Surgical planning for spinal deformity correction: the contribution of patient-specific rods.

STUDY

DESIGN

Retrospective analysis of a prospectively maintained single-center cohort.

OBJECTIVES

To evaluate the accuracy and mid-term durability of sagittal correction in adult spinal deformity (ASD) patients treated with patient-specific rods (PSR) using the SD-based goal-attainment method described by Smith et al. Secondary objectives were to identify predictors of alignment goal attainment and to characterize complication rates.

METHODS

Consecutive ASD patients undergoing thoracolumbar fusion with PSR (UNID®, cobalt–chrome, 6 mm) between 2015 and 2020 were analyzed. Planned sagittal targets (LL, SVA, TK, PT) were compared with preoperative, early postoperative (< 6 weeks), and ≥ 36-month follow-up measurements. Goal attainment was defined as achieving values within ± 1 cohort SD of the planned target. Multivariable logistic regression identified predictors of goal attainment.

RESULTS

Among 145 patients (mean age 65.3 years; 71.3% women; mean fusion length 11.8 levels), PSR increased lumbar lordosis from 31.8° to 52.0° postoperatively and 49.3° at last follow-up (planned 55.8°). Sagittal vertical axis decreased from 79.8 mm to 39.3 mm postoperatively and 53.0 mm at follow-up (planned 8.6 mm). Goal attainment was 60.9% for LL, 62.2% for SVA, 77.3% for TK, and 45.1% for PT; 45.5% achieved all three primary targets. Higher pelvic incidence predicted LL undercorrection, whereas > 3 osteotomies and lower BMI favored global goal attainment.ODI improved from 60.6 ± 13.4% to 35.7 ± 13.3% (Δ =−24.9, p < 0.001); EVAL from 7.0 ± 1.6 to 3.5 ± 1.7 (Δ =−3.5, p < 0.001); and EVAR from 5.4 ± 2.5 to 1.7 ± 2.0 (Δ=−3.7, p < 0.001).

CONCLUSIONS

Patient-specific rods appear to significantly improve the accuracy and mid-term durability of sagittal alignment in ASD. Nearly half of patients achieved all primary alignment goals. PSR may represent a promising tool to standardize sagittal realignment. LEVEL OF EVIDENCE: 3