Table 2 Cox proportional hazards regression analysis of factors predicting no-collapse survival following multiple drilling

Bisphosphonate medication

 No

Ref

 Yes

0.602

1.14(0.69—1.89)

Gender

 Female

Ref

 Male

0.545

1.21(0.65—2.28)

Laterality

 Unilateral MD and

contralateral THA

Ref

 Unilateral

0.302

1.33(0.77—2.31)

 Bilateral

0.252

0.74(0.45—1.24)

Etiology

 Idiopathic

Ref

 Corticosteroid

0.151

1.47(0.87—2.5)

 Alcohol-related

0.187

0.57(0.24—1.32)

ARCO classification

 ARCO I

Ref

Ref

 ARCO II

0.157

0.7(0.42—1.15)

0.157

0.69 (0.42—1.14)

 ARCO IIIA

0.005

2.12(1.25—3.59)

0.037

2.12 (1.25—3.58)

Bone marrow edema

 No

Ref

Ref

 Yes

0.011

2.13(1.19—3.81)

0.010

2.13 (1.19—3.81)

Location

 Type B

Ref

 Type C1

0.124

0.64(0.36—1.13)

 Type C2

0.051

1.73(1—2.98)

Age

 < 42.00

Ref

 ≥ 42.00

0.174

1.42(0.86—2.37)

BMI

 < 23.71

Ref

 ≥ 23.71

0.238

1.35(0.82—2.22)

Symptom duration

 < 2.00

Ref

 ≥ 2.00

0.526

0.85(0.52—1.4)

Combined necrotic angle

 < 210.50

Ref

Ref

≥ 210.50

0.001

2.42(1.44—4.07)

 < 0.001

2.41 (1.43—4.07)

Necrosis degree index

 < 109.67

Ref

 ≥ 109.67

0.001

2.35(1.39—3.95)