gms | German Medical Science

Objectives: Neurovascular anatomy has not been previously quantified for the arthroscopic snapping scapula approach with the patient in the most frequent patient position (chicken wing). The purposes of this study are to 1) determine anatomical relationships of the superomedial scapula and neurovascular structures at risk during arthroscopic surgical treatment of snapping scapula syndrome (SSS), 2) compare these measurements between the arm in neutral and "chicken wing" positions, and 3) to establish safe zones for arthroscopic treatment of SSS.

Methods: Eight fresh-frozen cadaveric hemi-torsos (mean age, 55.8 years; range, 52-66 years) were dissected to ascertain relevant anatomic structure locations including: 1) spinal accessory nerve, 2) dorsal scapular nerve, and 3) suprascapular nerve. A coordinate measuring device was utilized to collect the relationships of anatomic landmarks and at-risk structures during surgical approach.

Results and conclusion: The dorsal scapular nerve was a mean of 24.4 mm medial to the superomedial scapula in the neutral position and 33.1 mm medial in the "chicken wing" position (p<0.001); the dorsal scapular nerve was 21.7 mm medial to the medial border of the scapular spine in the neutral position and 35.5 mm medial in the "chicken wing" position (p<0.001). The mean distance from the superomedial angle (SMA) to the spinal accessory nerve intersection at the superior scapular border was 16.5 mm in the neutral position and 15.0 mm in the "chicken wing" position (p=0.031). Average distance from the superomedial angle to the closest point of the spinal accessory nerve was 11.6 mm and 10.4 mm in the neutral position and "chicken wing" positions, respectively (p=0.039).

Neurologic structures around the scapula vary significantly between a neutral arm position and the "chicken wing" position commonly used in the arthroscopic treatment of snapping scapula. The chicken wing position improves "safe" distances for the dorsal scapular nerve during medial portal placement and should be considered as a primary positioning for arthroscopic management of snapping scapula.