Boutonniere Versus Pseudoboutonniere Deformities: Pathoanatomy, Diagnosis, and Treatment.

Finger injuries involving the proximal interphalangeal (PIP) joint are common, particularly among athletes. Injury severity is often underappreciated at initial presentation and may be dismissed broadly as a "jammed finger" injury. Delayed diagnosis and treatment of certain injuries can have an important impact on the patient's chance of regaining full function. Central slip and PIP volar plate injuries are frequently encountered injuries that, if left untreated, can lead to the permanent loss of function of the proximal interphalangeal joint. Despite the differing mechanisms of these 2 pathologies, volar plate hyperextension injuries often present with a PIP joint flexion contracture and mild distal interphalangeal joint hyperextension deformity. This is similar to a boutonniere deformity seen after an injury to the central slip, and thus, has been referred to as a "pseudo-boutonnière" deformity. Distinguishing these 2 diagnoses is important, as treatment differs, and highlights the importance of thoroughly understanding the anatomy and relevant clinical applications when evaluating PIP joint injuries.