"Reasonable threshold" of spinopelvic parameters after fixation on distal stenosis in patients with degenerative thoracolumbar kyphosis: A STROBE-compliant article.

The short-segment instrument for precision treatment of lumbar stenosis syndrome (LSS) combined with degenerative thoracolumbar kyphosis (DTLK) receives more attention and the reasonable range of sagittal parameters is debatable in these elderly patients. This study aimed to include LSS patients combined with DTLK performed short-segmental fixation on LSS, to evaluate the efficacy of this procedure, and to determine the reasonable threshold of sagittal parameters. Overall 138 patients (female, 62.3%) were eligible (mean age of 68.8 ± 7.7 years) with a follow-up time of 24.6 ± 11.1 months. Spinopelvic sagittal parameters containing TLK, lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), and sagittal vertical axis were obtained at baseline and final visit, where |PI-LL|, PT, and sagittal vertical axis were seen as the main parameters. Quality of life was evaluated by the Oswestry Disability Index (ODI), which were divided into 4 quarters orderly. The reasonable threshold of parameters corresponding to ODI was determined by both linear regression and logistic regression. For all participants, TLK decreased by a mean of 8.3° and cases got TLK correction occupied 40.4%. ODI got improvement by the change of 29.9 ± 9.9. At baseline, ODI was correlated to |PI-LL|, while at final, ODI was correlated to |PI-LL| and PT. The independent factor affecting preoperative ODI was |PI-LL|, with ODI = 0.19 × |PI-LL| + 36.9 and the mean threshold of preoperative |PI-LL| was 10.7°. At final, PT was the influencing factor with ODI = 0.21 × PT + 3.16 and PT = 0.60 × |PI-LL| + 12.22. The mean threshold of postoperative |PI-LL| was 16.0° and PT was 23.1° by both linear regression and logistic regression. With short-segment fixation on LSS, >40% of patients with DTLK acquired TLK correction. |PI-LL| = 16.0° and PT = 23.1° was the "reasonable threshold" of sagittal parameters with the procedure for this population.