Lee, Nathan J.

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.

Study Design: Single-center retrospective analysis. Objective: To establish an empirically derived threshold to define both coronal and sagittal malalignment (CM & SM) based on preoperative patient-reported outcomes (PROs). Summary of Background Data: Currently, no radiographic alignment threshold defines preoperative CM in adult spinal deformity (ASD) patients based on disability. In a cohort of ASD patients undergoing corrective surgery, we sought to establish a threshold to define both CM and SM based on PRO and assess the clinical impact of CM and combined with SM. Methods: ASD patients with ≥6 level fusions were included. CVA and SVA were measured. PROs included preoperative ODI and SRS-22r scores. CVA and SVA thresholds were derived to accurately differentiate patients with ODI >40 and SRS-pain+function <5. Patients were then separated into 4 groups: (1) neutral alignment (NA); (2) CM; (3) SM; and (4) combined coronal and sagittal malalignment (CCSM). Results: Totally, 368 patients were included. Thresholds to distinguish patients with ODI ≥40 and SRS-pain/function <5 were: (1) CVA=3.96 cm (ODI) and 3.17 cm (SRS); (2) SVA=4.97 cm (ODI) and 7.52 cm (SRS). The lower numbers were chosen to define each threshold: CVA=3 cm and SVA=5 cm. Alignment breakdown was: NA=179 (48.6%), CM=66 (17.9%), SM=65 (17.7%), and CCSM=58 (15.8%). Both SM=( P =0.006) and CCSM ( P <0.001) patients had significantly worse ODI scores than NA patients, and CCSM patients were significantly worse than SM alone ( P =0.010). On the basis of preoperative total SRS-22r scores, only CCSM ( P =0.003) patients were significantly worse than the NA group. CVA significantly correlated with 4/7 (57.1%) preoperative PROs (ODI/SRS-total/function/image), while SVA correlated with 5/7 (71.4%) preoperative PROs (ODI/SRS-total/function/image/pain). A linear relationship was seen between increasing CVA and worsening ODI (β=0.92, 95% CI: 0.37–1.48, P =0.001). A significant and slightly stronger relationship was seen between increasing SVA and worsening ODI (β=1.28, 95% CI: 1.00–1.56, P <0.001). Conclusions: CM and SM thresholds that accurately distinguished ASD patients with severe pain and disability preoperatively were 3 cm for CVA and 5 cm for SVA, respectively. Preoperative CM was significantly associated with worse ODI, SRS-22r total/function/image scores. CCSM led to more disability than SM alone.

OBJECTIVE Patients with ankylosing spinal disorders (ASDs), including ankylosing spondylitis (AS) and diffuse idiopathic skeletal hyperostosis (DISH), have been shown to experience significantly increased rates of postoperative complications. Despite this, very few risk stratification tools have been validated for this population. As such, the purpose of this study was to identify predictors of adverse events and mortality in ASD patients undergoing surgery for 3-column fractures. METHODS All adult patients with a documented history of AS or DISH who underwent surgery for a traumatic 3-column fracture between 2000 and 2020 were identified. Perioperative variables, including comorbidities, time to diagnosis, and number of fused segments, were collected. Three instruments, including the Charlson Comorbidity Index (CCI), modified frailty index (mFI), and Injury Severity Score (ISS), were computed for each patient. The primary outcomes of interest included 1-year mortality, as well as postoperative complications. RESULTS A total of 108 patients were included, with a mean ± SD age of 73 ± 11 years. Of these, 41 (38%) experienced at least 1 postoperative complication and 22 (20.4%) died within 12 months after surgery. When the authors controlled for potential known confounders, the CCI score was significantly associated with postoperative adverse events (OR 1.20, 95% CI 1.00–1.42, p = 0.045) and trended toward significance for mortality (OR 1.19, 95% CI 0.97–1.45, p = 0.098). In contrast, mFI score and ISS were not significantly predictive of either outcome. CONCLUSIONS Complications in spine trauma patients with ASD may be driven by comorbidity burden rather than operative or injury-related factors. The CCI may be a valuable tool for the evaluation of this unique population.

Study Design: Prospective single-cohort analysis. Objectives: To compare the outcomes/complications of 2 robotic systems for spine surgery. Methods: Adult patients (≥18-years-old) who underwent robot-assisted spine surgery from 2016-2019 were assessed. A propensity score matching (PSM) algorithm was used to match Mazor X to Renaissance cases. Preoperative CT scan for planning and an intraoperative O-arm for screw evaluation were preformed. Outcomes included screw accuracy, robot time/screw, robot abandonment, and radiation. Screw accuracy was measured using Vitrea Core software by 2 orthopedic surgeons. Screw breach was measured according to the Gertzbein/Robbins classification. Results: After PSA, a total of 65 patients (Renaissance: 22 vs. X: 43) were included. Patient/operative factors were similar between robot systems ( P > .05). The pedicle screw accuracy was similar between robots (Renaissance: 1.1%% vs. X: 1.3%, P = .786); however, the S2AI screw breach rate was significantly lower for the X (Renaissance: 9.5% vs. X: 1.2%, P = .025). Robot time per screw was not statistically different (Renaissance: 4.6 minutes vs. X: 3.9 minutes, P = .246). The X was more reliable with an abandonment rate of 2.3% vs. Renaissance:22.7%, P = .007. Radiation exposure were not different between robot systems. Non-robot related complications including dural tear, loss of motor/sensory function, and blood transfusion were similar between robot systems. Conclusion: This is the first comparative analyses of screw accuracy, robot time/screw, robot abandonment, and radiation exposure between the Mazor X and Renaissance systems. There are substantial improvements in the X robot, particularly in the perioperative planning processes, which likely contribute to the X’s superiority in S2AI screw accuracy by nearly 8-fold and robot reliability by nearly 10-fold.