A 3D Anatomical Investigation of the Suprascapular Nerve: A Needle Placement Study for Radiofrequency Denervation of the Glenohumeral Joint

Abstract

BackgroundThe suprascapular nerve (SSN) is the main target for image‐guided denervation to manage chronic glenohumeral joint pain related to osteoarthritis. The suprascapular notch has been used as a landmark to completely denervate the SSN; however, this approach also results in paralysis of supraspinatus (SS) and infraspinatus. To propose function‐preserving denervation protocols, a detailed understanding of the suprascapular nerve branches and their relationship to bony and soft tissue landmarks are required.ObjectivesThe objectives of this study were to: 1) define the course of SSN and its branches in relation to bony and soft tissue landmarks visible with image‐guidance; 2) propose a novel denervation protocol based on anatomical findings; and 3) evaluate the needle placement and nerve capture rate of the proposed protocol.MethodsThe SSN and its branches were meticulously dissected from the suprascapular notch to the spinoglenoid notch in 15 formalin‐embalmed specimens. The course of SSN and its branches was documented relative to bony or soft tissue landmarks visible with image‐guidance. The innervation patterns and landmarks were used to develop a SS function sparing denervation protocol. The protocol was evaluated in a needle placement pilot study using 3 lightly embalmed specimens. Radiofrequency needles were placed using ultrasound guidance. Then, the SSN and its branches and needle tip were exposed, digitized and modeled in 3D. The lesion diameter was generated at the needle tip to evaluate nerve capture rate.ResultsIn all 15 specimens, SSN and its branches course along the floor of the supraspinous fossa deep to SS. After coursing through the suprascapular notch, SSN immediately bifurcated into medial and lateral trunks. The medial trunk of SSN coursed medially to supply motor innervation to the anterior region of SS. The lateral trunk coursed laterally along the floor of the supraspinous fossa, around the spinoglenoid notch, to the infraspinatus. The lateral trunk supplied: 1) motor innervation to the posterior region of SS; and 2) 1–4 sensory articular branches to the posterior glenohumeral joint capsule. The articular branches originated from the lateral trunk in the region of the midpoint of a line connecting the suprascapular and spinoglenoid notches. When this midpoint landmark was used, for ultrasound‐guided radiofrequency needle placement, the lateral trunk of SSN and its articular branches were captured while the medial trunk was spared, in all specimens.ConclusionsThis cadaveric study provides evidence that the medial trunk of SSN could be spared, while the posterior glenohumeral joint capsule would be denervated, by targeting the lateral trunk, at the midpoint of a line connecting the suprascapular and spinoglenoid notches. With sparing of medial trunk, SS may retain partial abduction function. Further clinical investigation is required to assess functional and pain relief outcomes.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.