Posterolateral rotatory instability of the elbow

Posterolateral rotatory instability of the elbow is the most common form of symptomatic chronic elbow instability characterized by posterior subluxation or dislocation of radial head on capitellum without injury to proximal radioulnar articulation. It caused by injury to the lateral collateral ligament complex, namely lateral ulnar collateral ligament, however, it has been shown that an additional injury to the remaining lateral elbow structuresstabilizers is also required to develop posterolateral rotatory instability of the elbow.

Clinical presentation

Patients may present with vague lateral elbow pain, popping, snapping, clicking. These symptoms may in particular brought up by activities which place the elbow in its unstable position of external rotation of the forearm with valgus and axial loading, such as pushing up from a chair or doing push-ups.

Most patients can recall a traumatic event, frank elbow dislocation or fall in outstretched hands. 

Active and passive provocative tests can be helpful to make a diagnosis; these include: lateral pivot shift, lateral pivot-shift apprehension test, posterolateral rotatory drawer test, chair sign,  or active floor push-up sign.

Pathology

In posterolateral rotatory instability of the elbow, forearm complex rotates externally in relation to the humerus, causing posterior subluxation or dislocation of the radial head.This is caused by loss of posterolateral elbow joint constraints including lateral collateral ligament complex, common extensor tendon, radiocapitellar articulation, and coronoid process. The lateral ulnar collateral ligament is invariably injured but it is not sufficient to develop PLRI; injury to at least one more soft tissue structure is required. 

• Trauma: is by far the most common cause. Others include
• Chronic attenuation of LUCL: due to chronic micro trauma or chronic cubitus varus from prior distal humeral fracture. 
• Iatrogenic: from steroid injection or lateral epicondylitis procedures with inadequate repair of LUCL, or radial head resection.

Radiographic features

Radiograph

Normal or “drop sign” which is posterior sublaxation of radial head compared to capitellum on a lateral X-ray.

MRI

Conventional MRI or MR arthrogram may be helpful to demonstrate lateral ulnar collateral and other ligament injuries.

Treatment and prognosis

Nonoperative management is often unsuccessful.

If injury is acute and good quality native ligamentous tissue present, best treatment option would be repair of the LUCL, otherwise reconstruction with autograft should be considered. f there is no established osteoarthritis of elbow joint at the time of surgery , the outcome would be very good to excellent.