A new predictive factor for postoperative neurological deficits in patients with severe post-tuberculous kyphosis: the deformity angular distance ratio.

PURPOSE

To investigate the effectiveness of sagittal deformity angular distance ratio (S-DADR; sagittal Cobb angle divided by the distance, in centimeters, between the midpoint of the upper endplate of the upper end vertebrae and the midpoint of the lower endplate of the lower end vertebrae) in evaluating neurological risks in patients with post-tuberculous kyphosis (PTK).

METHODS

A consecutive series of 102 patients with PTK who underwent corrective surgery between September 2010 and June 2024 were included. Measurements derived from preoperative radiographs were utilized to compute S-DADR. Potential risk factors of postoperative neurological deficits (PNDs) were assessed through univariate and multivariate analyses. Binary logistic regression was used to model the relationship between identified independent risk factors and PNDs, and the model was evaluated by the area under receiver operating characteristic curve (AUC).

RESULTS

The mean age of the 102 patients was 49.5 ± 12.1 years, and the incidence of PNDs was 22.5%. Univariate logistic regression revealed a positive correlation between the incidence of PNDs and S-DADR (OR = 1.103, P = 0.003), preoperative sagittal Cobb angle (OR = 1.025, P = 0.007), number of vertebrae resected (OR = 1.661, P = 0.024), operative time (OR = 1.005, P = 0.048) and total instrumented vertebrae (OR = 1.391, P = 0.014). Multivariate logistic regression identified S-DADR (OR = 1.091, P = 0.025) as an independent factor of PNDs. Patients with S-DADR ≥ 21.4 exhibited a 30% incidence of PNDs, which increased to 50% with an S-DADR of 30.0. The overall predictive performance of S-DADR (AUC = 0.720) for PNDs was deemed satisfactory.

CONCLUSIONS

S-DADR can be used to quantify the severity of the deformity in patients with PTK, which is an independent risk factor for PNDs during corrective surgery. Patients with S-DADR ≥ 21.4 face a 30% incidence of developing PNDs after corrective surgery.