Does the Suprascapular Nerve Move within the Suprascapular Notch? Biomechanical Perspective Using the Finite Element Method

Abstract

Purpose We aimed to analyze changes in suprascapular nerve (SSN) position within the suprascapular notch during in vivo shoulder abduction. Materials and Methods Three-dimensional models of the shoulder complex were constructed based on magnetic resonance imaging of the brachial plexus (BP-MR) in a patient diagnosed with SSN dysfunction but normal scapular movement. Using BP-MR in neutral position and computed tomography data on shoulder abduction, shoulder abduction was simulated as the transition between two positions of the shoulder complex with overlapping of a neutral and abducted scapula. SSN movement during abduction was evaluated using the finite element method. Contact stress on the SSN was measured in the presence and absence of the transverse scapular ligament (TSL). Results In the neutral position, the SSN ran almost parallel to the front of the TSL until entering the suprascapular notch and slightly contacted the anterior-inferior border of the TSL. As shoulder abduction progressed, contact stress decreased due to gradual loss of contact with the TSL. In the TSL-free scapula, there was no contact stress on the SSN in the neutral position. Towards the end of shoulder abduction, contact stress increased again as the SSN began to contact the base of the suprascapular notch in both TSL conditions. Conclusion We identified changes in the position of the SSN path within the suprascapular notch during shoulder abduction. The SSN starts in contact with the TSL and moves toward the base of the suprascapular notch with secondary contact. These findings may provide rationale for TSL release in SSN entrapment.

Outcomes After Rotator Cuff Repair With Transverse Scapular Ligament Release in Patients With Severe Fatty Degeneration of the Infraspinatus

“…Furthermore, posterior interval release requires an incision between the supraspinatus and infraspinatus muscles. Another reason why we performed TSL release was that the finite element model analysis showed that the suprascapular nerve position depends on shoulder position and contact with the TSL in the neutral position, 28 indicating that TSL release would help relieve dynamic contact with the suprascapular nerve and relieve distal tension. Recently, 1 study 26 evaluated the effect of suprascapular nerve decompression at the spinoglenoid notch in patients with a massive posterosuperior RCT.…”