Middle phalanx fracture displacement

(A) A lateral view, showing the prolonged insertion of the flexor superficialis tendon into the middle phalanx.
(B) A fracture through the neck of the middle phalanx is likely to have a volar angulation because the proximal fragment is flexed by the strong pull of the superficialis.
(C) A fracture through the base of the middle phalanx is more likely to have a dorsal angulation because of the extension force of the central slip on the proximal fragment and a flexion force on the distal fragment by the superficialis.