Diagnostic Ultrasound used to Assess Sub-Coracoid Impingement
by Sports Med Res | Mar 3, 2011 |
Sonography of the coracohumeral interval: a potential technique for diagnosing coracoid impingement
Tracy MR, Trella TA, Nazarian LN, Tuohy CJ, Williams GR. J Ultrasound Med. 2010 Mar;29(3):337-41.
At the shoulder the term “impingement” has become very well known even outside the sports medicine field. Although it is mainly referring to sub-acromial impingement, there have been several other forms of impingement introduced. Within sub-acromial impingement you could be even more specific and classify it as primary or secondary. Internal impingement has also gained popularity among overhead athletes and baseball players specifically. However, one form of impingement “sub-coracoid” commonly goes unrecognized and therefore misdiagnosed. Sub-coracoid impingement is when the subscapularis tendon (mainly the upper portion) is impinged between the coracoid process and the lesser tuberosity. This commonly occurs in a position of forward flexion, horizontal adduction, and internal rotation. Basically the position the shoulder is in during the follow-through phase of overhead throwing. The pain is typically within the anterior shoulder causing it to be misdiagnosed as sub-acromial impingement, biceps tendonitis, or anterior instability. This study describes a new way of diagnosing this injury with use of diagnostic ultrasound. It was hypothesized that a patients with sub-coracoid impingement will have a decrease in the coracohumeral interval (distance from the coracoid process to the lesser tuberosity with the shoulder horizontally adducted) compared to normal shoulders. They tested 27 subjects (19 asymptomatic volunteers and 8 with a clinical diagnosis of sub-coracoid impingement). They found that the patients with sub-coracoid impingement had a decreased coracohumeral interval compared to asymptomatic controls.
This study although simple and straightforward describes a very easy assessment for an otherwise difficult injury to diagnosis clinically. Sub-coracoid impingement is an injury that gets misdiagnosed more often then we think. The more clinicians are aware of this injury the better we can treat and prevent this injury from progressing into an upper subscapularis tendon tear. Currently additional research is required to indentify the role of scapular dyskinesis and alterations in the coracoid process morphology in the development of sub-coracoid impingement. I also know what everyone is thinking “Yeah that sounds great BUT we don’t have diagnostic ultrasounds in the athletic training room.” Well currently this is true but I think that will be changing in the near future. Diagnostic ultrasounds have become extremely advanced, portable, and therefore popular with the advances in computer technology. It has been moving into NFL athletic training rooms and progressing to MLB as well. As the popularity of these devices increases, the price will likely decrease; which will allow the transition into athletic training rooms across the country.
Written by: Stephen Thomas
Reviewed by: Jeffrey Driban
Hi Steve: Great post. I have a really simple question with probably no easy answer: If I properly diagnose the person with sub-coracoid impingement rather than subacromial impingement will it have much of an impact on the rehabilitation or other treatment options? Are there particular interventions/exercises I should be trying with these patients that might be more effective than they would be with someone with subacromial impingement?
I wonder how the diagnostic US would look when you compare subacromial vs. subcoracoid impingement? I would imagine that the difference would not be as drastic as between subcoracoid and "normal" shoulders. Could it be that while one area is "more impinged", most of the shoulder is affected and needs to be treated as such?
Jeff good question and your right there is no easy answer. Subcoracoid impingement is very under researched and therefore we don't know much about the mechanism of injury or the optimal way to treat it. It is just starting to be recognized because of the advancement of arthroscope rotator cuff tear procedures. With these advancements surgeons have started to observe more upper subscap tears and they can also observe this impingement occurring during surgery. In this situations many surgeons will perform a coracoplasty to eliminate the impingement. But the real question still is what is the source of this injury. Is it coracoid morphology or scapular dyskinesis or even just overuse. When we determine this then we can further develop rehabilitation protocols to address this injury and also prevent it. As for current treatment, I think it would be wise to stick with a similar protocol for subacromial impingement. I think the scapula could play role so focusing on scapular stabilization would be beneficial. Also staying away from the cross body internal rotation position that is causing the impingement. I.E stop throwing if it is an overhead athlete until the symptoms have been eliminated and other deficits have been addressed.
Andrew that is a great thought. It may be possible that subcoracoid impingement isn't just an isolated injury. There may also be involvement of subacromial impingement as well. That would be interesting to investigate. Surgeons commonly see upper subscap tears in association with supraspinatus tears so it may be that they occur simultaneously or one can lead to the other.