General information
A total of 85 patients (44 males and 41 females) with 106 hips, including 21 patients with ONFH, were enrolled in this study. The age ranged from 21 to 60 years with a mean age of 37.4 ± 8.12 years. The follow-up time was 2–4 years, with an average of 2.8 ± 0.6 years. Forty-five patients (57 hips) with ONFH who had femoral head collapse were included in the collapse group, and the remaining 40 patients (49 hips) were included in the non-collapse group. There was significant difference in JIC classification between the two groups (P < 0.05), most of which were C2 type in the collapse group and B type in the non-collapse group. There was a difference between the two groups in whether there was a cystic area in the femoral head, with 49.1% in the collapse group showing a cystic area, which was significantly higher than that in the non-collapse group (18.4%), and the difference was statistically significant (P < 0.05). In addition, the diameter of the cystic areas was significantly larger in the collapsed group than in the non-collapsed group (P < 0.05). There was no significant difference in age, gender, height, weight, BMI, and etiology between the two groups (P > 0.05) (Table 2).
Table 2
Comparison of general data between the two groups
Parameters
|
Collapse group
(n = 45(57 hips))
|
Non-collapse group
(n = 40(49 hips))
|
t /χ2
|
P-value
|
Age (years)
|
37.0 ± 11.36
|
37.9 ± 6.70
|
-0.496
|
0.621
|
Gender,n (%)
|
|
|
|
|
Male
|
23(51.1%)
|
21(52.5%)
|
0.016
|
0.898
|
Female
|
22(48.9%)
|
19(47.5%)
|
Height(cm)
|
164.6 ± 7.43
|
164.7 ± 7.26
|
-0.047
|
0.962
|
Weight(kg)
|
65.7 ± 13.6
|
63.9 ± 11.6
|
0.731
|
0.466
|
BMI(kg/m2)
|
23.4 ± 3.68
|
23.8 ± 3.97
|
0.501
|
0.617
|
Etiology,n(%)
|
|
|
|
|
Steroid
|
16(35.6%)
|
14(35.0%)
|
0.008
|
0.996
|
Alcoholic
|
17(37.8%)
|
15(37.5%)
|
Idiopathic
|
12(26.7%)
|
11(27.5%)
|
JIC type,n(%)
|
|
|
|
|
Type-A
|
0(0%)
|
2(5.0%)
|
37.25
|
0.000
|
Type-B
|
6(13.3%)
|
28(70.0%)
|
Type-C1
|
18(40.0%)
|
9(22.5%)
|
Type-C2
|
21(46.7%)
|
1(2.5%)
|
Cystic change area,n(%)
|
|
|
|
|
Yes
|
28(49.1%)
|
9(18.4%)
|
10.969
|
0.0012
|
No
|
29(50.9%)
|
40(81.6%)
|
Cystic change area diameter (mm)
|
15.8 ± 5.33
|
6.3 ± 2.94
|
10.995
|
0.000
|
Von Mises Stress Values for Different Capsule Diameter Models
The maximum and average stress values of cortical bone in the weight-bearing area of femoral head were the smallest in the 0 mm diameter cystic area model. The mean stress value of cortical bone in the weight-bearing area of the femoral head increased with the increase of the diameter of the resorption area, and the difference was statistically significant (P < 0.05). Similarly, the 0 mm model had the smallest mean and maximum stresses in the necrotic zone. The mean stress value of the necrotic area increased with the increase of the diameter of the absorption area, and there was no statistically significant difference between the 15 mm model and the 20 mm model, and the other differences were statistically significant (P < 0.05). Furthermore, the maximum stress and mean stress around the cystic area increased with the increase of the diameter of the absorption area, and there was a significant difference in the mean stress around the cystic area (P < 0.05) (Table 3 Fig. 2).
Table 3
Von Mises Stress Values (MPa) for Different Capsule Diameter Models
Grouping
|
Maximum stress of cortical bone
|
Average stress of cortical bone
|
Maximum stress of necrotic area
|
Average stress of necrotic area
|
Maximum stress of cystic area
|
Average stress of cystic area
|
0 mm
|
21
|
20.19 ± 1.01
|
3.11
|
2.85 ± 0.33
|
-
|
-
|
5 mm
|
23.5
|
22.45 ± 1.13*
|
3.55
|
3.43 ± 0.09*
|
4.03
|
3.72 ± 0.36
|
10 mm
|
25.4
|
24.0 ± 1.52*
|
4.95
|
4.75 ± 0.17*#
|
5.59
|
5.23 ± 0.38#
|
15 mm
|
27.3
|
26.3 ± 1.07*#▲
|
7.92
|
7.40 ± 0.94*#▲
|
8.29
|
8.01 ± 0.46#▲
|
20 mm
|
30.5
|
29.1 ± 1.10*#▲★
|
9.29
|
8.08 ± 0.90*#▲
|
9.37
|
9.19 ± 0.13#▲★
|
F-value
|
-
|
84.35
|
-
|
147.74
|
-
|
1416.9
|
P-value
|
-
|
< 0.001
|
-
|
< 0.001
|
-
|
< 0.001
|
*: Compared with the 0 mm model, the difference was statistically significant.#:Compared with the 5 mm model, the difference was statistically significant.▲:Compared with the 10 mm model, the difference was statistically significant.★:Compared with the 15 mm model, the difference was statistically significant. |
Relationship between the von Mises Stress of Model and Cystic Area Diameter
The maximum von Mises stresses in the femoral head cortex were 21, 23.5, 25.4, 27.3, and 30.5 in the 0, 5, 10, 15, and 20 mm FE models of the cystic region diameter, respectively. The relationship between the diameter of the cystic area and the maximum von Mises stress of the femoral head cortical bone was fitted by a linear regression curve, and the results showed that the diameter of the cystic area was linearly positively correlated with the maximum von Mises stress of the femoral head cortical bone (R2 = 0.9903, F = 307.0, P = 0.0004), and the fitted regression equation was: Y = 0.4560*X + 20.98. In addition, the maximum von Mises stresses in the necrotic zone were 3.11, 3.55, 4.95, 7.92, and 9.29 in the finite element models with 0, 5, 10, 15, and 20 mm capsule diameter, respectively. The relationship between the diameter of the cystic area and the maximum von Mises stress in the necrotic area was fitted by a linear regression curve, and the results showed that the diameter of the cystic area was linearly positively correlated with the maximum von Mises stress in the necrotic area (R2 = 0.9427, F = 49.40, P = 0.0059), and the fitted regression equation was: Y = 0.3346*X + 2.418(Fig. 2).
Relationship between von Mises stress around the cystic area and the diameter of the cystic area
The maximum von Mises stresses around the cystic area were 4.03, 5.59, 8.29, and 9.37 in the 5, 10, 15, and 20 mm diameter finite element models of the cystic area, respectively. The relationship between the diameter of the cystic area and the maximum von Mises stress around the cystic area was fitted by linear regression curve. The results showed that the diameter of the cystic area was linearly positively correlated with the maximum von Mises stress of the cortical bone of the femoral head (R2 = 0.9756, F = 79.92, P = 0.0123), and the fitted regression equation was: Y = 0.4560*X + 20.98(Fig. 2). The finite element stress distribution clouds show that there is a stress concentration area above the cystic region, and this region range gradually increases with the increase of the diameter of the cystic region (Fig. 3).
Typical case
Typical case 1: Male, 36 years, with left hip pain for more than 7 months, diagnosed as steroid-induced osteonecrosis of the femoral head. This is an ONFH patient with ARCO II and JIC type B.CT showed no obvious cystic change area. After 6 months of non-surgical hip preservation treatment, the area of necrosis was reduced and the joint space was acceptable. After 1.5 years of non-surgical hip preservation treatment, the femoral head did not collapse significantly, and the density of the necrotic area increased(Fig. 4).
Typical case 2:Male, 45 years, with left hip pain for more than 9 months, diagnosed as steroid-induced osteonecrosis of the femoral head. graded as JIC type B.CT showed obvious cystic change area. After 1 year of non-surgical hip-preserving treatment, the femoral head collapsed and the patient's pain became a little worse. After 2 years of non-surgical hip preservation treatment, the femoral head has become slightly flat(Fig. 5).