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Hinged External Fixators of the Elbow
Introduction
Interest in and use of external fixators has waxed and waned over the years. I continue to use this device to allow motion and simultaneously (1) maintain a reduced and balanced ulnohumeral joint, (2) protect repaired or reconstructed collateral ligaments, and (3) lessen force across the joint.
Rationale and Options
The mechanics and anatomic landmarks for the application of various fixator devices have been well defined. The axis of rotation of the distal humerus passes through the tubercle of origin of the lateral collateral ligament and through the anteroinferior aspect of the medial epicondyle ( Fig. 48.1 ). Accurate replication of the axis of rotation allows normal elbow motion and would seem to lessen pin stress. However, experiments in our laboratory suggest malpositioning of as much as 5 mm has little adverse consequences on the function of the dynamic fixator.
Indications
The features of hinged external fixators prompt their use in trauma and reconstructive circumstances. Specific indications for hinged fixator use include ankylosis or elbow contracture, acute or chronic elbow instability, or arthritis.
Trauma
In many traumatic circumstances, the goal is to neutralize the forces across the joint to allow articular and soft tissue healing while elbow motion is maintained. The fixator can be applied acutely as an adjunct to operative repair or as a secondary measure in case of reduction failure. The specific indications for dynamic external fixators of the elbow in acute trauma include (1) instability, (2) articular injury, and (3) residual or recurrent subluxation.
Instability
Elbow dislocation with extensive soft tissue injury typically results in gross instability, even after reduction or repair of involved structures. This is a good indication for the use of the fixator as an adjunct to management.
Articular Injury (Fracture–Dislocation)
This category includes instability with fractures of the radial head, some olecranon fractures (Mayo type III), as well as Regan-Morrey type II and III coronoid fractures. When gross instability persists or when fixation is deemed tenuous and prevents early motion, an external fixator is employed ( Chapters 36 and 43 ).
Residual or Recurrent Subluxation
Residual or recurrent subluxation after simple or complex fracture–dislocation is the third indication for use of a fixator. A percutaneous fixator application can assist in reducing a subluxated joint without having to revert to an open procedure. The added stability facilitates the regaining of functional motion during healing of the capsule and ligaments.
Reconstruction
The same basic goals are associated with the use of the fixator after reconstructive interventions: allow motion, protect soft tissue healing, and neutralize joint forces.
Ankylosis
With arthrolysis for posttraumatic joint stiffness, release of the collateral ligament is sometimes necessary, as well as excision of capsular and bone restraints. Application of the device protects the repaired collateral ligaments while allowing immediate motion of a stabilized concentric joint.
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