Metacarpal, phalangeal and tendon injuries

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Hand examination is anatomical. Compare the resting cascade and tenodesis effect, then isolate each tendon. Digital sensation is tested on both sides of each finger before anaesthesia. Capillary refill and temperature assess vessels, but crush and ring avulsion can injure arteries despite limited skin damage. Flex and extend the fingers to expose wounds in the position in which they occurred; a clenched-fist laceration can move away from the joint when the hand opens.

Fracture treatment preserves rotation, length, articular congruity and tendon glide. Angulation tolerance differs by ray, but no clinically important malrotation is acceptable. Stable fractures benefit from early protected motion; unstable ones need reduction and fixation that still permits rehabilitation. Tendon repairs require timely skilled surgery and hand therapy. Antibiotics complement wound and joint treatment for bites and open injury but cannot replace exploration, debridement and foreign-body removal.

Metacarpal and phalangeal fracture decisions are driven by rotation, stability, articular surface, shortening, open status and the demands of the injured ray. Border metacarpals tolerate more sagittal angulation than index and middle rays, but none tolerates scissoring. A stable neck or shaft fracture can use buddy strapping or an intrinsic-plus splint, leaving uninjured joints free. An unstable spiral fracture, condylar fracture, multiple rays or a carpometacarpal dislocation requires early hand review. Repeat the cascade after reduction because a technically improved radiograph can still hide rotation.

Tendon examination uses isolated actions. Hold the PIP extended to test FDP-driven DIP flexion; hold adjacent digits extended to isolate FDS. Assess extensors at MCP, PIP and DIP, using an Elson-type assessment when central slip injury is suspected. Tenodesis provides a passive clue but does not grade a partial laceration. Open flexor injury, jersey finger and significant extensor division need timely hand-surgery management. Mallet injury requires uninterrupted DIP extension with the PIP free, and every removal for skin care must maintain the DIP position.

Bites and contaminated wounds require mechanism-specific care. Explore a clenched-fist wound with the MCP positioned as it was at impact because tendon and joint penetration may shift away when the hand opens. Obtain radiographs for fracture, tooth or other foreign body. Give guideline-based co-amoxiclav when appropriate, use a penicillin-allergy alternative from the current antimicrobial pathway and assess tetanus. Septic joint, flexor-sheath infection, deep-space collection and devitalised crush tissue require surgical source control; a longer antibiotic course cannot rescue retained contamination.

Hand therapy begins with the first splint. The prescription states wrist, MCP, PIP and DIP positions, permitted active or passive movement, frequency, load and duration. Excess protection causes adhesions and stiffness; excess early load ruptures repairs or displaces fracture. Children need safeguarding consideration when mechanism and developmental ability conflict. Older adults need thinner-skin and stiffness precautions. Pregnancy and renal impairment modify analgesics and antibiotics. At every review, measure sensation, tendon action, cascade and total active movement rather than describing the hand only as improving.

Key points

Remove rings before swelling progresses and record hand dominance, occupation, contamination, timing and exact finger position at injury.
Examine before local anaesthetic: resting posture, tenodesis, digital cascade, active flexion and extension, two-point sensation and capillary refill.
Test flexor digitorum profundus by holding the PIP extended and asking for DIP flexion; test superficialis while adjacent fingers are held extended.
Test extensor function at each joint against gentle resistance and use Elson testing when a central-slip injury is suspected.
Ask the patient to flex all fingers toward the scaphoid; scissoring identifies rotation and is not corrected by accepting greater angulation.
Obtain AP, oblique and lateral hand or finger radiographs and image for foreign body when mechanism indicates.
Stable extra-articular fractures without rotation often use buddy support or an intrinsic-plus splint with early movement and defined review.
Open, intra-articular, malrotated, unstable or multiple fractures and tendon, nerve or vessel injuries need early hand-surgery management.
Treat a fight bite as deep contamination: explore with the hand in the injury position, irrigate appropriately, give antibiotic prophylaxis and arrange surgical review.
A mallet injury usually needs uninterrupted DIP-extension splintage, while suspected jersey finger requires urgent flexor-tendon referral.
Rehabilitation instructions must name which joints move and which remain protected; generic rest creates stiffness or repair failure.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Axial or punching force

Impact through a clenched fist commonly fractures a metacarpal neck and can create a contaminated MCP wound from another person's teeth.

Crush or twist

Industrial, door or sporting trauma causes comminuted metacarpal or phalangeal fractures, nail-bed injury and rotational deformity.

Sharp laceration

Glass, knife or metal can divide flexor or extensor tendon, digital nerve and vessel through a deceptively small skin wound.

Sudden tendon avulsion

Forced extension of a flexed DIP can avulse flexor digitorum profundus, while forced flexion of an extended DIP causes mallet injury.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Digital cascade disruption
Rotational malalignment causes the injured finger to cross neighbours during flexion, impairing grip far more than equivalent isolated angulation.
2
Tendon imbalance
Loss of one flexor or extensor changes resting posture and joint control; partial laceration can preserve motion yet rupture or trigger later.
3
Pulley and sheath constraint
Flexor tendons glide within a tight fibro-osseous system, so injury, repair bulk or infection can cause adhesions and major motion loss.
4
Joint inoculation
A tooth wound over the MCP can enter the joint or extensor mechanism when the fist opens, trapping polymicrobial contamination deeply.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Metacarpal fracture

Dorsal swelling, focal tenderness, lost knuckle prominence and pain gripping follow impact or punching.

Rotational deformityRed flag

The injured finger overlaps or scissors beneath a neighbour when the patient flexes toward the scaphoid.

Flexor-tendon divisionRed flag

Abnormal resting extension, disrupted tenodesis and loss of isolated DIP or PIP flexion follows a palmar wound.

Extensor injuryRed flag

A dorsal laceration or drooping joint with inability to extend suggests tendon division, mallet or central-slip injury.

Fight biteRed flag

A small dorsal MCP wound after punching teeth may inoculate extensor tendon, joint and bone.

Digital neurovascular injuryRed flag

Two-point sensory loss, pale digit or delayed refill after laceration or crush requires urgent hand assessment.

Red flags requiring action

A clenched-fist wound over a metacarpophalangeal joint is a human bite with possible tendon and joint inoculation until proved otherwise.
A pale digit, absent capillary refill, severe crush or ring avulsion requires immediate revascularisation-level hand assessment.
Loss of isolated flexor or extensor function, digital sensory loss or a deep laceration near tendon and nerve requires early surgical exploration planning.
Finger malrotation, overlap or scissoring during flexion is functionally unacceptable even when angular deformity appears small.
Fusiform swelling, flexed posture, sheath tenderness and passive-extension pain suggests flexor-sheath infection, an emergency covered separately in infection care.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
AP, oblique and lateral hand or digit radiographsFirst step
Why
Define fracture, dislocation, joint involvement and radiopaque foreign body.
Interpretation and limitations
Use a true lateral for the injured digit and correlate apparent alignment with the clinical cascade.
02
Pre-anaesthetic tendon examination
Why
Identify complete or partial flexor and extensor injury and document baseline function.
Interpretation and limitations
Preserved gross flexion does not exclude one divided tendon; isolate FDP and FDS separately.
03
Digital sensory and vascular mapping
Why
Detect digital-nerve or artery injury before local anaesthetic and surgery.
Interpretation and limitations
Record each side of the digit and compare two-point discrimination, refill and temperature.
04
Ultrasound or operative exploration
Why
Clarify selected uncertain tendon continuity or deep foreign body.
Interpretation and limitations
Imaging must not delay urgent treatment of obvious open tendon, joint, bite or vascular injury.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Simple hand contusion

Pain and swelling without focal bone tenderness, malrotation, wound or tendon deficit may represent soft-tissue injury, but repeat examination is needed.

Sagittal-band rupture

Extensor tendon subluxation at the MCP after a punch can cause snapping and inability to initiate extension without a fracture.

Pulley injury

Climbing trauma with bowstringing, focal flexor tenderness and load-related pain can impair grip despite preserved flexor-tendon continuity.

Compartment or infection

Severe pain, tense swelling, systemic features or progressive passive-stretch pain requires urgent assessment beyond routine fracture care.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01Initial hand assessmentExamine before numbingFirst stepA fracture, wound or tendon injury is suspected.

1Remove rings, control bleeding and record cascade, tenodesis, isolated tendons, sensation and perfusion.
2Expose and photograph wounds, identify bite or contamination and obtain appropriate radiographs.
3Give analgesia, cover and splint in a safe functional position and refer according to structural injury.

02Stable fractureAlign and move protected jointsThe closed fracture is stable, extra-articular and has no rotation or tendon deficit.

1Use buddy support or an intrinsic-plus splint matched to location and check skin and rotation.
2Begin movement of unprotected joints early and provide elevation and analgesia.
3EscalationReview alignment and hand function and escalate scissoring, displacement or failure to progress.

03Open or tendon injuryPrevent infection and preserve glideA bite, deep wound, open fracture, tendon, nerve or vessel injury is present.

1Give contamination-appropriate antibiotic and tetanus care and avoid closing an inadequately assessed bite wound.
2Arrange timely hand-surgery exploration, irrigation, repair or fixation with anatomy clearly documented.
3Start the exact therapist-led protection and motion protocol and monitor wound, infection and repair function.

Key medicines and prescribing safety2 treatments · regimens, roles and cautions

Provides polymicrobial prophylaxis or treatment while clenched-fist wound and joint or tendon involvement are assessed.

Co-amoxiclav for an adult human bite

When not penicillin-allergic and the local bite pathway agrees, give co-amoxiclav 625 mg orally three times daily; prophylaxis is commonly 3 days and treatment 5 days, extended for deeper infection.

Check allergy, renal and hepatic function, pregnancy and severity. Deep joint, tendon, bone or systemic infection needs urgent surgery and often intravenous treatment; use a local alternative for penicillin allergy.

Supports splint tolerance and early protected movement.

Paracetamol for adult hand pain

Give 500 mg to 1 g orally when required, at least 4 hours apart and no more than four doses or 4 g in 24 hours.

Reduce the maximum for low body weight or hepatic risk and count combination products.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Stiffness and adhesions

Oedema, scar and prolonged immobilisation rapidly reduce tendon glide and joint motion, making early specialist hand therapy central.

Malrotation or malunion

Persistent digital overlap, shortening or articular incongruity impairs grip, causes painful callosity and may eventually require corrective hand surgery.

Deep infection

Bite, open fracture, joint penetration or retained foreign body can cause septic arthritis, tenosynovitis and osteomyelitis.

Tendon rupture

Missed partial laceration, inadequate protection or failed repair can cause delayed loss of flexion or extension.

Neuroma and sensory loss

Digital-nerve division can leave persistent numbness, painful neuroma and unsafe pinch or grip unless identified and managed at an early stage.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Recheck swelling, skin, digital refill and sensation after splintage and elevation.
Repeat clinical rotation and cascade as pain improves and after reduction.
Follow isolated tendon actions within the repair-specific therapy protocol.
Inspect bites and open wounds for increasing pain, drainage, spreading erythema and flexor-sheath signs.
Measure total active motion, grip and functional use and address stiffness early with hand therapy.
Review antibiotics for allergy, diarrhoea, renal adjustment and the definitive surgical source-control plan.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Rotation is a clinical diagnosis

Radiographs can look acceptable while the fingertip crosses its neighbour during flexion, producing major grip dysfunction.

Examine in injury position

A clenched-fist wound moves relative to tendon and joint when the hand opens and can conceal deep penetration.

One flexor can hide another

Gross finger flexion may persist through either FDS or FDP, so each tendon must be isolated.

Splinting is an active prescription

The angle, protected joints, permitted exercises and uninterrupted duration determine whether tissue heals or stiffens.

11Common pitfallsFrequent interpretation and management errors.

01
Giving local anaesthetic before documenting tendon, digital nerve and perfusion findings.
02
Accepting metacarpal angulation without checking rotational overlap during finger flexion.
03
Closing a dorsal MCP fight-bite wound without assessing joint and extensor contamination.
04
Calling preserved gross flexion proof that both flexor tendons are intact.
05
Immobilising every finger joint for a stable fracture and causing avoidable stiffness.
06
Providing generic movement advice after tendon repair instead of the exact hand-therapy protocol.