Identifying the axillary nerve during shoulder surgery: an anatomic study using advanced imaging.

BACKGROUND: The axillary nerve (AXN) is one of the more commonly injured nerves during shoulder surgery. Prior anatomic studies of the AXN in adults were performed using cadaveric specimens with small sample sizes. Our research observes a larger cohort of magnetic resonance imaging (MRI) studies in order to gain a more representative sample of the course of the AXN and aid surgeons intraoperatively. METHODS: High-resolution 3T MRI studies performed at our institution from January 2010 to June 2019 were reviewed. Four blinded reviewers with musculoskeletal radiology or orthopedic surgery training measured the distance of the AXN to the surgical neck of the humerus (SNH), the lateral tip of the acromion (LTA), and the inferior glenoid rim (IGR). Intraclass correlation coefficient was calculated to assess reliability between reviewers. The nerve location was assessed relative to rotator cuff tear status. RESULTS: A total of 257 shoulder MRIs were included. Intraclass correlation coefficient was excellent at 0.80 for the SNH, 0.90 for the LTA, and 0.94 for the IGR. All intraobserver reliabilities were above 0.80. The mean distance from the AXN to SNH was 1.7 cm (range, 0.7-3.1 cm; interquartile range, 1.38-2.00) and that from the AXN to IGR was 1.6 cm (range, 0.6-2.6 cm; interquartile range, 1.33-1.88). The mean AXN to LTA distance was 7.1 cm, with a range of 5.2-9.0 cm across patient heights; there was a large effect size related to the LTA to AXN distance and patient height with a correlation of r = 0.603 (P < .001). Rotator cuff pathology appears to affect nerve location by increasing the distance between the AXN and SNH (P = .027). DISCUSSION/CONCLUSION: The AXN is vulnerable to injury during both open and arthroscopic shoulder procedures. This injury can be either a result of direct trauma to the nerve or secondary to traction placed on the nerve with reconstructive procedures that distalize the humerus. Our study demonstrates that the AXN can be found as little as 5.6 mm from the IGR and 6.9 mm from the SNH. In addition, we illustrate the relationship between patient height and the LTA to AXN distance and complete rotator cuff tears and the SNH to AXN distance. Our study is the first to demonstrate the nerve's proximity to important surgical landmarks of the shoulder using a large sample size of high-resolution images in living human shoulders.

The Effect of Head Rotation on the Relative Vascular Anatomy of the Neck: Implications for Central Venous Access.

CONTEXT: Previous studies have shown that safe venous cannulation is difficult when the internal jugular vein (IJV) overlies the carotid artery (CA) as the probability of inadvertent arterial penetration is greatly increased. AIMS: The goal of this study was to examine the anatomical relationships of the IJV and CA as a function of the degree of head rotation in order to minimize the risk for CA puncture. SETTINGS AND DESIGN: Our study was a prospective study using a sample of 496 Emergency Department patients. METHODS AND MATERIAL: The anatomic relationships of the right and left IJVs and CAs were recorded with head rotation at three different positions. Patients who had the IJV in a 45 to 135 degree relationship to the CA were deemed to be in the high-risk zone for arterial puncture. STATISTICAL ANALYSIS: Chi square, ANOVA. RESULTS: Right IJVs were in the high risk zone for 39.5%, 47.8% and 60.9% of cases at 0, 45 and 80 degrees of head rotation, respectively (P < 0.001). Left IJVs were in the high risk zone for 59.1%, 69.2% and 80.0% at 0, 45 and 80 degrees of head rotation, respectively. (P < 0.001). CONCLUSIONS: Head rotation should be minimized during IJV cannulation to decrease the overlap of CA by IJV. Cannulation of the left IJV appears to carry a higher degree of risk as compared to the right IJV. Placing the head in neutral position, avoiding rotation, and using ultrasound guidance are recommended to minimize complications during central venous access.

Outcomes of anatomic shoulder arthroplasty in primary osteoarthritis in type B glenoids.

BACKGROUND: Primary glenohumeral osteoarthritis with posterior wear of the glenoid and posterior subluxation of the humerus (Walch type B) presents a challenge to the treating surgeon. Our hypothesis was that glenoids with biconcavity (B2) would be associated with worse outcomes (functional scores and complications) than B1 glenoids. MATERIALS AND METHODS: We retrospectively analyzed prospectively collected data on 112 anatomic total shoulder arthroplasties (104 patients) with B glenoids. Preoperative computed tomography identified 64 B1 glenoids and 48 B2 glenoids (50 and 37 available for follow-up). RESULTS: A significant difference between B1 and B2 glenoids was noted in average retroversion (11° vs. 16°; P < .001) and average posterior humeral subluxation (65% vs. 75%; P < .001). No significant difference was seen in mean age (69.5 vs. 69.2 years) or body mass index (28.5 vs. 27.4) at time of surgery. At average follow-up of 60 months (range, 23-120 months), glenoid component radiolucencies (51.6%, B1; 47.9%, B2), range of motion, preoperative and postoperative scores of the shortened Disabilities of the Arm, Shoulder, and Hand questionnaire, and patient satisfaction were not significantly different between the 2 groups. Four revisions (4.6%) were documented for acute postoperative infection (2.3%), subscapularis failure (1.1%), and glenoid loosening (1.1%). CONCLUSIONS: Although biconcave glenoids commonly have more severe retroversion and posterior subluxation of the humerus, we were unable to find a clinical or radiographic difference in outcome of patients with B1 or B2 glenoids treated with anatomic total shoulder arthroplasty at intermediate-term follow-up. Continued clinical and radiographic follow-up of these cohorts will be necessary to assess any future divergence in outcome.