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The terrible triad injury of the elbow
April D. Armstrong
Purpose of review The purpose of this article is to provide a review of the pertinent anatomy as it pertains to the treatment of the ‘terrible triad’ elbow injury. Also, a standard surgical approach is outlined. It has become more apparent in recent literature that attention to all facets of this injury complex is important to optimizeresults. Recent findings In the past year, a standard surgical approach to elbow fracture dislocations has been the main focus. Both the bony and soft tissue injuries associated with this injury pattern need to be addressed to restore stability and function to the elbow. Summary When treating the terrible triad injury of the elbow, careful attention to bony and soft tissue injuries is essential.Using a systemic stepwise treatment approach will improve patient satisfaction and functional results. Keywords elbow, dislocation, fracture
Curr Opin Orthop 16:267—270. ª 2005 Lippincott Williams & Wilkins. — Penn State Milton S. Hershey Medical Centre, Penn State College of Medicine, Orthopaedics and Rehabilitation, Hershey, Pennsylvania, USA Correspondence to April D. Armstrong, Penn StateMilton S. Hershey Medical Centre, Penn State College of Medicine, Orthopaedics and Rehabilitation, H089, 500 University Drive, PO Box 850, Hershey, PA 17033-0850, USA Tel: 717 531 5638; fax: 717 531 0672; e-mail: aarmstrong@psu.edu Current Opinion in Orthopaedics 2005, 16:267—270 — ª 2005 Lippincott Williams & Wilkins. 1041-9918

Introduction
The ‘terrible triad’ injury of the elbow classicallyrefers to a combined injury involving a dislocation of the elbow in association with a radial head and coronoid fracture (Fig. 1). In contrast to simple elbow dislocations (no fracture), the terrible triad injury is a challenge to treat because it is prone to recurrent instability, stiffness, and late arthrosis. There are a limited number of clinical outcome studies for this injury complex, andinitial reports of results have been concerning. Ring et al. [1] reported unsatisfactory results in 7 of 11 patients treated with this injury complex. Varied surgical approaches were used to treat these patients. In some patients, comminuted radial head fractures were resected, which led to recurrent instability and early arthrosis within 2 years. The purpose of this article is to provide a review ofthe pertinent anatomy as it pertains to the treatment of this injury. A standard surgical approach to this injury complex is also provided, which is the main focus of the research studies published this past year.

Anatomy
As we have gained more experience treating elbow fracture dislocations, it has become apparent that one needs to pay attention to both the bony and soft tissue injuryassociated with this injury complex. The ulnohumeral articulation of the elbow is highly congruent, providing inherent stability to the joint. It has been shown that the osseous articulation provides 30% resistance to valgus stress and 75% resistance to varus stress with the elbow at 90° of flexion [2]. The coronoid, specifically, provides an anterior buttress to posteriorly directed forces across theelbow. It has been shown that approximately 50% of the coronoid is required to maintain stability against a direct posterior force in an otherwise intact elbow [3]. Wake et al. [4] used a two-dimensional finite element model and static loading experiments to simulate elbow fracture dislocations. They looked at the stress concentrations of the proximal ulna under axial load at varying elbow flexionangles. They found that the size of the proximal ulna fracture increased with flexion angle so that a type I coronoid fracture occurred from 15 to 30° of flexion. All these cases were also associated with a radial head or neck fracture. The radial head has been shown to bear 60% of the axial load across the elbow joint and acts as an important secondary stabilizer to valgus instability [2,5–8]....