Table 1. Patient demographics.

Demographics	Combined
Mean BMI	29.7
Age (y)	60.5
ASA grade  I  II  III  IV	256 3,237 2,004 18
Sex  Male  Female	3,226 2,289
Level of pathology  Cervical  Thoracic  Lumbar	1,385 120 4,010
Approach  Anterior  Posterior  Combined	354 5,130 31

Abbreviations: ASA, American Society of Anesthesiologists, BMI, body mass index.