Predictive effect of a novel regression model calculating lumbar lordosis on the mechanical complications after corrective surgery of adult spinal deformity

English Keywords:Adult spinal deformity  Mechanical complication  Pelvic incidence  Thoracic kyphosis  Lumbar lordosis  Lumbar apex

English Abstract:

  【Abstract】 Objectives: To explore the predictive effect of a novel regression model calculating lumbar lordosis based on pelvic incidence(PI) and thoracic kyphosis(TK) on the mechanical complications after corrective surgery of adult spinal deformity(ASD). Methods: The clinical data of ASD patients undergoing posterior corrective surgery from January 2011 to March 2019 with follow-up for at least 2 years were retrospectively analyzed. Demographic and radiographic(preoperative, immediately postoperative and final follow-up) information were collected. According to the regression model proposed by Pan et al, the deviations of the actual lumbar lordosis(LL), lumbar lordosis apex(LLA) and inflection point(IP) immediately after surgery from the theoretical values derived from postoperative PI and TK were defined as ΔLL, ΔLLA and ΔIP. The patients were divided into two groups based on the presence or absence of mechanical complications. Univariate and multivariate analysis were performed to identify independent risk factors for mechanical complications. Finally, the receiver operating characteristics(ROC) curves were plotted to determine the best cut-off values for the independent risk factors. Results: A total of 92 patients were included, including 77 females and 15 males. The average follow-up time was 2.00-4.60 years(averaged 2.93±0.63 years), amd mechanical complications occurred in 41 patients. Univariate analysis showed that BMI(24.32±2.09kg/m2 vs 23.34±2.26kg/m2), preoperative global tilt(34.26°±18.24° vs 25.68°±15.61°), preoperative pelvic tilt(27.70°±12.61° vs 22.47°±11.99°), and postoperative global tilt(23.29°±12.21° vs 18.35°±10.50°) were significantly higher in the mechanical complications group. Besides, greater postoperative ΔLL(12.19°±6.39° vs 5.49°±5.49°) and ΔLLA(0.74±0.48 vs 0.45±0.28) were significantly associated with mechanical complications(P＜0.05). Logistic regression analysis showed that greater postoperative ΔLL(OR=1.251, 95%CI=1.043-1.270, P=0.005) and ΔLLA(OR=4.357, 95%CI=1.484-19.334, P=0.01) were independent risk factors. The combined index=ΔLL+ΔLLA×1.678/0.140 was defined according to their partial regression coefficients to comprehensively evaluate the predictive effect of ΔLL and ΔLLA on mechanical complications. The area under the ROC curves established using ΔLL, ΔLLA and combined index were 0.777, 0.681 and 0.809. Moreover, the optimal cut-off values of ΔLL, ΔLLA and combined index were 9.17°, 0.71 and 12.93, respectively. Conclusions: Lumbar lordosis should be matched for both PI and TK during ASD corrective surgery. The differences between postoperative LL, LLA and the theoretical values calculated by the novel regression model can be used to effectively predict the occurrence of mechanical complications.