Table 1.

Demographics of male and female patients

	Male + Female (n = 322)	Male (n = 242)	Female (n = 80)	P (M vs F)
Age (years old)	64.7 ± 11.2	64.7 ± 11.6	64.6 ± 10.0	0.90
Diabetes Mellitus (%)	31.7%	31.8%	31.3%	0.92
BMI	25.7 ± 4.8	25.8 ± 4.8	25.5 ± 4.7	0.62
JOSL CT classification
Grade 1 (1 < cervical OP-index≤5)	169 (52.5%)	125 (51.7%)	44 (55%)	–
Grade 2 (6 < cervical OP-index ≤9)	107 (33.2%)	83 (34.3%)	24 (30%)	–
Grade 3 (10 < cervical OP-index)	46 (14.3%)	34 (14.0%)	12 (15%)	–
Cervical OP-index	5.83 ± 2.9	5.86 ± 2.9	5.75 ± 3.0	0.78
OP-index	9.21 ± 6.8	8.24 ± 5.5	12.1 ± 9.0	< 0.01
No. of patients with OP-index of > = 20 (%)	27 (8.3%)	11 (4.5%)	16 (20%)	< 0.01

Data are expressed as the mean ± standard deviation; BMI body mass index, OP-index ossification index of OPLL