Flexor Digitorum Profundus Tendon Avulsion With Large Extra-articular Bony Fragment Secondary to Dog Collar Entrapment: A Case Report.

Jersey finger (or rugby finger) refers to an avulsion of the flexor digitorum profundus (FDP) tendon, where it is torn from its distal attachment on the distal phalanx. FDP avulsion injuries typically occur in contact sports due to forced extension of the distal interphalangeal joint (DIPJ) while the finger is actively flexing. We present a unique case involving a 56-year-old female patient who sustained a rare pattern of FDP avulsion injury while attempting to restrain her dog via its collar. The patient presented to the accident and emergency (A&E) 12 hours following the incident. Radiographs revealed an unusually large extra-articular bony fragment of the distal phalanx (approximately 80% of its length) displaced volarly, resting against the middle phalanx. The patient was evaluated by both orthopaedics and plastic surgery. The injury was managed through open reduction and fixation with a Kirschner wire, resulting in a complete functional recovery following 2-3 months of regular physiotherapy sessions post-operatively. This injury pattern is underrepresented in the literature, as it involves an extra-articular disruption of the flexor digitorum, a mechanism that has not been described before. Early recognition and surgical intervention are critical for optimal outcomes.