Assessment and Treatment of Ulnar Fracture with Elbow Dislocation or Subluxation
The elbow joint consists of three bones, the upper arm, or humerus, and two bones in the forearm ,the ulna and the radius. The ulna forms the tip of the elbow, also known as the olecranon process. It is at the point where the ulna meets the humerus that an elbow dislocation or subluxation can occur; the dislocation can be with or without fracture of the ulna. Six major patterns have been described as causes of an ulnar fracture with subluxation or dislocation of the ulnohumeral joint.
The first is dislocation with radial head or neck facture, in which there is also injury to the lateral collateral ligament, LCL, and possibly the medial collateral ligament, MCL. A second injury is termed the terrible triad in which there is a fracture to the coronoid and radial head as well as injury to the LCL. Third is the varus posteromedial rotatory instability which involves fracture of the anteromedial facet of the coronoid with either LCL injury or olecranon fracture causing varus subluxation of the elbow. Fourth is an anterior olecranon fracture-dislocation when the proximal part of the ulna is fractured and an anterior dislocation of the forearm relative to the distal humerus occurs with no radioulnar dissociation. A fifth category is termed posterior olecranon fracture-dislocation in which the proximal ulnar fracture includes a posterior dislocation of the forearm. The two olecranon fracture-dislocations can be commonly misdiagnosed as a Monteggia fracture in which the fracture also results in a dislocation of the proximal radioulnar joint. The sixth and final category of ulnar fracture with dislocation is a dislocation with capitellar or trochlear fracture. The capitellum is fractured, with or without extension into the trochlea accompanied by injury to the capsule and ligamentous support resulting in ulnohumeral instability.
It is imperative to understand the categories of acute injury to the elbow in order for surgeons to anticipate what structures may be affected, particularly when assessing in a nonacute setting. Of the structure affected, understanding the coronoid fracture fragment is the most important when identifying the patterns of elbow instability with imaging, as research shows as significant association between the type of coronoid fracture and the type of fracture-instability pattern. There are three types of coronoid fracture: type I is a transverse fracture of the tip of the coronoid associated most commonly with terrible triad injuries, type II is a fracture of the anteromedial facet of the coronoid associated most commonly with varus posteromedial rotatory instability, type III is a fracture at the base of the coronoid associated most commonly with olecranon fracture-dislocation.
There are several factors that influence the outcome of an ulnar fracture with dislocation. Though it is uncommon to have an elbow fracture with persistent ulnohumeral subluxation or dislocation that has been left untreated for more than two weeks, it is clear that time from injury to treatment will effect outcomes. Patients treated within two weeks of injury have significantly better outcomes than those treated more than two weeks after injury when assessing range of motion, pain, and outcome measures. With this evidence, the acute period for treating elbow fracture with dislocation is within 2 weeks . If surgical management cannot take place in the first two weeks, an alternative is to reduce the joint and apply an external fixator. Type or extent of instability will also effect outcomes. Most acute simple dislocations are stable once the joint has been concentrically reduced, the ligaments will heal and function with early controlled motion. A nonacute simple dislocation, persisting beyond two weeks, can still be successfully treated with concentric reduction and early motion, however longer standing dislocations can also require surgical repair as the LCL is not successfully healing to the lateral epicondyle. These instabilities result in less favorable functional outcomes.
There is no consensus on what the optimal solution is for assuring stability of an elbow that has dislocated or subluxed. Temporary immobilization with either cross pinning or external fixation is most commonly used to help maintain elbow congruency while healing. An external fixator, however is difficult to apply, cumbersome to wear, can sometimes still allow the elbow to dislocate and can cause pin-site infection, pin breakage and/or radial nerve injury. Cross pinning of the joint is better at maintaining reduction, but the arm must be casted and there are risks of pin breakage and septic arthritis.
There are many side-effects to the treatment of ulnar fracture with dislocation or subluxation, Contracture and stiffness, particularly with weeks of immobilization, can co-exist with instability and heterotropic ossification, and can impede concentric reduction. Methods available to treat excessive contracture or stiffness include an open capsular release and excision of heterotropic ossification with or without radiation. One must be careful with these procedures as the contracture or ossification may be masking latent instability. Arthrosis develops in almost all patients with these injuries, though extent and symptoms are highly variable. Ulnar neuropathy can develop and negatively affect outcomes as can osseous and chondral erosion.
Aside from addressing the main injury to the ulna and humerus, there are other factors to consider with these an elbow subluxation or dislocation. It is most likely that both the LCL and MCL are damaged in an ulnar fracture with dislocation, thus it becomes important to assess and properly treat the radial head. The radial head can act as a secondary stabilizer when the MCL is insufficient and helps maintain valgus stability at the elbow to allow soft tissue structures to optimally heal. Prior to fracture healing, repair or prosthetic replacement of the radial head, depending on the number of fractures, is an important consideration. The coronoid must also be assessed. Research demonstrates that when more than fifty per cent of the coronoid is excised, or a combination of at least thirty per cent cornoid excision with radial head excision and lateral ulnar collateral ligament damage, there is a significantly greater chance of consistent dislocation. To repair these injuries, the radial head can be replaced and the discarded radial head bone can be used to repair the coronoid. The success rates largely depend on the original instability pattern and the size of the coronoid defect.
It is apparent that there is a lot to consider when assessing an ulnar fracture with an elbow dislocation or subluxation. The initial questions to answer should be what is the original mechanism of injury, whether past surgical procedures were performed, what the state of the radial head may be, and where the ulnar nerve is located. The surgeon should be prepared to remove any implants and should know how they are affixed, location of heterotropic ossification must be noted, the ulnar nerve must be protected throughout the procedure, collateral ligaments should be preserved when possible, and the surgeon should be prepared to perform any necessary capsular release to treat joint stiffness. These many factors and considerations will direct the surgical procedure performed and success rate for favorable long term outcomes.
References: Neal Chen et al. Non acute Treatment of Elbow Fracture with Persistent Ulnohumeral Dislocation or Subluxation. In The Journal of Bone and Joint Surgery. August 6, 2014. Vol. 96A. No 15. Pp 1308-1316.Back