The Daily Differential — Thursday, May 14, 2026

2 of 4

Tendon Lacerations of the Hand

Missed tendon injuries can cause permanent loss of hand function and are a common source of medicolegal risk. The ED priority is meticulous functional...

At the Bedside

History
Mechanism: knife, glass, saw, crush, bite, high-pressure injection.
Timing, contamination, foreign body risk.
Occupation/hand dominance.
Numbness, weakness, inability to flex/extend.
Exam principles
Examine before anesthesia if possible.
Document:
Active range of motion against resistance.
Two-point discrimination or light touch in digital nerve distributions.
Capillary refill and pulse oximetry waveform if concern for vascular injury.
Wound location relative to tendon zones.
Examine through full ROM because tendon ends may retract and laceration may not align with skin wound.
Flexor tendon testing
FDP: hold PIP extended, ask patient to flex DIP.
FDS: hold adjacent fingers extended, ask patient to flex PIP of injured finger.
Loss of flexion suggests tendon disruption.
Flexor injuries are especially high risk because of tendon sheath anatomy and need for precise repair.
Extensor tendon testing
Test extension at DIP, PIP, MCP against resistance.
Partial extensor lacerations may still extend due to juncturae tendinum, so compare strength and isolate joints.
Central slip injury: inability/weakness extending PIP; may evolve into boutonnière deformity.
Key injury patterns
Mallet finger: terminal extensor tendon injury at DIP; DIP held flexed.
Central slip injury: PIP extension weakness; risk boutonnière.
Jersey finger: FDP avulsion; inability to flex DIP, often ring finger.
Fight bite: MCP laceration after punching teeth; treat as contaminated joint/tendon injury until proven otherwise.
Imaging
Plain radiographs for:
Glass/metal foreign body.
Fracture.
Joint violation.
Bite wounds.
Ultrasound can help identify tendon discontinuity or foreign body if exam limited, but operator dependent.
ED wound management
Irrigate copiously.
Remove visible foreign material.
Avoid blind deep probing around neurovascular structures.
Skin closure may be appropriate after irrigation for clean wounds, but do not attempt definitive flexor tendon repair in typical ED practice.
Partial extensor tendon lacerations may sometimes be repaired in ED depending location, degree, clinician skill, and hand surgery guidance; when uncertain, splint and consult.
Consult hand surgery urgently for
Suspected flexor tendon laceration.
Tendon injury with neurovascular deficit.
Open fracture, joint violation, fight bite, gross contamination.
Complex laceration, crush injury, amputation, compartment concern.
Inability to ensure close follow-up.
Splinting
Suspected flexor tendon injury: dorsal blocking splint, wrist flexed ~20–30°, MCP flexed ~60–70°, IP joints slightly flexed; confirm with consultant/local protocol.
Extensor tendon injury: splint involved joint(s) in extension.
Mallet finger: DIP in full extension/slight hyperextension continuously.
Central slip: PIP in extension, DIP free.
Disposition
Clean, isolated tendon concern with intact neurovascular status: splint, antibiotics if indicated, urgent hand follow-up typically within 24–72 hours.
Immediate consult/admission/OR for fight bites, open joints, vascular compromise, complex injuries, or contaminated tendon sheath injuries.

A Classic Presentation

A 35-year-old chef cuts the volar aspect of his index finger with a kitchen knife. Before anesthesia, he can flex the PIP but cannot flex the DIP when the PIP is held extended. Sensation and cap refill are intact. X-ray shows no fracture or foreign body. The wound is irrigated, skin loosely approximated, tetanus updated, antibiotics considered based on depth/contamination, the hand is placed in a dorsal blocking splint, and hand surgery follow-up is arranged urgently for FDP laceration.

Study Directive

Draw the FDS/FDP anatomy and practice isolated testing on your own hand.
Memorize splint positions: dorsal blocking for flexor injuries, extension splinting for extensor injuries.
Review hand tendon zones and identify which zones mandate urgent hand surgery involvement.
Watch one procedural video on high-volume hand irrigation and safe wound exploration.

Key Medications

Local anesthesia
- Lidocaine 1% without epinephrine: local infiltration; max 4.5 mg/kg, commonly cited max 300 mg.
- Lidocaine 1% with epinephrine: max 7 mg/kg, commonly cited max 500 mg; avoid in ischemic/crush-compromised digits.
- Bupivacaine 0.25–0.5%: max ~2–2.5 mg/kg without epinephrine; check reference for institutional limits.
Antibiotics
- Clean simple hand laceration: antibiotics often not required.
- Contaminated wound/open tendon injury: cephalexin 500 mg PO QID for 3–5 days is common.
- Human bite/fight bite: amoxicillin-clavulanate 875/125 mg PO BID for 3–5 days; if severe, ampicillin-sulbactam 3 g IV every 6 hours.
- Penicillin allergy regimens vary; check local protocol. Common adult option: doxycycline plus metronidazole, or TMP-SMX plus clindamycin depending coverage needs.
Pain control
- Acetaminophen 650–1,000 mg PO every 6 hours PRN.
- Ibuprofen 400–600 mg PO every 6 hours PRN if no contraindication.
- Severe acute pain: oxycodone 5 mg PO every 4–6 hours PRN, short course if appropriate.
Tetanus
- Tdap/Td booster and tetanus immune globulin based on immunization status and wound contamination.

High-Yield Pearls

Always document tendon, nerve, and vascular function before anesthetic injection.
Flexor tendon lacerations generally require hand surgery repair; do not rely on skin closure as definitive care.
A fight bite over the MCP is an open joint/tendon sheath infection risk until proven otherwise.

Board Question

A patient has a volar laceration to the distal finger. You hold the patient’s PIP joint in extension and ask him to flex the fingertip, but he cannot flex the DIP. Which structure is most likely injured?

AFlexor digitorum superficialis
BFlexor digitorum profundus
CCentral slip of extensor tendon
DTerminal extensor tendon

Reveal answer

Correct: B

The FDP is isolated by holding the PIP extended and testing DIP flexion. FDS is tested by holding adjacent fingers extended and asking for PIP flexion.

Recent Literature

Review or guideline The management of partial extensor tendon lacerations of the hand and forearm: A systematic review
J Plast Reconstr Aesthet Surg, 2023 · cited 4×
Recent clinical The Utility of Plain Radiography in Flexor Tendon and Digital Nerve Lacerations of the Hand
J Hand Surg Glob Online, 2025

Full text · open access

3 of 4

Thumb Fractures

Thumb fractures can significantly impair pinch, grip, and hand function. The ED must identify unstable intra-articular base fractures, rotational deformity,...

At the Bedside

History
Mechanism:
Axial load to thumb: metacarpal base injuries.
Fall, sports injury, punching/crush.
Hyperabduction may also suggest UCL injury, sometimes with avulsion fracture.
Hand dominance, occupation, prior thumb injury.
Exam
Inspect for swelling, deformity, open wound, subungual hematoma.
Palpate:
Distal/proximal phalanges.
MCP joint.
First metacarpal shaft/base.
Anatomic snuffbox if wrist pain.
Assess:
Active flexion/extension at IP and MCP.
Opposition and abduction.
Pinch strength if tolerated.
Neurovascular status.
Check for rotational deformity: thumb alignment during flexion/opposition.
If MCP ulnar collateral ligament concern: valgus stress testing may be deferred or done after X-ray/anesthesia; instability suggests complete tear.
Imaging
Thumb radiographs: AP, lateral, oblique.
Consider dedicated hand/wrist views if mechanism suggests associated injury.
CT if intra-articular comminution, surgical planning, or unclear X-ray.
Important fracture patterns
Bennett fracture: intra-articular fracture-dislocation at base of first metacarpal; small volar-ulnar fragment remains attached via ligament while metacarpal shaft subluxes due to muscle pull. Usually unstable.
Rolando fracture: comminuted intra-articular fracture at base of first metacarpal, often Y- or T-shaped; unstable, worse prognosis.
Extra-articular first metacarpal base fracture: may be managed nonoperatively if acceptable alignment; consult/follow-up depending angulation/displacement.
Thumb metacarpal shaft fracture: assess angulation/rotation; thumb tolerates some angulation but not rotational deformity.
Phalanx fractures: splint if nondisplaced; consult for open, intra-articular, displaced, unstable, tendon involvement.
UCL avulsion fracture: may require surgery if displaced, unstable, or Stener lesion suspected.
ED management
Analgesia, ice, elevation.
Remove rings.
Irrigate open wounds; antibiotics/tetanus as indicated.
Reduce obvious dislocations or markedly displaced fractures when appropriate and after imaging unless neurovascular compromise requires immediate action.
Immobilize most thumb fractures in a thumb spica splint.
Post-reduction X-rays if reduction performed.
Consult hand surgery urgently for
Bennett or Rolando fracture.
Open fracture.
Neurovascular compromise.
Irreducible or unstable fracture-dislocation.
Rotational deformity.
Significantly displaced intra-articular fracture.
Associated tendon injury.
Suspected complete UCL tear/Stener lesion.
Disposition
Stable, closed, nondisplaced fracture: thumb spica, analgesia, hand/ortho follow-up within about 1 week.
Unstable intra-articular base fractures: ED hand consultation or very urgent follow-up depending local practice and reduction status.
Open/vascularly compromised/complex injuries: consult immediately, likely operative management.

A Classic Presentation

A 22-year-old skier falls onto an abducted thumb and presents with swelling and pain at the thumb base. X-ray shows an intra-articular fracture at the base of the first metacarpal with subluxation of the metacarpal shaft, consistent with a Bennett fracture. He is neurovascularly intact. The ED provides analgesia, places a thumb spica splint, consults hand surgery due to instability, and arranges urgent operative management/follow-up.

Study Directive

Compare X-rays of Bennett vs Rolando vs extra-articular first metacarpal base fractures.
Practice applying and checking a thumb spica splint, including neurovascular reassessment.
Memorize urgent consult criteria: open, neurovascular, rotational, intra-articular displaced, Bennett/Rolando.
Review valgus stress testing of the thumb MCP and the concept of a Stener lesion.

Key Medications

Analgesia
- Acetaminophen 650–1,000 mg PO every 6 hours PRN.
- Ibuprofen 400–600 mg PO every 6 hours PRN.
- Ketorolac 15 mg IV/IM once; some use 30 mg IV/IM in selected adults, but lower dosing often has similar analgesia with less toxicity.
- Oxycodone 5 mg PO every 4–6 hours PRN severe pain, short course.
Local anesthesia / reduction
- Hematoma block or digital block with lidocaine 1% without epinephrine; typical total 5–10 mL depending site.
- Max lidocaine without epinephrine: 4.5 mg/kg, commonly max 300 mg.
Open fracture antibiotics
- Cefazolin 2 g IV once, then per protocol; 3 g IV if ≥120 kg is commonly used.
- Add broader coverage for farm/soil, water exposure, or severe contamination per institutional protocol.
- Check local open fracture antibiotic pathway if uncertain.
Tetanus
- Tdap/Td ± tetanus immune globulin based on wound and immunization status.

High-Yield Pearls

Bennett and Rolando fractures are unstable intra-articular thumb base fractures: think hand surgery.
Thumb spica is the default ED splint for most thumb metacarpal and many phalanx fractures.
Do not miss associated UCL injury; avulsion fracture plus MCP instability may need operative repair.

Board Question

A patient has an intra-articular fracture at the base of the first metacarpal with a small volar-ulnar fragment and proximal/radial subluxation of the metacarpal shaft. What is the diagnosis?

ABoxer’s fracture
BBennett fracture
CRolando fracture
DGamekeeper’s thumb

Reveal answer

Correct: B

A Bennett fracture is a two-part intra-articular fracture-dislocation of the first metacarpal base. A Rolando fracture is a comminuted, often Y- or T-shaped intra-articular base fracture.

Recent Literature

Review or guideline Braces and Splints for Common Musculoskeletal Conditions
Am Fam Physician, 2018 · cited 25×
Recent clinical A Case Report on an Open Fracture Dislocation Injury of the Proximal Phalanx of the Thumb Resulting from Playing Cricket
J Educ Teach Emerg Med, 2026

Full text · open access

4 of 4

Triceps Tendon Rupture

Triceps tendon rupture is uncommon but frequently missed, especially when patients retain weak elbow extension through intact lateral expansions or gravity...

At the Bedside

History
Mechanisms:
Fall on outstretched hand with eccentric triceps contraction.
Direct blow to posterior elbow.
Weightlifting, especially bench press.
Risk factors:
Anabolic steroid use.
Chronic kidney disease/secondary hyperparathyroidism.
Fluoroquinolone use.
Local steroid injection.
Olecranon bursitis history.
Exam
Posterior elbow pain, swelling, ecchymosis.
Palpable gap proximal to olecranon may be present.
Weakness with resisted elbow extension.
In complete rupture: inability to actively extend elbow against gravity may occur, but some patients can still extend weakly.
Test in multiple positions:
Elbow flexed to 90°, ask for resisted extension.
Compare side-to-side strength.
Evaluate distal neurovascular status and associated fracture/dislocation.
Modified Thompson/squeeze test
Patient prone with elbow flexed over edge.
Squeeze triceps muscle belly.
Lack of passive elbow extension suggests rupture.
Less commonly used than Achilles Thompson test but can be helpful.
Imaging
X-ray elbow AP/lateral:
Look for olecranon avulsion fragment, “flake sign.”
Evaluate fracture/dislocation.
Ultrasound:
Can show tendon discontinuity, retraction, hematoma.
Useful in ED if skilled operator.
MRI:
Best for defining partial vs complete tear and operative planning; usually outpatient/consult-directed unless uncertain diagnosis with high stakes.
ED management
Analgesia, ice, elevation.
Immobilize in posterior long-arm splint.
Position often around 30–45° elbow flexion for suspected complete rupture; exact angle may vary by consultant preference.
Avoid forceful ranging.
Orthopedic consultation:
Urgent for complete rupture, large avulsion, high-demand patient, or diagnostic uncertainty.
Partial tears with preserved strength may be outpatient ortho follow-up but still need timely evaluation.
Definitive therapy
Complete rupture: usually surgical repair, ideally early.
Partial rupture:
Nonoperative if small tear and preserved extension strength.
Operative if large partial tear, significant weakness, or high-demand athlete/laborer.
Disposition
Discharge with splint/sling and urgent ortho follow-up if neurovascularly intact and pain controlled.
Admit/urgent operative planning if associated fracture-dislocation, open injury, compartment concern, or consultant recommendation.

A Classic Presentation

A 41-year-old weightlifter feels a sudden pop in the back of his elbow during bench press. He has posterior elbow swelling, a palpable defect just proximal to the olecranon, and marked weakness with resisted extension. X-ray shows a small avulsion fragment from the olecranon, the “flake sign.” The ED places him in a posterior long-arm splint, provides analgesia, and arranges urgent orthopedic evaluation for likely operative triceps tendon repair.

Study Directive

Practice resisted elbow extension testing and compare positioning at 90° flexion versus gravity-assisted extension.
Review elbow X-rays for olecranon avulsion fragments and associated dislocation/fracture.
Learn basic MSK ultrasound appearance of tendon discontinuity and retraction.
Make a disposition checklist: splint angle, neurovascular documentation, ortho timing, activity restrictions.

Mechanism Pearl of the Day: Today’s injuries are all about closed-space anatomy plus force transmission: blood trapped under the nail creates pressure pain; hand tendon lacerations disrupt force transfer through narrow tendon sheaths; thumb base fractures become unstable because muscle and ligament forces pull the metacarpal out of alignment; triceps rupture eliminates the terminal force generator for elbow extension.

Key Medications

Analgesia
- Acetaminophen 650–1,000 mg PO every 6 hours PRN.
- Ibuprofen 400–600 mg PO every 6 hours PRN if no renal/GI/bleeding contraindication.
- Naproxen 500 mg PO once, then 250–500 mg PO BID PRN.
- Oxycodone 5 mg PO every 4–6 hours PRN severe pain, short course.
Procedural/local anesthesia
- Usually not required unless wound care/reduction of associated injury.
Antibiotics
- Not indicated for closed tendon rupture.
- If open injury: cefazolin 2 g IV, 3 g if ≥120 kg; broaden per contamination and institutional open-fracture/open-joint protocol.
Pediatrics
- True triceps rupture is rare; consider avulsion fracture/physeal injury. Use weight-based analgesics and obtain orthopedic guidance.

High-Yield Pearls

Preserved weak elbow extension does not exclude triceps rupture because accessory expansions may remain intact.
The “flake sign” on elbow X-ray should trigger concern for distal triceps avulsion.
Complete triceps rupture is usually operative; early recognition improves functional outcome.

Board Question

Which radiographic finding is classically associated with distal triceps tendon rupture?

APosterior fat pad sign
BSail sign
COlecranon avulsion “flake sign”
DAnterior humeral line displacement

Reveal answer

Correct: C

Triceps tendon rupture may avulse a small bony fragment from the olecranon, producing the flake sign on lateral elbow radiograph. Posterior fat pad and sail signs suggest elbow effusion/fracture, especially radial head or pediatric supracondylar injury.

Recent Literature

Review or guideline Triceps Tendon Repair
J Hand Surg Am, 2015 · cited 28×
Recent clinical Diagnostic Musculoskeletal Ultrasound in the Evaluation of the Triceps Tendon
Int J Sports Phys Ther, 2025 · cited 2×

Full text · open access

TheDaily Differential

Subungual Hematoma Evacuation

At the Bedside

Study Directive

Recent Literature

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Tendon Lacerations of the Hand

Thumb Fractures

Triceps Tendon Rupture

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