Hand and finger injuries
Check rotation, every tendon and every digital nerve. A cut over a knuckle after a punch is a human bite into the joint.
A 22-year-old punched someone in a fight last night. The knuckle of his little finger is swollen. There's a 5 mm cut over the knuckle of his ring finger "from the other guy's tooth". When he makes a loose fist, his little finger overlaps the ring finger.
What two problems must you not miss, and who does he need to see today?
- Wound over a knuckle after a punchFight bite: antibiotics, hand surgeons for washout.
- RotationLoose fist: all fingertips should point to the scaphoid. Overlapping means malrotation.
- Test each tendon separatelyFDP, FDS, extensors, FPL.
- Test digital nervesSensation on both sides of each finger, before any local anaesthetic.
- X-rayTwo views of the hand or finger if bony tenderness.
- Remove rings and elevateBefore swelling.
- Splint in the safe positionKnuckles bent about 70–90°, fingers straight.
- Hand clinic or surgeonsMost within a week, some the same day.
- Fight bite or bite near a joint
- Malrotation
- Tendon or nerve injury
- Flexor sheath infection (Kanavel signs)
- High-pressure injection injury
- Amputation or devascularised finger
- Nail bed injury with fracture
- Fight bite joint infection
- Rotational deformity
- Flexor tendon cut
- Digital nerve injury
- Scaphoid fracture
- High-pressure injection injury
- Volar plate injury
| Fight bite | Co-amoxiclav 625 mg 3 times daily (or 1.2 g IV if infected), and surgical exploration |
| Boxer's fracture (5th metacarpal neck) | Angulation up to about 70° often accepted if no rotation |
| Malrotation | Needs reduction or fixation |
| Mallet finger | Splint the fingertip straight continuously for 6–8 weeks |
| Subungual haematoma | Trephine if painful |
| Ring block | Lidocaine 1% plain, 2–3 mL each side of the finger base |
Check every dose against a current drug reference and your hospital protocol.
On this page
History
- Mechanism: punch (boxer's fracture, fight bite), crush (tuft fracture, nail bed), ball on the fingertip (mallet), hyperextension (volar plate), cut (tendons, nerves), high-pressure gun (injection injury).
- Dominant hand, job (a surgeon, tailor and labourer have different needs).
- Time since injury, tetanus status.
- Numbness or weakness.
Examination
- LookSwelling, wounds, deformity, posture (a cut flexor tendon leaves the finger straighter than the others).
- RotationLoose fist: fingertips point to the scaphoid, no overlap.
- TendonsTest each one separately.
- NervesSensation on both sides of each finger (two-point discrimination), median, ulnar and radial territories.
- CirculationCapillary refill, colour, warmth of each finger.
Testing tendons
| Tendon | How to test |
|---|---|
| FDP | Hold the middle phalanx straight; ask to bend the fingertip |
| FDS | Hold the other fingers straight; ask to bend the finger at the middle joint |
| Extensors | Straighten each finger against resistance |
| FPL | Bend the tip of the thumb |
| Central slip | Straighten the middle joint against resistance |
Common injuries
- Boxer's fracture
- Check rotation
- Buddy strap or splint
- Fight bite
- Antibiotics, washout
- Mallet finger
- Splint 6–8 weeks
- Subungual haematoma
- Trephine if large and painful
- Volar plate injury
- Buddy strap, early movement
| Injury | Clues | Management |
|---|---|---|
| Boxer's fracture | Punch, swollen little finger knuckle | Buddy strap or splint, early movement; reduce if rotated or very angulated |
| Fight bite | Cut over the knuckle after a punch | Antibiotics, hand surgery for washout |
| Mallet finger | Ball hit the fingertip, drooping tip | Mallet splint 6–8 weeks continuously |
| Volar plate injury | Hyperextension, swollen middle joint | Buddy strap, early movement |
| Tendon laceration | Cut with loss of active movement | Hand surgery |
| Digital nerve injury | Numbness on one side of a finger | Hand surgery |
| Subungual haematoma | Crush, painful blood under the nail | Trephine if painful |
| Nail bed laceration with tuft fracture | Crush, nail lifted | Open fracture: antibiotics, repair |
| Thumb ulnar collateral ligament ("skier's thumb") | Fall with thumb pulled outwards | Splint, hand clinic |
A small wound over a knuckle after a punch is a human bite into the joint until proven otherwise. Teeth carry bacteria into the joint and tendon sheath, which can be destroyed within days. Never close it.
High-pressure injection injury
Paint, grease or diesel injected through a tiny wound by a high-pressure gun. It looks minor but causes massive tissue damage and can lead to amputation. Urgent hand surgery for exploration.
Treatment doses
Common mistakes
- Closing a fight bite.
- Not checking rotation in a metacarpal fracture.
- Giving a ring block before testing sensation.
- Missing a cut flexor tendon because the patient can "move the finger" using the other tendon.
- Letting a mallet finger bend once during splinting (restarts the 6–8 weeks).
- Treating a high-pressure injection injury as a small cut.
Frequently asked questions
What is a fight bite?
A cut over a knuckle from someone's teeth during a punch. It often enters the joint and becomes infected, so it needs antibiotics and surgical washout.
How is mallet finger treated?
A splint keeping the fingertip straight continuously for 6–8 weeks. If the tip bends even once, the clock restarts.
How do you check for rotation in a finger fracture?
Ask the patient to make a loose fist. All fingertips should point towards the scaphoid without overlapping. Scissoring means malrotation.
How is a boxer's fracture treated?
Most heal with buddy strapping or a splint and early movement. Rotation or severe angulation needs reduction or surgery.
Test yourself
Exam-style questions on this guide, from our two question banks. Choose an answer to see why each option is right or wrong.
1. A man has a small cut over the ring finger knuckle after punching someone in the mouth. What is the best management?
Answer: Antibiotics and washout. Fight bites need co-amoxiclav and washout because the joint and tendon are often involved.
- Topical antiseptic only: Not enough.
- Sutures: Never close a fight bite.
- Review in 2 weeks: Infection spreads fast.
- Steri-strips and home: Fight bites often enter the joint.
2. How is the FDP tendon tested?
Answer: Hold the middle phalanx and ask to bend the fingertip. Isolated DIP flexion tests flexor digitorum profundus.
- Straighten the finger against resistance: Tests extensors.
- Abduct the fingers: Interossei.
- Make an OK sign: Anterior interosseous.
- Hold other fingers straight and bend the finger: Tests FDS.
3. After a ball hit his fingertip, a man cannot straighten the tip of the finger. What is the treatment?
Answer: Extension splint. Mallet finger: continuous extension splint for 6–8 weeks.
- No treatment: Deformity persists.
- Immediate surgery for all: Most heal with splinting.
- Buddy strap for 1 week: Not enough.
- Steroid injection: No.
4. A cricketer was struck on the tip of the extended finger by the ball; he cannot actively extend the distal interphalangeal joint, which droops. X-ray shows no fracture. What is the treatment?
Answer: DIP extension splint 6–8 weeks. Mallet finger: disruption of terminal extensor tendon at the distal phalanx (± bony avulsion) from forced flexion of an extended DIP — drooping fingertip. Management: continuous extension splinting of the DIP (not PIP) for 6–8 weeks (any flexion restarts the clock), then night splint; surgery for large bony fragments with joint subluxation. Untreated → swan-neck deformity. Boutonnière: central slip rupture (PIP flexion, DIP hyperextension) — splint PIP in extension.
- Immediate surgical repair: Splinting comes first.
- Buddy strapping for one week: One week of buddy strapping is too short.
- Early active flexion exercises: Early flexion disrupts healing.
5. After a supracondylar fracture of the humerus, a child cannot flex the index finger when making a fist (pointing index, 'hand of benediction') and the thenar muscles are weak. Which nerve is injured?
Answer: Median nerve at the elbow. A median nerve injury at the elbow paralyses the forearm flexors it supplies (FDS, lateral FDP, FPL) and thenar muscles. On making a fist, the index (and middle) finger stays straight. Injury at the wrist (carpal tunnel) spares forearm flexors, causing only thenar weakness and sensory loss. Supracondylar fractures also risk the brachial artery (Volkmann's contracture).
- Ulnar nerve at the elbow: Clawing of ring and little fingers.
- Radial nerve in the spiral groove: Wrist drop.
- Median nerve at the wrist only: Spares the long finger flexors.
- Musculocutaneous nerve: Weak elbow flexion.
6. A woman with carpal tunnel syndrome has numbness of the thumb, index and middle fingers, but sensation over the thenar eminence is normal. Why?
Answer: Palmar branch passes above it. The carpal tunnel, bounded by the carpal bones and flexor retinaculum, contains the median nerve and nine tendons (four FDS, four FDP, FPL). Compression causes paraesthesia in the lateral three and a half digits (worse at night), wasting of the thenar eminence and weakness of abductor pollicis brevis and opponens. The palmar cutaneous branch arises about 5 cm above the wrist and passes over the retinaculum, so palm sensation is spared—helping to distinguish carpal tunnel syndrome from a more proximal median nerve lesion. Tests: Tinel's, Phalen's; nerve conduction studies.
- Thenar skin is ulnar-supplied: The ulnar nerve supplies the medial side.
- Thenar skin is radial-supplied: Radial nerve supplies the dorsal thumb base and snuffbox skin.
- No median fibres in the tunnel: The median nerve passes through it.
- Thenar skin has no supply: It has a sensory supply.
References and dose sources
- NICE NG38 — Fractures (non-complex)
- BSSH — hand injury guidance
- Co-amoxiclav (amoxicillin with clavulanic acid) dosing: Drugs.com: Amoxicillin/clavulanate dosage (see also our co-amoxiclav (amoxicillin with clavulanic acid) dose page)
- Lidocaine (lignocaine) dosing: Drugs.com: Lidocaine dosage (see also our lidocaine (lignocaine) dose page)
- Ibuprofen dosing: Drugs.com: Ibuprofen dosage (see also our ibuprofen dose page)
- Tetanus toxoid and immunoglobulin dosing: Drugs.com: Tetanus toxoid dosage (see also our tetanus toxoid and immunoglobulin dose page)
International guidance is linked where it reflects good practice. Where your hospital’s protocol differs, follow your hospital.