Teres major muscle – insertion footprint

Abstract

Teres major muscle (TM) and latissimus dorsi muscle (LD) are frequently used in muscle transfers around the shoulder girdle. Some authors have suggested harvesting techniques in which the muscle is detached in continuity with a bone segment. Information on the bony attachment footprint of these muscles is lacking. The purpose of this study was to investigate the region of attachment of the TM to facilitate safe and complete harvesting with a bone segment where it is indicated, and to determine the relationship of the TM footprint with that of the LD. Twenty‐eight upper extremities of 14 human cadavers (six female, eight male) were investigated during the students’ dissection course in the winter term 2012. The attachment footprints were photographed and the images were processed with imageJ Version 1.46r. The TM attachment footprint at the crest of the lesser tubercle had an average dimension of 187 ± 89 mm2. It was 49.6 ± 7.9 mm long and 7.4 ± 2.5 mm wide. The bony attachment of the LD within the bicipital groove, just below the tendon of the long head of the biceps muscle, had an area of 94 ± 37 mm2. It was 36.5 ± 8 mm long and 3.7 ± 1.2 mm wide. Both muscles were separated by 4.4 ± 1.7 mm and their attachments overlapped in the craniocaudal direction by 24.4 ± 12.4 mm. Earlier studies have investigated the dimensions of the muscles’ tendons close to the attachment not the bony attachment itself. The dimension of the attachment of the TM was larger than that of the LD. The ratio between the footprint areas was approximately 2:1. This information should be considered by surgeons undertaking transfers, which include a bony segment of the muscle insertion.

Anatomical study of the teres major muscle: description of an additional distal muscle slip

“…The dTMs has a separate (distal) but continuous (mediolateral) insertion at the humerus within a common epimyseal sheet around the TM. Other than the previously described TM accessorius [ 16 ], which lies proximally, the described additional head is located distal to the TM. This distal teres major slip was identified in 75% of our shoulder specimens, and its presence was defined by a distinct and separate bony insertion distal to the tendon insertion of the TM.…”

“…The LD tendon attaches more laterally and proximally compared to the TM tendon with the most inferior portion of the insertion area of the TM usually located inferior to that of the LD tendon [ 16 , 25 ], leaving parts of the TM bony insertion visible during a deltopectoral approach. Yet, separation of the LD and TM tendon insertions during this approach can be challenging.…”

“…Wang et al described additional muscle fibers, which cover the TM tendon posteriorly and attach directly to the periosteum of the humerus [ 10 ]. Moreover, Dancker et al described an additional strand of muscle fibers proximal to TM [ 16 ]. The authors assumed an additional head of the TM with considerable thickness and separate bony insertion by a short tendon and named it TM accessorius.…”

“…However, to the best of our knowledge, this is the first study describing an additional distal muscle slip of the TM. In contrast to the TM accessorious, which inserts proximally and medially to the main insertion of the TM [ 16 ], the dTMs inserts as a separate and distal tendon with a continuous insertion at the humerus within a common epimyseal sheet around the TM.…”

“…Several authors have therefore studied the relationship between LD and TM, particularly the insertion variants of the tendons [ 7 , 10 – 18 ], and described different anatomic variants of TM [ 19 – 24 ]. As such, an additional strand of muscle fibers proximal to TM was observed and named as the TM accessorius [ 16 ].…”