52 - Description and Clinical Implications of a Unique Teres Minor Variation

Poster Board Number: 52
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Co-authors:

Haley Juber - Physical Therapy - Indiana Wesleyan University; Luke Lushin - Student, Physical Therapy, Indiana Wesleyan University

Abstract Body : Understanding anatomical variations of the rotator cuff aids in medical intervention. Anatomic anomalies of the shoulder are relatively uncommon; specifically, variations of the teres minor ( TMi ) are exceedingly rare. We report a new occurrence of a TMi accessory slip originating from the proximal attachment of TMi and attaching perpendicular to the fascia of the middle deltoid. While accessory slips have been documented in the region, this unique TMi accessory slip has yet to be described in literature and should receive unique consideration based on rehabilitation and clinical implications.

Materials and Methods: The discussed anatomic variation was uncovered during routine academic anatomic dissection at Indiana Wesleyan University. All donors are provided by the Anatomic Education Program, a division of Indiana University School of Medicine.

Results: An accessory slip of muscle was discovered during routine anatomic dissection of a 73 year old male cadaver. The slip was found unilaterally and originated at the proximal attachment of TMi and inserted into the fascia of the middle deltoid. The slip was clearly delineated from the posterior and middle deltoid by fascia. The fibers were positioned perpendicular to the middle deltoid and ran over the top of the posterior deltoid. The donor also had an elongated proximal attachment of the posterior deltoid bilaterally, extending nearly to the medial border of the scapula. Innervation to the slip appears to have originated from a branch of the axillary nerve running to TMi; however, the nerves were damaged during dissection. Blood supply was also disrupted in the process of dissection.

Conclusion: While literature describing accessory slips of muscle in the posterior shoulder exists, most conclude that the slips are an additional portion of the posterior deltoid. In this case, the fibers at the proximal attachment of the slip are integrated with those of TMi. The position of the muscle fibers in this slip runs parallel with those of the TMi and perpendicular to those of the posterior and middle deltoid. A concluding proposal for slips of this nature should be referred to as accessory slips of TMi and not those of the deltoid.

Significance: The presence of accessory muscle slips can have implications for medical intervention and rehabilitation of the shoulder complex. Patient description of posterior shoulder pain is often poor, which creates difficulty in clinical decisions concerning the origin of pain. The presence of variant TMi anatomy would further complicate decision-making. Accessory slips of TMi should be considered as a potential origin of pain in regard to quadrangular space syndrome, rotator cuff pathology, and as a potential location of myofascial trigger points.