Review Question - QID 211210

Posterolateral rotatory instability (PLRI) can result from a "terrible triad" fracture-dislocation pattern (seen in Figure E), classically involving a radial head fracture, coronoid tip or base fracture, and an elbow dislocation.

Terrible triad injuries typically occur with axial loading, supination, and a valgus directed force through the elbow. In comparison to PLRI which results from a terrible triad injury, posteromedial rotatory instability (PMRI) commonly results from an anteromedial coronoid facet fracture following a varus-directed force. These injuries also very frequently also have a lateral collateral ligament complex injury but often have no radial head fracture. PLRI is far more common than PMRI. Generally with a PLRI pattern, the lateral collateral ligament complex fails first, followed by injury to the anterior capsule or coronoid, and lastly the medial collateral ligament complex is affected. Non-operative management is possible, but only indicated in small, non-displaced radial head fractures with small coronoid tip fractures. Typically, terrible triad injuries are addressed surgically with radial head fixation or arthroplasty, lateral collateral ligament repair, and, less commonly, coronoid fracture fixation or anterior capsule repair.

Ring et al. reviewed 56 patients who had been treated with an ORIF of the radial head at 48 months after injury. They found unsatisfactory outcomes for patients who had an ORIF of radial head fractures with greater than 3 articular fragments. The authors recommended ORIF of radial head fractures with 3 or few fragments.

Steinmann performed a review of coronoid process fractures. The author reports that with an anteromedial coronoid fracture, the anteroposterior (AP) radiograph of the elbow will demonstrate progressive narrowing of the joint space from lateral to medial. Dr. Steinmann concludes that an important determinant of stability is the involvement of the sublime tubercle (insertion point of the MCL), and that medial instability is likely with involvement of the sublime tubercle.

Mathew et al. review the anatomic, biomechanical, and operative principles of terrible triad injuries. The authors discuss that the primary goal of fixation is to stabilize the elbow and allow early range of motion. They underscore technical improvements and implant developments which have improved outcomes.

Figure A demonstrates a capitellum fracture.
Figure B demonstrates an olecranon fracture.
Figure C demonstrates a displaced radial head fracture.
Figure D demonstrates an anteromedial facet coronoid fracture.
Figure E demonstrates a terrible triad injury with a radial head fracture, coronoid tip fracture, and elbow subluxation.

Incorrect Answers:
Answer 1: A capitallar shear fracture most often results from an axial load through the elbow in a semi-flexed position.
Answer 2: Olecranon fractures typically occur via a direct blow and are not typically associated with ligamentous instability.
Answer 3: Isolated radial head fractures often occur through an axial load with the elbow in extension and forearm in pronation and in isolation are not typically associated with instability.
Answer 4: An anteromedial facet fracture of the coronoid process leads to PMRI.