Elbow instability refers to a rupture or stretching out of one of the main ligaments that keeps the elbow from dislocating or subluxing (“partial dislocation”). This may occur following trauma or as a result of repetitive stress and strain to the ligament. Often, instability is not obvious to the patient but rather manifests as pain or a decrease in athletic performance (such as loss of pitch speed and endurance in a throwing athlete). Rarely, patients are able to actually pop the elbow out of joint, and have had a history of dislocating the elbow in the past. There are several types of elbow instability but the two most commonly treated ones are:
- Posterolateral Rotatory Instability (PLRI)
- Valgus Instability
Posterolateral Rotatory Instability (PLRI)
Posterolateral Rotatory Instability of the elbow (PLRI) is caused by failure of the lateral ulnar collateral ligament (LUCL) of the elbow, resulting in pain in the outer back side of the elbow (posterolateral elbow). This may be caused by a prior elbow fracture or dislocation. Rarely, it may also happen after surgery or too many cortisone injections for tennis elbow. Patients usually feel pain at the posterolateral elbow, and may also have difficulty “locking out” the elbow because of a sense that the elbow may pop out of joint when it is held in a fully straightened position. Very rarely can patients cause the elbow to come out of joint on purpose. Physical exam is not usually reliable in picking up this diagnosis, unless a stress exam of the elbow under anesthesia is performed. Xrays are used to rule out other conditions (fractures, arthritis, loose bone chips in the joint). An MRI may even miss the diagnosis in mild cases.
When the condition is acute (within a few months following an elbow dislocation) it may be treated by keeping the arm in a long cast for about a month, followed by supervised physical/occupational therapy. If the condition has persisted for more than a few months then surgery is almost always required. This is usually in the form of a ligament reconstruction, in which a cadaver tendon or a wrist tendon (the palmaris longus) from the patient is harvested and used to recreate the lost ligament. Elbow arthroscopy is often performed at the same time if other conditions are suspected.
Video: Arthroscopic diagnosis and treatment of an unstable elbow
Following successful ligament reconstruction, the patient will need to be placed into a long arm cast for 3-4 weeks to allow healing of the tendon graft. This is then followed by 6-8 weeks of controlled, protected physical or occupational therapy. By 12 weeks after the surgery patients are allowed full return to activity if they are doing well. The vast majority of patients with PLRI do very well from such a ligament reconstruction.
Injury to the ulnar collateral ligament causes Valgus Instability, making the elbow unstable.