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New Shoulder Diagnosis: The Transient Luxation

An orthopedic surgeon from West Point has proposed a new classification for shoulder injury called the transient luxation. Based on a study of over 4,000 military cadets, this problem was identified in 38 students.

What is transient luxation? It's somewhere between a shoulder dislocation and subluxation (partial dislocation). The force of the injury was enough to cause a separation of the joint. But because the shoulder went back into place, it doesn't count as a complete dislocation. MRIs taken within two weeks of the injury showed damage to the surrounding tissues. The imaging studies were enough to show there was more than the disruption of a subluxation.

Transient luxation is diagnosed when a traumatic event causes a shoulder dislocation that is accompanied by either a Bankart lesion or a Hills-Sachs lesion. The Bankart lesion is a tear in the labrum (rim of fibrous cartilage around the shoulder joint). The labrum gives the shallow shoulder socket a bit of extra depth. It helps stabilize (hold) the shoulder in the socket.

The Hill-Sachs lesion refers to a dent in the head of the humerus (upper arm bone). When the shoulder subluxes or dislocates and then goes back into the socket, the smooth cartilage surface of the humeral head hits against the shallow socket causing this dent. Seeing the dent on X-ray tells the surgeon that the shoulder was disrupted enough to pop out of the socket and then shift back in.

This is the first study published reporting on first-time, acute shoulder injuries resulting in transient luxations. Most of the time, research is done on athletes who have a full dislocation or chronic, recurrent subluxations. But this is the first to look at the changes that occur within the joint when a first-time subluxation occurs that does not require manual or surgical reduction (putting the shoulder back in the socket).

Using X-rays and MRIs, the surgeons were able to show clear evidence of pathologic changes in the joints of these cadets. The head of the humerus was pulled away from the socket with enough force to completely separate the two joint surfaces, a process called luxation.

Because these injuries normally spontaneously reduce (head of the humerus goes back into the socket by itself), X-rays and MRIs aren't routinely taken. Having this information at the time of diagnosis helps plan treatment. Since there is a high rate of recurrence (a second) subluxation, knowing there is additional damage to the joint helps guide treatment.

Treatment is with physical therapy to try and rehabilitate the shoulder and restore joint stability. If recovery is not possible, then surgery is the next step. To give you some idea of how many patients recover without surgery, how many develop recurrent instability, and how many end up having surgery, here are a few statistics from this study.

There were 27 of the 38 cadets who had the necessary imaging studies done within two weeks of injury to qualify for this study. Most had both a Bankart and a Hill-Sachs lesion. About half (13 of the 27) opted for the conservative (nonsurgical) approach. Four of those 13 ended up having recurrent subluxations and required surgery. Follow-up was only for a year but at that time, the students who had surgery remained on active duty without any further shoulder problems.

Although this study was done in the military at West Point, the type of patients involved represent many athletes who sustain a similar shoulder subluxation (transient luxation) injury. Most of the injuries in this study were the result of missed punches (boxing), tackles (football or soccer), and falls (obstacle course). Only one injury was directly related to military training.

The authors concluded that diagnosing certain shoulder injuries as either a subluxation or dislocation doesn't tell the whole story. For some athletes, there has been a complete dislocation that has spontaneously reduced and appears as a subluxation. Imaging studies show enough disruption and damage to the joint and surrounding tissue to suggest a third (in-between) classification referred to as transient luxation.

The results of this study support the need for MRIs even with subluxations that reduce themselves. Management of the problem depends on knowing the extent of damage. Surgery may be needed to prevent recurrent subluxation and restore joint stability.

References: Lieutenant Colonel Brett D.Owens, MD, et al. Pathoanatomy of First-Time, Traumatic, Anterior Glenohumeral Subluxation Events. In The Journal of Bone and Joint Surgery. July 2010. Vol. 92-A. No. 7. Pp. 1605-1611.

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