Stephan, Stephen

Study Design: Single-center retrospective cohort study. Objective: To determine if the 4-rod construct (4RC) is protective against the occurrence of rod fractures when compared with the 3-rod construct (3RC) in adult spinal deformity (ASD) patients with long fusions to the sacrum. Summary of Background Data: Past studies have explored the different outcomes in subjects with dual-rod versus multirod constructs. There is a lack of literature distinguishing the ramifications of 3RC versus 4RC, particularly in the prevalence of rod fractures and rod fractures requiring subsequent revision surgery as a result of pseudarthrosis. Methods: ASD patients undergoing long instrumented fusions to the sacrum were dichotomized between the 3RC and 4RC cohorts. Outcomes of interest include the occurrence of rod fractures (RFs) and RFs requiring revision (RFR). Two-tailed independent-sample t test with Welch's correction and χ 2 /Fisher exact test were used for continuous and categorical variables, respectively. Multivariable logistic regression analysis was performed to assess whether the 4RC is protective against rod fractures when compared with the 3RC. Results: One hundred forty-five patients with a minimum 2-year follow-up were included (3RC=57, 4RC=88). Four RC had a greater body mass index (BMI) ( P =0.002), longer operating room (OR) time ( P =0.002), greater estimated blood loss (EBL) ( P =0.002), total instrumented levels (TIL) ( P =0.028), and more 3-column osteotomies (3COs) performed ( P =0.028). Four RC had greater baseline coronal vertical axis (CVA) (28.2±24.9 vs. 18.5±16.9 mm, P =0.006) and sagittal vertical axis (SVA) (55.1±64.8 vs. 30.4±41.8 mm, P =0.006). Three RC had a greater rate of RF (28.1% vs. 14.8%, P =0.0506) and RFR (14.9% vs. 10.2%, P =0.486) when compared with 4RC, but these findings were not statistically significant. After controlling for BMI, the use of 3-column osteotomies, total instrumented levels, change in coronal alignment (∆CVA), change in sagittal alignment (∆SVA), use of bone morphogenetic protein, and number of interbody fusions, 3RC was associated with 4.93× greater odds of experiencing RFs ( P =0.0078). However, significance fell short when adjusting for the occurrence of RFR [OR=2.58 (0.60–11.19), P =0.2067]. Conclusion: ASD patients having long fusions to the sacrum with 4RC across the lumbosacral junction are shown to be at lesser risk of developing rod fractures but not revision surgery as compared with 3RC at 2-year follow-up.

OBJECTIVE The objective of this study was to compare a multiple pelvic screw fixation strategy (dual bilateral 4 pelvic screw fixation [4PvS]) with the use of single bilateral 2 pelvic screw fixation (2PvS), with the aim of addressing lumbosacral junction stability. METHODS This analysis is a single-center, retrospective review of ASD patients treated between 2015 and 2021. All patients had a minimum 2-year follow-up and spinal fusion to the sacrum without sacroiliac fusion and met at least one radiographic and procedural criterion: pelvic incidence–lumbar lordosis ≥ 20°, T1 pelvic angle ≥ 20°, sagittal vertical axis ≥ 7.5 cm, scoliosis ≥ 50°, three-column osteotomy, or spinal fusion of ≥ 8 levels. Two sacropelvic fixation methods were compared: 4PvS versus 2PvS. Primary outcomes included spinal implant-related reoperation and screw breakage, while secondary outcomes included reoperation for symptomatic pelvic screws, screw loosening or bending, L5–S1 pseudarthrosis, and patient-reported outcomes. Propensity score matching and inverse probability of treatment weighting (IPTW) were used to minimize selection bias and estimate causal treatment effects. Clinical outcomes were assessed using conditional multivariable logistic regression. RESULTS In this study of 406 patients (67.98% female, mean age 64.48 years), 349 patients (85.96%) received 2PvS and 57 (14.04%) received 4PvS. Age (OR 1.081, 95% CI 1.027–1.145) and total number of osteotomies (OR 1.180, 95% CI 1.048–1.355) emerged as independent predictors of receiving the 4PvS technique. In unmatched cohorts (n = 406), 2-year implant-related reoperation rates (p = 0.1896) and pelvic screw breakage rates (p = 0.2498) were not significantly different between groups. However, in the 4:1 propensity score–matched cohort, the 2-year reoperation rate (10.53% for 2PvS vs 3.51% for 4PvS; OR 3.27, 95% CI 1.10–9.74 [p = 0.0312]) and the pelvic screw breakage rate (9.21% for 2PvS vs 3.51% for 4PvS; OR 2.87, 95% CI 1.08–7.63 [p = 0.0349]) were significantly higher among the 2PvS groups. The IPTW analysis confirmed these findings, with reoperation rates of 10.45% for 2PvS and 1.18% for 4PvS (p = 0.0244) and pelvic screw breakage rates of 8.72% and 1.18%, respectively (p = 0.0477). A safety assessment revealed comparable operative times and intra- and perioperative complications between the two techniques. CONCLUSIONS Patients who underwent 4PvS demonstrated significantly lower 2-year implant-related reoperation and pelvic screw breakage rates compared with 2PvS, with no differences in intraoperative or perioperative complications.