Latissimus dorsi muscle#Variations

{{multiple image|perrow = 1|image1 = Braus 1921 137.png|300|image2 = Grant 1962 27c.png|300|footer = Axillary arches shown from two different angles.}}

The number of dorsal vertebrae, to which it is attached, varies from four to eight; the number of costal attachments varies; muscle fibers may or may not reach the crest of the ilium.

A muscle slip, the axillary arch, varying from 7 to 10 cm in length, and from 5 to 15 mm in breadth, occasionally springs from the upper edge of the latissimus dorsi about the middle of the posterior fold of the axilla, and crosses the axilla in front of the axillary vessels and nerves, to join the under surface of the tendon of the pectoralis major, the coracobrachialis, or the fascia over the biceps brachii. This axillary arch crosses the axillary artery, just above the spot usually selected for the application of a ligature, and may mislead a surgeon. It is present in about 7% of the population and may be easily recognized by the transverse direction of its fibers. Guy et al. extensively described this muscular variant using MRI data and positively correlated its presence with symptoms of neurological impingement.{{cite journal | last1 = Guy | first1 = MS | last2 = Sandhu | first2 = SK | last3 = Gowdy | first3 = JM | last4 = Cartier | first4 = CC | last5 = Adams | first5 = JH | date = Jan 2011 | title = MRI of the axillary arch muscle: prevalence, anatomic relations, and potential consequences | journal = AJR Am J Roentgenol | volume = 196 | issue = 1| pages = W52–7 | doi = 10.2214/ajr.10.4380 | pmid = 21178031 }}

A fibrous slip usually passes from the upper border of the tendon of the Latissimus dorsi, near its insertion, to the long head of the triceps brachii. This is occasionally muscular, and is the representative of the dorsoepitrochlearis brachii of apes.{{cite journal | last1 = Haninec | first1 = P | last2 = Tomás | first2 = R | last3 = Kaiser | first3 = R | last4 = Cihák | first4 = R | year = 2009 | title = Development and clinical significance of the musculus dorsoepitrochlearis in men | journal = Clin. Anat. | volume = 22 | issue = 4| pages = 481–8 | pmid = 19373904 | doi = 10.1002/ca.20799 | s2cid = 221547558 }}Edwards, William E., The Musculoskeletal Anatomy of the Thorax and Brachium of an Adult Female Chimpanzee,6571st Aeromedical Research Laboratory, New Mexico, 1965. [https://web.archive.org/web/20200808175618/https://apps.dtic.mil/dtic/tr/fulltext/u2/462433.pdf] This muscular form is found in ~5% of humans and is sometimes termed the latissimocondyloideus.{{cite web|title=Anatomy Atlases: Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles: L:Latissimus Dorsi|url=http://www.anatomyatlases.org/AnatomicVariants/MuscularSystem/Text/L/06Latissimus.shtml|website=www.anatomyatlases.org}}

The latissimus dorsi crosses the inferior angle of the scapula. A study found that, of 100 cadavers dissected:{{Cite book|last1=Giacomo|first1=Giovanni Di|last2=Pouliart|first2=Nicole|last3=Costantini|first3=Alberto|last4=Vita|first4=Andrea de|title=Atlas of Functional Shoulder Anatomy|url=https://books.google.com/books?id=EGM73_guZB8C&q=latissimus+dorsi+scapula&pg=PA16|publisher=Springer Science & Business Media|language=en|date=25 September 2008|isbn=9788847007598}}

• 43% had "a substantial amount" of fibers in the latissimus dorsi originating from the scapula.
• 36% had few or no muscular fibers, but a "soft fibrous link" between the scapula and the latissimus dorsi
• 21% had little or no connecting tissue between the two structures.

• The lateral margin of the latissimus dorsi is separated below from the obliquus externus abdominis by a small triangular interval, the lumbar triangle of Petit, the base of which is formed by the iliac crest, and its floor by the obliquus internus abdominis.
• Another triangle is situated behind the scapula. It is bounded above by the trapezius, below by the latissimus dorsi, and laterally by the vertebral border of the scapula; the floor is partly formed by the rhomboideus major. If the scapula is drawn forward by folding the arms across the chest, and the trunk bent forward, parts of the sixth and seventh ribs and the interspace between them become subcutaneous and available for auscultation. The space is therefore known as the triangle of auscultation.
• The latissimus dorsi can be remembered best for insertion as "A Miss Between Two Majors". As the latissimus dorsi inserts into the floor of the intertubercular groove of the humerus it is surrounded by two major muscles. The teres major inserts medially on the medial lip of the intertubercular groove and the pectoralis major inserts laterally onto the lateral lip.

The latissimus dorsi is innervated by the sixth, seventh, and eighth cervical nerves through the thoracodorsal (long subscapular) nerve. Electromyography suggests that it consists of six groups of muscle fibres that can be independently coordinated by the central nervous system.{{cite journal | last1 = Brown | first1 = JM | last2 = Wickham | first2 = JB | last3 = McAndrew | first3 = DJ | last4 = Huang | first4 = XF | year = 2007 | title = Muscles within muscles: Coordination of 19 muscle segments within three shoulder muscles during isometric motor tasks | journal = J Electromyogr Kinesiol | volume = 17 | issue = 1| pages = 57–73 | doi = 10.1016/j.jelekin.2005.10.007 | pmid = 16458022 }}

The latissimus dorsi assists in depression of the arm with the teres major and pectoralis major. It adducts, extends, and internally rotates the shoulder. When the arms are in a fixed overhead position, the latissimus dorsi pulls the trunk upward and forward.{{Cite journal|last1=George|first1=Michael S.|last2=Khazzam|first2=Michael|date=February 2019|title=Latissimus Dorsi Tendon Rupture|journal=Journal of the American Academy of Orthopaedic Surgeons|language=en|volume=27|issue=4|pages=113–118|doi=10.5435/JAAOS-D-17-00581|pmid=30278013|s2cid=52910621|issn=1067-151X}}

It has a synergistic role in extension (posterior fibers) and lateral flexion (anterior fibers) of the lumbar spine, and assists as a muscle of both forced expiration (anterior fibers) and an accessory muscle of inspiration (posterior fibers).{{cite book|title=Muscles Testing and Function With Posture and Pain|year=2005|page=238|isbn=9780781747806|last1=Kendall|first1=Florence Peterson|last2=McCreary|first2=Elizabeth Kendall|last3=Provance|first3=Patricia Geise}}

Most latissimus dorsi exercises concurrently recruit the teres major, posterior fibres of the deltoid, long head of the triceps brachii, among numerous other stabilizing muscles. Compound exercises for the 'lats' typically involve elbow flexion and tend to recruit the biceps brachii, brachialis, and brachioradialis for this function. Depending on the line of pull, the trapezius muscles can be recruited as well; horizontal pulling motions such as rows recruit both latissimus dorsi and trapezius heavily.

The power/size/strength of this muscle can be trained with a variety of different exercises. Some of these include:

• Vertical pulling movements such as pull-downs and pull-ups (including chin-ups)
• Horizontal pulling movements such as bent-over row, T-bar row and other rowing exercises
• Shoulder extension movements with straight arms such as straight-arm lat pulldowns and pull-overs
• Deadlift

Tight latissimus dorsi has been shown to be a contributor to chronic shoulder pain and chronic back pain.Arnheim, D.D., Prentice, W.E., Principles of athletic training. 9th ed. McGraw Hill, pp 570-574, 1997. Because the latissimus dorsi connects the spine to the humerus, tightness in this muscle can manifest as either sub-optimal glenohumeral joint (shoulder) function which leads to chronic pain or tendinitis in the tendinous fasciae connecting the latissimus dorsi to the thoracic and lumbar spine.Francis, P., Applied anatomy and kinesiology, supplemental materials. KB Books., p 19-25, 1999.

The latissimus dorsi is a potential source of muscle for breast reconstruction surgery after mastectomy (e.g., Mannu flap) Mannu, G. S., Farooq, N., Down, S., Burger, A. and Hussien, M. I. (2013), Avoiding back wound dehiscence in extended latissimus dorsi flap reconstruction. ANZ J Surg, 83: 359–364. http://onlinelibrary.wiley.com/doi/10.1111/j.1445-2197.2012.06292.x/full or to correct pectoral hypoplastic defects such as Poland's syndrome.{{cite journal |vauthors=Yang CE, Roh TS, Yun IS, Kim YS, Lew DH |title=Immediate partial breast reconstruction with endoscopic latissimus dorsi muscle flap harvest |journal=Arch Plast Surg |volume=41 |issue=5 |pages=513–9 |year=2014 |pmid=25276643 |pmc=4179355 |doi=10.5999/aps.2014.41.5.513}}{{cite journal |vauthors=Lantzsch T, Lampe D, Kantelhardt EJ |title=Correction of Poland's Syndrome: Case Report and Review of the Current Literature |journal=Breast Care (Basel) |volume=8 |issue=2 |pages=139–42 |year=2013 |pmid=24419214 |pmc=3683949 |doi=10.1159/000350778}} An absent or hypoplastic latissimus dorsi can be one of the associated symptoms of Poland's syndrome.{{cite journal |vauthors=Masia J, Pons G, Loschi P, Sanchez Porro-Gil L, Nardulli ML, Olivares L |title=Autologous reconstruction of a complex form of Poland syndrome using 2 abdominal perforator free flaps |journal=Ann Plast Surg |volume=74 |issue=5 |pages=580–3 |year=2015 |pmid=24322640 |doi=10.1097/SAP.0b013e31829a39b1}}{{cite journal |vauthors=Beer GM, Kompatscher P, Hergan K |title=Poland's syndrome and vascular malformations |journal=Br J Plast Surg |volume=49 |issue=7 |pages=482–4 |year=1996 |pmid=8983554|doi=10.1016/S0007-1226(96)90037-5 |doi-access=free }}

For heart patients with low cardiac output and who are not candidates for cardiac transplantation, a procedure called cardiomyoplasty may support the failing heart. This procedure involves wrapping the latissimus dorsi muscles around the heart and electrostimulating them in synchrony with ventricular systole.

Injuries to the latissimus dorsi are rare.{{Cite journal |last=Donohue |first=Benjamin F. |last2=Lubitz |first2=Marc G. |last3=Kremchek |first3=Timothy E. |date=2016-12-20 |title=Sports Injuries to the Latissimus Dorsi and Teres Major |url=http://dx.doi.org/10.1177/0363546516676062 |journal=The American Journal of Sports Medicine |volume=45 |issue=10 |pages=2428–2435 |doi=10.1177/0363546516676062 |issn=0363-5465|url-access=subscription }} They occur disproportionately in baseball pitchers. Diagnosis can be achieved by visualization of the muscle and movement testing. MRI of the shoulder girdle will confirm the diagnosis. Muscle belly injuries are treated with rehabilitation while tendon avulsion injuries can be treated surgically, or with rehab. Regardless of treatment, patients tend to return to play without any functional losses.{{cite journal |last1=Donohue |first1=Benjamin |last2=Lubitz |first2=Marc |date=December 20, 2016|title=Sports Injuries to the Latissimus Dorsi and Teres Major |journal=The American Journal of Sports Medicine |volume=45 |issue=10 |pages=2428–2435 |doi=10.1177/0363546516676062 |pmid=28125914 |s2cid=3872258 }}

File:Latissimus dorsi muscle animation.gif|Position of the latissimus dorsi muscle (shown in red). Animation.

File:LumbarTriangle.jpg|Lumbar triangle

File:Slide9111.JPG|Latissimus dorsi

File:2019-05-24 Budapest Cup training pommel horse (Martin Rulsch) 466.jpg|Clearly visible latissimus dorsi muscle of an artistic gymnast on pommel horse.

File:Deutsche Jugendmeisterschaften Gerätturnen männlich Training at Internationales Deutsches Turnfest Berlin 2017 (Martin Rulsch) 0857.jpg|Contraction of the latissimus dorsi muscle of another artistic gymnast on still rings.

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Category:Muscles of the upper limb

Category:Shoulder adductors

Category:Shoulder extensors

Category:Shoulder flexors

Category:Shoulder medial rotators

Category:Spine lateral flexors