Sports Medicine Research: In the Lab & In the Field: What is the Role of the Long Head of the Bicep Tendon? (Sports Med Res)


Thursday, September 29, 2011

What is the Role of the Long Head of the Bicep Tendon?

Posterosuperior Displacement Due to Rotator Cuff Tears

Su WR, Budoff JE, Luo ZP. Arthroscopy. 2011 Sep 10. [Epub ahead of print]

Massive rotator cuff tears commonly occur and if left untreated lead to further complications within the shoulder joint. Complications range from long head of the biceps degeneration to glenohumeral osteoarthritis. It is thought that these complications are caused by mechanical alterations of the joint, stemming from the lack of dynamic restraint normally provided by the rotator cuff. Previous studies of shoulders with and without tears of the supraspinatus and infraspinatus have only examined the amount of humeral head displacement with loading in an anteriosuperior direction. However, none have examined the amount of displacement when the shoulder is loaded in a posteriosuperior direction. In addition, this has never been studied with a tear of the supraspinatus and the subscapularis, which has been increasingly reported (see clinical pearls). Therefore, Su et al used 10 cadaver shoulders to examine the amount of humeral head displacement following varying degrees of anterosuperior (i.e., supraspintatus + subscapularis) and posterior/superior (i.e., supraspintus + infraspinatus) rotator cuff tears when loaded in a posterosuperior direction. The effect of bicep tendon loading was also examined. The cadaver specimens were mounted and secured in a material testing system. Simulated muscle activity of the intact rotator cuff was performed based on muscle cross-sectional area and previous muscle activity (electromyography) data. The shoulder was loaded in a posterosuperior direction by the material testing system at 10, 20, 30, 40, and 50 Newton of load with the following combinations of tears 1) supraspinatus 2) supraspinatus and superior half of the infraspinatus 3) complete supraspinatus and infraspinatus 4) supraspinatus and superior half of the subscapularis 5) complete supraspinatus and subscapularis. For each condition testing was performed with and without 55N of biceps loading. They found that there was more posterosuperior translation at 50N when the superior half of the infraspinatus was cut compared to the superior half of the subscapularis. The same was found when each tendon was completely cut. The addition of a loaded biceps decreased translation in every condition and the amount of decreased translation increased with larger tears ranging from 16-43%. Translations at the lower loads were found to be minimal.

The results of this study are very interesting and raise our understanding of the mechanical consequences of different combinations of rotator cuff tears. This suggests that the infraspinatus is an important restraint to posterosuperior loading (pushing motions). This is more obvious with a complete rupture, although complete tears of the subscapularis also resulted in large translations. This is in agreement with Burkhart’s suspension bridge hypothesis. It states that there is a band of tissue called the rotator cable that extends from the subscapularis to the infraspinatus and acts like a suspension bridge. He suggests that if this cable is intact then the anterior/posterior force couple of the rotator cuff will be maintained and translations in the anterior/posterior direction will be minimized. However, if it is compromised then the force couple is disturbed and severe translations will occur and alter normal shoulder kinematics. The other interesting finding is the significant role of the biceps to minimize humeral head translation. The role of the biceps at the shoulder joint has not been completely understood. However, this study suggests that it plays a significant role in maintaining dynamic stability especially when the anterior/posterior force couple is disrupted. The increased reliance (overuse) on the biceps to provide joint stability may also be the mechanism of biceps degeneration in rotator cuff tear patients. Do your rotator cuff tear patients commonly present with biceps pain? Do you feel the biceps should still be released in these patients after observing these results? Is there anything we can do to prevent the biceps from becoming injured in these patients?

Written by: Stephen Thomas
Reviewed by: Jeffrey Driban

Su WR, Budoff JE, & Luo ZP (2011). Posterosuperior Displacement Due to Rotator Cuff Tears. Arthroscopy : the journal of arthroscopic & related surgery PMID: 21908156


Ian Hix said...

I do sometimes see patients with biceps tendon pain with rototor cuff pathology. This could be due to the fact that it aids in shoulder abduction when the extremity is externally rotated, which is also the function of the supraspinatus. Furthermore, the smaller rotator cuff muscles are already weak when compared to the larger muscles surrounding the shoulder joint. More stress could be placed on the biceps tendon when the infraspinatus and subscapularis are weakened.

It is also commonplace to incorporate shoulder flexion in a rehabilitation program when rotator cuff pathology is present owing to the argument that the biceps tendon aids in GH stabilization.

Furthermore, I would like to see which patients experience biceps tendon pain in conjunction with a rotator cuff tear. I would imagine that it would be associated with patients who normally don't need to use the rotator cuff stabilizers. In my experience, it is preached to strengthen this muscle group to prevent injury especially with a patient population such as overhead throwing athletes.

Stephen J. Thomas, PhD, ATC said...

Ian thanks for commenting. I would agree with your comments and approach to these patients.

Speaking with many orthopaedic surgeons, the prevalence of biceps pain is extremely high in patients with rotator cuff tears. When surgically repairing the rotator cuff the surgeons typically perform a tenodesis to eliminate the biceps symptoms and give the patient a better chance for an optimal recovery.

Based on this study, it seems the biceps contributes significantly to shoulder stability and when a tenodesis of the biceps is performed that patient may be at a higher risk for further joint damage.

Surgeons may want to rethink performing a tendodesis in rotator cuff tears patients and instead use rehab to improve biceps symptoms to avoid the risk of further shoulder injury.

Brandon Davis, ATC said...

The point brought up about the Burkhart suspension bridge hypothesis is an interesting concept as we know that joints within the body gain there stability from a combination of static and dynamic restraints. If the rotator cuff is a depressor and inward compressor of the humeral head, to me the role of the biceps is more of a sling acting to reduce the extent of posterior-superior translation. A tendodesis to me is not a favorable option if pain can be managed conservatively through therapy. Eccentric training or even more recently the concept of dynamic humeral centering may show positive outcomes for these patients depending on the extent of their rotator cuff pathology.

Stephen J. Thomas, PhD, ATC said...


Thanks for commenting. I agree I think it may be possible to treat the biceps without the need of a tendodesis. It ultimately comes down to the patient. If its a younger active individual that wants to remain physically active I think leaving the biceps and performing rehab is the best bet for that person. However, if its a 70 year old that just wants a reduction in pain during ADLs then a tendodesis might be the best option.

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