Hand injuries

• A hand injury is not just a wound: function depends on tendons, nerves, blood supply and stable bones acting together, so a small cut in the right place can steal grip or sensation.
• The first job in the emergency department is to decide what is damaged before anaesthetising or closing: test movement against resistance, sensation before local anaesthetic, and circulation of every digit.^[1]
• Flexor tendon lacerations are zone-specific injuries. Primary repair is usually preferred within 24 hours, and in zones 1 and 2 the repair window and technique strongly influence later function.^[2]
• Fight bite, felon and bite wounds are hand infections waiting to happen. They should not be closed primarily, need irrigation and antibiotics, and early surgical review prevents destroyed tendons and joints.^[9][4]
• Compartment syndrome of the hand is defined at a lower pressure than elsewhere in the upper limb: above 15 mmHg in a hand compartment. It needs fasciotomy within hours, not days.^[8]

By the end of this page you should be able to:

1. Assess a hand injury systematically for tendons, nerves and circulation, and document what you found before any local anaesthetic.
2. Explain flexor and extensor tendon zones, the tests that isolate the flexor digitorum superficialis and profundus, and the early management and rehabilitation windows.
3. Manage fingertip injuries, including subungual haematoma, mallet finger, nail-bed injury and skin closure options.
4. Treat human and animal bite wounds, including fight bite, and incise and drain a felon safely.
5. Recognise pyogenic flexor tenosynovitis and decide between a trial of antibiotics and urgent washout.
6. Assess an amputated digit or hand, preserve and transfer it, and state the indications, contraindications and ischemia times for replantation.
7. Diagnose hand compartment syndrome from clinical signs and pressure criteria and arrange urgent fasciotomy.
8. Modify care when microsurgery, imaging or specialist theatre is not available.

Hand injuries are among the commonest presentations to emergency departments. Hand injuries overall make up around one in five emergency department visits, and lacerations to the fingers account for nearly half of non-work-related injuries.^[2][3] The hand is a precision machine of tendons, pulleys, joints, nerves and vessels packed into a small space. Because the same skin wound can hide a cut tendon, a divided digital nerve, a fractured phalanx or a joint penetration, a hand injury is never just a wound. A missed flexor tendon division in zone 2 can produce a permanent loss of active bending of a finger; a delayed recognition of a felon can progress to osteomyelitis.

This topic is an emergency-medicine overview. It covers the assessment of tendons, nerves and circulation, flexor and extensor tendon injuries, fingertip injuries, fight bite and felon, amputation and replantation, and compartment syndrome of the hand. It draws on the British Society for Surgery of the Hand (BSSH) Standards of Care in Hand Trauma and BSSH/GIRFT pathways, and on StatPearls educational syntheses for the individual conditions. It is educational material, not a substitute for local protocols or specialist hand-surgery advice.

A hand injury is damage to any structure between the wrist and the fingertips caused by trauma, pressure, temperature, electricity or biological agents. For management it is useful to classify the injury in four overlapping ways.

By tissue: skin and soft tissue, tendon, nerve, vessel, bone, joint, fingertip and nail complex.

By wound: closed (no skin breach, for example a crush or torsion injury, or an infection tracking along a tendon sheath), clean open laceration, contaminated laceration, bite wound, or open fracture.

By tendon zone. The flexor tendons cross the hand and digit in five zones. The extensor tendons are described in zones 1 to 8 counting from the fingertip proximally. These zones dictate which repair, splinting and therapy are appropriate.

By urgency: immediate threat to circulation or compartment, infection with risk of loss of the part, then tendon or nerve requiring repair within defined windows, then clean wounds that can be closed primarily or delayed.

Hand injuries are common across ages, but working-age young men predominate for flexor tendon injuries. Traumatic injuries to the fingertips are the most common injuries to the hand overall.^[3] Flexor tendon injuries occur at an estimated rate of 30 to 42 per 100,000 persons, and they occur most often in zones 2 to 5, most commonly in the index or small finger.^[2] Hand injuries overall make up approximately 20% of emergency department visits.^[2]

About 3% of people with trauma have a peripheral nerve injury, of which 60.5% involve the upper limb, and the radial nerve is the most frequently injured overall.^[6] Peripheral nerve injuries are therefore a constant risk in lacerations, fractures and crush injuries of the hand.

Acute compartment syndrome of any type has an estimated incidence of 7.3 per 100,000 in males and 0.7 per 100,000 in females.^[7] Hand compartment syndrome itself is rare outside trauma and iatrogenic causes such as vascular access. Felons and paronychias together account for almost one third of hand infections, and felons most commonly occur in the first and second digits, usually caused by penetrating trauma.^[4]

The usual mechanisms are laceration from knives, glass or sheet metal, crush, machinery and saws, falls onto the outstretched hand, bites, burns, electrical injury and infection. Occupations with knives, glass, woodwork and machinery raise risk, as do alcohol and recreational drug use, which blunt judgement and delay care. Patients with diabetes or immunosuppression are more likely to progress from a trivial puncture to deep infection.

A fight bite is a special mechanism: a closed fist striking teeth. The skin wound looks minor, but the tooth may have penetrated the extensor tendon over the metacarpal head or entered the metacarpophalangeal joint. When the fist opens, the tendon and skin slide in opposite directions and trap contamination in deep tissue. This is the most dangerous of the everyday hand injuries and it must be treated as an open fracture or joint injury even when the skin breach is small.

Other risk factors for poor outcome are delayed presentation, gross contamination, segmental tendon or nerve loss, multiple injuries, smoking, and lack of access to hand therapy.

Two large flexor tendons run in each finger. The flexor digitorum superficialis (FDS) splits at the proximal phalanx and inserts on the sides of the middle phalanx; it flexes the proximal interphalangeal (PIP) joint. The flexor digitorum profundus (FDP) passes through the split to insert on the base of the distal phalanx; it flexes the distal interphalangeal (DIP) joint. Fibro-osseous pulleys (A1 to A5, and cruciate pulleys) hold the tendons close to the phalanges so that flexion is efficient. Cutting one or both tendons, or venting a pulley, changes both movement and repair options. (1)

The extensor mechanism is more complex. The extensor digitorum communis sends a central slip to the middle phalanx and lateral bands that run to the distal phalanx via the terminal tendon. A cut at different levels produces different deformities: a mallet finger when the terminal tendon is disrupted, a boutonnière when the central slip is divided, and a more proximal injury when the tendon is cut over the metacarpal or wrist.

Each finger receives digital arteries from the superficial and deep palmar arches and is supplied by paired digital nerves from the median nerve (thumb, index, middle and the radial half of the ring finger) and the ulnar nerve (little finger and the ulnar half of the ring finger). Sensation is tested before any anaesthetic because a digital nerve can be divided even when movement is preserved. (1)(6)

The fingertip is defined as the tissue distal to the insertion of the flexor and extensor tendons on the distal phalanx, or distal to the interphalangeal joint for the thumb. The nail bed has a sterile matrix (where the nail adheres) and a germinal matrix proximal to it that generates about 90% of nail growth. The pulp is divided by vertical fibrous septae into small closed compartments, which is why a felon becomes so painful and requires drainage. (3)(4) ^[3]

Tendon division. When a flexor tendon is cut, the proximal stump retracts under the pull of the muscle belly. In zone 1, a type I FDP avulsion retracts into the palm; a type II injury with a small bony fragment stops at the level of the PIP joint at the A3 pulley. The distal stump loses active flexion at the DIP. In zone 2, both FDP and FDS may be divided, and adhesion between tendon and sheath is the main late problem, because both tendons must glide independently within a tight fibro-osseous tunnel. (2)

Early repair allows the tendon ends to heal while preserving the sheath and pulleys. Delay allows retraction, scarring and joint stiffness, and after about 7 to 10 days an isolated FDP division is generally considered irreparable in simple terms, needing reconstruction or grafting.^[1]

Nerve division. A sharply transected peripheral nerve undergoes anterograde Wallerian degeneration distal to the injury, with axonal continuity typically lost within 24 to 72 hours. Schwann cells activate within 24 hours and the degenerative process continues for 5 to 8 weeks. Axons regenerate at roughly 1 mm per day (range 0.5 to 3 mm), so recovery depends heavily on the distance to the target muscle or skin. For first- and second-degree injuries repair begins quickly, but when target endplates are more than about 18 months of regeneration away, recovery can be poor.^[6]

Infection. Bites inoculate mouth organisms, including Eikenella corrodens in human bites. In a felon the closed pulp compartments have no room to swell, so pressure rises until vascular compromise and necrosis threaten. Pyogenic flexor tenosynovitis spreads along the closed flexor sheath; the same compartment logic means infection raises pressure and can destroy the tendon unless decompressed. (4)(9)

Compartment syndrome. Bleeding and oedema inside a closed fascial compartment raise pressure. Capillary perfusion falls when compartment pressure approaches diastolic pressure, and muscle and nerve ischaemia follow. Failure to treat within roughly four hours can cause irreversible muscle damage and nearly complete myonecrosis within eight hours. (7)(8) ^[8]

Ask how the injury happened, in the patient's own words, and then make it precise. Was it sharp, a crush or a bite? Was the hand open or closed at impact? Is the patient right- or left-handed? What is their occupation, and what does work require? What was the force, the contaminant (soil, glass, metal, animals), and the time since injury? Ask about tetanus status, diabetes, immunosuppression, bleeding disorders and prior hand surgery. Ask what they can and cannot do with the hand now: that single question separates tendon injury from pain-limited movement. (1)

Red flags in the history: a bite, any mechanism with high-pressure injection (grease or paint), grossly contaminated or soil-laden wounds, an amputation or near-amputation, a change in colour, temperature or sensation in a digit, and relentless pain increasing after the first two hours.

Look first, before cleaning or anaesthetising. Inspect hand posture at rest: the normal finger cascade has each finger slightly more flexed than its neighbour from index to little. A gap in the cascade suggests an FDP division. A finger held in extension when the others flex suggests a flexor injury; a finger held flexed when the others extend suggests an extensor injury. Watch the ease of putting the hand flat (tenodesis): with the wrist extended, the fingers should flex; with the wrist flexed, they should extend. (1)(2)

Clean and photograph the wound. Test every joint, actively and passively, comparing with the other hand. Then test against resistance, because partial tendon divisions hurt but may still allow movement; a tendon can be 90% cut and still flex weakly. (1)

Check colour, temperature and capillary refill of every digit, including the volar pulp and nail bed. Delayed capillary refill or poor pulp turgor suggests digital artery laceration.^[2] Remove rings early because oedema can convert a ring into a tourniquet. Control active bleeding with direct pressure. Do not clamp blindly in the wound. (1)(9)

Before injecting any local anaesthetic, test pain and light touch in median, ulnar and radial territories. Useful fixed points: the palmar aspect of the thumb and index for median, the volar little finger for ulnar, and the dorsum of the hand between thumb and index for radial. Two-point discrimination adds quantitative detail when available. Record exactly what you found, in which digit and on which side. (1)(6)

FDP is isolated by blocking PIP flexion and asking the patient to flex the DIP against resistance. FDS is tested by preventing flexion of the other digits (because all FDS tendons share a common muscle belly) and evaluating isolated PIP flexion. If the ability to flex against resistance is absent or reduced, there is tendon damage. Extensor tendons are tested by asking the patient to extend each joint against resistance from MCP to DIP. (1)(2)

Loss of the normal flexor or extensor cascade visible on passive tenodesis is consistent with complete transection. (2)

A useful warning: patients can mimic tendon movement by using adjacent tendons or gravity, so always test resistance, joint by joint, and always test extension as well as flexion. If you remain unsure about tendon integrity, re-evaluate in 2 to 3 days. (1)

Examine for the clenched-fist injury specifically. With the fist clenched, test passive movement of the affected MCP joint and palpate the dorsum of the hand for swelling and warmth. Any pain, swelling, warmth or limitation of passive movement of an MCP joint after a human bite wound suggests tendon or joint sepsis until proved otherwise. (9)

For felon: tissue tension, non-pitting oedema and erythema of the fingertip pulp at the distal phalanx, often with pain out of proportion. The oedema classically does not extend proximal to the distal phalanx because of the septae. (4)

For pyogenic flexor tenosynovitis, Kanavel's signs are held flexion, fusiform swelling, tenderness along the tendon sheath and pain on passive extension. These are classic clinical findings rather than a validated score. (9)

Order radiographs of the affected digit and hand in two to three views. Associated avulsion fractures are common with flexor injuries, especially FDP insertional avulsion. (1) Suspect a nail-bed laceration if the haematoma covers more than half the nail surface or the nail itself is fractured. ^[3]

The common differential is not which diagnosis but which structures are injured.

Radiography comes first. Obtain two to three views of the digit and hand to look for fracture, avulsion, dislocation, foreign body and air in the joint or tendon sheath. Suspect an open joint if air is seen in the joint space or the mechanism penetrated a joint.

More specialist tests are used selectively. Ultrasound can show tendon gaps, foreign bodies and sheath fluid in experienced hands, but it is operator-dependent. Nerve conduction and electromyography help later: if no signs of reinnervation are evident 3 to 4 months after a closed injury, suspect neurotmesis and consider exploration with intraoperative electrodiagnostic testing.^[6]

For infection, send wound swabs or tissue samples when infection is present, with blood tests as needed. In a bite with systemic symptoms, check full blood count and C-reactive protein, and arrange blood-borne virus and tetanus assessment as local policy dictates. Human bite pathways recommend storing clotted blood for later testing when only one person is known.^[9]

There is no single score that stages a hand injury, but several criteria recur.

Tendon zones are the staging tool for flexor and extensor injuries, and zone 2 flexor injuries carry the worst prognosis because of adhesions.

Kanavel signs for pyogenic flexor tenosynovitis: finger held in flexion, fusiform (sausage) swelling, tenderness over the tendon sheath, and pain on passive extension. The presence of these classic signs is an indication for urgent surgical evaluation, with most patients ultimately requiring washout.^[9]

Fingertip amputations (Allen classification): type 1 pulp only; type 2 pulp and nail bed; type 3 partial loss of distal phalanx; type 4 injury proximal to the lunula. (3)

Mallet finger and boutonnière surgery thresholds: surgical intervention is required for an open mallet injury, when 30% to 50% of the articular surface is involved, in type III injuries where more than 25% of the articular surface is involved, or when bony avulsion involves one third or more of the articular surface of the distal phalanx; for boutonnière, surgery is required with an intra-articular fracture involving greater than 30%. (1)(3) ^[1][3]

Compartment pressure thresholds differ by site. In the hand, compartment pressures greater than 15 mmHg in one or more of the 10 compartments define compartment syndrome. Elsewhere in the upper extremity the traditional cut-off is 30 mmHg or higher. In any region, a normal compartment pressure is under 10 mmHg (or 0 to 8 mmHg by one measurement), and intracompartmental pressure within 10 to 30 mmHg of diastolic blood pressure indicates inadequate perfusion. Delta pressure is diastolic pressure minus measured compartment pressure, and a delta pressure of 30 mmHg or less indicates the need for fasciotomy. (7)(8) ^[7]

Control bleeding with direct pressure. Follow ATLS principles for any patient with multiple injuries. Remove rings. Give analgesia, including nerve blocks where appropriate (avoid epinephrine in digits unless using established WALANT technique). Consider tetanus according to national guidance. For open fractures give IV antibiotics according to local open fracture guidelines and do not close the wound primarily if grossly contaminated. Clean and photograph the wound, and obtain radiographs of the limb and, in amputation, of the amputated part. (9)

For an amputated part, wrap it in gauze dampened with normal saline, place it in a sealed plastic bag, and put the bag in an ice-and-water mixture. Never place the part directly on ice. (5)(9)

Irrigate lacerations copiously with tap water or saline. Delayed primary closure is acceptable for wounds presenting after 6 hours, and antibiotics should be prescribed according to antibiotic guidelines, with tetanus toxoid administered as necessary. (1) ^[1]

Operative management is the rule for divided flexor tendons. A non-operative route exists only for minor partial lacerations in selected, reliable patients with hand-therapy supervision, and for certain zone 1 and 2 injuries under a hand surgeon's plan. (2)

BSSH standards specify referral and timing: flexor lacerations are "referral category green", ideally seen at the next soft-tissue hand clinic within 24 hours, with urgent repair as early as possible within safe working hours and within a maximum of 24 hours of the decision to operate; the expected outcome is a functional range of active motion at 3 months in the absence of rupture or infection.^[9]

Zone-specific windows from the StatPearls review: type I zone 1 FDP avulsion (retracted into the palm) requires repair within one week; type II, with a small fragment of distal phalanx and retraction to the A3 pulley, can be repaired up to 6 weeks; zone 2 injuries generally up to 3 weeks; zone 5 injuries within 3 weeks. Primary repair within 24 hours is preferred when medically and surgically feasible, and delayed primary repair after 24 hours but under 2 weeks is reasonable.^[2]

Most authors repair FDP and FDS when more than 60% of tendon cross-section is disrupted. If the distal FDP stump is under 1 cm, FDP advancement with primary tendon-to-bone repair is usually indicated, and advancement beyond 1 cm is not recommended because of the flexion contracture risk. (2) ^[2]

Repair quality matters. BSSH specifies a core suture suited to tendon size; for an adult zone 2 repair this means a minimum 4-strand locking configuration with at least a 3.0 calibre suture, with documentation of technique, laceration level and pulley status. (9) ^[9]

Rehabilitation is part of treatment, not optional. BSSH requires access to a competent hand therapist for a controlled active motion regime; the first therapist visit should be within 3 to 5 days, at least weekly for the first 6 weeks, with rapid access to the surgical team. (9) The StatPearls review describes an extension-block splint with the wrist in 30 degrees of flexion, MCP joints in 45 to 70 degrees of flexion, and interphalangeal joints near full extension or slight (15 degrees) flexion, with sutures removed after two weeks. (2) Early active motion can start the day after surgery when the sheath has been washed, and graded loading progresses over 6 to 12 weeks. (2)(9) ^[2][9]

Complications include rupture, which is slightly more common in the flexor pollicis longus at approximately 5% of total repairs, adhesions, and tenolysis, which can be considered 3 to 6 months after a still-intact repair. (2) Access to WALANT anaesthesia can help identify and repair tendon gaps before skin closure and reportedly reduced rupture rates by 7% (2), although this should not replace established local practice. Healing of extrasynovial tendons can achieve 85% to 100% of normal digital motion in good circumstances. (2) ^[2]

Extensor tendons are more superficial than flexors and divide more easily. Management depends on zone and on whether the wound is open or closed.

For open lacerations BSSH specifies repair within 4 days, by a surgeon competent in extensor tendon repair, with a smooth (non-locking) suture technique, appropriate splintage and hand therapy. Referral is usually "green", with standards of non-operative therapy where chosen. (9) BSSH also notes that expected outcomes for extensor injuries have not been fully delineated, and audit should include infection, rupture and tenolysis rates. (9)

Partial extensor tendon lacerations and closed injuries are often managed non-operatively with splinting and hand therapy. Stable boutonnière injuries, for example, may be splinted with the PIP in extension while allowing DIP flexion, and mallet injuries need splint protection.

Mallet finger. Maintain the DIP joint in slight hyperextension in a splint for a minimum of 6 weeks. (1) Surgery is required when there is an open injury, an avulsion fracture involving 30% to 50% of the articular surface, joint subluxation, or when more than 25% of the articular surface is involved. (1)(3) Suspicion of nail-bed injury, open wound and displacement guide referral. (3) ^[1]

Boutonnière deformity. Closed injuries are initially splinted with the PIP joint in extension. Operative repair is required when there is an associated intra-articular fracture involving greater than 30% of the articular surface. (1)

Ulnar collateral ligament injury of the thumb (skier's thumb). Stress the ligament at 30 degrees of flexion and in full extension. Complete rupture shows loss of end-feel and more than 10 to 20 degrees of valgus deviation in both positions. (1) Surgery is generally indicated for complete rupture in an active patient; thumb immobilisation in a splint is used for partial injuries. ^[1]

The fingertip is both a tool and a sensory surface. Management balances length, sensibility, nail support and acceptable scarring.

Evaluation should include sensation, range of motion at the interphalangeal joints, and capillary refill, with two to three view radiographs of the affected digit and hand. (3) Amputation closure can be performed operatively if little tissue is lost; removal of bone should not compromise nail-bed support, and where it would, flap reconstruction is indicated. (3)

Skin closure options include direct primary closure when little bone or soft tissue is lost, local flaps such as V-Y advancement, homodigital neurovascular island flap or first dorsal metacarpal flap for larger defects, and composite grafting for distal tip loss. (3)

Subungual haematoma occupying more than 50% of the nail surface generally needs trephination, and X-ray is required because up to 50% of nail-bed injuries have an associated distal phalanx fracture. Avulsion injuries involving the nail bed have a poor prognosis. Lacerations of the nail bed should be repaired to avoid future nail deformity. (1)(3) ^[1][3]

Mallet-type fingertip injuries and partial tendon injuries follow the extensor guidance earlier. Distal phalanx fractures, particularly tuft fractures, are usually managed non-operatively with a protective splint and leave good function.

Bite wounds should not be closed primarily. Lavage copiously, prescribe antibiotics according to local guidelines, ensure tetanus cover and review. (1) The BSSH/GIRFT bite pathway recommends: if the dermis is breached, start antibiotics; irrigate with copious tap water; photograph the cleaned wound; apply a non-adherent dressing; X-ray if indicated; consider blood tests and blood-borne virus prophylaxis for human bites, with specialist risk assessment; consider tetanus and rabies for animal bites; and arrange safeguarding referral as needed. If the dermis is breached, arrange review within 24 hours by a clinician experienced in treating bites, which may be a senior emergency physician. (9) ^[9]

Acute surgical debridement or exploration is recommended when there is sepsis, open fracture, potential open joint or vascular compromise. Timing is within 24 hours of specialist review, with excision of skin edges and non-viable tissue, extension of the wound to inspect damaged structures, copious washout, splinting in the position of safe immobilisation if mobilisation must be delayed, and microbiological samples if infection is present. (9)

Fight bite specifically should be assumed to have penetrated tendon or joint until proved otherwise. Inspect the joint at the time of any required debridement, send tissue for culture, give antibiotics with activity against organisms from the human mouth including Gram-negative and anaerobic coverage where guidelines advise, splint the hand in the position of safe immobilisation, and keep the wound open or loosely packed. Early infection of a fight bite can lead to septic arthritis, osteomyelitis and permanent hand disability. (9)

Superficial paronychia and mild cellulitis can be treated with warm soaks, elevation and antibiotics, with drainage for abscess. (3)

A felon is an abscess of the fingertip pulp, usually after minor penetrating trauma, most commonly caused by Staphylococcus aureus. It presents with tissue tension, non-pitting oedema and erythema confined distal to the DIP joint, with severe pain that may be pulsatile. (4)

Treatment in early cases without fluctuation may be warm soaks and elevation with antibiotics, but once an abscess is established incision and drainage is needed. For a deep felon, make a single lateral incision at least 0.5 cm distal to the DIP joint, parallel to the nail plate, and maintain at least 0.5 cm from the nail plate, to avoid injury to the flexor tendon sheath, digital neurovascular structures, nail matrix and contracture. (4) Volar longitudinal incision can be used for superficial felons. Avoid the fish-mouth, hockey-stick and transverse palmar incisions, which are associated with neurovascular damage and painful scarring. (4) ^[4]

Pack removal occurs 24 to 48 hours after the procedure, with re-examination of the finger. Reassess within 12 to 24 hours; lack of improvement, or extensive or recurrent disease, warrants surgical referral. (4) Prescribe a 7 to 10-day course of antibiotics covering S. aureus and streptococci, such as a first-generation cephalosporin or an anti-staphylococcal penicillin. Add doxycycline, trimethoprim/sulfamethoxazole or clindamycin when MRSA is suspected; cover Eikenella corrodens for bite wounds or immunosuppressed patients. (4) Tetanus toxoid is given to patients without a 3-dose primary series and to those whose most recent dose was more than 5 years ago. (4) ^[4]

An age-appropriate tetanus toxoid-containing vaccine should be administered to all patients who cannot confirm a 3-dose primary vaccination series or who received their most recent dose more than 5 years ago. (4)

Pyogenic flexor tenosynovitis is an infection of the flexor tendon sheath. Most patients require urgent surgical washout of the sheath. Early mild cases may be given a trial of 24 hours of IV antibiotics. (9) ^[9]

BSSH management: referral category orange, because the patient may need theatre within 24 hours and should be treated under consultant hand-surgeon supervision. Give empirical IV antibiotics, rest the digit in a splint in the position of safe immobilisation, and provide early access to hand therapy to supervise early active motion from the day after surgery. (9)

Operative timing is urgent: as early as possible within safe working hours and within a maximum of 24 hours of the decision to operate. Technical aspects include washing the sheath with high volumes of normal saline, with or without local antibiotics, via a catheter from proximal to distal until the outflow is clear, using limited incisions at the A1 pulley and the DIP joint, and ensuring an outflow pathway so tissue pressure is not raised. Purulent infections need a planned repeat washout at 48 hours. (9) ^[9]

Kanavel signs are held flexion, fusiform swelling, tenderness along the sheath and pain on passive extension. These classic findings guide the diagnosis, but they are not a validated scoring tool. (9)

The BSSH/GIRFT pathway structures the assessment. Control haemorrhage and follow ATLS. Remove rings. Consider tetanus. Give IV antibiotics as per local open fracture guidelines. Administer analgesia and consider a nerve block. Clean and photograph the wound. X-ray limb and amputated part. (9)

Ask whether the part is available. If so, wrap the part in gauze made damp with normal saline, place it in a sealed plastic bag, and put the bag on ice and water. (9) Keep the patient nil by mouth while awaiting specialist opinion; arrangements should be made for emergency transfer where replantation or composite grafting is supported. (9)

Composite grafting is recommended in normal working hours, even if this delays reattachment by up to 12 hours, when the injury is a distal fingertip only. Terminalisation is appropriate when the amputation is proximal to the metacarpophalangeal joints, or when replantation is not indicated or not possible. Perioperative antibiotics and dressing or local flap closure should be individualised, and complex cases need multidisciplinary follow-up. (9) ^[9]

Replantation indications and facts from StatPearls: general indications include thumb amputation, multiple-digit amputation, mid-palm amputation, single-digit amputations distal to FDS insertion (zone 1), and any amputation in a child. Contraindications include severe crush or avulsion, multiple-level injury, single-finger amputation proximal to FDS insertion, prolonged ischemia time, and an unstable or uncooperative patient. (5)

Ischemia tolerance: digits amputated in zones 1 and 2 tolerate up to 12 hours of warm ischemia and up to 24 hours of cold ischemia. More proximal extremities tolerate no more than 6 hours warm or 12 hours cold. (5) The sequence of repair is bone, extensor tendon, flexor tendon, artery, nerve, vein, then soft tissue. (5) ^[5]

Replant viability should be at least 80% when performed by an experienced hand and microsurgeon; motion averages only about 50% of normal; patients average about 10 days in hospital and about 7 months off work. (5) Venous congestion strategies include nail plate removal, fishmouth incisions with heparin pledget, or leeches; leech therapy requires ciprofloxacin prophylaxis against Aeromonas hydrophila. (5) ^[5]

The best results come from thumb, hand, distal forearm and zone 1 finger replantation. Replantation between zone 1 and FDS insertion is substantially less successful. ^[5]

Although acute compartment syndrome most often follows tibial fracture, it can occur in the hand after crush, fractures, vascular procedures or bleeding disorders. It is a surgical emergency because ischemia progresses to necrosis.

Clinical features are pain out of proportion, pain with passive stretch of the intrinsic muscles, tense or "wood-like" compartments, sensory change, and sometimes the classic five P's (pain, pulselessness, paraesthesia, paralysis, pallor), although pulses may persist until late. The hand is held in the intrinsic-minus position, with MCP extension and IP flexion, when intrinsic compartments are involved. (7)(8)

Pressure measurement should not delay treatment when the diagnosis is obvious, but it helps when pain is hard to assess. Hand compartment syndrome is defined at above 15 mmHg in one or more of the 10 compartments of the hand, rather than the 30 mmHg traditional cut-off used elsewhere in the upper extremity. (8) Normal pressures are under 10 mmHg. A carpal tunnel release may also be needed because neurological involvement occurs about 21% of the time, and prophylactic hand release can be argued when the forearm is affected, particularly with visible dorsal hand deformity or trauma. (8) ^[8]

For the whole limb, an intracompartmental pressure above 30 mmHg or a delta pressure (diastolic minus compartment pressure) of 30 mmHg or less indicates fasciotomy; a pressure within 10 to 30 mmHg of diastolic pressure indicates inadequate perfusion. (7) If pressure is above 30 mmHg or delta pressure is 30 or less, fasciotomy should be done. (7)

Timing is critical: the ideal window for fasciotomy is within 6 hours of injury or onset, with almost 100% recovery of limb function when performed within 6 hours, about two-thirds normal function within 12 hours, and fasciotomy not recommended after 36 hours. Muscle damage becomes potentially irreversible after 4 hours and nearly complete myonecrosis occurs within 8 hours. (7)(8) ^[7]

Operative technique requires release of the thenar, hypothenar, adductor, dorsal interosseous, volar interosseous and carpal tunnel as indicated, with careful skin closure and later grafting or delayed primary closure. (8)

Delayed or missed injuries produce predictable complications: adhesion and stiffness after tendon repair; rupture of repair; joint contracture; infection progressing to tenosynovitis, septic arthritis and osteomyelitis; complex regional pain syndrome; cold intolerance after nerve injury; neuroma; amputation after vascular failure; and permanent disability after compartment syndrome or hand infection. Track audits of infection, rupture and tenolysis as BSSH standards specify. (2)(9)

Prognosis is driven mostly by mechanism, tissue loss, blood supply and compliance with therapy. Sharp, clean lacerations repaired on time have good outcomes; crush and avulsion injuries, combined nerve/tendon/vessel injuries, and delayed presentation do less well. Flexor tendon (extrinsic) repairs can achieve 85% to 100% of normal digital motion when healing is good. (2) Replanted digits retain viability in at least 80% of cases but motion is only about 50% of normal, with substantial time off work. (5) Nerve recovery depends on regeneration distance; injuries needing more than about 18 months to reach the target have poorer prognosis. (6) ^[5]

Prevention is mostly occupational and safety measures: blade and machine guards, cut-resistant gloves, safe handling of glass and metal, sports protective equipment, and discouraging alcohol around power tools. Tetanus prophylaxis for at-risk wounds and clear discharge advice about warning signs reduce delayed presentation. No general population screening is appropriate for hand injury. Recognising fight bite early, and asking about occupation and hand dominance at first presentation, are the highest-value clinical preventive actions.

Children may have smaller structures and less cooperation; they require a lower threshold for exploration under general anaesthesia and have good capacity for healing. Handle amputations in children seriously because any amputation in a child is a replantation indication. (5)

Older adults have more fragile skin and comorbidities; infection progresses more quickly and functional recovery is slower, but the same principles apply. Diabetes and immunosuppression raise the risk of deep infection, and infected or ischaemic tissue is debrided more aggressively.

Pregnancy is not a contraindication to hand surgery, but anaesthetic and drug choices should follow local obstetric policy.

People who inject drugs are at risk of severe hand sepsis from the needle tract, and any hand infection in this group needs early review by a hand surgeon.

When imaging, microsurgery and hand therapy are limited, focus on what changes outcomes. Irrigation and debridement, infection control, tetanus prophylaxis, immobilisation in the position of function, and prompt referral to the nearest hand surgeon still save hands. When replantation or microvascular repair is unavailable, primary closure after terminalisation or local flap coverage is acceptable and often preferable to a failed replantation. (5)(9)

Use the flexor and extensor zones as a referral language, because a photograph and a marked zone tell a specialist more than a long note. If tendon repair cannot be performed locally, protect the digit in a splint and arrange transfer within the window. For wounds over 6 hours old, delayed primary closure is acceptable. (1)

When specialist theatre is delayed, an early IV antibiotic trial for very early flexor sheath infection may be used, but do not allow this to delay transfer when the Kanavel signs are established. (9)

Hand rehabilitation can be improvised with volar splints in the position of function, gentle active motion, and patient education; weekly contact, even by phone, improves adherence. Keep every resected or amputated fingertip under cold saline if transfer is planned, and always document sensory findings before anaesthesia because later examination will not be reliable.

• The first priority is identifying damage before anaesthetising: test sensation, active and resisted motion, and circulation in every digit. (1)
• Hand injury is rarely just a skin wound; tendons, nerves, vessels and joints can all be divided by a small laceration. (1)(2)
• Flexor tendon injuries are zone-specific. Primary repair within 24 hours is preferred; zone windows are type I within 1 week, type II up to 6 weeks, zones 2 and 5 up to 3 weeks. (2)
• Most authors repair FDP and FDS when more than 60% of tendon cross-section is disrupted; FDP advancement is limited to 1 cm. (2)
• An adult zone 2 flexor repair needs a minimum 4-strand locking core with at least a 3.0 calibre suture, and early controlled active motion with hand therapist support. (9)
• Extensor open lacerations should be repaired within 4 days; mallet finger needs 6 weeks of DIP hyperextension splinting, with surgery for significant intra-articular involvement. (1)(9) ^[9]
• Sharply divided nerves are best repaired within 72 hours; axons regenerate at about 1 mm per day and recovery is poor when target endplates are beyond about 18 months. (6)
• Do not miss a fight bite: treat as an open fracture or joint injury, do not close primarily, give antibiotics and arrange debridement. (9)
• Felon is a pulp abscess, usually S. aureus; use a lateral incision 0.5 cm distal to the DIP and 0.5 cm from the nail plate; avoid fish-mouth incisions. (4)
• Flexor sheath infection usually needs urgent washout within 24 hours; very early cases may receive a 24-hour IV antibiotic trial. (9)
• Amputated parts are stored in a saline-moistened gauze within a bag in ice and water, never directly on ice. (5)(9)
• Replantation indications include thumb, multiple digits, zone 1 single digit and paediatric amputations; zone 1 and 2 digits tolerate 12 hours warm or 24 hours cold ischemia. (5)
• Hand compartment syndrome is defined at above 15 mmHg in 10 compartments; fasciotomy is indicated within 6 hours, with almost 100% recovery within 6 hours and about two-thirds within 12 hours. (7)(8)
• Low-resource care still depends on irrigation, debridement, infection control, immobilisation and early referral. (1)(9)

No MedGrasp topics are linked automatically. Concepts that belong alongside this topic include wound infection, open fractures, local anaesthesia of the hand, arterial injury and sepsis. Where MedGrasp topics exist for these, they should be connected in the registry.