Fig. 6

Logistic regression analysis showed that covariates, including PMCS, DCSA, sex, age, BMI, TAD and LWT, had no significant effect on internal fixation failure (P > 0.05). After excluding other mixed factors (PMCS: positive medial cortex support; DCSA: difference in cervical shaft angle; BMI: body mass index; TAD: tip-apex distance; LTW: lateral wall thickness), the SI (I ~ II) and SI (III ~ IV) groups had adjusted ORs of 3.56 (95% CI, 1.64 to 7.72) and 2.42 (95% CI, 1.08 to 5.41), respectively, with P = 0.00 and P = 0.03. The Singh index was an independent factor for predicting the failure of internal fixation. Every decrease in the Singh index can increase the failure rate of internal fixation