Summary Boutonniere Deformities are Zone III extensor tendon injuries characterized by PIP flexion and DIP extension. Diagnosis is made clinically with PIP flexion and DIP extension of a digit with presence of a positive Elson test. Treatment of acute injuries involves splinting of the PIP joint with operative management reserved for chronic, symptomatic injuries. EPIDEMIOLOGY Incidence common in rheumatoid patients Up to 50% of patients with rheumatoid arthritis develop a boutonniere deformity in at least one digit Etiology Mechanism caused by rupture of the central slip over PIP joint from laceration traumatic avulsion (jammed finger) capsular distension in rheumatoid arthritis Pathoanatomy pathoanatomic sequence includes rupture of central slip login to view 2 more bullets attenuation of triangular ligament login to view 2 more bullets palmar migration of collateral bands and lateral bands login to view 2 more bullets bone deformity injury involves all three phalanges the middle phalanx flexes on the proximal phalanx at the PIP joint the distal phalanx is hyperextended relative to the middle phalanx at the DIP joint Associated conditions rheumatoid arthritis pseudo-boutonniere refers to PIP joint flexion contracture in the absence of DIP extension Anatomy Muscle lumbrical muscles originate from the FDP and insert on the lateral bands Ligament anatomy extensor hood and central slip the extrinsic extensor tendon joins the extensor hood at the MCP the central portion of the extensor hood forms the central slip the central slip inserts onto the middle phalanx and acts to extend the PIP joint lateral bands the lateral bands are formed from the deep head of the dorsal interossei combining with the volar interossei the lateral bands insert onto the base of the distal phalanx to extend the DIP joint triangular ligament spans the two lateral bands, preventing them from subluxing volarly transverse retinacular ligament prevents dorsal subluxation of the lateral bands Blood supply interosseous muscles receive blood from vessels formed by a combination of the deep palmer arch and the ulnar artery Presentation Physical exam deformity characterized by PIP flexion DIP extension Elson test is the most reliable way to diagnose a central slip injury before the deformity is evident bend PIP 90° over edge of a table and extend middle phalanx against resistance. login to view 4 more bullets Imaging Radiographs recommended view radiographs are not required in evaluation and treatment of Boutonniere deformity Treatment Nonoperative splint PIP joint in full extension for 6 weeks indications login to view 1 more bullet technique login to view 2 more bullets Operative primary central band repair indications login to view 2 more bullets lateral band relocation vs. terminal tendon tenotomy vs. tendon reconstruction indications login to view 1 more bullet technique login to view 3 more bullets PIP arthrodesis indications login to view 2 more bullets