoy, Segmuller, and extended Segmuller) are the “workhorse” flaps we recommend because they provide good sensation.
- 5.
Hybrid flaps with self-regeneration are a popular option as they extend the flap cover possible with these flaps.
As many tissue losses at the tip are sloping, the distal parts of these advancement flaps are denuded of skin only and the advancing flap only achieves subcutaneous tissue cover of bone distally, not distal skin-to-nail suture. In other words, the tip injury is converted to a skin loss, which is then reepithelialized under moist antiseptic dressings. This extends the length of the advancement flaps and allows them to cover longer defects without shortening the length of the digit ( Fig. 22.6 ).
For finger pulp defects with tendon or bone exposure larger than 1.5 to 2 cm 2 , various direct homodigital neurovascular island flaps are useful. The digital artery-based advancement flaps with digital nerve inclusion, such as the Neurovascular Tranquilli-Leali/Atasoy, the extended Segmuller, and the modified Venkataswami flap , and pivot flap, are the best choices because they are of adequate size and provide good tip sensation.
There are many other flaps, but they suffer a variety of deficiencies, particularly poor or no sensation, and may be technically complicated and/or less reliable. Therefore, the above homodigital neurovascular flaps have become the workhorse flaps in many regions of the world. A few surgeons use flaps harvested from the dorsum of the fingers and reverse digital artery flaps. However, both have poor sensation and the latter sacrifices a digital artery. Consequently, these flaps have fallen out of fashion and are used by fewer and fewer surgeons.
Hybridization.
Using an advancement flap that purposefully leaves an area not covered by the flap is called a hybrid method (see Box 22.2 ). A hybrid advancement flap and self-regeneration at the tip, as described previously, extends the application of these advancement flaps to repair wounds larger than possible if distal skin to skin suture is attempted.
The radial aspect of the index finger should be treated with special care.
The radial side of the index finger is of prime importance for sensation. , Self-regeneration under moist antiseptic dressings restores good sensation for small defects. Where flap reconstruction is necessary, provision of a sensate flap is of great importance. A switch flap should be considered if the ulnar side of the index fingertip is intact, because the sensation on the radial aspect is more important (for pinch and grip and touch sensation) than the ulnar aspect. Alternatively, a sensate advancement flap should be considered.
The goals and options for the little finger are different.
The sensation and length of the little finger is of less importance and concern. In the little finger, advancement of a pedicled flap is very limited, even when it is elevated proximally to the distal palm. Shortening of the little finger can be useful and is acceptable to some patients. A free flap transfer can be considered in the little finger if its length is to be preserved, and insensate local flaps can be used because sensation for the little finger is much less important than for the index finger.
Commonly used local flap transfers for the distal finger
Palmar V-Y advancement flap.
This flap was first described by Tranquilli-Leali in 1935 and Atasoy et al in 1970. It is used for distal fingertip pulp defects beyond the middle part of the nail bed. A triangular flap is designed with the base at the edge of the amputation and the apex at the DIP joint crease of the finger ( Fig. 22.7 ). Its blood supply relies on the small terminal arterial branches of the digital arteries, with the neurovascular bundles being preserved and not dissected. The fibrous septa that anchor the skin to deeper structures, including the palmar surface of the distal phalanx, are carefully divided. The skin flap is then advanced over the exposed bone. The base of the triangle is sutured to the nail bed, and the V-shaped donor site defect is closed as a Y or left open to epithelialize under moist dressings ( Fig. 22.8 ).
The advancement of this flap is limited by its distal blood supply and the small size of the flap, and its sensation may be reduced as advancement is achieved only with some tension on the flap. It can be made much more useful by enlarging the flap, so the proximal “V” extends back to the middle of the middle phalanx, and mobilizing it on the two neurovascular bundles. This “neurovascular” Tranquilli-Leali flap will cover all tip defects with an amputation angle of 30 degrees or less ( Fig. 22.8 ). This flap also can be used at any level of amputation of the finger as far proximally as the proximal phalanx.
Lateral V-Y flaps.
These are divided into unilateral V-Y flaps, bilateral V-Y flaps, and lateral pedicled V-Y flaps. The unilateral V-Y flap was described by Geissendorf in 1943, based on the same small terminal vessels and used for very small defects. Bilateral V-Y flaps, described by Kutler in 1947, are also harvested without dissection of the vascular pedicles. Although two flaps can be pulled toward the midline of the tip defect with slightly greater ease than the single flap described earlier, this reconstruction is limited in its use by the small size of the flaps and the limited advancement possible. It has largely been superseded by the more substantial lateral pedicled V-Y flaps, described by Segmuller in 1976 and by Biddulph in 1979, which are harvested from the lateral sides of the digit proximally to the DIP joint crease with dissection of their neurovascular pedicles to increase flap advancement to cover the tip defect. Lanzetta et al and Smith and Elliot extended the pedicled flap proximally to the PIP joint crease of the finger to further increase its size and the ease of advancement, improving its usefulness further ( Fig. 22.9 ).
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