Table 3. Incidence and hazard ratio for osteonecrosis among the severity of osteoporosis.

	Case no.	IR †	Adjusted a HR (95% CI)
Overall
Comparison	110	5.32	1.00
Osteoporosis
Mild	93	10.70	1.91 (1.45–2.53)**	1.00
Serious	28	17.17	2.71 (1.77–4.14)***	1.33 (0.86–2.06)
P for trend			<0.0001
Non-cancer
Comparison	107	5.33	1.00
Osteoporosis
Mild	86	10.32	1.84 (1.39–2.45)***	1.00
Serious	25	16.04	2.52 (1.61–3.93)***	1.27 (0.80–2.02)
P for trend
Cancer
Comparison	3	4.90	1.00
Osteoporosis
Mild	7	19.81	1.19 (1.08–16.2)*	1.00
Serious	3	41.72	8.10 (1.62–40.5)*	1.94 (0.49–7.67)
P for trend

HR, hazard ratio; CI, confidence interval.

^aAdjusted model, adjusted for age, gender, hypertension, diabetes and cancer.

^†IR, incidence ratio, per 10000 person-years.

**P<0.01;

***P<0.001.