Chronic elbow instability presents with pain, apprehension or subluxation of the elbow joint on movement with three types recognized: valgus, posterolateral, and posteromedial.
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Clinical presentation
Patients present with pain, apprehension on movement and subluxation of the elbow joint. In valgus instability, the ulnar collateral ligament (UCL) of the elbow is commonly injured. Valgus stress test can be performed to elicit any injury to UCL.
In posterolateral instability, the radial collateral ligament (RCL) is commonly injured. A lateral pivot test can be performed to test this ligament. There are other tests such as the posterolateral rotatory drawer test, chair push-up test or prone push-up test, which can also be performed.
In posteromedial instability, usually, the coronoid facet along with RCL is injured. The gravity-assisted varus test can be performed to test this ligmanet.
Pathology
There are a few types of elbow instability with the most common type being posterolateral instability 1. Instability can occur from chronic overuse or post-trauma. Both bony articulation and soft tissue play an important role in providing stability to the elbow joint 2. Three primary static constraints are the ulnohumeral joint, ulnar collateral ligament (UCL) and the radial collateral ligament (RCL).
Radiographic features
Plain radiograph / CT
Avulsion injuries can indicate UCL and/or RCL injuries of the elbow. In chronic cases, loose bodies or osteoarthritis can be noted. Valgus stress radiographs can be obtained to note any increase in ulnohumeral gapping in elbows with valgus instability.
The drop sign of elbow joint can indicate unstable elbow joint, which is noted when the ulnohumeral distance is >4 mm on lateral elbow x-rays 1. CT scans help to further assess fracture patterns and for pre-operative planning.
MRI
MRI is a highly specific for identifying soft tissue injuries, especially to the collateral ligaments, and can also identify chondral injuries.
Treatment and prognosis
Chronic elbow instability is usually managed surgically. The underlying cause for the instability is addressed with surgical fixation with either repair +/- reconstruction techniques 3.
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