Summary Mallet Finger is a finger deformity caused by disruption of the terminal extensor tendon distal to DIP joint Diagnosis is made clinically when the distal phalanx 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 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 (most common), ring and small fingers of dominant hand Zone 1 in the Kleinert and Verdant classification of extensor tendon injuries 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 avulsion fracture Type II Open injury (laceration) Type III Open injury (deep soft tissue abrasion involving loss of 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 recommended views AP/Lateral of the finger findings often see bony avulsion at the base of the distal phalanx may be a ligamentous injury with normal bony anatomy assess for distal phalanx subluxation Ultrasound not typically necessary findings loss of tendon motion complete or partial thickness tears avulsion fracture fluid at the tendon insertion Treatment Nonoperative extension splinting of DIP joint for 6-8 weeks for 24 hours daily indications acute soft tissue injury (<12 weeks) small or minimally displaced bony mallet injury without joint subluxation chronic injury (>12 weeks) with supple, congruent, and nonarthritic joint technique maintain free movement of the PIP joint if in a swan-neck posture at the time of injury, block PIP full extension with dorsal blocking splint worn for 6-8 weeks typically followed by 4 weeks of nocturnal splinting (controversial) bony injuries splinted until fracture union volar splinting has fewer complications than dorsal splinting avoid hyperextension due to risk of skin necrosis begin progressive flexion exercises at 6 weeks Outcomes No differences in patient satisfaction or extensor lag between operative and nonoperative treatment ~80% of patients have satisfactory outcome Operative CRPP vs ORIF indications absolute indications volar subluxation of distal phalanx relative indications >50% of articular surface involved >2mm articular gap open injuries surgical repair of the terminal tendon indications traumatic tendon laceration surgical reconstruction of terminal tendon indications chronic injury (> 12 weeks) without contracture segmental tendon loss 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 direct repair often accompanied by trans-articular pin 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 in up to 40% after either closed or operative treatment, however, no functional deficit. lengthening of the terminal tendon by 1mm leads to a 25 degree extensor lag Reduced DIP flexion risk for adhesions due to close proximity to the skin and the DIP joint shortening the extensor tendon by 1mm leads to reduced DIP flexion 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 Skin issues (maceration, ulceration, and nail deformities) occurs at some degree in about 70% of those treated nonoperatively limited soft tissue coverage puts the wound at risk of dehiscence and infection