Table 1. Patient demographics (n = 49).

Variable	n (%) or average ± SD
Age	59.6 ± 15.46
Gender (M/F)	21/28
BMI	28.7 ± 7.25
Current smoker	12 (24.4%)
Diabetic	6 (12.2%)
Current steroid medication user	2 (4.1%)
Previous surgery at index level	14 (28.6%)
At an outside center	7 (14.3%)
At our own center	5 (10.2%)
At both outside and our own center	2 (4.1%)
Preoperative diagnosis
Spondylolisthesis	29 (59.1%)
Degenerative disk disease	14 (28.6%)
Previous nonunion/pseudarthrosis	5 (10.2%)
Post laminectomy syndrome	4 (8.1%)
Instrumentation/mechanical failure	6 (12.2%)
Scoliosis	1 (2%)
Trauma	1 (2%)

Abbreviations: BMI, body mass index; SD, standard deviation.