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Suprascapular neuropathy

Overview

Suprascapular neuropathy presents in young, active cohorts primarily as either pain or weakness, though its exact association and etiology in patients with rotator cuff pathology remain unclear [1, 4]. While complete neurogenic fatty replacement of the rotator cuff can occur in patients with intact tendons absent traction or compression mechanisms [3], initial management for isolated cases is typically nonoperative. This approach consists of physical therapy, nonsteroidal anti-inflammatory drugs, and activity modification [9]. In the absence of a well-defined lesion producing mechanical compression, suprascapular neuropathy should be treated non-operatively [6].

Operative intervention via open or arthroscopic decompression is warranted for isolated suprascapular neuropathy when there is extrinsic nerve compression or progressive pain and/or weakness [9]. Arthroscopic decompression at the suprascapular and/or spinoglenoid notch in the absence of major concomitant glenohumeral pathology results in good functional outcomes with significant improvements from before to after surgery [5]. However, decompression at the spinoglenoid notch did not lead to a better functional outcome compared to repair alone in patients with posterosuperior massive rotator cuff tears and suprascapular neuropathy [8]. Combined arthroscopic release of the superior transverse scapular ligament and rotator cuff repair in patients with large or massive tears did not produce statistically significant improved outcomes compared with repair of the rotator cuff alone [18], and no recommendations regarding suprascapular nerve release in conjunction with rotator cuff repair can be made at this time [19].

Shoulder surgeons should consider electrophysiologic evaluation of patients with clinical or radiographic signs of suprascapular neuropathy and be cognizant of the parameters that constitute an abnormal study [2]. Preoperative suprascapular nerve injuries do not have a significant clinical impact and do not predispose to an acute postoperative lesion after reverse total shoulder arthroplasty [7].

Anatomy & Pathophysiology

Osseous Variations: Anatomical variations at the suprascapular notch, including abnormally oriented subscapularis muscle fibers, an anterior coracoscapular ligament, and a calcified superior transverse scapular ligament, are predisposing factors for suprascapular nerve entrapment [28]. Regardless of height and sex, the distance from the posterolateral corner of the acromion to the suprascapular notch is approximately 43 mm [27], while the distance to the spinoglenoid notch is approximately 32 mm [27].

Kinematics & Safe Zones: The suprascapular nerve is furthest away from the posterior edge of the glenoid with the shoulder at 90 degrees of external rotation [16]. Knowledge of the safe zone for avoiding suprascapular nerve injury is important, and gender and specific scapular dimensions influence the dimensions of the safe zone [31]. Placement of superior and posterior screws in the glenoid baseplate during reverse total shoulder arthroplasty risks injury to the suprascapular nerve [29], and a malpositioned superior screw can cause suprascapular nerve entrapment [22].

Pathophysiology & Etiology: Suprascapular neuropathy can be caused by a large hematoma of the scapula [14] or a lipoma [10]. The exact association and etiology of suprascapular neuropathy in patients with rotator cuff pathology remain unclear [1]. Suprascapular nerve injury is an underlying mechanism leading to compromise of the rotator cuff enthesis structure [11] and can cause complete neurogenic fatty replacement in patients with intact rotator cuff tendons in the absence of traction or compression mechanisms [3]. In clinical settings, suprascapular nerve injury may cause severe fatty changes and inhibition of postoperative tendon healing in large rotator cuff tears [34].

Classification

Historical Context: Suprascapular nerve entrapment syndrome was first described and correctly interpreted by André Thomas in 1936 [17].

Etiology and Pathophysiology: The exact association and etiology of suprascapular neuropathy in patients with rotator cuff pathology remain unclear [1]. While chronic rotator cuff tendon tears and suprascapular neuropathy are both associated with fatty infiltration and muscle atrophy of the rotator cuff muscles, the pattern of fatty infiltration is markedly different in the two situations [12]. Notably, suprascapular neuropathy can cause complete fatty infiltration of intact rotator cuff tendons in the absence of traction or compression mechanisms [3].

Anatomical Considerations: Entrapment of the suprascapular nerve usually occurs at the suprascapular or spinoglenoid notch [15]. The suprascapular nerve is furthest away from the posterior edge of the glenoid with the shoulder at 90 degrees of external rotation [16].

Clinical Presentation: In young, active cohorts, suprascapular neuropathy presents with one of two distinct primary complaints: pain or weakness [4].

Other Considerations: Preoperative suprascapular nerve injuries do not have a significant clinical impact and do not predispose to an acute postoperative lesion after reverse total shoulder arthroplasty [7].

Clinical Presentation

The clinical history of suprascapular neuropathy varies by patient demographic. In young, active cohorts, the condition presents with one of two distinct primary complaints: pain or weakness [4]. While the exact association and etiology of suprascapular neuropathy in patients with rotator cuff pathology remain unclear [1], the condition can cause complete fatty infiltration of intact rotator cuff tendons in the absence of traction or compression mechanisms [3]. Chronic rotator cuff tendon tears and suprascapular neuropathy are both associated with fatty infiltration and muscle atrophy of the rotator cuff muscles, but the pattern of fatty infiltration is markedly different in the two situations [12].

Physical examination and imaging reveal specific anatomical and pathological features. Entrapment of the suprascapular nerve usually occurs at the suprascapular or spinoglenoid notch [15]. Specific etiologies include an intraosseous ganglion of the glenoid invading adjacent soft tissue [21] or varicose veins at the spinoglenoidal notch, which represent an unusual cause of suprascapular nerve compression [15]. Anatomically, the suprascapular nerve is furthest away from the posterior edge of the glenoid with the shoulder at 90 degrees of external rotation [16].

Regarding surgical implications and historical context, preoperative suprascapular nerve injuries do not have a significant clinical impact and do not predispose to an acute postoperative lesion following reverse total shoulder arthroplasty [7]. The condition was first described and correctly interpreted by André Thomas in 1936 [17].

Investigations

Clinical Presentation: Suprascapular neuropathy presents with one of two distinct primary complaints: pain or weakness [4]. Entrapment of the suprascapular nerve usually occurs at the suprascapular or spinoglenoid notch [15]. Unusual causes of compression include varicose veins at the spinoglenoidal notch [15] and malpositioned superior screws from reverse shoulder arthroplasty [22].

Electrophysiologic Evaluation: Electrophysiologic evaluation should be considered for patients with clinical or radiographic signs of suprascapular neuropathy to identify abnormal study parameters [2]. Outcomes are improved when the nerve is decompressed in overhead athletes with electrodiagnostic evidence of suprascapular neuropathy, though further studies are needed to corroborate these findings with more sensitive outcome measures [20].

Magnetic Resonance Imaging: High-resolution magnetic resonance imaging is recommended to evaluate complex cases of nerve entrapment [30]. Chronic rotator cuff tendon tears and suprascapular neuropathy are both associated with fatty infiltration and muscle atrophy of the rotator cuff muscles, but the pattern of fatty infiltration is markedly different in the two situations [12]. Suprascapular neuropathy can cause complete neurogenic fatty replacement in patients with intact rotator cuff tendons in the absence of traction or compression mechanisms [3]. Suprascapular nerve injury is an underlying mechanism leading to compromise of the rotator cuff enthesis structure [11].

Aspiration: Clinical and radiologic improvement was observed after needle aspiration for suprascapular nerve entrapment caused by an intraosseous ganglion of the glenoid [21]. Spontaneous resolution of a spinoglenoid notch cyst and associated suprascapular nerve palsy has been documented, suggesting surgical treatment could be withheld if patients show signs of clinical recovery provided they are followed closely [35]. Full recovery of shoulder function was achieved in a case of suprascapular nerve entrapment caused by a large hematoma of the scapula [14].

Other Considerations: The exact association and etiology of suprascapular neuropathy in patients with rotator cuff pathology remain unclear [1]. Preoperative suprascapular nerve injuries do not have a significant clinical impact and do not predispose to an acute postoperative lesion [7]. A complete history and physical, careful attention to auxiliary tests, and treatment of multiple diagnoses in the same shoulder avoids missed pathologic features and necessity for revision operations [10]. Release of the spinoglenoid ligament with resultant suprascapular nerve decompression may result in relief of pain and a return of normal shoulder function [13].

Treatment

Non-Operative

In the absence of a well-defined lesion producing mechanical compression of the suprascapular nerve, suprascapular neuropathy should be treated non-operatively [6]. Initial management for isolated cases typically consists of physical therapy, nonsteroidal anti-inflammatory drugs, and activity modification [9].

Operative

Indications: Open or arthroscopic operative intervention is warranted when there is extrinsic nerve compression or progressive pain and/or weakness [9]. Preoperative suprascapular nerve injuries do not have a significant clinical impact and do not predispose to an acute postoperative lesion [7].

Surgical Approach / Technique: Arthroscopic release of the suprascapular nerve can be performed safely and effectively, with all patients showing improvement in postoperative electromyographic findings and marked improvement in pain relief and function [25]. Arthroscopic release of the suprascapular nerve and transverse ligament is a safe and effective treatment for competitive swimmers with suprascapular neuropathy, allowing return to sport with resolution of pain and improvement in function [26]. Release of the spinoglenoid ligament with resultant suprascapular nerve decompression may result in relief of pain and a return of normal shoulder function [13]. Arthroscopic suprascapular nerve decompression at the suprascapular and/or spinoglenoid notch in the absence of major concomitant glenohumeral pathology results in good functional outcomes with significant improvements from before to after surgery [5].

Adjuncts: In patients with posterosuperior massive rotator cuff tears and suprascapular neuropathy, decompression of the suprascapular nerve at the spinoglenoid notch did not lead to a better functional outcome compared to repair alone [8]. Combined arthroscopic release of the superior transverse scapular ligament and rotator cuff repair in patients with large/massive rotator cuff tears and suprascapular neuropathy did not produce statistically significant improved outcomes compared with repair of the rotator cuff alone [18]. No recommendations regarding suprascapular nerve release in conjunction with rotator cuff repair can be made at this time, and further research is necessary to better delineate the indications in the future [19].

Complications

Nerve palsy: The exact association and etiology of suprascapular neuropathy in patients with rotator cuff pathology remain unclear [1]. Suprascapular nerve injury is an underlying mechanism leading to compromise of the rotator cuff enthesis structure [11], and can cause complete fatty infiltration of intact rotator cuff tendons in the absence of traction or compression mechanisms [3]. While chronic rotator cuff tendon tears and suprascapular neuropathy are both associated with fatty infiltration and muscle atrophy, the pattern of fatty infiltration is markedly different in the two situations [12]. In young, active cohorts, suprascapular neuropathy presents with one of two distinct primary complaints: pain or weakness [4]. Preoperative suprascapular nerve injuries do not have a significant clinical impact and do not predispose to an acute postoperative lesion following reverse total shoulder arthroplasty [7].

Management: In the absence of a well-defined lesion producing mechanical compression of the suprascapular nerve, suprascapular neuropathy should be treated non-operatively [6]. Initial treatment of isolated suprascapular neuropathy is typically nonoperative, consisting of physical therapy, nonsteroidal anti-inflammatory drugs, and activity modification [9]. Open or arthroscopic operative intervention is warranted for suprascapular neuropathy when there is extrinsic nerve compression or progressive pain and/or weakness [9]. Arthroscopic suprascapular nerve decompression at the suprascapular and/or spinoglenoid notch in the absence of major concomitant glenohumeral pathology results in good functional outcomes with significant improvements from before to after surgery [5]. However, decompression of the suprascapular nerve at the spinoglenoid notch did not lead to a better functional outcome compared to repair alone in patients with posterosuperior massive rotator cuff tears and suprascapular neuropathy [8]. A complete history and physical, careful attention to auxiliary tests, and treatment of multiple diagnoses in the same shoulder avoids missed pathologic features and the necessity for revision operations [10].

Other Considerations: Evidence regarding the specific etiology of neuropathy in rotator cuff pathology remains inconclusive [1], and distinct patterns of fatty infiltration differentiate neuropathy from chronic tears [12].

Recovery

Initial Management: In the absence of a well-defined lesion producing mechanical compression of the suprascapular nerve, suprascapular neuropathy should be treated non-operatively [6]. Initial treatment of isolated suprascapular neuropathy is typically nonoperative, consisting of physical therapy, nonsteroidal anti-inflammatory drugs, and activity modification [9]. Operative intervention (open or arthroscopic) is warranted for suprascapular neuropathy when there is extrinsic nerve compression or progressive pain and/or weakness [9].

Surgical Outcomes: Arthroscopic suprascapular nerve decompression at the suprascapular and/or spinoglenoid notch in the absence of major concomitant glenohumeral pathology results in good functional outcomes with significant improvements from before to after surgery [5]. Release of the spinoglenoid ligament with resultant suprascapular nerve decompression may result in relief of pain and a return of normal shoulder function [13]. Full recovery of shoulder function was achieved in a case of suprascapular nerve entrapment caused by a large hematoma of the scapula [14]. Suprascapular neuropathy in patients with rotator cuff pathology may present with one of two distinct primary complaints: pain or weakness [4].

Rotator Cuff Pathology Considerations: Decompression of the suprascapular nerve at the spinoglenoid notch did not lead to a better functional outcome compared to repair alone in patients with posterosuperior massive rotator cuff tears and suprascapular neuropathy [8]. Combined arthroscopic release of the superior transverse scapular ligament and rotator cuff repair in patients with large or massive rotator cuff tears and associated suprascapular neuropathy did not produce statistically significant improved outcomes compared with repair of the rotator cuff alone [18]. Preoperative suprascapular nerve injuries do not have a significant clinical impact and do not predispose to an acute postoperative lesion following reverse total shoulder arthroplasty [7].

Key Evidence

  • [L3] The exact association and etiology of suprascapular neuropathy in patients with rotator cuff pathology remain unclear. (10.1016/j.jse.2013.06.011)
  • [L4] Shoulder surgeons should consider electrophysiologic evaluation of patients with clinical or radiographic signs of suprascapular neuropathy and be cognizant of the parameters that constitute an abnormal study. (10.1016/j.jse.2010.10.039)
  • [L4] This is the first description of suprascapular neuropathy with complete neurogenic fatty replacement in patients with intact rotator cuff tendons in the absence of traction or compression mechanisms. (10.1016/j.arthro.2014.01.010)
  • [L4] In this young, active cohort, suprascapular neuropathy presented with one of two distinct primary presenting complaints: pain or weakness. (10.1177/2325967123s00003)
  • [L4] Arthroscopic SSN decompression for suprascapular neuropathy at the suprascapular and/or spinoglenoid notch in the absence of major concomitant glenohumeral pathology results in good functional outcomes with significant improvements from before to after surgery. (10.1016/j.arthro.2020.10.020)
  • [L4] In the absence of a well-defined lesion producing mechanical compression of the suprascapular nerve, suprascapular neuropathy should be treated non-operatively. (10.2106/00004623-199708000-00007)
  • [L1] Preoperative suprascapular nerve injuries do not have a significant clinical impact and do not predispose to an acute postoperative lesion. (10.1016/j.jse.2023.06.026)
  • [L3] Decompression of the suprascapular nerve at the spinoglenoid notch did not lead to a better functional outcome compared to repair alone in patients with posterosuperior massive rotator cuff tears and suprascapular neuropathy. (10.1186/s12891-021-04075-1)
  • [L5] Initial treatment of isolated suprascapular neuropathy is typically nonoperative, consisting of physical therapy, nonsteroidal anti-inflammatory drugs, and activity modification; however, open or arthroscopic operative intervention is warranted when there is extrinsic nerve compression or progressive pain and/or weakness. (10.2106/jbjs.i.01743)
  • [L4] A complete history and physical, careful attention to auxiliary tests, and treatment of multiple diagnoses in the same shoulder avoids missed pathologic features and necessity for revision operations. (10.1097/01.blo.0000063791.32430.59)
  • [L5] This study identifies suprascapular nerve injury as an underlying mechanism leading to compromise of the rotator cuff enthesis structure. (10.1016/j.jse.2019.12.028)
  • [L4] Chronic rotator cuff tendon tears and suprascapular neuropathy are both associated with fatty infiltration and muscle atrophy of the rotator cuff muscles, but the pattern of fatty infiltration is markedly different in the two situations. (10.1016/j.jse.2013.01.028)
  • [L4] Release of the spinoglenoid ligament with resultant suprascapular nerve decompression may result in relief of pain and a return of normal shoulder function. (10.1177/03635465990270062101)
  • [Case_report] Full recovery of shoulder function was achieved. (10.1186/s12891-023-06723-0)
  • [L4] Entrapment of the suprascapular nerve usually occurs at the suprascapular or spinoglenoid notch. (10.1016/j.jse.2011.05.022)
  • [L5] The suprascapular nerve is furthest away from the posterior edge of the glenoid with the shoulder at 90 of external rotation. (10.1007/s00167-014-2900-1)
  • [L4] Suprascapular nerve entrapment syndrome was first described and correctly interpreted by André Thomas in 1936, predating the commonly credited work of Kopell and Thompson. (10.2106/00004623-200108000-00018)
  • [L1] Combined arthroscopic release of the superior transverse scapular ligament and rotator cuff repair in patients with large/massive RCTs and suprascapular neuropathy did not produce statistically significant improved outcomes compared with repair of the rotator cuff alone. (10.1177/03635465211021834)
  • [L4] No recommendations regarding suprascapular nerve release in conjunction with rotator cuff repair can be made at this time, and further research is necessary to better delineate the indications in the future. (10.1016/j.jse.2011.11.033)
  • [L5] Tsikouris et al. have raised awareness of suprascapular neuropathy and suggested that outcomes are improved when the nerve is decompressed in overhead athletes with electrodiagnostic evidence of suprascapular neuropathy, though further studies are needed to corroborate these findings with more sensitive outcome measures. (10.1016/j.arthro.2018.05.017)
  • [Case_report] This is the first report of an intraosseous ganglion of the glenoid invading adjacent soft tissue to cause suprascapular nerve entrapment syndrome, which showed clinical and radiologic improvement after needle aspiration. (10.1016/j.jse.2008.10.014)
  • [Case_report] This case is the first report of malpositioned superior screw from reverse shoulder arthroplasty causing suprascapular nerve entrapment. (10.1016/j.jse.2009.10.004)
  • [L4] Arthroscopic release of the suprascapular nerve can be performed safely and effectively, with all patients showing improvement in postoperative electromyographic findings and marked improvement in pain relief and function. (10.1016/j.arthro.2006.10.003)
  • [L4] Arthroscopic release of the suprascapular nerve and transverse ligament is a safe and effective treatment for competitive swimmers with suprascapular neuropathy, allowing return to sport with resolution of pain and improvement in function. (10.1177/0363546513477383)
  • [L4] Regardless of height and sex, the distances from the posterolateral corner of the acromion to the suprascapular and spinoglenoid notches were approximately 43 and 32 mm, respectively. (10.1016/j.jseint.2022.04.002)
  • [L4] Anatomical variations at the suprascapular notch, including abnormally oriented subscapularis muscle fibers, anterior coracoscapular ligament, and calcified superior transverse scapular ligament, are predisposing factors for suprascapular nerve entrapment. (10.1007/s00167-003-0378-3)
  • [L5] Placement of the superior and posterior screws in the glenoid baseplate during rTSA risks injury to the SSN. (10.1016/j.jse.2020.07.008)
  • [L5] They recommend high-resolution magnetic resonance imaging to evaluate complex cases of nerve entrapment. (10.1007/s11552-014-9652-8)
  • [L5] Knowledge of the safe zone for avoiding suprascapular nerve injury is important; gender and specific scapular dimensions should be evaluated as they influence the dimensions of the safe zone. (10.1016/j.jse.2011.01.033)
  • [L5] In clinical settings, SN injury may cause severe fatty changes and inhibition of postoperative tendon healing in large RCTs. (10.5397/cise.2022.01207)
  • [Case_report] The authors report the first MRI-documented spontaneous resolution of a spinoglenoid notch cyst and associated suprascapular nerve palsy, proposing that surgical treatment could be withheld if patients show signs of clinical recovery, provided they are followed closely. (10.1016/j.jse.2006.06.014)

See Also

References

[1] Association of suprascapular neuropathy with rotator cuff tendon tears and fatty degeneration. Journal of Shoulder and Elbow Surgery. 2014. DOI: 10.1016/j.jse.2013.06.011

[2] Suprascapular neuropathy in a shoulder referral practice. Journal of Shoulder and Elbow Surgery. 2011. DOI: 10.1016/j.jse.2010.10.039

[3] Complete Fatty Infiltration of Intact Rotator Cuffs Caused by Suprascapular Neuropathy. Arthroscopy. 2014. DOI: 10.1016/j.arthro.2014.01.010

[4] Paper 03: Suprascapular Neuropathy: Two Distinct Presentations and Outcomes of Decompression. Orthopaedic Journal of Sports Medicine. 2023. DOI: 10.1177/2325967123s00003

[5] Clinical Outcomes of Arthroscopic Suprascapular Nerve Decompression for Suprascapular Neuropathy. Arthroscopy. 2020. DOI: 10.1016/j.arthro.2020.10.020

[6] Suprascapular Neuropathy. Results of Non-Operative Treatment. The Journal of Bone & Joint Surgery*. 1997. DOI: 10.2106/00004623-199708000-00007

[7] Suprascapular nerve injury after reverse total shoulder arthroplasty: correlation with screw out of vault penetration and functional situation: prospective study. Journal of Shoulder and Elbow Surgery. 2023. DOI: 10.1016/j.jse.2023.06.026

[8] Comparison of clinical outcome of decompression of suprascapular nerve at spinoglenoid notch for patients with posterosuperior massive rotator cuff tears and suprascapular neuropathy. BMC Musculoskeletal Disorders. 2021. DOI: 10.1186/s12891-021-04075-1

[9] Suprascapular Neuropathy. Journal of Bone and Joint Surgery. 2010. DOI: 10.2106/jbjs.i.01743

[10] Suprascapular Nerve Entrapment Secondary to a Lipoma. Clinical Orthopaedics & Related Research. 2003. DOI: 10.1097/01.blo.0000063791.32430.59

[11] Effect of suprascapular nerve injury on rotator cuff enthesis. Journal of Shoulder and Elbow Surgery. 2020. DOI: 10.1016/j.jse.2019.12.028

[12] A comparative analysis of fatty infiltration and muscle atrophy in patients with chronic rotator cuff tears and suprascapular neuropathy. Journal of Shoulder and Elbow Surgery. 2013. DOI: 10.1016/j.jse.2013.01.028

[13] Suprascapular Nerve Entrapment at the Spinoglenoid Notch in a Professional Baseball Pitcher. The American Journal of Sports Medicine. 1999. DOI: 10.1177/03635465990270062101

[14] Suprascapular nerve entrapment caused by a large hematoma of the scapula: a case report. BMC Musculoskeletal Disorders. 2023. DOI: 10.1186/s12891-023-06723-0

[15] Varicose veins at the spinoglenoidal notch: an unusual cause of suprascapular nerve compression. Journal of Shoulder and Elbow Surgery. 2011. DOI: 10.1016/j.jse.2011.05.022

[16] The safe zone for avoiding suprascapular nerve injury in bone block procedures for shoulder instability. A cadaveric study. Knee Surgery, Sports Traumatology, Arthroscopy. 2014. DOI: 10.1007/s00167-014-2900-1

[17] Who Really First Described and Explained the Suprascapular Nerve Entrapment Syndrome?. The Journal of Bone and Joint Surgery-American Volume. 2001. DOI: 10.2106/00004623-200108000-00018

[18] Outcomes of Arthroscopic Nerve Release in Patients Treated for Large or Massive Rotator Cuff Tears and Associated Suprascapular Neuropathy: A Prospective, Randomized, Double-Blinded Clinical Trial. The American Journal of Sports Medicine. 2021. DOI: 10.1177/03635465211021834

[19] Suprascapular neuropathy: what does the literature show?. Journal of Shoulder and Elbow Surgery. 2012. DOI: 10.1016/j.jse.2011.11.033

[20] Editorial Commentary: Suprascapular Neuropathy in Overhead Athletes: To Release or Not to Release?. Arthroscopy. 2018. DOI: 10.1016/j.arthro.2018.05.017

[21] Intraosseous ganglion of the glenoid causing suprascapular nerve entrapment syndrome: A case report. Journal of Shoulder and Elbow Surgery. 2009. DOI: 10.1016/j.jse.2008.10.014

[22] Suprascapular neuropathy secondary to reverse shoulder arthroplasty: A case report. Journal of Shoulder and Elbow Surgery. 2010. DOI: 10.1016/j.jse.2009.10.004

[25] Arthroscopic Release of Suprascapular Nerve Entrapment at the Suprascapular Notch: Technique and Preliminary Results. Arthroscopy. 2007. DOI: 10.1016/j.arthro.2006.10.003

[26] Suprascapular Neuropathy as a Cause of Swimmer’s Shoulder. The American Journal of Sports Medicine. 2013. DOI: 10.1177/0363546513477383

[27] An anatomical study for the location of suprascapular and spinoglenoid notches using three-dimensional computed tomography images of scapula. JSES International. 2022. DOI: 10.1016/j.jseint.2022.04.002

[28] Variations in anatomy at the suprascapular notch possibly causing suprascapular nerve entrapment: an anatomical study. Knee Surgery, Sports Traumatology, Arthroscopy. 2003. DOI: 10.1007/s00167-003-0378-3

[29] Risk of suprascapular nerve injury during glenoid baseplate fixation for reverse total shoulder arthroplasty: a cadaveric study. Journal of Shoulder and Elbow Surgery. 2021. DOI: 10.1016/j.jse.2020.07.008

[30] Subclavius Posticus: An Anomalous Muscle in Association with Suprascapular Nerve Compression in an Athlete. HAND. 2014. DOI: 10.1007/s11552-014-9652-8

[31] The safe zone for avoiding suprascapular nerve injury during shoulder arthroscopy: an anatomical study on 500 dry scapulae. Journal of Shoulder and Elbow Surgery. 2011. DOI: 10.1016/j.jse.2011.01.033

[34] Effect of suprascapular nerve injury on muscle and regenerated enthesis in a rat rotator cuff tear model. Clinics in Shoulder and Elbow. 2023. DOI: 10.5397/cise.2022.01207

[35] Spontaneous resolution of a spinoglenoid notch cyst and associated suprascapular nerve palsy: A case report. Journal of Shoulder and Elbow Surgery. 2007. DOI: 10.1016/j.jse.2006.06.014

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a. reproduce and Share the Licensed Material, in whole or in part, for NonCommercial purposes only; and

b. produce, reproduce, and Share Adapted Material for NonCommercial purposes only.

2. Exceptions and Limitations. For the avoidance of doubt, where Exceptions and Limitations apply to Your use, this Public License does not apply, and You do not need to comply with its terms and conditions.

3. Term. The term of this Public License is specified in Section 6(a).

4. Media and formats; technical modifications allowed. The Licensor authorizes You to exercise the Licensed Rights in all media and formats whether now known or hereafter created, and to make technical modifications necessary to do so. The Licensor waives and/or agrees not to assert any right or authority to forbid You from making technical modifications necessary to exercise the Licensed Rights, including technical modifications necessary to circumvent Effective Technological Measures. For purposes of this Public License, simply making modifications authorized by this Section 2(a) (4) never produces Adapted Material.

5. Downstream recipients.

a. Offer from the Licensor -- Licensed Material. Every recipient of the Licensed Material automatically receives an offer from the Licensor to exercise the Licensed Rights under the terms and conditions of this Public License.

b. No downstream restrictions. You may not offer or impose any additional or different terms or conditions on, or apply any Effective Technological Measures to, the Licensed Material if doing so restricts exercise of the Licensed Rights by any recipient of the Licensed Material.

6. No endorsement. Nothing in this Public License constitutes or may be construed as permission to assert or imply that You are, or that Your use of the Licensed Material is, connected with, or sponsored, endorsed, or granted official status by, the Licensor or others designated to receive attribution as provided in Section 3(a)(1)(A)(i).

b. Other rights.

1. Moral rights, such as the right of integrity, are not licensed under this Public License, nor are publicity, privacy, and/or other similar personality rights; however, to the extent possible, the Licensor waives and/or agrees not to assert any such rights held by the Licensor to the limited extent necessary to allow You to exercise the Licensed Rights, but not otherwise.

2. Patent and trademark rights are not licensed under this Public License.

3. To the extent possible, the Licensor waives any right to collect royalties from You for the exercise of the Licensed Rights, whether directly or through a collecting society under any voluntary or waivable statutory or compulsory licensing scheme. In all other cases the Licensor expressly reserves any right to collect such royalties, including when the Licensed Material is used other than for NonCommercial purposes.

Section 3 -- License Conditions.

Your exercise of the Licensed Rights is expressly made subject to the following conditions.

a. Attribution.

1. If You Share the Licensed Material (including in modified form), You must:

a. retain the following if it is supplied by the Licensor with the Licensed Material:

i. identification of the creator(s) of the Licensed Material and any others designated to receive attribution, in any reasonable manner requested by the Licensor (including by pseudonym if designated);

ii. a copyright notice;

iii. a notice that refers to this Public License;

iv. a notice that refers to the disclaimer of warranties;

v. a URI or hyperlink to the Licensed Material to the extent reasonably practicable;

b. indicate if You modified the Licensed Material and retain an indication of any previous modifications; and

c. indicate the Licensed Material is licensed under this Public License, and include the text of, or the URI or hyperlink to, this Public License.

2. You may satisfy the conditions in Section 3(a)(1) in any reasonable manner based on the medium, means, and context in which You Share the Licensed Material. For example, it may be reasonable to satisfy the conditions by providing a URI or hyperlink to a resource that includes the required information.

3. If requested by the Licensor, You must remove any of the information required by Section 3(a)(1)(A) to the extent reasonably practicable.

4. If You Share Adapted Material You produce, the Adapter's License You apply must not prevent recipients of the Adapted Material from complying with this Public License.

Section 4 -- Sui Generis Database Rights.

Where the Licensed Rights include Sui Generis Database Rights that apply to Your use of the Licensed Material:

a. for the avoidance of doubt, Section 2(a)(1) grants You the right to extract, reuse, reproduce, and Share all or a substantial portion of the contents of the database for NonCommercial purposes only;

b. if You include all or a substantial portion of the database contents in a database in which You have Sui Generis Database Rights, then the database in which You have Sui Generis Database Rights (but not its individual contents) is Adapted Material; and

c. You must comply with the conditions in Section 3(a) if You Share all or a substantial portion of the contents of the database.

For the avoidance of doubt, this Section 4 supplements and does not replace Your obligations under this Public License where the Licensed Rights include other Copyright and Similar Rights.

Section 5 -- Disclaimer of Warranties and Limitation of Liability.

a. UNLESS OTHERWISE SEPARATELY UNDERTAKEN BY THE LICENSOR, TO THE EXTENT POSSIBLE, THE LICENSOR OFFERS THE LICENSED MATERIAL AS-IS AND AS-AVAILABLE, AND MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND CONCERNING THE LICENSED MATERIAL, WHETHER EXPRESS, IMPLIED, STATUTORY, OR OTHER. THIS INCLUDES, WITHOUT LIMITATION, WARRANTIES OF TITLE, MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, NON-INFRINGEMENT, ABSENCE OF LATENT OR OTHER DEFECTS, ACCURACY, OR THE PRESENCE OR ABSENCE OF ERRORS, WHETHER OR NOT KNOWN OR DISCOVERABLE. WHERE DISCLAIMERS OF WARRANTIES ARE NOT ALLOWED IN FULL OR IN PART, THIS DISCLAIMER MAY NOT APPLY TO YOU.

b. TO THE EXTENT POSSIBLE, IN NO EVENT WILL THE LICENSOR BE LIABLE TO YOU ON ANY LEGAL THEORY (INCLUDING, WITHOUT LIMITATION, NEGLIGENCE) OR OTHERWISE FOR ANY DIRECT, SPECIAL, INDIRECT, INCIDENTAL, CONSEQUENTIAL, PUNITIVE, EXEMPLARY, OR OTHER LOSSES, COSTS, EXPENSES, OR DAMAGES ARISING OUT OF THIS PUBLIC LICENSE OR USE OF THE LICENSED MATERIAL, EVEN IF THE LICENSOR HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH LOSSES, COSTS, EXPENSES, OR DAMAGES. WHERE A LIMITATION OF LIABILITY IS NOT ALLOWED IN FULL OR IN PART, THIS LIMITATION MAY NOT APPLY TO YOU.

c. The disclaimer of warranties and limitation of liability provided above shall be interpreted in a manner that, to the extent possible, most closely approximates an absolute disclaimer and waiver of all liability.

Section 6 -- Term and Termination.

a. This Public License applies for the term of the Copyright and Similar Rights licensed here. However, if You fail to comply with this Public License, then Your rights under this Public License terminate automatically.

b. Where Your right to use the Licensed Material has terminated under Section 6(a), it reinstates:

1. automatically as of the date the violation is cured, provided it is cured within 30 days of Your discovery of the violation; or

2. upon express reinstatement by the Licensor.

For the avoidance of doubt, this Section 6(b) does not affect any right the Licensor may have to seek remedies for Your violations of this Public License.

c. For the avoidance of doubt, the Licensor may also offer the Licensed Material under separate terms or conditions or stop distributing the Licensed Material at any time; however, doing so will not terminate this Public License.

d. Sections 1, 5, 6, 7, and 8 survive termination of this Public License.

Section 7 -- Other Terms and Conditions.

a. The Licensor shall not be bound by any additional or different terms or conditions communicated by You unless expressly agreed.

b. Any arrangements, understandings, or agreements regarding the Licensed Material not stated herein are separate from and independent of the terms and conditions of this Public License.

Section 8 -- Interpretation.

a. For the avoidance of doubt, this Public License does not, and shall not be interpreted to, reduce, limit, restrict, or impose conditions on any use of the Licensed Material that could lawfully be made without permission under this Public License.

b. To the extent possible, if any provision of this Public License is deemed unenforceable, it shall be automatically reformed to the minimum extent necessary to make it enforceable. If the provision cannot be reformed, it shall be severed from this Public License without affecting the enforceability of the remaining terms and conditions.

c. No term or condition of this Public License will be waived and no failure to comply consented to unless expressly agreed to by the Licensor.

d. Nothing in this Public License constitutes or may be interpreted as a limitation upon, or waiver of, any privileges and immunities that apply to the Licensor or You, including from the legal processes of any jurisdiction or authority.

Creative Commons is not a party to its public licenses. Notwithstanding, Creative Commons may elect to apply one of its public licenses to material it publishes and in those instances will be considered the “Licensor.” The text of the Creative Commons public licenses is dedicated to the public domain under the CC0 Public Domain Dedication. Except for the limited purpose of indicating that material is shared under a Creative Commons public license or as otherwise permitted by the Creative Commons policies published at creativecommons.org/policies, Creative Commons does not authorize the use of the trademark "Creative Commons" or any other trademark or logo of Creative Commons without its prior written consent including, without limitation, in connection with any unauthorized modifications to any of its public licenses or any other arrangements, understandings, or agreements concerning use of licensed material. For the avoidance of doubt, this paragraph does not form part of the public licenses.

Creative Commons may be contacted at creativecommons.org.