summary Mallet Finger is a finger deformity caused by disruption of the terminal extensor tendon distal to DIP joint Diagnosis is made clinically with a presence of a distal phalanx that rests at ~45° of flexion with lack of active DIP extension. Treatment is usually extension splinting of DIP joint for 6-8 weeks. Surgical management is indicated for volar subluxation of the distal phalanx, chronic injuries, or with the presence of significant arthritis. Epidemiology Risk factors usually occur in the work environment or during participation in sports Demographics common in young to middle-aged males and older females Anatomic location most frequently involves long, ring and small fingers of dominant hand Etiology Pathophysiology mechanism of injury traumatic impaction blow usually caused by a traumatic impaction blow (i.e. sudden forced flexion) to the tip of the finger in the extended position. forces the DIP joint into forced flexion dorsal laceration a less common mechanism of injury is a sharp or crushing-type laceration to the dorsal DIP joint Classification Doyle's Classification of Mallet Finger Injuries Type I Closed injury with or without small dorsal avulusion fracture Type II Open injury (laceration) Type III Open injury (deep soft tissue abrasion involving loss skin and tendon substance) Type IV Mallet fracture A = distal phalanx physeal injury (pediatrics) B = fracture fragment involving 20% to 50% of articular surface (adult) C = fracture fragment >50% of articular surface (adult) Presentation Symptoms primary symptoms painful and swollen DIP joint following impaction injury to finger often in ball sports Physical exam inspection fingertip rest at ~45° of flexion motion lack of active DIP extension Imaging Radiographs findings usually see bony avulsion of distal phalanx may be a ligamentous injury with normal bony anatomy Treatment Nonoperative extension splinting of DIP joint for 6-8 weeks for 24 hours daily indications acute soft tissue injury (< than 12 weeks) small or minimally displaced bony mallet injury without joint subluxation technique maintain free movement of the PIP joint worn for 6-8 weeks volar splinting has less complications than dorsal splinting avoid hyperextension begin progressive flexion exercises at 6 weeks Operative CRPP vs ORIF indications absolute indications volar subluxation of distal phalanx relative indications >50% of articular surface involved >2mm articular gap surgical reconstruction of terminal tendon indications chronic injury (> 12 weeks) with healthy joint outcomes tendon reconstruction has a high complication rate (~ 50%) DIP arthrodesis indications painful, stiff, arthritic DIP joint Swan neck deformity correction indications Swan neck deformity present Techniques CRPP approach percutaneous fixation dorsal extension block pinning with joint pinned in extension Ishiguro technique vs. Modified Ishiguro technique ORIF approach dorsal midline incision fixation simple pin fixation dorsal blocking pin Surgical reconstruction of terminal tendon repair this may be done with direct repair/tendon advancement, tenodermodesis, or spiral oblique retinacular ligament reconstruction Swan neck deformity correction techniques to correct Swan neck deformity include lateral band tenodesis FDS tenodesis Fowler central slip tenotomy minimal Swan Neck deformities may correct with treatment of the DIP pathology alone Complications Extensor lag a slight residual extensor lag of < 10° may be present at completion of closed treatment, however, no functional deficit. Swan neck deformities occurs due to retracted terminal insertion leading to proportionally excessive pull on P2 from central slip attenuation of volar plate and transverse retinacular ligament at PIP joint dorsal subluxation of lateral bands resulting PIP hyperextension contracture of triangular ligament maintains deformity