Demographic Information
In total, 271 patients (157 male patients and 124 female patients) and 447 knees (222 left knees and 225 right knees) were included. The mean age of the patients was 60.11 ± 0.59 years (ranging from 18 to 86 years). In total, 374 knees had varus deformity and 73 knees had valgus deformity. Radiological measurements are presented in Table 1. Among the varus deformities,106 knees were rated as K–L grade I and classified into the non-KOA group. 67 knees were K–L grade II, 68 knees were grade III, and 133 knees were grade IV.
1. Radiological comparison between non-KOA and varus OA groups
In the non-KOA group,with 106knees, the mean of HKA,MPTA,TFC,PFC,DFC,FTD and FTA were 2.74 ± 0.23°,87.59 ± 0.2°,177.94 ± 0.17°,177.7 ± 0.14°,177.27 ± 0.14°,3.16 ± 0.04cm and 46.02 ± 1.1cm2, respectively. In the varus OA group, with 268 knees, the mean of HKA,MPTA,TFC,PFC,DFC,FTD and FTA were 6.99 ± 0.31°,86.7 ± 0.17°,177.63 ± 0.11°, 177.37 ± 0.1°,177.11 ± 0.11°,3.24 ± 0.03cm and 45.04 ± 0.66 cm2, respectively. HKA was significantly larger in the OA group than in the non-KOA group(P<0.001), and MPTA was significantly smaller in the OA group than in the non-KOA group(P = 0.022). No significant differences in TFC,PFC, DFC,FTD and FTA were observed between the groups (P>0.05).(Table 1)
Binary logistic regression was used to assess the effects of HKA, MPTA, TFC, PFC, DFC, FTD and TTA on the risk of KOA. The Box–Tidwell procedure was used to test for a linear relationship between continuous independent variables, and dependent variables were logit transformed. The linear test model included 8 items, and the significance level was adjusted using Bonferroni correction to 0.00625. The results indicated a linear relationship between all continuous variables and logit-transformed dependent variables. The final logistic model was statistically significant, χ2 = 98.051, P < 0.001. The model correctly classified 73.8% of the participants. It had a sensitivity of 88.1%, specificity of 37.7%, positive predictive value of 78.4%, and negative predictive value of55.6%. HKA(p<0.001), MPTA༈p = 0.019༉, DFC༈p = 0.13༉和FTD༈p = 0.001༉ were statistically significant (Table 2). Coefficients for HKA, MPTA and FTD were positive, indicating they are risk factors for KOA, whereas coefficients for DFC were negative, indicating it as a protective factor for KOA (Fig. 4).
Table 1
Radiological measurements in KOA and non-KOA groups.
| n | HKA | MPTA | TFC | PFC | DFC | FTD(cm) | FTA(cm2) |
Non-KOA | 106 | 2.75 ± 0.23 | 87.59 ± 0.2 | 177.94 ± 0.17 | 177.7 ± 0.14 | 177.28 ± 0.14 | 3.16 ± 0.04 | 46.02 ± 1.1 |
KOA | 268 | 6.99 ± 0.31 | 86.7 ± 0.17 | 177.67 ± 0.11 | 177.37 ± 0.1 | 177.11 ± 0.11 | 3.24 ± 0.03 | 45.04 ± 0.66 |
p | | <0.001 | 0.022 | 0.242 | 0.123 | 0.46 | 0.116 | 0.837 |
Table 2
Logistic regression analysis results in KOA and non-KOA groups.
| | | | The 95% confidence intervals of the OR |
| B | P value | OR | lower limit value | upper limit value |
HKA | 0.371 | 0.000 | 1.450 | 1.305 | 1.610 |
MPTA | 0.172 | 0.019 | 1.187 | 1.028 | 1.371 |
TFC | -0.071 | 0.362 | 0.932 | 0.801 | 1.085 |
PFC | 0.041 | 0.686 | 1.042 | 0.852 | 1.275 |
DFC | -0.239 | 0.013 | 0.787 | 0.652 | 0.950 |
FTD(cm) | 1.906 | 0.001 | 6.727 | 2.108 | 21.461 |
FTA(cm2) | -0.038 | 0.060 | 0.963 | 0.926 | 1.002 |
2. Comparison of radiological results of varus KOA at different K–L grades
Varus deformity OA was divided into four groups by K–L grade: Grade I with 106 knees; Grade II with 67 knees; Grade III with 68 knees; Grade IV with 133 knees. In Grade I,the mean of HKA,MPTA,TFC,PFC,DFC, FTD and FTA were 2.74 ± 0.23°,87.59 ± 0.2°,177.94 ± 0.17°, 177.69 ± 0.14°,177.27 ± 0.14°,3.16 ± 0.04cm and 46.02 ± 1.1cm2, respectively. In Grade II ,the mean of HKA,MPTA,TFC,PFC,DFC,FTD and FTA were3.5 ± 0.34°,87.64 ± 0.2°,177.8 ± 0.2°, 177.24 ± 0.17°,177.08 ± 0.21°,3.25 ± 0.05cm和46.25 ± 1.17cm2, respectively. In Grade III,the mean of HKA,MPTA,TFC,PFC,DFC,FTD and FTA were 5.57 ± 0.45°,87.37 ± 0.3°,177.74 ± 0.24°,177.69 ± 0.19°,177.29 ± 0.15°,3.25 ± 0.05cm and 46.64 ± 1.41cm2, respectively.In Grade IV ,the mean of HKA,MPTA,TFC,PFC,DFC,FTD and FTA were 9.48 ± 0.46°,85.89 ± 0.28°,177.57 ± 0.16°,177.27 ± 0.16°,177.03 ± 0.15°,3.22 ± 0.04cm and 43.62 ± 0.93cm2, respectively. Statistical analysis revealed that as K–L grade increased, HKA significantly increased(P<0.001) and MPTA significantly decreased(P<0.001). No significant differences in TFC,PFC,DFC,FTD and FTA were observed between the groups(P>0.05)..(Table 3)
The associations between average values HKA,MPTA,TFC,PFC,DFC,FTD and FTA on K–L grade were assessed using ordinal logistic regression. In general, the model fit information P < 0.001 indicates that at least one partial regression coefficient is not equal to 0, signifying that the regression equation is meaningful. The parallel lines test of the model showed a P = 0.466, indicating that the regression coefficients do not change when the cutoff points of the K–L grade change, suggesting that the parameter estimates obtained are stable and reliable. In this study, the Wald test revealed that the regression coefficients of HKA(p<0.001),MPTA༈p = 0.027༉,DFC༈p = 0.002༉and FTD༈p<0.001༉, indicating a significant effect on the dependent variable, or disease severity.(Table 4). Moreover, the coefficients of HKA,MPTA and FTD were positive, confirming these variables as risk factors for KOA severity. Conversely, DFC exhibited negative coefficient values, indicating that DFC is a protective factor against KOA severity(Fig. 5).
Table 3
Radiographic measurements of KOA with different K–L grades.
| n | HKA | MPTA | TFC | PTC | DFC | FTD(cm) | FTA(cm2) |
I级 | 106 | 2.74 ± 0.23 | 87.59 ± 0.2 | 177.94 ± 0.17 | 177.69 ± 0.14 | 177.27 ± 0.14 | 3.16 ± 0.04 | 46.02 ± 1.1 |
II 级 | 67 | 3.5 ± 0.34 | 87.64 ± 0.2 | 177.8 ± 0.2 | 177.24 ± 0.17 | 177.08 ± 0.21 | 3.25 ± 0.05 | 46.25 ± 1.17 |
III级 | 68 | 5.57 ± 0.45 | 87.37 ± 0.3 | 177.74 ± 0.24 | 177.69 ± 0.19 | 177.29 ± 0.15 | 3.25 ± 0.05 | 46.64 ± 1.41 |
IV级 | 133 | 9.48 ± 0.46 | 85.89 ± 0.28 | 177.57 ± 0.16 | 177.27 ± 0.16 | 177.03 ± 0.15 | 3.22 ± 0.04 | 43.62 ± 0.93 |
p | | <0.001 | <0.001 | 0.496 | 0.08 | 0.615 | 0.452 | 0.142 |
Table 4
Logistic regression results of KOA with different K–L grades.
| | | | The 95% confidence intervals of the OR |
| B | P value | OR | lower limit value | upper limit value |
HKA | 0.365 | <0.001 | 1.441 | 1.345 | 1.545 |
MPTA | 0.124 | 0.027 | 1.132 | 1.014 | 1.263 |
TFC | -0.080 | 0.187 | 0.923 | 0.819 | 1.040 |
PFC | 0.045 | 0.556 | 1.047 | 0.899 | 1.218 |
DFC | -0.230 | 0.002 | 0.795 | 0.688 | 0.918 |
FTD(cm) | 1.600 | <0.001 | 4.953 | 2.062 | 11.900 |
FTA(cm2) | -0.027 | 0.085 | 0.974 | 0.944 | 1.004 |
3. Comparative radiographic analysis of fibular morphology in varus and valgus KOA
In varus group with 374 knees, the mean of HKA,MPTA,TFC,PFC,DFC, FTD and FTA were 5.79 ± 0.25°,86.96 ± 0.14°,177.94 ± 0.17°,177.46 ± 0.08°,177.16 ± 0.09°,3.22 ± 0.02cm and 45.32 ± 0.56cm2, respectively. In valgus group with 73 knees, the mean of HKA,MPTA, TFC, PFC,DFC, FTD and FTA were − 3.28 ± 0.4°,90.31 ± 0.3°,177.63 ± 0.11°,177.85 ± 0.18°, 177.34 ± 0.21°,3.17 ± 0.05cm and 46.88 ± 1.35cm2, respectively. The values of MPTA,DTC and PFC in the valgus group were significantly greater than those in the varus group, and no significant between-group differences in TFC,PFC and DFC were observed.(Table 5).
Binary logistic regression was used to investigate the effects of HKA,MPTA,TFC,PFC,DFC, FTD and FTA on whether the participants had varus or valgus deformities. The Box–Tidwell method was used to test for linearity between continuous independent variables and the logit-transformed dependent variables. The the negative HKA value is defined as a valgus deformity ,but negative values cannot undergo logit transformation. Therefore, the HKA angle values underwent transformation(HKA*=180-HKA, >180°is vaggus, <180°is varus). The linear test included A variables, and the Bonferroni method was used to correct the significance level to 0.00625. The linear test results showed a linear relationship between all continuous independent variables and logit-transformed dependent variables. The final logistic model obtained was statistically significant, with χ2 = 63.7 and P < 0 .001. The model could correctly classify the participants of A, with a sensitivity of 98.4%, specificity of 8.8%, positive predictive value of 87.5%, and negative predictive value of 50%. Among the A independent variables included in the model, HKA༈p<0.001༉and FTD༈p = 0.035༉were statistically significant(Table 6).
. The coefficient values of HKA were negative, indicating that HKA as a protective factor for determining whether KOA is varus or valgus. Conversely, the coefficient values of FTD were positive, indicating that FTD is a risk factor for determining whether KOA is varus or valgus(Fig. 6).
Table 5
Radiographic results of varus and valgus KOA.
| n | HKA | MPTA | TFC | PFC | DFC | FTD(cm) | DFC(cm2) |
varus | 374 | 5.79 ± 0.25 | 86.96 ± 0.14 | 177.94 ± 0.17 | 177.46 ± 0.08 | 177.16 ± 0.09 | 3.22 ± 0.02 | 45.32 ± 0.56 |
valgus | 73 | −3.28 ± 0.4 | 90.31 ± 0.3 | 177.63 ± 0.11 | 177.85 ± 0.18 | 177.34 ± 0.21 | 3.17 ± 0.05 | 46.88 ± 1.35 |
p | | <0.001 | <0.001 | 0.078 | 0.047 | <0.001 | 0.454 | 0.176 |
Table 6
Logistic regression results of varus and valgus KOA.
| | | | The 95% confidence intervals of the OR |
| B | P value | OR | lower limit value | upper limit value |
HKA* | -0.238 | <0.001 | 0.788 | 1.164 | 1.384 |
MPTA | 0.034 | 0.641 | 1.034 | 0.897 | 1.193 |
TFC | -0.027 | 0.744 | 0.973 | 0.826 | 1.146 |
PFC | 0.018 | 0.874 | 1.018 | 0.814 | 1.274 |
DFC | -0.153 | 0.136 | 0.858 | 0.702 | 1.049 |
FTD(cm) | 1.310 | 0.035 | 3.707 | 1.095 | 12.557 |
FTA(cm2) | -0.019 | 0.358 | 0.981 | 0.941 | 1.022 |