title: Effect of scapular external rotation on the axillary nerve during the arthroscopic Latarjet procedure: an anatomical investigation.
abstract: OBJECTIVE
  The first purpose of this study is to measure the distance between the axillary nerve and the exit point of K-wires placed retrograde through the glenoid in the setting of an arthroscopic Latarjet procedure. The second objective is to evaluate whether manual external rotation of the scapula alters that distance.
  
  
  METHODS
  In seven fresh-frozen specimens, two 2.0-mm K-wires were drilled through the glenoid using an arthroscopic Latarjet retrograde glenoid guide. These were drilled into the glenoid at the 7- and 8-o'clock positions (right shoulders) and at the 4- and 5-o'clock positions (left). K-wires were oriented parallel to the glenoid articular surface and perpendicular to the long superoinferior axis of the glenoid, 7 mm medial to the joint surface. Two independent evaluators measured the distances between the axillary nerve and the exit point of the K-wires in the horizontal plane (AKHS for the superior K-wire and AKHI for the inferior K-wire) and in the vertical plane (AKV). Measurements were taken with the scapula left free and were repeated with the scapula placed at 15° and 30° of external rotation.
  
  
  RESULTS
  With the scapula left free, scapular external rotation was 34° ± 2.3°. In this position, the AKHS was 2.5 ± 1.6, 6.3 ± 1.2 mm at 15° of external rotation (ER) and 11.4 ± 1.4 mm at 30° ER. The AKHI distance was 0.37 ± 1.6, 3.4 ± 1.4 and 10.6 ± 2.1 mm, respectively, for the scapula left free, at 15° ER and 30° of ER. The AKV distances were, respectively, 0.12 ± 0.2, 4.9 ± 1.6 and 9.9 ± 1.7 mm. The increase in all distances was statistically significant (p < 0.001).
  
  
  CONCLUSIONS
  Increasing scapular external rotation significantly increases the distance between the axillary nerve and the exit point of the K-wires, increasing the margin of safety during this procedure. Therefore, increased external rotation of the scapula could be an effective tool to decrease the risk of iatrogenic axillary nerve injury.
  
  
  METHODS
  Cadaveric study, Level V.
authors.affiliation: Department of Shoulder Surgery, Institut de la Main, Clinique Jouvenet, 6 Square Jouvenet, 75016, Paris, France.
authors.forename: Felipe
authors.initials: F
authors.lastname: Reinares
authors.affiliation: Department of Shoulder Surgery, Institut de la Main, Clinique Jouvenet, 6 Square Jouvenet, 75016, Paris, France. jdwerthel@gmail.com.
authors.forename: Jean-David
authors.initials: JD
authors.lastname: Werthel
authors.affiliation: Department of Shoulder Surgery, Institut de la Main, Clinique Jouvenet, 6 Square Jouvenet, 75016, Paris, France.
authors.forename: Constantina
authors.initials: C
authors.lastname: Moraiti
authors.affiliation: Department of Shoulder Surgery, Institut de la Main, Clinique Jouvenet, 6 Square Jouvenet, 75016, Paris, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Valenti
mesh_terms: D001182:Arthroscopy / Q000009:adverse effects / Q000379:methods*; D001917:Brachial Plexus; D002102:Cadaver; D006801:Humans; D059348:Peripheral Nerve Injuries / Q000209:etiology / Q000517:prevention & control; D012399:Rotation; D012540:Scapula / Q000601:surgery; D012782:Shoulder; D012785:Shoulder Joint / Q000601:surgery*
keywords: Arthroscopic Latarjet procedure; Axillary nerve; Nerve injury; Shoulder arthroscopy; Shoulder instability