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