Updated: 11/20/2022

Extensor Tendon Injuries

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  • summary
    • Extensor Tendon Injuries are traumatic injuries to the extensor tendons that can be caused by laceration, trauma, or overuse.
    • Diagnosis is made clinically by physical examination and performing various provocative tests depending on the location of the injury.
    • Treatment can be nonoperative or operative depending on the zone of injury. 
  • Epidemiology
    • Anatomic location
      • most commonly injured digit is the long finger
      • zone VI is the most frequently injured zone
  • Etiology
    • Mechanism
      • Zone I
        • forced flexion of extended DIP joint
      • Zone II
        • dorsal laceration or crush injury
      • Zone V
        • commonly from "fight bite"
        • sagittal band rupture ("flea flicker injury")
          • forced extension of flexed digit
          • most common in long finger
  • Classification
      • Zones of Extensor Tendon Injuries
      • Zone I
      • Disruption of terminal extensor tendon distal to or at the DIP joint of the fingers and IP joint of the thumb (EPL)
      •  Mallet Finger 
      • Zone II
      • Disruption of tendon over middle phalanx or proximal phalanx of thumb (EPL)
      • Zone III
      • Disruption over the PIP joint of digit (central slip) or MCP joint of thumb (EPL and EPB
      •  Boutonniere deformity
      • Zone IV
      • Disruption over the proximal phalanx of digit or metacarpal of thumb (EPL and EPB)
      • Zone V
      • Disruption over MCP joint of digit or CMC joint of thumb (EPL and EPB)
      • "Fight bite" common
      •  Sagittal band rupture 
      • Zone VI
      • Disruption over the metacarpal
      • Nerve and vessel injury likely
      • Zone VII
      • Disruption at the wrist joint
      • Must repair retinaculum to prevent bowstringing
      • Tendon repair followed by immobilization with wrist in 40° extension and MCP joint in 20° flexion for 3-4 weeks
      • Zone VIII
      • Disruption at the distal forearm
      • Extensor muscle belly
      • Usually from penetrating trauma
      • Often have associated neurologic injury
      • Tendon repair followed by immobilization with elbow in flexion and wrist in extension
  • Presentation
    • Zone I
      • Inability to extend at the DIP joint
    • Zone III
      • Elson test
        • flex the patient's PIP joint over a table 90 degrees and ask them to extend against resistance
        • if central slip is intact, DIP will remain supple
        • if central slip disrupted, DIP will be rigid
    • Zone V
      • extensor lag and flexion loss common
      • junctura tendinae may allow partial/temporary extension by connecting with intact adjacent extensor tendons
      • sagittal band rupture
        • rupture of stronger radial fibers of sagittal band may lead to extensor tendon subluxation
        • finger held in flexed position at MCP joint with no active extension
  • Imaging
    • Radiographs
      • AP and lateral of digit to verify no bony avulsion (boney mallet)
  • Treatment
    • Nonoperative
      • immobilization with early protected motion
        • indications
          • lacerations < 50% of tendon in all zones if patient can extend digit against resistance
      • DIP extension splinting
        • indications
          • acute (<12 weeks) Zone 1 injury (mallet finger)
          • nondisplaced bony mallet
          • chronic mallet finger (>12 weeks) if joint supple, congruent
        • techniques
          • full-time splinting for six weeks
          • part-time splinting for four to six weeks
          • avoid hyperextension, which may cause skin necrosis
          • maintain PIP motion
        • outcomes
          • noncompliance is a common problem
      • PIP extension splinting
        • indications
          • closed central slip injury (zone III)
        • techniques
          • full-time splinting for six weeks
          • part-time splinting for four to six weeks
          • maintain DIP flexion
      • MCP extension splinting
        • indications
          • closed zone V sagittal band rupture
        • techniques
          • full-time splinting for four to six weeks
    • Operative
      • immediate I&D
        • indications
          • fight bite to MCP joint
        • techniques
          • close loosely or in delayed fashion
          • treat with culture-specific antibiotics, although Eikenella corrodens is a common mouth organism
      • tendon repair
        • indications
          • laceration > 50% of tendon width in all zones
      • fixation of bony avulsion
        • indications
          • boney mallet finger with P3 volar subluxation
        • techniques
          • closed reduction and percutaneous pinning through DIP joint
          • extension block pinning
          • ORIF if it involves >50% of the articular surface
      • tendon reconstruction
        • indications
          • chronic tendon injury or when repair not possible
      • central slip reconstruction
        • techniques
          • tendon graft
          • extensor turndown
          • lateral band mobilization
          • transverse retinacular ligament
          • FDS slip
      • EIP to EPL tendon transfer
        • indications
          • chronic EPL rupture
  • Techniques
    • Tendon Repair
      • incision technique
        • utilize laceration, when present, and extend incision as needed to gain appropriate exposure
        • longitudinal incision may be utilized across joints on the dorsum of digits, unlike the palmar side
      • suture technique
        • # of suture strands that cross the repair site is more important than the number of grasping loops
        • in general strength increases with increasing number of sutures crossing the repair site, thickness of the suture, and locking of the stitch
        • 4-6 strands provide adequate strength for early active motion
      • circumferential epitendinous suture
        • Optional for reinforcement
      • repair failure
        • tendon repairs are weakest between postoperative day 6 and 12
        • repair usually fails at knots
    • Tendon Reconstruction
      • usually done as two stage procedure
        • first a silicon tendon implant is placed to create a favorable tendon bed
        • wait 3-4 months and then place biologic tendon graft
      • available grafts include
        • palmaris longus (absent in 15% of population)
          • most common
        • plantaris (absent in 19%)
          • indicated if longer graft is needed
        • long toe extensor
    • Tenolysis
      • indications
        • adhesion formation with loss of finger flexion
        • wait for soft tissue stabilization (> 3 months) and full passive motion of all joints
      • postoperative
      • follow with extensive therapy
  • Rehabilitation
    • Early active short-arc motion (SAM)
      • indications
        • after zone III central slip repair
      • advantages over static immobilization
        • increases total arc of motion
        • decrease duration of therapy
        • increase DIP motion
        • creates 4mm of tendon excursion and prevents adhesions.
    • Relative motion splint (yoke splint)
      • positions the involved MCP joint in hyperextension relative to adjacent digits
      • Indications
        • after zone 4-7 extensor tendon repair
      • advantages over static immobilization and dynamic splinting
        • increased early active range of motion
        • decreases strain on tendon and prevents adhesions
        • easy for patient compliance
        • earlier return to work
  • Complications
    • Adhesion formation
      • leads to loss of finger flexion
      • common in zone IV and VII and older patients
      • prevented with early protected ROM and dynamic splinting (zone IV)
      • treatment
        • extensor tenolysis with early motion indicated after failure of nonoperative management, usually 3-6 months
        • tenolysis contraindicated if done in conjunction with other procedures that require joint immobilization
    • Tendon rupture
      • causes include poor suture material or surgical technique, aggressive therapy, and noncompliance
      • incidence
        • 5%
        • most frequently during first 7 to 10 days post-op
      • treatment
        • early recognition may allow revision repair
        • tendon reconstruction for late rupture or rupture with excessive scarring
    • Swan neck deformity
      • caused by prolonged DIP flexion with dorsal subluxation of lateral bands and PIP joint hyperextension
      • treatment
        • Fowler central slip tenotomy
        • spiral oblique ligament reconstruction
    • Boutonniere deformity (DIP hyperextension)
      • caused by central slip disruption and lateral band volar subluxation
      • treatment
        • dynamic splinting or serial casting for maximal passive motion
        • terminal extensor tenotomy, PIP volar plate release
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Questions (6)
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(OBQ17.34) A 28-year-old male sustains a laceration to the dorsal aspect of his left hand during an assault as shown in Figure A. He is unable to actively extend his ring finger. He undergoes primary repair of the injured structure and is placed into the relative motion splint (yoke splint) shown in figure B. All of the following are benefits of this splint when compared to full-time extension splinting or dynamic splinting, EXCEPT:

QID: 210121

Interferes less with activities of daily living



Better at limiting motion of the digit



Decreased risk of adhesions



Allows more range of motion of adjacent digits



Higher patient compliance with therapy



L 2 B

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(OBQ16.245) A patient sustains an acute, closed injury to his index finger. The clinical appearance of the finger is shown in Figure A. The patient is asked to extend the finger against resistance, with the PIP joint in 90 degrees of flexion. You note that PIP joint extension was weak, with hyperextension and restricted passive flexion of the DIP joint. When planning to treat this injury non-operatively which active joint motion is encouraged?

QID: 9007

DIP flexion



MCP flexion



MCP extension



PIP extension



PIP flexion



L 4 B

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Evidence (10)
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