Fingertip injuries are commonly seen by Family Physicians and in the Accident and Emergency Department. In this article, we will review the anatomy of the fingertip and outline the management of common fingertip pathologies that are frequently encountered.
The primary goal of treatment in all fingertip injuries is to achieve a painless fingertip with durable, sensate skin cover1. A hypersensitive tip that results from suboptimal repair of a fingertip injury can be a considerable source of pain and disability to a patient.

The fingertip refers to all tissues found distal to the insertion of the flexor and extensor tendons into the distal phalanx (Figure 1).² It is a complex of three tissue subunits: the nail complex, pulp (soft tissue) and distal phalanx (bone). We will briefly go through each subunit in turn.

Nail Complex

The nail complex or perionychium consists of the nail bed, nail folds and nail plate (Figure 1).

The nail bed consists of the germinal matrix, which produces 90% of the nail plate, and the sterile matrix, which allows for adherence of the nail plate. A white arc, known as the lunula, separates the two matrices. It demarcates the point where germinal cells become transparent in the process of nail plate formation.

The proximal nail fold (eponychium) and lateral nail folds (paronychium) form the proximal and lateral borders of the nail complex respectively. The lateral folds direct the growth vector of the nail by constricting the nail plate. The proximal fold has dorsal and ventral surfaces. The dorsal surface produces the shine of the nail, and the ventral surface is contiguous with the germinal matrix.

As the most visible part of the fingertip, the nail plays important functional and aesthetic roles. It protects the dorsal fingertip, increases the sensitivity of the fingertip by acting as a counterforce, and is essential for fine pinch.

The Pulp

The pulp contributes more than 50% of the fingertip volume. It is covered with glaborous skin, which is thick and deeplyridged. The pulp skin is anchored by fibrous septa extending from the distal phalanx to the dermis. This produces a stable, bulky surface that is critical for grip and fine touch.

Distal Phalanx

The distal phalanx forms the structural core of the fingertip. Proximally, the flexor and extensor tendons insert into its volar and dorsal surfaces respectively. The dorsal surface of the distal phalanx lies directly below the nail bed, with no intervening soft tissue or dermis. Consequently, in situations where the nail is avulsed, distal phalanx fractures with nail bed lacerations are considered open fractures.

In addition, the dorsal cortex of the distal phalanx plays a critical role in supporting the nail bed. If support is deficit, a hook nail deformity results (Figure 2).

Evaluation and Treatment of Fingertip Injuries

Obtain a thorough history of the mechanism of injury (i.e. crush, avulsion, guillotine), patient age, co-morbidities, occupation and handedness. Assess the skin integrity, vascularity (capillary refill), sensation (two-point discrimination) and flexor/extensor tendon function. Evaluate two-point discrimination with both ends of an unfolded paperclip (Figure 3). Compare this with a normal digit – it should be less than or equal to 5 mm. Obtain postero-anterior and lateral X-ray films of the finger. Administer antibiotics and tetanus prophylaxis.

Assess each tissue subunit of the fingertip. Fingertip trauma may affect a single subunit (e.g. shave injury to pulp) or multiple subunits (e.g. nail avulsion injury with concomitant pulp laceration and distal phalanx fracture). The specific wound characteristics determine the optimal method of treatment. Table 1 summarises the pertinent assessment points.

Table 1 Important aspects of fingertip subunit assessment

Nail Bed Injuries

Nail bed injuries range from lacerations to crush and avulsions of nail bed tissue. Patients who sustain a crushed fingertip may present with a subungal haematoma.

Subungal Haematoma

   If the nail plate is adherent and the lateral nail folds are not disrupted, painless subungal haematomas can be treated conservatively i.e. with simple analgesia and hand elevation. Painful subungal haematomas can be decompressed (trephination) under aseptic conditions.

Technique: (Figure 5)

1. Administer a digital or wrist block. Under aseptic conditions, trephine the nail plate with a sterile heated needle.
2. Successful trephination should result in decompression of the haematoma with immediate pain relief.
3. Apply tulle gras, gauze and crepe bandage. Prescribe antibiotics for 3 days.

Subungal haematomas with concomitant distal phalanx fractures require removal of the nail plate and repair of the underlying nail bed laceration.

Nail Bed Repair

Table 2

Simple nail bed lacerations may be repaired in the outpatient setting with fine, absorbable suture (Vicryl 6/0) or with Dermabond.⁴ Accurate approximation of the lacerated edges of the nail bed maximises the chance of normal nail plate growth post injury. Injuries with nail bed defects should be referred for possible nail bed grafting.⁵

Technique:

1. Administer a digital or wrist block. Apply a digital or forearm tourniquet.
2. Remove the nail plate (or remnant) with a blunt dissector.
3. Debride the nail bed conservatively and irrigate copiously with normal saline.
4. Repair the nail bed laceration with Vicryl 6/0 (Figure 6). Alternatively, apply Dermabond over the entire sterile matrix in three layers, with a 30-second interval between layers. Be careful not to use too much pressure during Dermabond application as this will force the lacerated edges apart, allowing adhesive to enter the wound and compromise healing.
5. Lateral incisions may be required to adequately expose the germinal matrix for repair (Figure 7).
6. After repair, splint the proximal nail fold open by replacing the patient’s original nail, or a thin layer of tulle gras into the nail fold. This is important to prevent adhesion of the nail fold resulting in pterygium. Anchor the nail with non-absorbable sutures.
7. Remove the tourniquet. Dress the fingertip with tulle gras, gauze and crepe bandage.

Complications of a suboptimal nail bed repair include split nail, pterygium and non-adherence of the nail plate (Figure 8). Secondary reconstructive procedures may be required.

Pulp

Wounds with no soft tissue loss may be closed primarily. Isolated defects of the pulp (e.g. shaving injuries) that are superficial (no exposed bone) and less than 1 cm² may be left to granulate with simple regular dressing changes (tulle gras, gauze and crepe bandage). Complete healing will occur within 3 to 5 weeks. The patient should be encouraged to mobilise the hand after the first week.¹

Wounds larger than 1 cm² require a full thickness skin graft for durable skin cover and to reduce excessive wound contraction. The medial forearm or hypothenar skin are the preferred donor sites. Injuries with exposed bone require coverage by local or regional flaps and specialist referral is indicated.

Distal Phalanx

An associated distal phalanx fracture occurs with 50% of nail bed injuries.⁶ Fractures of the distal phalanx tuft are managed conservatively, and are splinted in position by the repaired nail bed. Patients should be advised that they may have a painful pulp on tip pressure for 2 to 3 months post-injury.

Displaced fractures of the shaft should be referred to a specialist for reduction and Kirschner wire fixation.

Mallet Finger

Mallet finger injuries are caused by disruption of the terminal extensor tendon. This produces the characteristic extension lag at the distal interphalangeal joint. They are classified as soft tissue (tendon rupture) or bony (avulsion fracture) mallets (Figure 10).

Mallet injuries result from the sudden forced flexion of an extending distal interphalangeal joint. A compensatory hyperextension at the proximal interphalangeal joint results in a swan neck deformity as the central slip of the extensor tendon retracts proximally.

The vast majority of closed mallet injuries are treated with splinting. A mallet splint is worn full time for 6 to 8 weeks to maintain the distal interphalangeal joint in extension. The patient is weaned off the splint (night time splinting only) over 1 month.

For the first 6 to 8 weeks, the splint is maintained and taken off only for hygiene purposes. The distal interphalangeal joint must be kept extended when the splint is taken off.

Intermittent proximal interphalangeal joint flexion exercises are encouraged after 6 weeks of total immobilisation to prevent stiffness and to slacken the tension in the lateral bands. Patients should be advised that a 10° residual extensor lag at the distal interphalangeal joint is common.⁶

Open mallet injuries or mallet fractures that are associated with subluxation of the distal interphalangeal joint (Figure 11) should be referred to the specialist for fixation.

Conclusion

Fingertip injuries are common, many of which may be treated in a primary healthcare setting. Special care must be taken in evaluating the 3 subunits of the fingertip.

Indications for specialist referral

1. Complex nail bed injuries
2. Displaced distal phalanx shaft fractures
3. Pulp wounds more than 1 cm2 and/or exposed bone, nerve or vessels
4. Fingertip amputations

GPs can call for appointments through the GP Appointment Hotline at 6321 4402.

By: Dr Darryl Chew, Consultant, Department of Hand Surgery, Singapore General Hospital
Dr Fong Hui Chai, Medical Officer, Department of Hand Surgery, Singapore General Hospital

Dr Darryl Chew is a Consultant with the Department of Hand Surgery at the Singapore General Hospital. Hand trauma forms the bulk of his caseload at SGH. His sub-specialty interest is the paediatric hand and sees children presenting with hand problems at KK Women’s and Children’s Hospital.

Dr Fong Hui Chai is a Junior Resident with the Department of Plastic, Reconstructive & Aesthetic Surgery at the Singapore General Hospital. He has a keen interest in limb reconstruction, and has just completed a rotation in the Department of Hand Surgery.

References

1. Fassler PR. Fingertip Injuries: Evaluation and Treatment. J Am Acad Orthop Surg. 1996 Jan;4(1):84-92.
2. Zook EG. Anatomy and physiology of the perionychium. Hand Clin. 2002 Nov;18(4):553-9, v.
3. Zook EG, Guy RJ, Russell RC. A study of nail bed injuries: causes, treatment, and prognosis. J Hand Surg Am. 1984 Mar;9(2):247-52.
4. Yam A, Tan SH, Tan AB. A novel method of rapid nail bed repair using 2-octyl cyanoacrylate (Dermabond). Plast Reconstr Surg. 2008 Mar;121(3):148e-149e
5. Zook EG. Reconstruction of a functional and aesthetic nail, Hand Clin 18:577-594, 2002.
6. Green, D. P., & Wolfe, S. W. Green’s operative hand surgery. Philadelphia: Elsevier/Churchill Livingstone. 2011.