A novel cadaveric study of the morphometry of the serratus anterior muscle: one part, two parts, three parts, four?

Background Previously reported outcomes after tendon transfers to reconstruct the subscapularis are unpredictable and often unsatisfactory, especially in the presence of anterior humeral head subluxation. We studied the anatomic feasibility of the lower trapezius and the rhomboid minor transfer to reconstruct irreparable tendon tears of the subscapularis. The aim of this study was to determine the feasibility of lower trapezius and rhomboid minor transfer to reconstruct irreparable subscapularis tendon tears. Materials and methods We measured the tendons dimensions, muscles excursions, distances to pedicles, and dissection needed to complete a successful lower trapezius and/or rhomboid minor transfer to the subscapularis footprint in 10 cadaveric shoulders. The transferred muscles were detached distally, augmented with a semitendinosus and gracilis autograft, and passed anteriorly between the scapula and the subscapularis remnant through a small serratus window to reach the lesser tuberosity. The risk of pedicle compression was subjectively assessed in all cases. Results The trapezius and rhomboid tendons were asymmetric with an average length of 37.6 mm and 21.7 mm, an average width of 63 mm and 33.4 mm, respectively. The mean distances from each distal insertion to the lesser tuberosity were 109 mm for the trapezius and 144 mm for the rhomboid. Mean distances from tendon to pedicle were 57.9 mm and 33.1 mm, respectively. The mean size of the necessary serratus window was 49.4 mm, which was measured at maximal excursion achieved at maximal external rotation 90° representing two digitations. All of the tendon transfers were feasible, and the risk of pedicle compression was 20% for the trapezius and 10% for the rhomboid. Superior migration of the transfer was observed during passive external rotation if the insertion point was too high. Conclusions Transfer of the lower trapezius and rhomboid minor to the lesser tuberosity to reconstruct an irreparable subscapularis tear is feasible without extensive dissection and with a low risk of nerve compression. We recommend not to transfer the rhomboid minor routinely, owing to the risk of tendon luxation after external rotation of the shoulder.

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“…The inferior part is the biggest and most important segment, which also has a synergistic protraction effect. 9 , 11 , 33 , 42 , 46 …”

Section: Discussionmentioning

confidence: 99%

Feasibility of lower trapezius and rhomboid minor transfer for irreparable subscapularis tears: an anatomic cadaveric study

Cartaya

Canales

Werthel³

et al. 2021

JSES International

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“…The middle belly of the SA originates from the 2nd, 3rd, and 4th ribs and inserts into the medial scapular border 43 . The lower muscle belly of the SA is where the MTrPs frequently exist, originating from the 5th to the 9th ribs and inserting into the inferior angle of the scapula 43,44 . The SA muscle is innervated by the long thoracic nerve, which originates from the anterior rami of spinal nerves C5-C7 45 .…”

Section: Discussionmentioning

confidence: 99%

Intramuscular Neural Distribution of the Serratus Anterior Muscle: Guidelines to the Injective Method for Treating Myofascial Pain Syndrome

Yi¹,

Lee²,

Seo³

et al. 2021

Preprint

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The serratus anterior muscle is commonly involved in myofascial pain syndrome and is treated with many different injective methods. Currently, there is no definite injection point for the muscle. This study provides an ideal injection point for the serratus anterior muscle considering the intramuscular neural distribution using the whole mount staining method. A modified Sihler method was applied to the serratus anterior muscles (15 specimens). The intramuscular arborization areas were identified in terms of the anterior (100%), middle (50%), posterior axillary line (0%), and from the first to the ninth ribs. The intramuscular neural distribution for the serratus anterior muscle had the largest arborization patterns in the 5th to 9th rib portion between 50% and 70%, and the 1st to 4th rib portion had between 20% and 40%. Clinicians can administer safe and effective treatments with botulinum neurotoxin injections and other types of injections, following the methods in our study. We propose optimal injection sites in relation to the external anatomical line for the frequently injected facial muscles to facilitate the efficiency of botulinum neurotoxin injections. Lastly, these guidelines would assist practice more accurately without the harmful side effects of trigger point injections and botulinum neurotoxin injections.

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“…When the fractured fragment of the ISA is small, the lower part of the SA and a part of the latissimus dorsi originating from the scapula remain attached to it; when the fragment is large, the lower parts of the rhomboid major and teres major may also be attached to it [17, 19]. The SA consists of digitations arising from the upper eight to ten ribs and intercostal fascia and is divided into three parts: upper, middle, and lower; the lower part is formed by the lower four to five digitations and is attached to the ISA [24, 25]. The powerful lower part of the SA pulls the fracture fragment inferolaterally.…”

Section: Discussionmentioning

confidence: 99%

Overlooked Fracture of the Inferior Scapular Angle Treated Conservatively

Ogawa

Inokuchi

Honma

2019

Case Reports in Orthopedics

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Isolated fracture of the inferior scapular angle is extremely rare. We present the case of a 20-year-old female with persistent periscapular pain and a winged scapula caused by delayed union of an inferior scapular angle (ISA) fracture. Ten months previously, the patient had a car accident while seated in the left rear passenger seat. The patient visited an orthopedic clinic where a surgeon diagnosed left shoulder contusion without any abnormal radiographic findings. The left arm was kept in a sling for 2 months, as left arm elevation caused severe pain in the upper back. After sling removal, the dull pain around the left scapula continued. The patient presented at our clinic because her mother had noticed the deformity of her back. Radiographs showed a small bony fragment in the ventral side of the ISA. Computed tomography revealed a narrow gap between the ISA and the fragment. The patient's symptoms resolved with conservative treatment that consisted of relative rest for 2 months and subsequent reinforcement exercises of the serratus anterior for 2 months.

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A novel cadaveric study of the morphometry of the serratus anterior muscle: one part, two parts, three parts, four?

Cited by 6 publications

References 34 publications

Feasibility of lower trapezius and rhomboid minor transfer for irreparable subscapularis tears: an anatomic cadaveric study

Feasibility of lower trapezius and rhomboid minor transfer for irreparable subscapularis tears: an anatomic cadaveric study

Intramuscular Neural Distribution of the Serratus Anterior Muscle: Guidelines to the Injective Method for Treating Myofascial Pain Syndrome

Overlooked Fracture of the Inferior Scapular Angle Treated Conservatively

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