EM@3AM: Extensor Tendon Laceration

Answer: Extensor tendon laceration

Epidemiology:

• Hand extensor injuries make up >25% of orthopedic soft tissue injuries^{2, 3}
• Common in young men in manual labor
• Dominant hand more likely to be injured⁴
  • 2012 study on 86 patients reported 83% men with a mean age of 34.2 years and the dominant hand involved 60% of the time⁴
• Most common finger injuries are thumb (25.7%), index (24.8%), middle (23.8%) fingers, respectively^{4, 5, 6}

Anatomy:

• Tendons are more superficial on the dorsal hand and are therefore more commonly injured⁸
• Extensor retinaculum overlays the wrist, which can make tendon repair difficult⁹
• Primary muscles of hand extension
  • Primary wrist extensors: Extensor carpi radialis longus/brevis, extensor carpi ulnaris
  • Primary thumb extensors: Extensor pollicis longus/brevis, abductor pollicis longus
  • Primary finger extension: Extensor digiti minimi, extensor digitorum, extensor indicis

Classic injuries: 

Mallet finger

• Forced flexion of the DIP while extended
• May include bony avulsion fracture^{10, 11}

Clinical Presentation:

• Extensor injuries typically from more superficial lacerations to the dorsal surface of the hand
• Loss of strength with extension effected digit(s)
• Deeper lacerations may have neurovascular injury with loss of sensation or motor control

Evaluation:

• History should include mechanism, occupation, handedness, time of injury, tetanus status, prior injuries¹⁰
• Examine prior to anesthesia to obtain accurate sensorimotor function¹⁰
• Isolate each joint to test strength against resistance
• Test for neurovascular deficits with light touch/pinprick sensation, doppler
• Evaluate for bruising, wounds, deformities
• Adequate anesthesia should be used for wound exploration and decontamination
  • Utilize finger, radial, ulnar nerve blocks or local anesthesia
  • Evaluate wounds by reducing blood flow and irrigation; consider use of finger tourniquets¹⁰
  • Note wounds involving joint spaces or open fractures
• Painful nodule may be seen with tendon retraction
• X-ray should be used to identify fractures or retained foreign bodies
  • Ultrasound is effective for identifying hand fractures and foreign bodies¹²
• Ultrasound may be useful to evaluate for tendon disruption¹³
• Evaluate the zone of injury

Zones of injury 

• Tendon zones will help identify structures injured and guide further treatment

• More relevant as treatment may vary depending on zone
• I: DIP joint – injuries are typically closed injuries^{14, 15}
• II: Middle phalanx
• III: PIP joint
• IV: Proximal phalanx
• V: Metacarpophalangeal (MCP) joint
• VI: Dorsum of the hand
• VII: Wrist
• VIII: Distal forearm
• TI: Interphalangeal (IP) joint of thumb
• TII: Proximal phalanx of thumb
• TIII: MCP of the thumb
• TIV: Carpometacarpal (CMC) joint

Treatment: 

• Treatment depends on the zone of injury
• All tendon injuries, open or closed, should be referred to a hand specialist
  • In general, patients with simple extensor tendon injuries should be followed up outpatient by a hand specialist, if one is not available in the area, transfer to a higher level of care should be considered
• Most patients get a short course of antibiotics in open tendon injuries, but not required
  • Several prospective, randomized control trials show no statistical significance in wound infection with hand lacerations^16,17,18
  • Cephalexin 500mg for 5-7 days would be appropriate for open tendon injuries
  • Consider extensive contamination, open fractures, which would warrant orthopedic consultation
    • Type I: open fracture with <1cm clean laceration, minimal soft tissue damage
      • Cefazolin 2g IV three times daily in adults
        • 30mg/kg three times daily in children
    •  Type II: open fracture with 1-10 cm clean laceration without extensive injury
      • Same as Type I
    • Type III: open fracture >10cm with extensive soft tissue damage or heavily contaminated/farm injury
      • Cefazoline 2G IV Three times daily
      • Gentamicin 5-7 mg/kg IV once daily in adults; 2.5 mg/kg IV three times daily in pediatrics¹⁹

• Zone I and II: For closed injuries, place DIP in hyperextension and immobilize finger with a splint for 6-8 weeks²¹
  • Patient compliance with splint will determine success of treatment²²
  • Open injuries should be repaired with a roll stitch (see image 6)²³
    • 4-0 or 5-0 non absorbable suture used to involve both skin and tendon
• Zone III: Tendon should not be repaired in the ED
  • Repair requires hand specialist to prevent Boutonniere deformity^{23, 24}
  • If in a community setting, suture overlying skin, splint wrist in 30° extension, MCP in 15° flexion and PIP in neutral²⁴

• Zone IV: Tendons are larger and more amenable for repair in ED²³
  • Use modified Kessler/Bunnell technique with low tissue reactivity and high strength suture such as 4-0 ethibond or mersilene (see image 7)²⁵
    • https://www.youtube.com/watch?v=yGJ5JzcFJYQ
    • https://www.youtube.com/watch?v=paXHJl_Hccc
  • Splint similar to zone III injuries
• Zone V: Have a high suspicion for fight bite injuries^{14, 22}
  • If physician suspects above, extensively irrigate and do not close skin
  • Tendon repair similar to zone IV, splint wrist 45° extension, MCP 20° flexion²²
  • Patient will need antibiotics i.e. Augmentin if fight bite suspected²²
    • Amoxicillin/clavulanate 875 mg/125 mg by mouth twice daily in adults
      • 25 mg/kg by mouth twice daily in children
  • Patient should follow up within 24 hours
•  Zone VI: Tendons are large and superficial on the dorsum, making for an easier repair
  • Modified Kessler/Bunnell technique with 4-0 non-absorbable sutures similar to above¹
  • Splint wrist in 30° of extension, MCP neutral with digits free
•  Zone VII and VIII: Beyond scope of ED repair
  • Junctions with muscle bodies become involved²⁴
  • Close overlying skin, place in volar splint, ortho consultation vs urgent referral
  • Consider consulting orthopedics or transfer to a center with hand specialist if extensor tendon injury is more proximal to wrist, as this eventually requires surgical repair
•  Ensure the patient is up to date with their tetanus vaccination
  • Past vaccination unknown or <3 total
    • Wound is clean: Td
    • Wound is dirty: Td + tetanus immunoglobulin
  • At least 3 prior Td vaccinations
    • Wound is clean: Td if last vaccine >10 years ago
    • Wound is dirty: Td if last vaccine >5 years ago²⁶

Disposition: 

• If there is no extensive injury to soft tissue, patients can be discharged
  • Ensure urgent follow-up with orthopedics if there is suspected flexor/extensor damage²⁷
  • Concern for open fractures/joints should prompt orthopedics consultation
  • Depending on extent of injury/local practice, orthopedics may need ED consultation

Pearls: 

• Complete a thorough physical exam, noting neurovascular status as well as isolated joint mobility and strength
• Extensor injuries should be repaired based on location of injury zone
• Use non-absorbable 4-0 suture with modified Kessler or Burnell technique when repairing extensor tendons
• Patients generally have tendon repair, splinting, and outpatient hand specialist follow-up, but consider hand consultation if damage is extensive or consider transferring if no hand specialist for follow up