Coronoid Fractures - Chris Huber 14/11/2002

Usu. occur with posterior dislocation (2-10% of dislocations)

Caused by indirect transmission of force axially up forearm (AAAmis Injury '95)

Classification by Regan and Morrey   '89

Type I                Coronoid tip                                            A: no assoc dislocation

Type II                < 50% coronoid height                             B: associated dislocation

Type III               > 50 % coronoid height

Stabilisation role

Bony                  Acts as anterior buttress

                                    Resists posterior subluxation

                                    Esp at >60 degrees flexion

            Soft tissues        Attachments for

                                                Anterior capsule

                                                Brachialis

                                                Anterior bundle of MCL

Morrey showed radial head takes most of load at 0-30 deg flexion (JBJS '88)

Theory that load transmission shifts from radius to ulna as flexion increases

Morrey also showed that as fragment size increases, stability and prognosis worsens

Even though biomechanically a type I or II gives little instability if isolated ,   once combined with a radial head fracture, even a small coronoid frature fragment assumes a much greater significance (Ring, Jupiter JBJS April 2002)

"Terrible Triad"

            Posterior dislocation

            Radial head fracture

            Coronoid fracture

Affects young, active patients, yet many complications and poor prognosis

            Persistent instability

            Non union and malunion

            Proximal radioulnar synostosis

Recommendations from Jupiter, Morrey et al in Instructional Course Lecture on The Unstable Elbow at the American Academy 2000

In terrible triad injuries do ORIF from lateral side, retracting fractured radial head to expose coronoid.

Approach medially if there is a large medial coronoid fragment

Types I and II " if fixation needed can use 2 braided sutures over top of fragment, pulled out via drill holes in ulna, tied over bone. If capsule involved pass suture through capsule.

Type III " ORIF with buttress plate and screws, esp if medial.

If not fixable (eg comminution) consider reconstructing "buttress" with

            Portion of radial head, fixed with screws

            Iliac crest tricorticate graft

            Prox tip of olecranon

            Allograft coronoid