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Letter to the Editor |
Radiology SpR (Severn and Wessex Training Scheme, United Kingdom)
Dear Editor,
I read with interest the excellent article by Gleason et al, in the January 2006 edition of the American Journal of Sports Medicine, titled "The Transverse Humeral Ligament: A Separate Anatomical Structure or a Continuation of the Osseous Attachment of the Rotator Cuff?" (pages 72–77).
This article supports the findings of previous and ongoing studies that have cast doubt on the traditional teaching that the transverse humeral ligament (THL) is a distinct anatomical entity.
Cash et al,2 from the Departments of Radiology and Orthopaedic Surgery at Addenbrooke’s, Cambridge, United Kingdom, were the first to suggest that the THL might not be a distinct anatomical structure, after a study examining the variations in the MRI appearance of the insertion of the tendon of subscapularis. This study, presented at the British Association of Clinical Anatomists Meeting 2002, stated that on MRI imaging, in only 20% (n = 50) of cases was the tendon of subscapularis inserting exclusively onto the lesser tubercle of the shoulder, and in the majority of patients, they could not identify a distinct THL.
In a subsequent dissection study by Boon et al,1 all shoulders examined (n = 43) were found to have a continuous band of tissue extending over the bicipital groove and biceps tendon. This tissue was neither separate from the tendon of subscapularis medially nor supraspinatous laterally, and histologically this band of tissue was tendinous rather than ligamentous.
Further dissection studies performed at the Department of Anatomy, University of Cambridge, United Kingdom, failed to identify a distinct THL in any of the 85 shoulders dissected (K. J. MacDonald, J. Bridger, C. J. C. Cash, I. Parkin, unpublished data). In addition, the tendon of subscapularis was found to rarely insert exclusively into the lesser tubercle in agreement with both Gleason et al and Cash et al.2
In conclusion, there is mounting evidence that the traditional textbook description of a ligamentous structure (THL) retaining the long tendon of biceps within the intertubercular sulcus is incorrect.
REFERENCES
1 Chief of Radiology Services, Clinical Radiology of Oklahoma Oklahoma City, Oklahoma2 Associate Professor of Orthopedic Surgery and Rehabilitation University of Oklahoma Health Sciences Center Oklahoma City, Oklahoma
In response to the letter to the editor, we agree with Dr MacDonald that it is not a novel observation that the transverse humeral ligament (THL) is not a separate and well-defined anatomical structure whose main function is to restrict the anterior and/or medial movement of the long head of the biceps brachii tendon. The concept that the THL is the primary stabilizer of the biceps tendon has been disputed by anatomical studies ranging back to 1928,4 as well as a Scandinavian biomechanical study that also called this function into question.5 The relationship between the supraspinatus, subscapularis, and rotator cuff interval has also previously been described by Clark and Harryman in 1992.3
The letter to the editor credits Cash et al as the first to suggest that the THL might not be a distinct anatomical structure.2 This abstract references a presentation to the British Association of Clinical Anatomists in 2002 that describes the MRI insertion pattern of the subscapularis. The relationship of the subscapularis to the THL is not mentioned in this brief abstract, and we were unfortunately not present at the original presentation.
The study cited by Boon et al1 describes the tendinous merging of the subscapularis and supraspinatus in the region of the rotator cuff interval and defines some of the variations that may be seen, including the differing attachments to the greater and lesser tuberosities. The focus of this article was the merging of the anterosuperior rotator cuff tendons and the effect this anatomical observation may have on rotator cuff repair. The THL is not effectively discussed in this article as it pertains to the role to which it has been ascribed by other authors. The concept of a merged anterosuperior rotator cuff is emphasized and is similar to our own findings.
It appears that MacDonald et al (K. J. MacDonald, J. Bridger, C. J. C. Cash, I. Parkin, unpublished data) have made a similar conclusion in regard to the THL given their reference to unpublished data. Based on our published observations, we are in complete agreement and are pleased that this work has been replicated in another venue.
In conclusion, we appreciate Dr MacDonald’s well thought-out evaluation of our article and the opportunity to reply to her comments. As stated in our article, the greatest benefit of this study is that it gives histological support and anatomical credence to the clinical observations that have been made throughout the literature regarding the THL, its tissue of origin, and its association to rotator cuff interval injuries.
REFERENCES
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