Table 2 Cox proportional hazards regression model showing the association of variables with collapse-free survival
Variable | Univariate analysis | Multivariate analysis | ||
|---|---|---|---|---|
HR (95% CI) | P value | HR (95% CI) | P value | |
Factors selected | ||||
 Symptom | ||||
  Delayed onset of symptom | 1 (reference) | NA | 1 (reference) | NA |
  Acute onset of symptom | 3.28(1.26–8.58) | 0.015 | 2.78(1.03–7.48) | 0.043 |
  Asymptomatic | 1.73(0.70–4.25) | 0.230 | 2.26(0.918–5.58) | 0.076 |
 Necrotic location | ||||
  A/B | 1 (reference) | NA | 1 (reference) | NA |
  C1/C2 | 8.94(3.20–25.03) | < 0.001 | 3.67(1.20–11.27) | 0.023 |
 Necrotic angle | ||||
  < 200° | 1 (reference) | NA | 1 (reference) | NA |
  200–249° | 3.62(1.24–10.62) | 0.019 | 2.67(0.87–8.25) | 0.087 |
  250–299° | 11.62(4.30–31.37) | < 0.001 | 5.08(1.73–14.93) | 0.003 |
  > 299° | 16.36(5.64–47.48) | < 0.001 | 9.96(3.23–30.70) | < 0.001 |
 BME before CD | ||||
  No | 1 (reference) | NA | 1 (reference) | NA |
  Yes | 3.09(1.65–5.77) | < 0.001 | 2.03(1.02–4.02) | 0.042 |
Factors not selected | ||||
 Age (years) | 1.00(0.96–1.03) | 0.913 | NA | NA |
Gender | ||||
  Female | 1 (reference) | NA | NA | NA |
  Male | 0.81(0.34–1.91) | 0.626 | NA | NA |
 Body mass index (kg/m2) | 1.04(0.97–1.13) | 0.285 | NA | NA |
 Etiology | ||||
  Alcohol abuse | 1 (reference) | NA | NA | NA |
  Corticosteroid use | 1.17(0.54–2.54) | 0.700 | NA | NA |
  Idiopathic | 0.67(0.26–1.72) | 0.401 | NA | NA |
 Ficat classification | ||||
  Stage I | 1 (reference) | NA | NA | NA |
  Stage IIA | 1.27(0.45–3.55) | 0.649 | NA | NA |
 ARCO classification | ||||
  IA | 0.32(0.08–1.34) | 0.117 | NA | NA |
  IB | 0.20(0.05–0.86) | 0.031 | NA | NA |
  IC | 0.00(0.00–0.00) | 0.977 | NA | NA |
  IIA | 0.06(0.02–0.17) | < 0.001 | NA | NA |
  IIB | 0.23(0.11–0.48) | < 0.001 | NA | NA |
  IIC | 1 (reference) | NA | NA | NA |
 Bone grafting (no. of hips) | ||||
  No | 1 (reference) | NA | NA | NA |
  Yes | 0.65(0.35–1.22) | 0.177 | NA | NA |
 Triglyceride | 1.08(0.85–1.37) | 0.536 | NA | NA |
 Total cholesterol | 0.84(0.60–1.17) | 0.304 | NA | NA |
 White blood cell | 0.97(0.83–1.14) | 0.699 | NA | NA |
 Hemoglobin | 0.99(0.98–1.01) | 0.425 | NA | NA |
 Platelet | 1.00(0.99–1.01) | 0.642 | NA | NA |
 Antithrombin III | 1.00(0.98–1.03) | 0.852 | NA | NA |