Jersey finger (also called rugby finger or sweater finger) describes a type of injury where there is avulsion of the flexor digitorum profundus (FDP) from the volar aspect of the distal phalanx base ¹. It classically occurs during certain sports resulting from sudden hyperextension of an actively flexed finger (e.g. grabbing an opponent's jersey during rugby or American football.)

It most commonly affects the 4^th digit because the FDP insertion into the ring finger is anatomically weaker than the middle finger ².

Clinical presentation

It is characterised by an inability to flex the finger at the distal interphalangeal (DIP) joint. There is a slight extension at this joint. There is pain and tenderness over the volar distal finger ¹.

Classification

• Leddy and Packer classification

Radiographic features

Plain radiograph

Radiographs can often be normal ³. If there is a bony avulsion, a triangular avulsion fragment at the volar aspect of the distal phalanx base and overlying soft tissue swelling may be seen.

MRI

Disruption of flexor digitorum profundus (FDP) at the volar base of distal phalanx ± avulsion fragment. MRI also allows visualisation of the location of the end of tendons which will affect the surgical classification and management of the patient ^4,5.

Treatment and prognosis

• conservative for partial tear (i.e. splinting, NSAIDs, physical therapy)

• surgical intervention: all complete flexor tendon injuries should be surgically repaired or at least referred to an orthopaedic hand surgeon; tendon retraction and time from injury are key ¹

Complications

• unstable DIP joint

• development of secondary osteoarthritic changes

• DIP flexion contracture or quadrigia