Finger Nail and Tip Injuries

As the terminal extension of the fingers and hand, the fingertips are the portions of the upper extremity through which we touch, feel, write, draw, and perform activities of daily living. With the advent of new technology, our dependence on our fingertips for everyday living continues to increase, as we more often surf the Internet, program handheld organizers, use smart phones, operate the TV remote control, or research topics in online journals such as Medscape Drugs and Diseases. ^[1] See the image below.

One third of all traumatic injuries affect the hands; the fingertips are the most frequently injured portion of the hand. ^{[2, 3, 4, 5]}  According to the Bureau of Labor Statistics, 439,000 disabling hand and finger injuries occur annually in the United States. Consequent to these injuries, 121,800 hours of labor are lost each year. ^[6]

In a study of fingertip injuries in children, Yorlets et al, reviewing information for 1807 patients who presented to Boston Children’s Hospital’s emergency department with fingertip injuries, found that the highest percentage of such trauma (46%) resulted from a finger being crushed in a door or window. Patients were a mean age of 8 years when the injury occurred, with 25% of cases requiring surgery. ^[7]

Successful treatment of fingertip injuries depends on many considerations, including patient age, sex, and occupation, and the anatomy of the fingertip defect. An algorithm to the treatment of fingertip injuries is reviewed below to assist in the management of these injuries.

The fingertip is the portion of the digit distal to the insertion of the flexor and extensor tendons on the distal phalanx. From the periosteum of the distal phalanx, fibrous septae anchor the skin and palmar pulp to the bone. The volar pulp is also stabilized by the Grayson and Cleland ligaments, extending from the flexor sheath and distal phalanx volar and dorsal to the neurovascular bundles, respectively. The volar surface of the fingertips contains grooves and ridges, uniquely patterned for each individual, termed fingerprints.

The digital arteries and nerves arborize or trifurcate near the distal interphalangeal joint. ^[8] The proper digital artery crosses the distal interphalangeal joint, sending a branch to the nail fold, nail bed, and finger pad. Each digital nerve trifurcates near the distal interphalangeal joint, sending branches to the perionychium, fingertip, and volar pad. The digital nerves lie volar to the digital arteries near the fingertip. The fingertip is the organ of touch and feel and is abundantly supplied with sensory receptors, including Pacinian and Meissner corpuscles and Merkel cell neurite complexes.

The dorsal surface of the fingertip comprises the nail fold, nail bed, and nail plate. The perionychium includes the entire nail bed and paronychium complex. The paronychium is the skin surrounding the nail plate radially and ulnarly. The eponychium is the epidermal shelf at the base of the nail. The lunula is the white semicircle at the base of the nail bed. The fingernail is a specialized epidermal structure, like hair.

The proximal one third of the nailbed, from the nail fold to the edge of the lunula, is the germinal matrix. It has two components, the dorsal and intermediate nail. The two thirds of the nailbed distal to the lunula is the sterile matrix or ventral nail. Fingernail production occurs in 3 areas of the nailbed, the dorsal nail and intermediate nail of the germinal matrix and the ventral nail of the sterile matrix. Of these areas the intermediate germinal matrix produces 90% of nail volume. The remainder of the nail substance is produced by dorsal nail of the germinal matrix and ventral nail of the sterile matrix.

The dorsal roof of the germinal matrix deposits cells on the nail surface. The two thirds of the nail bed distal to the lunula, the ventral nail or sterile matrix, acts as a conveyor belt for the advancing nail and adds squamous cells to the nail, making it thicker and stronger. ^[9] The nail is not merely attached to the bed but rather is a continuum of a single structure from basilar cells in the nail bed. Nail growth occurs at a rate of 3-4 mm a month. It takes 3-4 months for growth to full nail length and 1 year for the nail to achieve maximal pre-injury smoothness.

The approach to management of fingertip injuries is based on several factors, including, age, hand dominance, digit involvement, sex, preexisting medical conditions, mechanism of injury, occupation, and anatomy of fingertip defect. ^[10] Obtain the patient's history to ascertain the treatment approach. ^[11] The age of the patient can contraindicate certain treatment options, including crossfinger or thenar flaps, as the delay required before flap division can result in joint contractures in older patients.

Composite grafting is less reliable and discouraged for patients older than 6 years. Injuries to the dominant hand are occasionally treated more aggressively. Moreover, digit involvement can direct management in considering the importance of contribution to overall hand function and applicability of specific flaps (ie, thenar flaps work better for index and middle fingertip injuries; Moberg flaps, which are suitable for small thumb defects, are discouraged for finger injuries).

The sex and ethnicity of the patient can influence reconstructive options; ^[12] crossfinger flaps, which transpose hair-bearing skin to the palmar surface, are discouraged for women. The use of a crossfinger flap in a patient with dark skin can also lead to an aesthetically displeasing color mismatch. Preexisting conditions like Dupuytren contracture or rheumatoid arthritis are contraindications to crossfinger and thenar flaps because of the risk for resultant joint stiffness. The mechanism of injury can influence availability of certain local flaps.

A literature review by Sindhu et al indicated that in the United States, up to 90% of fingertip amputations are not treated with replantation, while in Asian countries, as a result of moral values and the importance of body integrity, most patients with fingertip amputations undergo replantation. ^[13]

Occupation and hobbies can be an important determinant in selecting fingertip treatment options for those concerned with returning to work. For example, a piano teacher is approached differently than a manual laborer. In performing the examination, the clinician must determine the size of the defect, the circulation of the remaining soft tissue, and the angle and level of the injury, as well as nail bed involvement. Noteworthy is bone or tendon exposure, which contraindicates certain treatment options. Radiographs should be obtained to evaluate for fracture or a retained foreign body. ^[4]

A retrospective study by van den Berg et al suggested that in patients treated for fingertip injuries (Allen II-IV levels of severity), treatment outcomes are comparable no matter which therapy is chosen. The 53 patients (59 injuries) in the study received either reconstructive treatment, bone-shortening, or conservative therapy. Comparing the injured fingers with uninjured ones after a mean follow-up period of 4.5 years, treatment outcomes with regard to strength, sensibility, and mobility were not significantly different between the treatment groups. Cold intolerance and nail distortion also did not significantly differ from one group to the next, and aesthetic outcomes were considered comparable. ^[14]

Healing by Secondary Intention - Open Technique

The open technique involves allowing the wound to heal by secondary intention with wound contraction, which pulls innervated pulp into the wound. This technique is applicable to distal and volar directed fingertip injuries without protruding bone. Some small fingertip wounds with a minimal amount of protruding bone can be treated with the open technique if this bone is debrided with a rongeur. The open technique is discouraged for wounds larger than 1 cm because healing time exceeds 3-4 weeks and significantly delays return to work. This approach is suitable for fingertip injuries in children because of their increased capacity to regenerate soft tissues. The complications potentially encountered with the open technique include loss of volume and pulp. ^[15]

Primary Closure and Revision Amputation

Many fingertip injuries can be closed primarily or by recruiting adjacent soft tissues. Viability of the remaining soft tissues must be ascertained before application of a tourniquet. Occasionally, the fillet flap principle can be applied in reconstructing these wounds. Occasionally, bone shortening or revision amputation is required to allow tension-free primary closure of the soft tissues and adequate padding. Furthermore, in an effort to minimize recovery time and hasten return to work, some fingertip injuries are treated with revision amputation. ^[16]

Complications of amputation procedures include the hook nail deformity, stump neuroma formation, and the quadriga effect. ^[17] When the injury is located proximal to the lunula, the residual germinal matrix must be removed to prevent nail horn formation. Moreover, the hook nail deformity is prevented by trimming the distal nail bed 2 mm proximal to the bone. Removal of abnormal bone edges and preservation of the articular cartilage, which can minimize inflammation and provide a smooth contour to drape the wound edges over, can limit stump sensitivity.

A traction neurectomy can also minimize stump sensitivity. This severs the nerve while applying distal longitudinal traction, which results in 0.5-1 cm of proximal nerve retraction to prevent neuroma formation over the fingertip. Avoiding the approximation of the extensor and flexor tendons over the distal bone end minimizes the risk for quadriga effect. In general, revision amputations are frequently performed on manual laborers to allow for earlier return to work or on retired elderly patients for quicker wound closure and therapy, ultimately to minimize stiffness.

Skin Grafts

Skin graft application is considered for distally located and volarly directed fingertip wounds without exposed bone or tendon. Controversy exists as to whether split- or full-thickness grafts are better. Advocates for split grafts maintain the take is earlier and more reliable and wounds contract more, resulting in a smaller defect, while others favor full-thickness grafts for earlier re-innervation and more reliable, durable coverage. ^{[18, 19, 20, 21]}

In other words, split grafts may be preferable for wounds in which greater contraction is desirable. Full-thickness grafts can be obtained from the amputated tip by merely defatting the underside. ^[22]

However, when the amputated part is crushed and macerated, this should not be used as a graft. Moreover, when the amputated tip is not available, a skin graft can be obtained from multiple areas. Glabrous skin provides a better aesthetic appearance and match of texture and color. Glabrous skin can be harvested from the hypothenar eminence or feet. ^[23] Nonglabrous skin can be obtained from the wrist crease, forearm, medial upper arm, or groin.

Split-thickness skin can be harvested from the hypothenar eminence using a Weck blade after infiltrating with 1% lidocaine containing 1:100,000 epinephrine. Full-thickness grafts are harvested in the configuration of an ellipse to allow for donor closure. The graft is secured circumferentially with 3-0 nylon sutures, which are left long to tie over an Adaptic gauze and a bolus of cotton, creating a bolster/stent. The finger is placed in a splint. This bolster dressing is removed at 5-7 days, and active range of motion is begun immediately.

Composite Tip Grafts

Reapplication of composite tip grafts, amputated parts containing bone fat or nail bed, can be considered for children younger than age 6 years. As composite tip grafts must initially survive by plasmatic imbibition until neovascularization, revascularization is not reliable for adults and tip grafts should not be reapplied for adults. The distal phalanx fracture is reduced and secured with internal fixation using a K-wire. The surrounding skin is approximated with absorbable chromic suture to avoid the hassle of suture removal in a child. Moreover, the child's upper extremity is placed in a soft splint using multiple Kerlix rolls from the hand to the upper arm. The splint is removed at 2 weeks. ^[24]

Local Flap Options for the Fingers

When bone or tendon is exposed at the base of a fingertip wound, a local flap is required. The various local flaps used to reconstruct fingertips include volar V-Y, bilateral V-Y flaps, crossfinger flap, thenar flap, and island flaps. ^{[25, 26, 27, 28]} Flap choice depends on orientation and configuration of the wound, injured finger, and sex of the patient. Surgeons can optimize the reliability of these local flaps by avoiding tension on the suture line and preserving the traversing sub-dermal blood vessels into the flap.

Volar V-Y flap

Though frequently termed the Atasoy flap, Tranquilli-Leali first described the volar V-Y flap in 1935. ^{[29, 30]} The volar V-Y flap is a triangular-shaped volar advancement flap outlined with its tip at the distal interphalangeal crease. The local flap is most applicable for transverse and dorsal avulsions when a relative abundance of pulp skin is present. The technique of raising the volar V-Y flap involves designing a V with the distal flap width at least as wide as the defect. Then the V is scored through the dermis only to avoid injuring the traversing vessels into the triangular-shaped flap.

The deep aspect of the flap is carefully elevated from the distal phalanx by releasing the fibrous septae with iris scissors. The proximal donor is closed as a longitudinal line to create a Y. This longitudinal limb is short and usually only needs two or three sutures. Distally, the flap can be repaired to the nail plate or nail bed. It is critical not to transect the arborizing vessels entering the flap in the subcutaneous plane and to avoid tension on the distal suture line to the nail plate. This flap can be mobilized to reconstruct distal transverse and dorsal oblique fingertip wounds smaller than 1 cm. ^[31]

A retrospective study by Sérane-Fresnel et al indicated that a palmar bipedicular island flap, as modified from the Tranquilli-Leali flap, is effective in fingertip reconstruction. The investigators reported that use of the flap in fingertip amputations of Allen severity levels II-III leads to restoration of proper balance between skin, bone, and nail. Employing the Weber two-point discrimination test, a mean discrimination of 3.8 mm was found. The study also found mean total active motion to be 268.3° and the patient satisfaction grade to be 8.7 points out of 10. ^[32]

Bilateral V-Y flaps

In 1947 Kutler described the bilateral V-Y flaps for fingertip injuries. These local V-Y advancement flaps are harvested from the ulnar and radial aspect of the injured fingertip and advanced distally to cover the defect. This technique is best applied to volar and transverse avulsions with exposed bone when excess lateral skin is present. These flaps are designed along the midlateral line and should not extend proximal to the distal interphalangeal joint. In raising these flaps, the incisions are performed through the dermis only to preserve arborizing vessels.

The flaps are mobilized for distal advancement by dissecting fibrous septae from the distal phalanx. The proximal donor site is closed as a straight line creating a Y, and the distal edges are approximated in the mid line tension free. The disadvantages of Kutler flaps include partial or complete flap necrosis, risk for pincher nail deformity, and excess scar on fingertip risking hypersensitivity. These disadvantages are increased compared to other flaps.

Crossfinger flap

Originally termed the transdigital flap by Gurdin and Pangman in 1950, ^[33] the crossfinger flap is commonly used for volar-directed tip injuries with exposed bone or tendon when insufficient pulp for the volar V-Y flap is present. Use of this flap is reserved for fingertip wounds associated with deficiency of local tissues, which would allow for a single-stage flap because the crossfinger flap involves two operations. Moreover, the fingers become stiff during the delay between these two stages. At the first stage, a template of the defect is fashioned from the Esmarch bandage and superimposed to the adjacent finger dorsum from which the flap will be harvested. Generally, the flap is harvested from the finger radial to the injury, except when reconstructing the index.

The flap is elevated from the adjacent finger dorsum in the plane above the peritenon to allow for grafting of the donor site. A full-thickness graft can be taken from the groin to close the donor finger dorsum. The flap is opened like a book cover, turned 180°, and inset into the fingertip defect. The fingers may be sutured together or even pinned to prevent flap dehiscence. During the delay, gentle active range-of-motion exercises are critical to prevent joint stiffness of both fingers. At 2-3 weeks, the flap is divided and inset and more aggressive active and passive range-of-motion exercises are begun.

The advantages of the crossfinger flap include a reliable and large flap that can even be innervated. ^[34] However, several reports describe very good 2-point discrimination (2PD) without innervating the crossfinger flap. ^{[35, 36, 37]} The disadvantage to the crossfinger flap is the need for a second operation and the delay that results in stiffness. Accordingly, this flap is contraindicated for older patients (>40 y) or those with Dupuytren syndrome or rheumatoid arthritis. In addition, since the crossfinger flap brings hair-bearing skin to the palmar side of the finger and leaves a donor site on the hand dorsum, this flap has been discouraged for women.

Thenar flap

The classic description of the thenar flap by Gatewood in 1926 was proximally based. ^[38] In 1976, Smith and Albin ^[39] described the H-shaped modification of the thenar flap. With the H modification, both proximal and distal flaps are raised in the configuration of an H. These flaps are both sutured to the injured finger, but, at flap division, one flap is inset to the finger while the other is advanced to repair the donor site.

The thenar flap was classically elevated from the thenar eminence, which placed a potentially tender scar where we rest the hand. A better location for this donor scar is the metacarpophalangeal (MCP) joint flexion crease of the thumb. ^[40] A 2 cm X 4 cm thenar flap can be harvested from the MCP crease and still allow primary closure of the donor site with thumb flexion. Care must be exercised in harvesting this thenar flap at the MCP crease to avoid injury to the neurovascular bundles and flexor pollicis longus tendon. ^[40]

This flap can easily reach the index and long fingers and is preferred for women because it is hairless and does not scar the hand dorsum. The thenar flap can be used for volar, transverse, and dorsal injuries. The disadvantages of the thenar flap are that two operations are required with a 2-3 week delay and consequent risk for joint stiffness and contracture. Accordingly, the thenar flap is discouraged for older patients and the small and ring fingers.

A study by Barr et al reported thenar flaps to be safe and effective in the treatment of pediatric fingertip amputations. The study, which included 16 children, found the average postoperative range of motion for the proximal interphalangeal (PIP) joint to be 103° in flexion, while the average range of motion for the distal interphalangeal (DIP) joint was 60° in flexion, and the MCP joint range of motion (in all patients) was 85°. ^[41]

Reverse homodigital arterial flap

The reverse digital flap is an arterialized homodigital flap described by Lai in 1989, ^[42] which replaces injured tissue with like tissue from the same digit in a single stage. The flap is harvested from the lateral aspect of the proximal phalanx of the same finger, preferably the nonopposition side. The reverse digital flap is an axial flap based on collateral flow through the contralateral digital artery, thus it is only applicable to defects distal to the crossover communication from the contralateral digital artery. ^{[43, 44]}

The pedicle is harvested with a cuff of soft tissue to include the digital artery venae comitante. The digital nerve can be preserved. The pedicle is harvested to 5 mm proximal to the distal interphalangeal joint to capture crossover vessels from the contralateral digital artery. If doubt exists concerning reverse blood supply to the flap, the proximal digital artery can be temporarily clamped to evaluate retrograde flow to the skin island. The donor site usually requires a skin graft.

Karamese et al described the use of a reverse homodigital adipofascial flap, which allows primary closure of the donor site. The investigators, who reported on 14 fingertip amputations, determined that range of motion of the proximal and distal interphalangeal joints of the reconstructed fingers was similar to that of the contralateral finger joints. ^[45]

Homodigital arterial flap

This flap is similar to the reverse digital artery flap, as it is an island flap harvested from the same injured finger in one stage. This flap is harvested based on dorsal branches of the proper digital artery and venous supply within a 5-mm wide bridge of fat of the dorsal branch of the proper digital artery at the distal finger crease. This flap can be harvested with dorsal digital nerve branches to be a sensate flap. The donor site usually requires a skin graft. The arc of motion of this flap makes it difficult to reach the fingertip.

Homodigital dorsal middle phalangeal neurovascular island flap

In fingers with large pulp defects, a homodigital dorsal middle phalangeal neurovascular island flap procedure showed good long-term outcomes. The procedure is based on a single neurovascular pedicle and preserves the length of the finger. ^[46]

Visor flap

The visor flap is a bipedicled dorsal finger skin flap that can be used to cover fingertip wounds after digital amputations proximal to the nail bed. ^[47] Blood supply through this flap is provided through dorsal branches of the volar digital arteries and this is more reliable distal to the proximal phalanx. In elevating the visor flap it is critical to preserve the extensor peritenon to allow this donor site to be skin grafted.

Local Flaps for Thumb

Rectangular volar advancement flap

Though often termed the Moberg flap, the volar advancement flap was first described by Littler in 1956 ^[48] before being popularized by Moberg in 1964. ^[49] This is a rectangular volar flap based on both neurovascular bundles. The flap is undermined in the distal to proximal direction to the MCP crease superficial to the flexor pollicis sheath and advanced in the distal direction. This flap can usually be advanced 1.5 cm distally.

Other manipulations that can improve distal flap advancement include flexion of the interphalangeal joint, Burrow triangles at the base, extending the lateral incisions into the palm past the MCP joint, and incising the skin at the base to create an island flap and skin graft the proximal defect. Larger thumb defects with exposed bone require consideration for Littler flap or first dorsal metacarpal artery flap. The volar advancement flap is discouraged for the fingers because the inclusion of both neurovascular bundles jeopardizes blood supply to the dorsum of the fingers and causes severe flexion contractures of the fingers.

Littler flap

The neurovascular island flap was first described by Littler in 1960. He termed it the interdigital flap. It is most applicable for large defects of the volar thumb. Rose in 1983 described use of the Littler flap for 6 wounds longer than 5.5 cm. ^[50] Smaller defects are routinely reconstructed with the Moberg flap. The neurovascular island flap is harvested from the ulnar aspect of the middle finger or the radial aspect of the ring finger, basically on the common neurovascular bundle to the third web space within the median nerve supply. Before division of the distal branch of the proper digital artery, temporarily clamp to assess blood supply to the donor finger through what will be the remaining digital artery.

The advantage to the use of the Littler flap in thumb reconstruction is that it provides a large skin paddle with glabrous skin that is sensate, ultimately to preserve thumb length. The disadvantage is the donor site, which usually requires a skin graft and is prone to flexion contracture deformity. The key to avoiding this donor flexion contracture is to design the flap confines to avoid harvesting across the flexion creases. In fact, the flap should be darted to avoid harvesting from the flexion creases. This excludes them from the flap to avoid flexion contracture of the donor finger. Also, if the donor defect requires a skin graft, a full-thickness graft should be used to decrease risk for donor finger contracture.

Moreover, as soon as the skin graft has taken in the donor site, begin active range-of-motion exercises to minimize stiffness of the donor finger. Most young patients learn to recognize pressure on this flap as the thumb and not the middle finger at approximately 12 months postoperatively. This potential complication is termed correction of cortical misinterpretation.

First dorsal metacarpal artery flap

The first dorsal metacarpal artery flap is a neurovascular island flap raised from the dorsum of the index proximal phalanx based on the first dorsal metacarpal artery and branch of the superficial radial nerve. The first dorsal metacarpal artery flap reaches defects on the volar thumb tip, thumb dorsum, first web space, the MCP joint of the small finger, and even the wrist and carpal joints. A second dorsal metacarpal artery flap can be used for defects on the dorsum of the other fingers or ulnar aspect of the hand. ^[51]

The first dorsal metacarpal artery is a constant vessel arising from the radial artery just proximal to the point at which the latter pierces between the two heads of the first dorsal interosseous muscles in the apex of the triangular first interosseous space. In performing the dissection, the flap is designed over the index proximal phalanx and the knuckles of the PIP and MCP joint should be avoided if possible.

The pedicle is fashioned by elevating a narrow skin flap over the first interosseous space and subcutaneous tissue to include subdermal veins to drain the flap. The branch of the radial nerve to the index finger is frequently not visible as it courses at a slightly deeper plane than the subdermal vein plexus. The radial border of the second metacarpal bone must be exposed while performing the elevation of the pedicle, dissecting close to the periosteum of the metacarpal shaft.

The plane of dissection is deepened to expose the fascial layer of the first dorsal interosseous muscle, which is sharply incised and readily separated from the muscle in a radial direction, at which point the first dorsal metacarpal artery should be visible just superficial to this layer of fascia. Thus, the plane of dissection for raising the first dorsal metacarpal artery pedicle is subfascial over the first dorsal interosseous muscle to include the fascia through which the first metacarpal artery can be visualized.

Distally, the skin flap should be elevated in the plane superficial to the paratenon over the dorsum of the proximal phalanx to provide a bed appropriate for skin grafting of the donor site. Proximally, the pedicle is dissected from the paratenon of the tendon of the first dorsal interosseous muscle and then from the muscle itself in the distal to proximal direction. It is usually not necessary to skeletonize the first dorsal metacarpal artery back to its origin from the radial artery for the distal edge of the skin flap to reach the thumb volar tip.

The first dorsal metacarpal artery flap has several advantages over the Littler flap for sensate resurfacing of the thumb when the Moberg flap is not an option because the thumb tip defect is larger than 1.5 cm. The dissection of the first dorsal metacarpal artery flap is easier than the Littler flap and contains a more reliable venous drainage plexus than the mere venae comitante with the digital artery to the Littler flap. A larger and more reliable skin paddle can be elevated with the first dorsal metacarpal artery flap than with the Littler flap. The donor site of the first dorsal metacarpal artery flap is more desirable compared to the Littler flap. ^[52]

Sensation of the dorsal index finger skin is reliably provided by radial nerve branches to the level of the proximal interphalangeal joint but should be confirmed preoperatively by blocking the index finger digital nerves or median nerve. ^[53] The sensation of the first dorsal metacarpal artery flap, as assessed by 2PD, rivals other modes of thumb reconstruction. ^{[54, 52]} The skin from the dorsum of the index finger has 3-7 mm 2PD. ^[55]

In a series of first dorsal metacarpal artery (FDMA) flaps, 5 of 6 flaps achieved a 2PD of 8-15 mm. ^[54] The skin over the dorsum of the index finger has also been described as wear and tear resistant when transferred to the volar thumb surface. ^{[56, 57, 54]} However, large skin defects of the thumb are best reconstructed with a neurovascular flap from the great toe/first web space. ^[58]

Crossfinger to thumb flap

On occasion, the Littler flap and first dorsal metacarpal artery flap are not available for sensate resurfacing of the thumb; a crossfinger flap from the dorsum of the index finger is required. The disadvantage to the use of this flap is that it requires two stages and a neurorrhaphy of the radial nerve branch to the ulnar aspect digital nerve of the thumb. Therefore, the Littler and first dorsal metacarpal artery flaps are preferred for larger thumb defects that cannot be reconstructed with the Moberg flap. The flap is harvested superficial to the paratenon of the dorsum of the finger to allow for skin grafting of the donor.

Nail Bed Repairs

Subungual hematomas result from the disruption of nail bed vessels. In the short term, even small hematomas can cause severe pain, requiring treatment with trephination. In performing nail trephination, a hole can be fashioned in the nail plate with cautery, a heated paper clip, or a drill to relieve this associated pain. In the long term, these small hematomas can become incorporated into the nail bed. Larger hematomas are associated with significant lacerations in the nail bed, which may result in significant scarring. Longitudinal scars in the nail bed can result in split-nail deformity. Transverse nail bed scars can result in nail nonadherence. Both split-nail deformities and nail nonadherence are risk factors for frequent paronychial infections, which may eventually require nail bed ablation.

Recent studies have indicated that significant nail bed abnormalities do not usually complicate. Significant scarring of the germinal matrix may result in impaired nail plate growth. Accordingly, the former recommendation for large subungual hematomas was for nail bed exploration to repair the nail bed and minimize the risk of nail bed scarring and consequent nail plate abnormalities. ^[59] Recent studies have indicated that significant nail bed abnormalities usually don't complicate subungual hematomas. However, the studies demonstrated that patients are at risk for nail abnormalities if the nail has been avulsed or torn; this is an indication for nail plate removal and nail bed repair. Nail bed lacerations should be repaired with 7-0 chromic sutures and loupe magnification. ^[60]

Occasionally, defects of the nail bed cannot be primarily approximated, and residual nail bed fragments can be found on the underside of the avulsed nail plate or harvested as a split-thickness graft from an uninjured area on this nail bed or from the second toe. This split-thickness nail bed can be applied as a graft. Then, the nail plate is replaced into the eponychial fold; ^[61] if not available, a silicone sheet or Adaptic cane is used alternatively to splint the eponychial edges open. Associated distal phalangeal fractures may require K-wire (0.028) fixation if unstable.

A study by Rao et al indicated that in adults with nail bed lacerations, the risk for nail deformities is not significantly different in patients who are treated nonoperatively than it is in those who undergo nail plate removal and nail bed repair. Patients in the study, all of whom had an intact nail plate, were adults in whom fingertip injuries manifested as a subungual hematoma of greater than 50% “or in any subungual hematoma in the setting of a distal phalanx fracture.” Nail deformity rates in the nonoperatively and operatively managed groups were 13% and 23%, respectively. ^[62]

Several established goals exist in the treatment of fingertip injuries, including preserving useful sensation, maximizing functional length, preventing joint contractures, providing satisfactory appearance, and avoiding donor disfigurement and functional loss. ^{[63, 64]} Most fingertip injuries can be successfully treated in the emergency room with digital tourniquet and block. Crossfinger flaps, thenar flaps, and Moberg flaps can be performed in the emergency department but are probably best suited for the operating room in case a proximal tourniquet or bipolar cautery is needed.

In the emergency department, the whole forearm and hand are prepped and draped. A digital or intrathecal block can be used to anesthetize the fingertip. Alternatively, a superficial radial nerve and median nerve block can be used if a thenar flap or Moberg flap has been chosen as the reconstructive option. If multiple digital blocks are needed, a selective nerve block or wrist block may be more appropriate. For example, a superficial radial nerve and median nerve block can be used for a crossfinger flap of the index from the middle finger. In performing digital and wrist blocks, use 1% lidocaine with or without epinephrine. ^[65] The addition of epinephrine provides a hemostatic effect, minimizes the need for a tourniquet, and lengthens the duration of action of the lidocaine 4-fold. ^{[65, 66]}

A 5-mL syringe and 27-gauge needle are optimal for a digital block. The smaller syringe allows for better control and the smaller needle decreases the risk of irreversible, bilateral digital artery and nerve injury. The digital block can be performed dorsally or volarly. The dorsal approach allows for puncture through the less sensitive dorsal skin. Alternatively, an intrathecal block can be used specifically for fingertip injuries because this technique does not anesthetize the dorsum of the finger proximal to the PIP joint. With the intrathecal block 1 mL of lidocaine is injected volarly into the flexor sheath, proximal to the A1 pulley. ^[67]

Regarding tourniquet control, a 1-in Penrose can be placed around the finger base. The Penrose should be held flat to apply uniform pressure circumferentially around the finger base and a hemostat applied, pulling the drain just tightly enough to occlude arterial and venous flow. ^{[68, 69]} Another option for tourniquet control of the digit involves the use of the small finger cut from a glove at least a half size smaller than the patient's size. The small finger from the glove is opened on both ends and rolled over the finger to exsanguinate the finger. ^[70] This tourniquet is also clamped with a hemostat to remind the surgeon to remove the tourniquet before dressing the finger. ^[70]

The most common complications encountered in the treatment of fingertip injuries, hypersensitivity and cold intolerance, are complications of the injury and not the treatment. The rates of hypersensitivity and cold intolerance approximate 50% regardless of the treatment, including healing by secondary intention, skin grafting, and local flap reconstruction. This hypersensitivity and cold intolerance is self-limited and almost always resolves after 1-2 years. Initial treatment includes scar massage, desensitization, and edema control.

The treatment of fingertip injuries can be complex and controversial, with more than one treatment option for most injuries. Treatment of fingertip injuries must be individualized to the patient's age, sex, configuration and composition of defect, digit injured, hand dominance, pre-existing medical conditions, occupation, hobbies, and mechanism of injury. This algorithm can serve as a guide to facilitate management of fingertip injuries. ^[71]

The fingertip wound should be assessed for tissue loss. If there is minimal tissue loss the wound can be debrided and closed primarily. If the fingertip wound cannot be repaired primarily, no bone is exposed, and the wound measures less than 1 cm, consider open treatment or skin grafting. If the wound is larger than 1 cm, skin grafting would provide quicker wound healing.

If bone is exposed within the wound base, a local flap or bone shortening is required. If the wound is small and involving a finger with a transverse or dorsal oblique configuration, the volar V-Y flap can be used. If the wound is volar oblique without enough volar pulp for a volar V-Y flap, then a crossfinger, thenar, or neurovascular island flap (reverse digital artery or homodigital artery flap) is preferred. Single-stage reconstructions with the volar V-Y flap, reverse homodigital artery, and antegrade homodigital artery, decrease the risk for finger contractures.

If the patient is older or has preexisting medical conditions that place him or her at risk for joint contractures during the delay of the two-stage flap procedures, avoid the crossfinger and thenar flaps. Patients with concerns about returning to work, those who are older, and patients with significant comorbidity may require revision amputations. In general, women should avoid crossfinger flaps to prevent an aesthetically unacceptable donor site on the hand dorsum and hair-bearing skin on the palmar surface of the hand.

Thumb tip defects should be aggressively treated to preserve thumb length, which is more important to the thumb's overall contribution to hand function than joint flexibility, in contradistinction to the fingers. Accordingly, the rectangular volar advancement ^[49] is the preferred option for small thumb tip defects as it brings sensate durable skin to the thumb tip. Larger full-thickness defects of the thumb require sensate resurfacing with either the first dorsal metacarpal artery flap or the Littler flap. Alternatively, very large thumb defects can be reconstructed with a free sensate flap from the great toe or first web space of the foot.