Minimally invasive multiple-rod constructs with robotics planning in adult spinal deformity surgery: a case series.

PURPOSE: Multiple-rod constructs (MRCs) are often used in deformity correction for increased stability and rigidity. There are currently no reports showing minimally invasive placement of MRCs in adult deformity surgery and its technical feasibility through preoperative software planning. METHODS: Data were collected retrospectively from medical records of six consecutive patients who underwent minimally invasive MRCs with robotics planning by a single surgeon at an academic center between March-August 2020. RESULTS: A total of six patients (4 females, mean age 69.7 years) underwent minimally invasive long-segment (6 +) posterior fixation with multiple rods (3 +) using the Mazor X Stealth Edition robotics platform. Average follow-up was 14.3 months. All patients underwent oblique lumbar interbody fusion (OLIF) as a first stage, followed by second stage posterior fixation in the same day. The mean number of levels posteriorly instrumented was 8.8. One patient underwent 3 rod fixation (1 iliac, 2 S2AI) and 5 patients underwent quad rod fixation (2 iliac, 2 S2AI). The mean time to secure all rods was 8 min 36 s. Mean improvement in spinopelvic parameters was -4.9 cm sagittal vertical axis, 18.0° lumbar lordosis, and -10.7° pelvic tilt with an average pelvic incidence of 62.5°. Estimated blood loss (EBL) was 100-250 cc with no blood transfusions, and all but one patient ambulated on postoperative day 1 or 2. CONCLUSION: Spinal robotics brings us into a new era of minimally invasive construct design. To our knowledge, this is the first description of the technical feasibility of MRCs in minimally invasive adult spinal deformity surgery.

Restoring the ideal Roussouly sagittal profile in adult scoliosis surgery decreases the risk of mechanical complications.

PURPOSE: There are still no data proving whether restoring the ideal sagittal profile (according to Roussouly classification) in adult scoliosis (AS) patients leads to any additional benefit, especially regarding mechanical complications. METHODS: Retrospective analysis of operated AS patients recorded in a prospective multicenter database. Demographic and radiographic (preoperative and 6-week postoperative) data were analyzed. Patients with and without mechanical complications were compared looking especially at the surgical restoration of the ideal (based on Pelvic Incidence) sagittal profile. Univariate and multivariate analysis was performed to identify causes of mechanical complications at 2-year minimum follow-up. RESULTS: Ninty-six AS patients were analyzed. Thirty-nine patients suffered a mechanical complication (18 PJK, 11 pseudoarthrosis, 10 screw pull-out), and 57 patients had no mechanical complications. Postoperatively, 72% of patients not matching the ideal Roussouly-type suffered mechanical complications compared to 15% of matched patients (P < 0.001). Univariate analysis showed that older patients 64.9 ± 13 versus 40.7 ± 15.6 years (P < 0.001), higher postoperative Global Tilt (27° vs. 14.7°) and Pelvic Tilt (25° vs. 16°) (P < 0.001), upper instrumented vertebra at the thoracolumbar junction (62% vs. 21%) (P < 0.001), fixation to the Iliac (76% vs. 6%) (P < 0.001), and postoperative Roussouly-type mismatch (72% vs. 15%) (P < 0.001) significantly increased the rate of mechanical complications. Multivariate logistic regression analysis selected: postoperative Roussouly-type mismatch (OR = 41.9; 95%CI = 5.5-315.7; P < 0.001), iliac instrumentation (OR = 19.4; 95%CI = 2.6-142.5; P = 0.004), and age (OR = 1.1; 95%CI = 1.02-1.16; P = 0.004), as the most important variables. CONCLUSIONS: Adult scoliosis surgery should restore the ideal Roussouly sagittal profile to decrease the rate of mechanical complications, especially in patients older than 65, instrumented to the pelvis. These slides can be retrieved under Electronic Supplementary Material.

Effect of lumbar pedicle subtraction osteotomy level on lordosis distribution and shape.

PURPOSE: Little is known about the qualitative results (postoperative upper/lower lumbar arches distribution and lumbar apex or inflection point positioning) of lumbar pedicle subtraction osteotomies (L-PSO) depending on the level of L-PSO. METHODS: We conducted a retrospective analysis of prospectively collected data of adult deformity patients undergoing single-level L-PSO. We analyzed several variables in preoperative and postoperative sagittal radiographs: L-PSO level, Roussouly classification (R-type), inflection point (InfP), lumbar apex (LApex), spinopelvic parameters, lordosis distribution index (LDI = L4-S1/L1-S1), and number of levels in the lordosis (NVL). Comparisons between PSO levels were performed to determine lordosis distribution and sagittal shape using ANOVA test and Chi-squared statistics. RESULTS: A total of 126 patients were included in this study. L5-PSO mainly increased the lower lumbar arch, thereby increasing LDI. L4 increased upper/lower arches similarly. PSOs at and above L3 increased the upper lumbar arch, thereby decreasing LDI (P < 0.001). L4-PSO added 1 vertebra into the lordosis (NVL = + 1.2 ± 2.2). PSOs above L3 added 2 vertebrae into the lordosis (NVL = + 2.3 ± 1.4). Overall P = 0.007. PSOs above L4 shifted the LApex cranially in 70% of the cases (mean 1.12 levels) and the InfP in 85% of the cases (mean 2.4 levels). L5-PSO shifted the LApex caudally in 70% of the cases (mean - 1.1 levels) and the InfP in 50% of the cases (mean - 1.6 levels). Overall P < 0.006. The L-PSO level was not associated with a specific Roussouly-type P > 0.05. CONCLUSIONS: The level of L-PSO influenced upper/lower lumbar arches distribution, and lumbar apex and inflection point positioning. The correct level should be chosen based on the individual assessment of each patient.

Morphological description of sagittal lumbar spinal alignment using curve magnitude, span, and apex-the multiethnic alignment normative study (MEANS).

BACKGROUND CONTEXT: Current definition of lumbar lordosis uses the L1-S1 angle. Prevailing classification of sagittal spinal morphology, derived from a young adult population, classifies the spine into four subtypes defined by their sacral slope (SS) and curve morphology. PURPOSE: To describe physiological sagittal alignment of the lumbar spine across age groups using three main parameters that dictate the lumbar curve: angular magnitude, span, and apex. STUDY DESIGN: A large, multicenter, cross-sectional radiographic comparison study. PATIENT SAMPLE: Four hundred sixty-eight healthy, asymptomatic subjects aged 18 to 80 years from five countries (184 males, 284 females; 98 France, 119 Japan, 79 Singapore, 80 Tunisia, 92 USA, mean age 40.61±14.99 years). OUTCOME MEASURES: Sagittal lumbar profile subtypes clustered based on lumbar curve angular magnitude (ie, Cobb angle of the lumbar lordosis), span, and apex, and described by sagittal radiographic parameters. METHODS: Subjects underwent whole-body low-dose EOS stereoradiographs. Comparisons between conventional L1-S1 lumbar lordosis (cLL) and true lumbar lordosis (tLL, defined by the inflection-S1 angle) were conducted. Using the K-means clustering algorithm, lumbar curve angular magnitude, span and apex were used to classify sagittal spinal morphology into subtypes, stratified across age groups. Further univariate and multivariate analyses were conducted to compare radiographic parameters across subtypes, and identify predictors for the lumbar curve's angular magnitude, span and apex. RESULTS: Mean cLL was -57.27±11.37°, and tLL was -62.62±10.76°. Using tLL, instead of cLL, to describe sagittal spinal morphology, we found significant differences in terms of angular magnitude of the lumbar curve, the median thoracolumbar inflection vertebral level and pelvic incidence-lumbar lordosis mismatch Multivariate analysis found a larger SS, more positive T9 tilt, and more kyphotic T4-T12 predictive for a more lordotic tLL, while a larger overhang distance predicted for a less lordotic tLL (p-values<.001). In addition, a larger T9 tilt, less lordotic L1-L5 and smaller PT were predictors of a more caudal thoracolumbar inflection and lumbar apical vertebral levels (p-values<.001). Sagittal lumbar profiles of subjects age<30 years, 30≤age<60 years and age≥60 years, could be classified into 4, 6, and 3 subtypes, respectively. CONCLUSIONS: Sagittal lumbar profile subtypes vary across age groups, with more homogenous morphologies at the extremes of ages. Improved understanding of the morphological evolution of sagittal spinal profiles with age in asymptomatic individuals will help guide future individualized surgical treatment.

Sacropelvic Fixation for Adult Deformity Surgery Comparing Iliac Screw and Sacral 2 Alar-Iliac Screw Fixation: Systematic Review and Updated Meta-Analysis.

OBJECTIVE: Two commonly used techniques for spinopelvic fixation in adult deformity surgery are iliac screw (IS) and sacral 2 alar-iliac screw (S2AI) fixations. In this article, we systematically meta-analyzed the complications of sacropelvic fixation for adult deformity surgery comparing IS and S2AI. METHODS: The PubMed, Embase, Web of Science, and Cochrane clinical trial databases were systematically searched until March 29, 2023. The proportion of postoperative complications, including implant failure, revision, screw prominence, and wound complications after sacropelvic fixation, were pooled with a random-effects model. Subgroup analyses for the method of sacropelvic fixation were conducted. RESULTS: Ten studies with a total of 1,931 patients (IS, 925 patients; S2AI, 1,006 patients) were included. The pooled proportion of implant failure was not statistically different between the IS and S2AI groups (21.9% and 18.9%, respectively) (p = 0.59). However, revision was higher in the IS group (21.0%) than that in the S2AI group (8.5%) (p = 0.02). Additionally, screw prominence was higher in the IS group (9.6%) than that in the S2AI group (0.0%) (p < 0.01), and wound complication was also higher in the IS group (31.7%) than that in the S2AI group (3.9%) (p < 0.01). CONCLUSION: IS and S2AI fixations showed that both techniques had similar outcomes in terms of implant failure. However, S2AI was revealed to have better outcomes than IS in terms of revision, screw prominence, and wound complications.

Factors affecting disc angle restoration in oblique lateral interbody fusion at L5-S1.

BACKGROUND CONTEXT: Optimal restoration of the L5-S1 disc angle (DA) is an important surgical goal in spinal reconstructive surgery. Anterior approach is beneficial for L5-S1 DA reconstruction and fusion. However, factors associated with a greater DA restoration in oblique lateral interbody fusion (OLIF) at L5-S1 have not been studied. PURPOSE: This study aimed to identify factors that aid in achieving a greater DA in OLIF at L5-S1. STUDY DESIGN/SETTING: A retrospective analysis. PATIENT SAMPLE: This study involved 61 consecutive patients who underwent OLIF at L5-S1 for lumbar degenerative disease and were followed for more than 1 year. Patients with incomplete data or posterior column osteotomy at L5-S1 were excluded. OUTCOME MEASURES: The L5-S1 DA was measured preoperatively, postoperatively, and at the last follow-up on standing lateral lumbar radiographs. The associations between demographics and/or surgical and/or radiological factors and the L5-S1 DA at the last follow-up were analyzed using multiple regression analysis. METHODS: Demographics and surgical factors were reviewed from the medical records with respect to age, sex, body mass index, bone mineral density, diagnosis, surgery level, cage parameters (cage lordotic angle and height), laminectomy performed and/or not performed, estimated blood loss, operative time, configuration of the left common iliac vein. Radiological factors were measured with respect to sagittal parameters, the L5-S1 disc parameters, and the postoperative cage parameters. RESULTS: The mean preoperative DA at L5-S1 was 5.4±5.0°, which increased to 18.9±5.6° postoperatively (p<.001) and was maintained as 16.5±5.9° at the last follow-up (p<.001). The preoperative DA, end plate lesions, anterior spur, facet joint osteoarthritis, or cage position at L5-S1 did not affect the DA at the last follow-up (all p>.05). Multiple regression analysis showed four independent variables, including increased age, increased cage lordotic angle, laminectomy performed, and absence of cage subsidence as the factors associated with the greater DA at L5-S1. CONCLUSIONS: OLIF at L5-S1 showed favorable DA restoration regardless of the preoperative conditions. To achieve a greater DA, surgeons should try to distract the anterior disc space for insertion of a larger lordotic cage. Laminectomy during posterior fixation is recommended for achieving additional DA restoration.

Comparison of whole body sagittal alignment during directed vs natural, relaxed standing postures in young, healthy adults.

BACKGROUND CONTEXT: Imaging for adult spinal deformity is conventionally performed in a directed manner to assess the most upright standing posture one can assume. However, this method does not reflect an individual's natural, relaxed posture, which is the posture a patient likely reverts to postoperatively, and also the posture likely to explain spinal pathologies. PURPOSE: To identify radiographic differences between directed and natural, relaxed standing postures in young healthy subjects. STUDY DESIGN: A randomized, prospective, radiographic study. PATIENT SAMPLE: Sixty healthy 21-year-old subjects (48 male, 12 female). OUTCOME MEASURES: Radiographic parameters including sagittal vertical axis (SVA), C2 SVA, C2-7 SVA global cervical angle, T1-slope, global thoracic angle (GTA), thoracolumbar angle (TLA), global lumbar angle (GLA), sacral slope, pelvic tilt (PT), pelvic incidence, femoral alignment angle (FAA), and knee alignment angle (KAA). METHODS: The EOS whole body radiographs of patients in directed and natural, relaxed standing postures were obtained, with subsequent comparison of radiographic parameters. Differences in Roussouly curve types, sagittal curve apices, and end vertebrae were also evaluated. Univariate analyses using Wilcoxon sign-rank, paired t tests, and paired chi-square tests were performed. RESULTS: Compared with directed standing, natural, relaxed standing results in a more kyphotic spinal profile marked by a significantly less lordotic GLA, larger GTA, TLA, and T1-slope. The PT+FAA demonstrated true hip movement during sagittal balancing. Lower thoracic and lumbar apices, lower thoracolumbar end vertebrae, and lower Roussouly curve types were observed during natural, relaxed standing. CONCLUSIONS: Our study found significant differences in sagittal radiographic parameters between directed standing and the natural, relaxed standing posture, with the latter demonstrating a more kyphotic spinal profile in terms of magnitude and span, as well as complementary changes in cervical and spinopelvic alignment. The natural, relaxed standing posture, a marker for energy conservation principles in standing, may infer value in less aggressive lordotic restoration, as well as concentration of lordosis in the lower lumbar spine.

Clinical Results and Functional Outcomes in Adult Patients After Revision Surgery for Spinal Deformity Correction: Patients Younger than 65 Years Versus 65 Years and Older.

STUDY DESIGN: Retrospective comparison. OBJECTIVE: To compare complications and radiographic and functional outcomes of patients undergoing revision spinal deformity surgery, who were 40-64 years of age and 65 years of age or older. SUMMARY OF BACKGROUND DATA: The effect of age on radiographic and functional outcomes has not been well established in the literature for patients undergoing revision adult deformity surgery. The hypothesis was that the complications and radiographic and functional outcomes of younger and older adult patients would be comparable. METHODS: The authors retrospectively reviewed prospectively collected data on 109 consecutive patients (84 women and 25 men) undergoing revision spinal deformity surgery who were 40 years of age or older. All surgeries were performed at 1 institution by the senior author. Patients were divided into groups based on age: younger than 65 years of age (70 patients) or 65 years of age or older (39 patients), and complications and radiographic and functional outcomes were compared. All patients had at least 2 years' clinical follow-up. Hotelling's t2 test and the χ2 test were used to compare differences; statistical significance was set at p < .05. RESULTS: There was no significant difference between the 2 groups in major complications (p = .62), minor complications (p = .34), or reoperation rate (p = .08). Major correction was achieved in the coronal and sagittal planes in both groups after surgery. By final follow-up, patients in both groups had significant improvements from baseline in Oswestry disability index (p < .05) and in all Scoliosis Research Society-22 domains (p < .001); there was no significant difference in any domain score between groups (p > .05). CONCLUSIONS: Older adult patients undergoing revision deformity correction surgery achieved functional outcome benefits comparable to those in younger adults without significantly more complications. Surgeons should be aware of these factors when counseling patients regarding revision surgery for deformity correction.