39. Optimizing safety in robotic lumbar instrumented fusions: a risk factor analysis of robotic failures [Meeting Abstract]
BACKGROUND CONTEXT: Robot-guided lumbar instrumented fusion (RGLF) has the potential to improve safety and accuracy of pedicle screw placement. However, there are pitfalls in adopting this new technology and, as in adopting any new OR technology, there may be early complications. Optimizing workflow by avoiding interbody placement prior to pedicle screws placement (interbody-first workflow, IFW) and using caution in patients with poor bone quality (L1 Hounsfield units [HU] under 148) may improve outcomes. PURPOSE: To determine risk factors for robot-related complications and suggest optimal OR workflow. STUDY DESIGN/SETTING: Single-center retrospective study. PATIENT SAMPLE: A total of 344 RGLF cases from 2018 to 2021. OUTCOME MEASURES: L1 and UIV HU, levels fused, L5-S1 inclusion, interbody placed first workflow (IFW), hyperlordotic interbody, robot registration method, robot registration failure, intraoperative robot mechanical failures and pedicle screw malpositioning.
METHOD(S): Retrospective analysis of RGLFs at a single institution. Univariate analysis with t-tests, Mann-Whitney U tests, or chi-squared analysis assessed demographics, L1 and UIV HU, levels fused, L5-S1 inclusion, IFW, hyperlordotic cage, and robot registration method as risk factors for robot registration failure, intraoperative robot mechanical failures, and pedicle screw malpositioning. Multivariate logistic regression of risk factors approaching or achieving significance was conducted. A receiver operating characteristic (ROC) curve was created to determine a threshold for independent risk factors.
RESULT(S): A total of 344 RGLFs were included. In registered vs registration failure cases, smoking (12.73% vs 28.57%; p=0.041), L1HU (139.81+/-46.86 vs 177.16+/-55.74; p=0.009), L5-S1 inclusion (50.00% vs 80.95%; p=0.006), and IFW (58.07% vs 85.71%; p=0.014) were significant risk factors on univariate analysis. On multivariate analysis, smoking (p=0.003), L1HU (p=0.006), and L5-S1 inclusion (p=0.022) were independent risk factors and IFW approached significance (p=0.099) for risk of registration failure. In successful vs all robot failures cases, age (55.72+/-13.38 vs 59.92+/-11.38 years; p=0.046), female gender (48.70% vs 69.44%; p=0.018), levels fused (1.37+/-0.63 vs 1.67+/-0.76; p=0.010), L5-S1 inclusion (50.00% vs 69.44%; p=0.027), and IFW (57.47% vs 77.78%; p=0.012) were significant risk factors on univariate analysis. On multivariate analysis, female gender (p=0.047) and L5-S1 inclusion (p=0.049) were independent risk factors and IFW approached significance (p=0.055) for risk of mechanical failure. In successful vs pedicle screw malpositioned cases, IFW was a significant independent risk factor for pedicle screw malpositioning on multivariate analysis (p=0.038). On subanalysis of 124 robot-guided anterior-posterior lumbar fusion (RG APLF), L1 HU was an independent risk factors for registration failure (p=0.007) and approached significance for mechanical failures (p=0.051). ROC analysis revealed a cutoff of L1 HU of 148.55 for mechanical failures (area under the curve = 0.778). Levels fused (1.41+/-0.69 vs 2.00+/-0.54; p=0.018) was a significant risk factor for pedicle screw malpositioning on univariate analysis.
CONCLUSION(S): In all RGLFs, IFW was a risk factor for robot-related complications. In RG APLF, low L1 HU was a risk factor. Robot-related complications may be avoided by placing pedicle screws prior to interbody and by using caution in patients with poor bone quality. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
41. Robotic pedicle screw placement has a dynamic learning curve based on spine surgery invasiveness index [Meeting Abstract]
BACKGROUND CONTEXT: Robot-guided lumbar instrumented fusion (RGLF) for accurate pedicle screw placement is increasingly popular. Learning curve (LC) has been reported to be short, but simple comparison of a set number of early to later cases may oversimplify the LC. This study offers an analysis of a single institution LC for RGLF as it relates to increasing case complexity as determined by Spine Surgical Invasive Index (SII) as described by Mirza, and advanced techniques. PURPOSE: To determine if RGLF is related to SII and is more dynamic than previously described. STUDY DESIGN/SETTING: Single-center retrospective cohort study. PATIENT SAMPLE: A total of 346 patients undergoing RGLF at a single institution from 2018 to 2021. OUTCOME MEASURES: Case complexity indicators (levels fused, SII, iliac fixation, single position surgery), radiation dose, procedure/operative time (PTime/OpTime), EBL, LOS, failed registration, robotic mechanical failures, perioperative complications and OR returns.
METHOD(S): All RGLFs at a single institution were included. Outcome measures indicating case complexity (levels fused, SII, iliac fixation, single position surgery) underwent regression analysis to determine risk factors for robot-related complications. Peaks in these characteristics over the course of 346 cases were identified. Outcomes including radiation dose, procedure/operative time (PTime/OpTime), EBL, LOS, failed registration, robotic mechanical failures, perioperative complications, and returns to OR were analyzed in stepwise fashion by each consecutive case using independent samples t-tests and chi-squared analyses as appropriate.
RESULT(S): A total of 346 RGLFs included. No significant changes in demographics over time. SII was an independent risk factor for robot registration and intraoperative mechanical failures on multivariate regression analysis (p<0.001). SII had significant peaks between 10 to 20 cases and 165 to 330 cases. The following outcomes were overcome during a first LC corresponding to an early SII peak: PTime (401.2+/-135.6 vs 361.4+/-99.7 min; p= 0.047), OpTime (326.0+/-129.4 vs 279.4+/-91.9 min; p= 0.034), robot mechanical failures (26.7% vs 10.1%; p=0.046), all postop complications (60.0% vs 29.2%; p=0.037), ileus (9.0% vs 3.3%; p=0.046), urinary complications (6.4% vs 1.9%; p=0.043). A later LC corresponding to a second SII peak saw significant changes in PTime per level (291.1+/-84.7 vs 259.5+/-108.5 min; p=0.017), OpTime per level (223.6+/-70.4 vs 200.9+/-90.7 min; p= 0.038), EBL (316.7+/-264.0 vs 247.4+/-204.6 mL; p=0.035), LOS (3.8+/-2.2 vs 2.7+/-1.1 days; p=0.001), all intraoperative complications (23.8% vs 13.2%; p=0.036), surgical site infections (2.54% vs 10.34%; p=0.022), robot registration failures (8.3% vs 2.1%; p=0.039), new neurological deficits (5.2% vs 0.0%; p=0.050), instrumentation failures (1.7% vs 3.7%; p =0.043), and returns to OR for pedicle screw revision (1.2% vs 8.9%; p=0.046) or for neurological deficit (3.9% vs 0.0%; p=0.050).
CONCLUSION(S): Two learning curves were observed that mirrored significant peaks in SII. The second, more significant, wave of complications was observed with increased surgical complexity. This suggests a longer, more dynamic learning curve than has been previously described. Avoiding surgeries with high SII at the beginning of RGLF experience may prevent early complications. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
P6. Spinopelvic alignment changes between seated and standing positions in pre and post total hip replacement patients [Meeting Abstract]
BACKGROUND CONTEXT: The inter-relationship between the hip and spine has been increasingly studied in recent years, particularly as it pertains to the effect of spinal deformity and hip osteoarthritis (OA). Changing from standing (ST) to seated (SE) requires rotation of the femur from an almost vertical plane to the horizontal. OA of the hip significantly limits hip extension, resulting in less ability to recruit pelvic tilt (PT) in ST, and requiring increased PT in SE to compensate for loss of hip flexion. To date, the effect of total hip arthroplasty (THA) in altering spinopelvic SE and ST mechanics has not been reported. PURPOSE: To investigate the change in spinopelvic alignment parameters between seated and standing positions in pre and post THA patients. STUDY DESIGN/SETTING: Retrospective review at a single academic institution. PATIENT SAMPLE: Adult patients undergoing THA with full body sitting and standing radiographs pre- and post-THA. OUTCOME MEASURES: Spinopelvic alignment measures including pelvic incidence (PI), pelvic tilt (PT), T1 pelvic angle (TPA), sacral slope (SS), sagittal vertical axis (SVA), pelvic incidence and lumbar lordosis mismatch (PI-LL), and lumbar lordosis (LL).
METHOD(S): Patients >=18yo undergoing THA for hip OA with full spine SE and ST radiographs pre and post THA were included. Spinopelvic alignment was analyzed pre-THA and post-THA in both ST and SE positions in a relaxed posture with the fingers on the clavicles. Paired t-test analysis was performed to compare Pre-and Post-THA groups. The effect of TL deformity (SVA>50, TPA>20, PI-LL>10) on these changes was also analyzed. Statistical significance set at p<0.05.
RESULT(S): There were 192 patients assessed. 179 patients had thoracolumbar (TL) deformity; TPA>20 (N=46), PI-LL>10 (N=55), and SVA>50 (N=78). In standing position, patients have a significant reduction in SVA post THA vs pre THA (34.09+/-42.69 vs 45.03+/-46.87, p=0.001) as a result of an increase in PT (15.7+/-9.74 o vs 14.6+/-9.88o,p=0.028), without significant changes in spinal alignment parameters including lumbar lordosis (-51.26+/-14.59 vs -50.26+/-14.87, p=0.092), thoracic kyphosis (35.98+/-12.72 vs 35.40+/-13.16, p=0.180), sacral slope (38.15+/-10.77 vs 38.83+/-11.31, p=0.205), T1 pelvic angle (14.22+/-9.94 vs 14.51+/-10.13, p=0.053) and PI-LL mismatch (2.59+/-14.61 vs 3.35+/-14.92, p=0.183). This change in ST_SVA was larger in patients with TL deformity, specifically in those with SVA>50 (61.29+/-45.69 vs 89.48+/-35.91, p=0.001), in PI-LL > 10 (59.08+/-45.49 vs 73.36+/-48.50, p=0.001) and in TPA>20 subsets (62.14+/-49.94 vs 82.28+/-49.55, p=0.001). When moving from ST to SE, the DELTAPT was reduced post THA (16.70+/-15.27o vs 20.85+/-17.27o, p=0.001) in addition to a smaller SE_PT vs pre-THA (32.41+/-14.47 vs 35.46+/-14.20, p=0.006).
CONCLUSION(S): Post Total Hip Arthroplasty (THA), patients demonstrated an increased recruitment of pelvic retroversion to achieve a better global balance by reduction in standing SVA. This compensation was achieved solely by greater mobility of their hip and pelvis, and without a significant change in spinal alignment. ST_SVA reduction was more pronounced in patients with thoracolumbar (TL) spinal deformity (SVA>50, TPA>20, PI-LL>10). On the converse, PT was reduced in sitting (SE) post-THA compared to pre-THA, and the compensatory change in PT was also reduced between ST and SE as a result of restoration of hip flexion. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
Patient Outcomes After Single-level Coflex Interspinous Implants Versus Single-level Laminectomy
STUDY DESIGN/METHODS:Retrospective cohort analysis. OBJECTIVE:The aim of this study was to compare postoperative outcomes of Coflex interspinous device versus laminectomy. SUMMARY OF BACKGROUND DATA/BACKGROUND:Coflex Interlaminar Stabilization device (CID) is indicated for one- or two-level lumbar stenosis with grade 1 stable spondylolisthesis in adult patients, as an alternative to laminectomy, or laminectomy and fusion. CID provides stability against progressive spondylolisthesis, retains motion, and prevents further disc space collapse. METHODS:Patients â‰¥18 years' old with lumbar stenosis and grade 1 stable spondylolisthesis who underwent either primary single-level decompression and implantation of CID, or single-level laminectomy alone were included with a minimum 90-day follow-up at a single academic institution. Clinical characteristics, perioperative outcomes, and postoperative complications were reviewed until the latest follow-up. Ï‡2 and independent samples t tests were used for analysis. RESULTS:Eighty-three patients (2007-2019) were included: 37 cases of single-level laminectomy (48.6% female) were compared to 46 single-level CID (50% female). CID cohort was older (CID 69.0â€ŠÂ±â€Š9.4 vs. laminectomy 64.2â€ŠÂ±â€Š11.0, Pâ€Š=â€Š0.042) and had higher American Society of Anesthesiologists (ASA) grade (CID 2.59â€ŠÂ±â€Š0.73 vs. laminectomy 2.17â€ŠÂ±â€Š0.48, Pâ€Š=â€Š0.020). CID patients had higher estimated blood loss (EBL) (97.50â€ŠÂ±â€Š77.76 vs. 52.84â€ŠÂ±â€Š50.63â€ŠmL, Pâ€Š=â€Š0.004), longer operative time (141.91â€ŠÂ±â€Š47.88 vs. 106.81â€ŠÂ±â€Š41.30â€Šminutes, Pâ€Š=â€Š0.001), and longer length of stay (2.0â€ŠÂ±â€Š1.5 vs. 1.1â€ŠÂ±â€Š1.0â€Šdays, Pâ€Š=â€Š0.001). Total perioperative complications (21.7% vs. 5.4%, Pâ€Š=â€Š0.035) and instrumentation-related complication was higher in CID (10.9% vs. 0% laminectomy group, Pâ€Š=â€Š0.039). There were no other significant differences between the groups in demographics or outcomes. CONCLUSION/CONCLUSIONS:Single-level CID devices had higher perioperative 90-day complications, longer operative time, length of stay, higher EBL compared to laminectomies alone. Similar overall revision and neurologic complication rates were noted compared to laminectomy at last follow-up.Level of Evidence: 3.
Residual lumbar hyperlordosis is associated with worsened hip status 5 years after scoliosis correction in non-ambulant patients with cerebral palsy
BACKGROUND:Cerebral palsy (CP) is a static encephalopathy with progressive musculoskeletal pathology. Non-ambulant children (GMFCS IV and V) with CP have high rates of spastic hip disease and neuromuscular scoliosis. The effect of spinal fusion and spinal deformity on hip dislocation following total hip arthroplasty has been well studied, however in CP this remains largely unknown. This study aimed to identify factors associated with worsening postoperative hip status (WHS) following corrective spinal fusion in children with GMFCS IV and V CP. METHODS:Retrospective review of GMFSC IV and V CP patients in a prospective multicenter database undergoing spinal fusion, with 5Â years follow-up. WHS was determined by permutations of baseline (BL), 1Â year, 2Â years, and 5Â years hip status and defined by a change from an enlocated hip at BL that became subluxated, dislocated or resected post-op, or a subluxated hip that became dislocated or resected. Hip status was analyzed against patient demographics, hip position, surgical variables, and coronal and sagittal spinal alignment parameters. Cutoff values for parameters at which the relationship with hip status was significant was determined using receiver operating characteristic curves. Logistic regression determined odds ratios for predictors of WHS. RESULTS:Eighty four patients were included. 37 (44%) had WHS postoperatively. ROC analysis and logistic regression demonstrated that the only spinopelvic alignment parameter that significantly correlated with WHS was lumbar hyperlordosis (T12-L5)â€‰>â€‰60Â° (pâ€‰=â€‰0.028), ORâ€‰=â€‰2.77 (CI 1.10-6.94). All patients showed an increase in pre-to-postop LL. Change in LL pre-to-postop was no different between groups (pâ€‰=â€‰0.318), however the WHS group was more lordotic at BL and postop (pre44Â°/post58Â° vs pre32Â°/post51Â° in the no change group). Age, sex, Risser, hip position, levels fused, coronal parameters, global sagittal alignment (SVA), thoracic kyphosis, and reoperation were not associated with WHS. CONCLUSION/CONCLUSIONS:Postoperative hyperlordosis(>â€‰60Â°) is a risk factor for WHS at 5Â years after spinal fusion in non-ambulant CP patients. WHS likely relates to anterior pelvic tilt and functional acetabular retroversion due to hyperlordosis, as well as loss of protective lumbopelvic motion causing anterior femoracetabular impingement. LEVEL OF EVIDENCE/METHODS:III.
2021 Otto Aufranc Award: A simple Hip-Spine Classification for total hip arthroplasty : validation and a large multicentre series
AIMS/OBJECTIVE:Patients with spinal pathology who undergo total hip arthroplasty (THA) have an increased risk of dislocation and revision. The aim of this study was to determine if the use of the Hip-Spine Classification system in these patients would result in a decreased rate of postoperative dislocation in patients with spinal pathology. METHODS:This prospective, multicentre study evaluated 3,777 consecutive patients undergoing THA by three surgeons, between January 2014 and December 2019. They were categorized using The Hip-Spine Classification system: group 1 with normal spinal alignment; group 2 with a flatback deformity, group 2A with normal spinal mobility, and group 2B with a stiff spine. Flatback deformity was defined by a pelvic incidence minus lumbar lordosis of > 10Â°, and spinal stiffness was defined by < 10Â° change in sacral slope from standing to seated. Each category determined a patient-specific component positioning. Survivorship free of dislocation was recorded and spinopelvic measurements were compared for reliability using intraclass correlation coefficient. RESULTS:A total of 2,081 patients met the inclusion criteria. There were 987 group 1A, 232 group 1B, 715 group 2A, and 147 group 2B patients. A total of 70 patients had a lumbar fusion, most had L4-5 (16; 23%) or L4-S1 (12; 17%) fusions; 51 patients (73%) had one or two levels fused, and 19 (27%) had > three levels fused. Dual mobility (DM) components were used in 166 patients (8%), including all of those in group 2B and with > three level fusions. Survivorship free of dislocation at five years was 99.2% with a 0.8% dislocation rate. The correlation coefficient was 0.83 (95% confidence interval 0.89 to 0.91). CONCLUSION/CONCLUSIONS:Â 2021;103-B(7 Supple B):17-24.
The Impact of Global Spinal Alignment on Standing Spinopelvic Alignment Change After Total Hip Arthroplasty
STUDY DESIGN/UNASSIGNED:Retrospective cohort study. OBJECTIVES/UNASSIGNED:The interactions between hip osteoarthritis (OA) and spinal malalignment are poorly understood. The purpose of this study was to assess the influence of total hip arthroplasty (THA) on standing spinopelvic alignment. METHODS/UNASSIGNED:In this retrospective cohort study, patients undergoing THA for OA with pre-and postoperative full-body radiographs were included. Standing spinopelvic parameters were measured. Contralateral hip was graded on the Kellgren-Lawrence scale. Pre-and postoperative alignment parameters were compared by paired t-test. The severity of preoperative thoracolumbar deformity was measured using TPA. Linear regression was performed to assess the impact of preoperative TPA and changes in spinal alignment. Patients were separated into low and high TPA (<20 or >/=20â€‰deg) and change in parameters were compared between groups by t-test. Similarly, the influence of K-L grade, age, and PI were also tested. RESULTS/UNASSIGNED:= .004). Preoperative TPA was significantly associated with the change in PI-LL, SVA, and TPA. High TPA patients significantly decreased SVA more than low TPA patients. There was no significant impact of contralateral hip OA, PI, or age on change in alignment parameters. CONCLUSION/UNASSIGNED:Spinopelvic alignment changes after THA, evident by a reduction in SVA. Preoperative spinal sagittal deformity impacts this change. Level of evidence: III.
Not Frail and Elderly: How Invasive Can We Go In This Different Type of Adult Spinal Deformity Patient?
STUDY DESIGN/METHODS:Retrospective review of a single-center spine database. OBJECTIVE:Investigate the intersections of chronological age and physiological age via frailty to determine the influence of surgical invasiveness on patient outcomes. SUMMARY OF BACKGROUND DATA/BACKGROUND:Frailty is a well-established factor in preoperative risk stratification and prediction of postoperative outcomes. The surgical profile of operative adult spinal deformity (ASD) patients who present as elderly and not frail has yet to be investigated. Our aim was to examine the surgical profile and outcomes of ASD patients who were not frail and elderly. METHODS:Included: ASD patientsâ‰¥18â€Šyears old, â‰¥4 levels fused, with baseline(BL) and follow up data. Patients were categorized by ASD frailty index: Not Frail[NF], Frail[F], Severely Frail [SF]. An elderly patient was defined as â‰¥70â€Šyears. Patients were grouped into NF/elderly and F/elderly. SRS-Schwab modifiers were assessed at baseline and 1-year(0, +, ++). Logistic regression analysis assessed the relationship between increasing invasiveness, no reoperations, or major complications, and improvement in SRS-Schwab modifiers[Good Outcome]. Decision tree analysis assessed thresholds for an invasiveness risk/benefit cutoff point. RESULTS:598 ASD pts included(55.3yrs, 59.7%F, 28.3â€Škg/m2). 29.8% of patients were above age 70. At baseline, 51.3% of patients were NF, 37.5% F, and 11.2% SF. 66(11%) of patients were NF and elderly. 24.2% of NF-Elderly patients improved in SRS-Schwab by 1-year and had no reoperation or complication postoperatively. Binary regression analysis found a relationship between worsening SRS-Schwab, postop complication, and reoperation with invasiveness score(OR: 1.056[1.013-1.102], pâ€Š=â€Š0.011). Risk/benefit cut-off was 10(pâ€Š=â€Š0.004). Patients below this threshold were 7.9[2.2-28.4] times more likely to have a Good Outcome. 156 patients were elderly and F/SF with 16.7% having Good Outcome, with a risk/benefit cut-off point of <8 (4.4[2.2-9.0], pâ€Š<â€Š0.001). CONCLUSIONS:Frailty status impacted the balance of surgical invasiveness relative to operative risk in an inverse manner, while the opposite was seen amongst elderly patients with a frailty status less than their chronologic age. Surgeons should perhaps consider incorporation of frailty status over age status when determining realignment plans in patients of advanced age.Level of Evidence: ???
Clinical photographs in the assessment of adult spinal deformity: a comparison to radiographic parameters
OBJECTIVE:The goal of this study was to reliably predict sagittal and coronal spinal alignment with clinical photographs by using markers placed at easily localized anatomical landmarks. METHODS:A consecutive series of patients with adult spinal deformity were enrolled from a single center. Full-length standing radiographs were obtained at the baseline visit. Clinical photographs were taken with reflective markers placed overlying C2, S1, the greater trochanter, and each posterior-superior iliac spine. Sagittal radiographic parameters were C2 pelvic angle (CPA), T1 pelvic angle (TPA), and pelvic tilt. Coronal radiographic parameters were pelvic obliquity and T1 coronal tilt. Linear regressions were performed to evaluate the relationship between radiographic parameters and their photographic "equivalents." The data were reanalyzed after stratifying the cohort into low-body mass index (BMI) (< 30) and high-BMI (â‰¥ 30) groups. Interobserver and intraobserver reliability was assessed for clinical measures via intraclass correlation coefficients (ICCs). RESULTS:A total of 38 patients were enrolled (mean age 61 years, mean BMI 27.4 kg/m2, 63% female). All regression models were significant, but sagittal parameters were more closely correlated to photographic parameters than coronal measurements. TPA and CPA had the strongest associations with their photographic equivalents (both r2 = 0.59, p < 0.001). Radiographic and clinical parameters tended to be more strongly correlated in the low-BMI group. Clinical measures of TPA and CPA had high intraobserver reliability (all ICC > 0.99, p < 0.001) and interobserver reliability (both ICC > 0.99, p < 0.001). CONCLUSIONS:The photographic measures of spinal deformity developed in this study were highly correlated with their radiographic counterparts and had high inter- and intraobserver reliability. Clinical photography can not only reduce radiation exposure in patients with adult spinal deformity, but also be used to assess deformity when full-spine radiographs are unavailable.
The Impact of Global Alignment and Proportion Score and Bracing on Proximal Junctional Kyphosis in Adult Spinal Deformity
STUDY DESIGN/UNASSIGNED:Retrospective chart review. OBJECTIVE/UNASSIGNED:The goal of this study is to examine the relationship between global alignment and proportion (GAP) score and postoperative orthoses with likelihood of developing proximal junctional kyphosis (PJK). METHODS/UNASSIGNED:Patients who underwent thoracic or lumbar fusions of â‰¥4 levels for adult spinal deformity (ASD) with 1-year post-operative alignment x-rays were included. Chart review was conducted to determine spinopelvic alignment parameters, PJK, and reoperation. RESULTS/UNASSIGNED:< .05. GAP change was not correlated with PJKA change. Postoperative orthoses were used in 46% of patients and did not impact sPJK. CONCLUSIONS/UNASSIGNED:There was no correlation between PJK and GAP or change in GAP. Greater correction of UIV-PA and larger postop T1-UIV was associated with greater PJKA change; suggesting that the greater alignment correction led to greater likelihood of failure. Postoperative orthoses had no impact on PJK.