PURPOSE: This study provides an insight on the extent of muscular variability at the suprascapular notch and elaborates on its anatomical interference in suprascapular nerve arthroscopic decompression procedures. METHODS: The suprascapular notch was dissected and its muscular topography was observed in 115 cadaveric specimens. High resolution imaging of the suprascapular notch was captured by a handheld digital microscope (Q-scope). The supraspinatus and subscapularis muscles were traced as they course at the suprascapular notch vicinity. The omohyoid muscle attachment onto the suprascapular ligament was measured. A scoping review and meta-analysis were done to investigate the observed rare muscular variants. RESULTS: In 3.48%, the suprascapular notch anterior surface was fully covered by the subscapularis muscle. The omohyoid muscle inserted onto the suprascapular ligament in 31.25% and extended up to 3/4th of the suprascapular ligament length in 2.61%. Two rare variant muscles were encountered: subclavius posticus muscle and a newly reported "coracoscapularis muscle". CONCLUSIONS: Four categories of muscles with topographical relationship to the suprascapular notch and its arthroscopic feasibility have been classified: (1) constant muscles not intervening with the suprascapular notch space - supraspinatus muscle; (2) constant muscles with variable positions that can intervene with the suprascapular notch space - subscapularis muscle; (3) constant muscles with variable positions that can intervene with the surgical approach - omohyoid muscle; (4) variable muscles intervening with the suprascapular notch space and surgical approach - subclavius posticus and coracoscapularis muscles. This study elucidates the necessity to assess/secure the omohyoid muscle attachment onto the suprascapular ligament in suprascapular nerve decompression ligamentectomy. LEVEL OF EVIDENCE: V Basic Science Research.

Centre for Endoscopic Surgical and Clinical Anatomy 2nd Faculty of Medicine Charles University Prague Czech Republic

Department of Anatomy 2nd Faculty of Medicine Charles University 5 Uvalu 84 Prague 150 06 Czech Republic

Department of Bioinformatics 2nd Faculty of Medicine Charles University Prague Czech Republic

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Agrawal V (2009) Arthroscopic decompression of a bony suprascapular foramen. Arthroscopy 25(3):325–328. https://doi.org/10.1016/j.arthro.2008.06.014 PubMed DOI

Akita K, Ibukuro K, Yamaguchi K, Heima S, Sato T (2000) The subclavius posticus muscle: a factor in arterial, venous or brachial plexus compression. Surg Radiol Anat 22:111–115. https://doi.org/10.1007/s00276-000-0111-6 PubMed DOI

Al-Redouan A, Holding K, Kachlik D (2021a) Suprascapular canal: anatomical and topographical description and its clinical implication in entrapment syndrome. Ann Anat 233:151593. https://doi.org/10.1016/j.aanat.2020.151593 PubMed DOI

Al-Redouan A, Hudak R, Nanka O, Kachlik D (2021b) The morphological stenosis pattern of the suprascapular notch is revealed yielding higher incidence in the discrete type and elucidating the inevitability of osteoplasty in horizontally oriented stenosis. Knee Surg Sports Traumatol Arthrosc 29(7):2272–2280. https://doi.org/10.1007/s00167-020-06168-1 PubMed DOI

Al-Redouan A, Kachlik D (2022) Scapula revisited: new features identified and denoted by terms using consensus method of Delphi and taxonomy panel to be implemented in radiologic and surgical practice. J Shoulder Elb Surg 31(2):e68–e81. https://doi.org/10.1016/j.jse.2021.07.020 DOI

Arksey H, O’Malley L (2005) Scoping studies: towards a methodological framework. Int J Soc Res Methodol 8:19–32. https://doi.org/10.1080/1364557032000119616 DOI

Avery BW, Pilon FM, Barclay JK (2002) Anterior coracoscapular ligament and suprascapular nerve entrapment. Clin Anat 15(6):383–386. https://doi.org/10.1002/ca.10058 PubMed DOI

Balduzzi S, Rücker G, Schwarzer G (2019) How to perform a meta-analysis in R: a practical tutorial. Evid Based Ment Health 22:153–160. https://doi.org/10.1136/ebmental-2019-300117 PubMed DOI PMC

Barber FA (2008) Percutaneous arthroscopic release of the suprascapular nerve. Arthroscopy 24(2):236e1–236e4. https://doi.org/10.1016/j.arthro.2007.05.004 DOI

Barwood SA, Burkhart SS, Lo IK (2007) Arthroscopic suprascapular nerve release at the suprascapular notch in a cadaveric model: an anatomic approach. Arthroscopy 23(2):221–225. https://doi.org/10.1016/j.arthro.2006.11.011 PubMed DOI

Bayramoglu A, Demiryürek D, Tüccar E, Erbil M, Aldur MM, Tetik O, Doral MN (2003) Variations in anatomy at the suprascapular notch possibly causing suprascapular nerve entrapment: an anatomical study. Knee Surg Sports Traumatol Arthrosc 11:393–398. https://doi.org/10.1007/s00167-003-0378-3 PubMed DOI

Bhat N, Pandey AK, Divya C, Kotian SR, Kalthur SG (2018) Omohyoid muscle: an anatomical study. JKIMSU 7:21–26

Bhatia DN, de Beer JF, van Rooyen KS, du Toit DF (2006) Arthroscopic suprascapular nerve decompression at the suprascapular notch. Arthroscopy 22(9):1009–1013. https://doi.org/10.1016/j.arthro.2006.05.012 PubMed DOI

Bhavya BS, Myageri M, Smitha M, Eligar RC (2021) A cadaveric study on subclavius posticus muscle. J Anat Soc India 70:97–100. https://doi.org/10.4103/JASI.JASI_45_20 DOI

Boykin RE, Friedman DJ, Higgins LD, Warner JJ (2010) Suprascapular neuropathy. J Bone Joint Surg Am 92(13):2348–2364. https://doi.org/10.2106/JBJS.I.01743 PubMed DOI

Buitrago QER, Quintero PID, Ballesteros ALE (2021) Morphological evaluation of the subclavian muscle in a sample of autopsy material. Clin Inferences Int J Morphol 39:1559–1563. https://doi.org/10.4067/S0717-95022021000601559 DOI

Buntine JA (1970) The omohyoid muscle and fascia: morphology and anomalies. ANZ J Surg 40:86–88. https://doi.org/10.1111/j.1445-2197.1970.tb04034.x DOI

Cano-Martínez JA, Nicolás-Serrano G, Villodres Corpás J, Bento-Gerard J (2021) Arthroscopic release of proximal supra-scapular nerve entrapment: medium-term results. Rev Esp Cir Ortop Traumatol (Engl Ed) 65(2):91–98. https://doi.org/10.1016/j.recot.2020.10.001 PubMed DOI

Christensen R (2023) Ordinal-Regression Models for Ordinal Data. R package version. 2023:12-4. https://CRAN.R-project.org/package=ordinal

Cogar AC, Johnson PH, Potter HG, Wolfe SW (2015) Subclavius Posticus: an anomalous muscle in association with suprascapular nerve compression in an athlete. HAND 10:76–79. https://doi.org/10.1007/s11552-014-9652-8 PubMed DOI

Crepaz-Eger U, Lambert S, Hörmann R, Knierzinger D, Brenner E, Hengg C (2022) The anatomy and variation of the coracoid attachment of the subclavius muscle in humans. J Anat 240(2):376–384. https://doi.org/10.1111/joa.13548 PubMed DOI

Dietrich LN, Bentley A, Savage JA, Momaya AM, Larrison MC, McGwin G, Ponce BA (2015) Arthroscopic decompression at the suprascapular notch: a radiographic and anatomic roadmap. J Shoulder Elb Surg 24(3):433–438. https://doi.org/10.1016/j.jse.2014.07.018 DOI

Florczynski M, Paul R, Leroux T, Baltzer H (2021) Prevention and treatment of nerve injuries in shoulder arthroplasty. J Bone Joint Surg Am 103(10):935–946. https://doi.org/10.2106/JBJS.20.01716 PubMed DOI

Gigas H (1941) [Untersuchengen über Musckelvaritäten an Zwillingen. Z Morphol Anthropol] 39:480–537 In German

Gürses İA, Gayretli Ö, Coşkun O, Kale A, Öztürk A (2015) Anatomical relations between anterior coracoscapular ligament and suprascapular neurovascular structures and a proposal for classification. Acta Orthop Traumatol Turc 49(4):433–437. https://doi.org/10.3944/AOTT.2015.14.0333 PubMed DOI

Henry BM, Tomaszewski KA, Walocha JA (2016) Methods of evidence-based anatomy: a guide to conducting systematic reviews and meta-analysis of anatomical studies. Ann Anat 205:16–21. https://doi.org/10.1016/j.aanat.2015.12.002 PubMed DOI

Kim SH, Kim SJ, Sung CH, Koh YG, Kim YC, Park YS (2009) Arthroscopic suprascapular nerve decompression at the suprascapular notch. Knee Surg Sports Traumatol Arthrosc 17(12):1504–1507. https://doi.org/10.1007/s00167-009-0858-1 PubMed DOI

Kumar R, Borthakur D, Rani N, Singh S (2023) Anatomical diversity of inferior belly of the omohyoid muscle - anatomical, physiological and surgical paradigm. Morphologie 107(356):142–146. https://doi.org/10.1016/j.morpho.2022.01.003 PubMed DOI

Lafosse L, Tomasi A, Corbett S, Baier G, Willems K, Gobezie R (2007) Arthroscopic release of suprascapular nerve entrapment at the suprascapular notch: technique and preliminary results. Arthroscopy 23(1):34–42. https://doi.org/10.1016/j.arthro.2006.10.003 PubMed DOI

Lubowitz JH, D’Agostino RB Jr, Provencher MT, Poehling GG (2012) Shoulder arthroscopy literature remains controversial. Arthroscopy 28(11):1581–1583. https://doi.org/ PubMed DOI

Lubowitz JH, Poehling GG (2009) Shoulder arthroscopy: evolution of the revolution. Arthroscopy 25(8):823–824. https://doi.org/10.1016/j.arthro.2009.06.015 PubMed DOI

Maurya S, Renganathan G, Bharti RV R (2021) Outcomes of shoulder functions in spinal accessory to suprascapular nerve transfer in Brachial Plexus Injury: a comparison between anterior and posterior Approach. Indian J Plast Surg 54(2):152–156. https://doi.org/10.1016/j.arthro.2012.07.001 PubMed DOI PMC

Memon M, Kay J, Ginsberg L, Simunovic N, Bak K, Lapner P, Ayeni OR (2018) Arthroscopic management of suprascapular neuropathy of the shoulder improves pain and functional outcomes with minimal complication rates. Knee Surg Sports Traumatol Arthrosc 26(1):240–266. https://doi.org/10.1007/s00167-017-4694-4 PubMed DOI

Mizen KD, Mitchell DA (2005) Anatomical variability of omohyoid and its relevance in oropharyngeal cancer. Br J Oral Maxillofac Surg 43:285–288. https://doi.org/10.1016/j.bjoms.2004.11.019 PubMed DOI

Mori M (1964) Statistics on the musculature of the Japanese. Okajimas Folia Anat Jpn 40:195–300. https://doi.org/10.2535/ofaj1936.40.3_195 PubMed DOI

Moyano PJ, Capurro M, Apa SN, Albanese EF (2018) Subclavius posticus muscle with anomalous posterior insertion: case report. Int J Morphol 36:22–25. https://doi.org/10.4067/S0717-95022018000100022 DOI

Nolte PC, Woolson TE, Elrick BP, Tross AK, Horan MP, Godin JA, Millett PJ (2021) Clinical outcomes of arthroscopic suprascapular nerve decompression for suprascapular neuropathy. Arthroscopy 37(2):499–507. https://doi.org/10.1016/j.arthro.2020.10.020 PubMed DOI

Ong JZ, Tham AC, Tan JL (2021) A systematic review of the Omohyoid muscle syndrome (OMS): clinical presentation, diagnosis, and Treatment options. Ann Otol Rhinol Laryngol 130(10):1181–1189. https://doi.org/10.1177/0003489421995037 PubMed DOI

Piyawinijwong S, Sirisathira N (2010) Supernumerary subclavius muscle in Thais: predisposing cause of thoracic outlet syndrome. J Med Assoc Tha I 93:1065–1069

Podgórski M, Topol M, Sibiński M, Domżalski M, Grzelak P, Polguj M (2015) What is the function of the anterior coracoscapular ligament? - a morphological study on the newest potential risk factor for suprascapular nerve entrapment. Ann Anat 201:38–42. https://doi.org/10.1016/j.aanat.2015.06.005 PubMed DOI

Polguj M, Jędrzejewski K, Topol M (2012) The bifid anterior coracoscapular ligament: a new morphological variation and its potential clinical implications. Folia Morphol (Warsz) 71(4):282–284 PubMed

Polguj M, Jędrzejewski K, Topol M (2013) Variable morphology of the anterior coracoscapular ligament - a proposal of classification. Ann Anat 195(1):77–81. https://doi.org/10.1016/j.aanat.2012.06.003 PubMed DOI

Polguj M, Synder M, Borowski A, Wojciechowski M, Wysiadecki G, Topol M (2016) Anterior Coracoscapular Ligament as a factor predisposing to or protective for Suprascapular Neuropathy. Biomed Res Int 2016(4134280). https://doi.org/10.1155/2016/4134280

Rabi S, Madhavi C (2008) Case reports with special reference to the innervation, development and clinical significance of the subclavius posticus and the termination of the facial vein in South Indian cadavers. Eur J Anat 12:133–136

Reid RW, Taylor S (1879) Anatomical variations. In: Cory R, Mason F, eds. Saint Thomas’s Hospital Reports. London: J. & A. Churchill 43–51.

Romeo AA, Ghodadra NS, Salata MJ, Provencher MT (2010) Arthroscopic suprascapular nerve decompression: indications and surgical technique. J Shoulder Elb Surg 19(2):118–123. https://doi.org/10.1016/j.jse.2010.01.006 DOI

Singh N, Kathole M, Kaur J, Mehta V, Suri RK, Rath G, Kohli M (2018) Bilateral clavicular attachment of omohyoid muscle. Morphologie 102:87–90. https://doi.org/10.1016/j.morpho.2017.08.001 PubMed DOI

Tubbs RS, Loukas M, Shoja MM, Spinner RJ, Middlebrooks EH, Stetler WR Jr, Acakpo-Satchivi L, Wellons JC 3rd, Blount JP, Oakes WJ (2007) Endoscopically assisted decompression of the suprascapular nerve in the supraspinous fossa: a cadaveric feasibility study. Laboratory investigation. J Neurosurg 107(6):1164–1167. https://doi.org/10.3171/JNS-07/12/1164 PubMed DOI

Ulusoy OL, Alis D, Oz A, Barlas SB, Sokmen BK, Sever S, Mutlu A, Colakoglu B (2018) The prevalence and characteristics of the subclavius posticus muscle in the adult population on MRI. Surg Radiol Anat 40:1141–1145. https://doi.org/10.1007/s00276-018-2065-6 PubMed DOI

Verma L, Jaiswal P, Ghulyani T, Gupta S (2016) The cleidohyoid: a variant of omohyoid muscle? J Case Rep 6:277–279. https://doi.org/10.17659/01.2016.0068 DOI

Wood J (1868) Variations in human myology observed during the winter session of 1867-68 at King’s College, London. Proceedings of the Royal Society of London 1867–1868. 16:483–525. https://doi.org/10.1098/rspl.1867.0110

Yamakado K (2015) Quantification of the learning curve for arthroscopic suprascapular nerve decompression: an evaluation of 300 cases. Arthroscopy 31(2):191–196. https://doi.org/10.1016/j.arthro.2014.08.029 PubMed DOI

Yang HJ, Gil YC, Jin JD, Ahn SV, Lee HY (2012) Topographical anatomy of the suprascapular nerve and vessels at the suprascapular notch. Clin Anat 25:359–365. https://doi.org/10.1002/ca.21248 PubMed DOI

Zlotolow DA, Low SL, Lin IC, Williamson C, Tinsley B, Kozin SH (2019) Suprascapular ligament release from an anterior approach: an anatomic feasibility study. J Hand Surg Am 44(10):900e1–e4. https://doi.org/10.1016/j.jhsa.2018.12.005 DOI