Faculty Bibliography

OBJECTIVE:The present study utilized recently developed in-construct measurements in simulations of cervical deformity surgery in order to assess undercorrection and predict distal junctional kyphosis (DJK). METHODS:A retrospective review of a database of operative cervical deformity patients was analyzed for severe DJK and mild DJK. C2-lower instrumented vertebra (LIV) sagittal angle (SA) was measured postoperatively, and the correction was simulated in the preoperative radiograph in order to match the C2-LIV by using the planning software. Linear regression analysis that used C2 pelvic angle (CPA) and pelvic tilt (PT) determined the simulated PT that matched the virtual CPA. Linear regression analysis was used to determine the C2-T1 SA, C2-T4 SA, and C2-T10 SA that corresponded to DJK of 20° and cervical sagittal vertical axis (cSVA) of 40 mm. RESULTS:Sixty-nine cervical deformity patients were included. Severe and mild DJK occurred in 11 (16%) and 22 (32%) patients, respectively; 3 (4%) required DJK revision. Simulated corrections demonstrated that severe and mild DJK patients had worse alignment compared to non-DJK patients in terms of cSVA (42.5 mm vs 33.0 mm vs 23.4 mm, p < 0.001) and C2-LIV SVA (68.9 mm vs 57.3 mm vs 36.8 mm, p < 0.001). Linear regression revealed the relationships between in-construct measures (C2-T1 SA, C2-T4 SA, and C2-T10 SA), cSVA, and change in DJK (all R > 0.57, p < 0.001). A cSVA of 40 mm corresponded to C2-T4 SA of 10.4° and C2-T10 SA of 28.0°. A DJK angle change of 10° corresponded to C2-T4 SA of 5.8° and C2-T10 SA of 20.1°. CONCLUSIONS:Simulated cervical deformity corrections demonstrated that severe DJK patients have insufficient corrections compared to patients without DJK. In-construct measures assess sagittal alignment within the fusion separate from DJK and subjacent compensation. They can be useful as intraoperative tools to gauge the adequacy of cervical deformity correction.

STUDY DESIGN/SETTING/METHODS:This was a retrospective cohort study. BACKGROUND:Little is known of the intersection between surgical invasiveness, cervical deformity (CD) severity, and frailty. OBJECTIVE:The aim of this study was to investigate the outcomes of CD surgery by invasiveness, frailty status, and baseline magnitude of deformity. METHODS:This study included CD patients with 1-year follow-up. Patients stratified in high deformity if severe in the following criteria: T1 slope minus cervical lordosis, McGregor's slope, C2-C7, C2-T3, and C2 slope. Frailty scores categorized patients into not frail and frail. Patients are categorized by frailty and deformity (not frail/low deformity; not frail/high deformity; frail/low deformity; frail/high deformity). Logistic regression assessed increasing invasiveness and outcomes [distal junctional failure (DJF), reoperation]. Within frailty/deformity groups, decision tree analysis assessed thresholds for an invasiveness cutoff above which experiencing a reoperation, DJF or not achieving Good Clinical Outcome was more likely. RESULTS:A total of 115 patients were included. Frailty/deformity groups: 27% not frail/low deformity, 27% not frail/high deformity, 23.5% frail/low deformity, and 22.5% frail/high deformity. Logistic regression analysis found increasing invasiveness and occurrence of DJF [odds ratio (OR): 1.03, 95% CI: 1.01-1.05, P =0.002], and invasiveness increased with deformity severity ( P <0.05). Not frail/low deformity patients more often met Optimal Outcome with an invasiveness index <63 (OR: 27.2, 95% CI: 2.7-272.8, P =0.005). An invasiveness index <54 for the frail/low deformity group led to a higher likelihood of meeting the Optimal Outcome (OR: 9.6, 95% CI: 1.5-62.2, P =0.018). For the frail/high deformity group, patients with a score <63 had a higher likelihood of achieving Optimal Outcome (OR: 4.8, 95% CI: 1.1-25.8, P =0.033). There was no significant cutoff of invasiveness for the not frail/high deformity group. CONCLUSIONS:Our study correlated increased invasiveness in CD surgery to the risk of DJF, reoperation, and poor clinical success. The thresholds derived for deformity severity and frailty may enable surgeons to individualize the invasiveness of their procedures during surgical planning to account for the heightened risk of adverse events and minimize unfavorable outcomes.

BACKGROUND AND OBJECTIVES/OBJECTIVE:Achieving spinopelvic realignment during adult spinal deformity (ASD) surgery does not always produce ideal outcomes. Little is known whether compensation in lower extremities (LEs) plays a role in this disassociation. The objective is to analyze lower extremity compensation after complex ASD surgery, its effect on outcomes, and whether correction can alleviate these mechanisms. METHODS:We included patients with complex ASD with 6-week data. LE parameters were as follows: sacrofemoral angle, knee flexion angle, and ankle flexion angle. Each parameter was ranked, and upper tertile was deemed compensation. Patients compensating and not compensating postoperatively were propensity score matched for body mass index, frailty, and T1 pelvic angle. Linear regression assessed correlation between LE parameters and baseline deformity, demographics, and surgical details. Multivariate analysis controlling for baseline deformity and history of total knee/hip arthroplasty evaluated outcomes. RESULTS:Two hundred and ten patients (age: 61.3 ± 14.1 years, body mass index: 27.4 ± 5.8 kg/m2, Charlson Comorbidity Index: 1.1 ± 1.6, 72% female, 22% previous total joint arthroplasty, 24% osteoporosis, levels fused: 13.1 ± 3.8) were included. At baseline, 59% were compensating in LE: 32% at hips, 39% knees, and 36% ankles. After correction, 61% were compensating at least one joint. Patients undercorrected postoperatively were less likely to relieve LE compensation (odds ratio: 0.2, P = .037). Patients compensating in LE were more often undercorrected in age-adjusted pelvic tilt, pelvic incidence, lumbar lordosis, and T1 pelvic angle and disproportioned in Global Alignment and Proportion (P < .05). Patients matched in sagittal age-adjusted score at 6 weeks but compensating in LE were more likely to develop proximal junctional kyphosis (odds ratio: 4.1, P = .009) and proximal junctional failure (8% vs 0%, P = .035) than those sagittal age-adjusted score-matched and not compensating in LE. CONCLUSION/CONCLUSIONS:Perioperative lower extremity compensation was a product of undercorrecting complex ASD. Even in age-adjusted realignment, compensation was associated with global undercorrection and junctional failure. Consideration of lower extremities during planning is vital to avoid adverse outcomes in perioperative course after complex ASD surgery.

STUDY DESIGN/METHODS:Multi-centre retrospective cohort study. OBJECTIVE:To evaluate the feasibility and safety of the single-position prone lateral lumbar interbody fusion (LLIF) technique for revision lumbar fusion surgery. BACKGROUND CONTEXT/BACKGROUND:Prone LLIF (P-LLIF) is a novel technique allowing for placement of a lateral interbody in the prone position and allowing posterior decompression and revision of posterior instrumentation without patient repositioning. This study examines perioperative outcomes and complications of single position P-LLIF against traditional Lateral LLIF (L-LLIF) technique with patient repositioning. METHOD/METHODS:A multi-centre retrospective cohort study involving patients undergoing 1-4 level LLIF surgery was performed at 4 institutions in the USA and Australia. Patients were included if their surgery was performed via either: P-LLIF with revision posterior fusion; or L-LLIF with repositioning to prone. Demographics, perioperative outcomes, complications, and radiological outcomes were compared using independent samples t-tests and chi-squared analyses as appropriate with significance set at P <0.05. RESULTS:101 patients undergoing revision LLIF surgery were included, of which 43 had P-LLIF and 58 had L-LLIF. Age, BMI and CCI were similar between groups. The number of posterior levels fused (2.21 P-LLIF vs. 2.66 L-LLIF, P =0.469) and number of LLIF levels (1.35 vs. 1.39, P =0.668) was similar between groups. Operative time was significantly less in the P-LLIF group (151 vs. 206 min, P =0.004). EBL was similar between groups (150 mL P-LLIF vs. 182 mL L-LLIF, P =0.31) and there was a trend toward reduced length of stay in the P-LLIF group (2.7 vs. 3.3 d, P =0.09). No significant difference was demonstrated in complications between groups. Radiographic analysis demonstrated no significant differences in preoperative or postoperative sagittal alignment measurements. CONCLUSION/CONCLUSIONS:P-LLIF significantly improves operative efficiency when compared to L-LLIF for revision lumbar fusion. No increase in complications was demonstrated by P-LLIF or trade-offs in sagittal alignment restoration. LEVEL OF EVIDENCE/METHODS:Level IV.

STUDY DESIGN/SETTING/METHODS:Retrospective single-center study. BACKGROUND:The global alignment and proportion score is widely used in adult spinal deformity surgery. However, it is not specific to the parameters used in adult cervical deformity (ACD). PURPOSE/OBJECTIVE:Create a cervicothoracic alignment and proportion (CAP) score in patients with operative ACD. METHODS:Patients with ACD with 2-year data were included. Parameters consisted of relative McGregor's Slope [RMGS = (MGS × 1.5)/0.9], relative cervical lordosis [RCL = CL - thoracic kyphosis (TK)], Cervical Lordosis Distribution Index (CLDI = C2 - Apex × 100/C2 - T2), relative pelvic version (RPV = sacral slope - pelvic incidence × 0.59 + 9), and a frailty factor (greater than 0.33). Cutoff points were chosen where the cross-tabulation of parameter subgroups reached a maximal rate of meeting the Optimal Outcome. The optimal outcome was defined as meeting Good Clinical Outcome criteria without the occurrence of distal junctional failure (DJF) or reoperation. CAP was scored between 0 and 13 and categorized accordingly: ≤3 (proportioned), 4-6 (moderately disproportioned), >6 (severely disproportioned). Multivariable logistic regression analysis determined the relationship between CAP categories, overall score, and development of distal junctional kyphosis (DJK), DJF, reoperation, and Optimal Outcome by 2 years. RESULTS:One hundred five patients with operative ACD were included. Assessment of the 3-month CAP score found a mean of 5.2/13 possible points. 22.7% of patients were proportioned, 49.5% moderately disproportioned, and 27.8% severely disproportioned. DJK occurred in 34.5% and DJF in 8.7%, 20.0% underwent reoperation, and 55.7% achieved Optimal Outcome. Patients severely disproportioned in CAP had higher odds of DJK [OR: 6.0 (2.1-17.7); P =0.001], DJF [OR: 9.7 (1.8-51.8); P =0.008], reoperation [OR: 3.3 (1.9-10.6); P =0.011], and lower odds of meeting the optimal outcome [OR: 0.3 (0.1-0.7); P =0.007] by 2 years, while proportioned patients suffered zero occurrences of DJK or DJF. CONCLUSION/CONCLUSIONS:The regional alignment and proportion score is a method of analyzing the cervical spine relative to global alignment and demonstrates the importance of maintaining horizontal gaze, while also matching overall cervical and thoracolumbar alignment to limit complications and maximize clinical improvement.

OBJECTIVE:The aim of this study was to determine if spinal deformity patients with L5 sacralization should have pelvic incidence (PI) and other spinopelvic parameters measured from the L5 or S1 endplate. METHODS:This study was a multicenter retrospective comparative cohort study comprising a large database of adult spinal deformity (ASD) patients and a database of asymptomatic individuals. Linear regression modeling was used to determine normative T1 pelvic angle (TPA) and PI - lumbar lordosis (LL) mismatch (PI-LL) based on PI and age in a database of asymptomatic subjects. In an ASD database, patients with radiographic evidence of L5 sacralization had the PI, LL, and TPA measured from the superior endplate of S1 and then also from L5. The differences in TPA and PI-LL from normative were calculated in the sacralization cohort relative to L5 and S1 and correlated to the Oswestry Disability Index (ODI). Patients were grouped based on the Scoliosis Research Society (SRS)-Schwab PI-LL modifier (0, +, or ++) using the L5 PI-LL and S1 PI-LL. Baseline ODI and SF-36 Physical Component Summary (PCS) scores were compared across and within groups. RESULTS:Among 1179 ASD patients, 276 (23.4%) had transitional anatomy, 176 with sacralized L5 (14.9%) and 100 (8.48%) with lumbarization of S1. The 176 patients with sacralized L5 were analyzed. When measured using the L5 superior endplate, pelvic parameters were significantly smaller than those measured relative to S1 (PI: 24.5° ± 11.0° vs 55.7° ± 12.0°, p = 0.001;TPA: 11.2° ± 12.0° vs 20.3° ± 12.5°, p = 0.001; and PI-LL: 0.67° ± 21.1° vs 11.4° ± 20.8°, p = 0.001). When measured from S1, 76 (43%), 45 (25.6%), and 55 (31.3%) patients had SRS-Schwab PI-LL modifiers of 0, +, and ++, respectively, compared with 124 (70.5%), 22 (12.5%), and 30 (17.0%), respectively, when measured from L5. There were significant differences in ODI and PCS scores as the SRS-Schwab grade increased regardless of L5 or S1 measurement. The L5 group had lower PCS functional scores for SRS-Schwab modifiers 0 and ++ relative to same grades in the S1 group. Offset from normative TPA (0.5° ± 11.1° vs 9.6° ± 10.8°, p = 0.001) and PI-LL (4.5° ± 20.4° vs 15.2° ± 19.3°, p = 0.001) were smaller when measuring from L5. Moreover, S1 measurements were more correlated with health status by ODI (TPA offset from normative: S1, R = 0.326 vs L5, R = 0.285; PI-LL offset from normative: S1, R = 0.318 vs L5, R = 0.274). CONCLUSIONS:Measuring the PI and spinopelvic parameters at L5 in sacralized anatomy results in underestimating spinal deformity and is less correlated with health-related quality of life. Surgeons may consider measuring PI and spinopelvic parameters relative to S1 rather than at L5 in patients with a sacralized L5.

AIMS/UNASSIGNED:The aim of this study was to reassess the rate of neurological, psoas-related, and abdominal complications associated with L4-L5 lateral lumbar interbody fusion (LLIF) undertaken using a standardized preoperative assessment and surgical technique. METHODS/UNASSIGNED:This was a multicentre retrospective study involving consecutively enrolled patients who underwent L4-L5 LLIF by seven surgeons at seven institutions in three countries over a five-year period. The demographic details of the patients and the details of the surgery, reoperations and complications, including femoral and non-femoral neuropraxia, thigh pain, weakness of hip flexion, and abdominal complications, were analyzed. Neurological and psoas-related complications attributed to LLIF or posterior instrumentation and persistent symptoms were recorded at one year postoperatively. RESULTS/UNASSIGNED:(SD 5.5). A mean of 1.2 levels (SD 0.6) were fused with LLIF, and a mean of 1.6 (SD 0.9) posterior levels were fused. Femoral neuropraxia occurred in six patients (1.2%), of which four (0.8%) were LLIF-related and two (0.4%) had persistent symptoms one year postoperatively. Non-femoral neuropraxia occurred in nine patients (1.8%), one (0.2%) was LLIF-related and five (1.0%) were persistent at one year. All LLIF-related neuropraxias resolved by one year. A total of 32 patients (6.2%) had thigh pain, 31 (6.0%) were LLIF-related and three (0.6%) were persistent at one year. Weakness of hip flexion occurred in 14 patients (2.7%), of which eight (1.6%) were LLIF-related and three (0.6%) were persistent at one year. No patients had bowel injury, three (0.6%) had an intraoperative vascular injury (not LLIF-related), and five (1.0%) had ileus. Reoperations occurred in five patients (1.0%) within 30 days, 37 (7.2%) within 90 days, and 41 (7.9%) within one year postoperatively. CONCLUSION/UNASSIGNED:LLIF involving the L4-L5 disc level has a low rate of persistent neurological, psoas-related, and abdominal complications in patients with the appropriate indications and using a standardized surgical technique.

OBJECTIVE:The objective of this study was to identify the effect of baseline cervical deformity (CD) on proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) in patients with adult spinal deformity (ASD). METHODS:This study was a retrospective analysis of a prospectively collected, multicenter database comprising ASD patients enrolled at 13 participating centers from 2009 to 2018. Included were ASD patients aged > 18 years with concurrent CD (C2-7 kyphosis < -15°, T1S minus cervical lordosis > 35°, C2-7 sagittal vertical axis > 4 cm, chin-brow vertical angle > 25°, McGregor's slope > 20°, or C2-T1 kyphosis > 15° across any three vertebrae) who underwent surgery. Patients were grouped according to four deformity classification schemes: Ames and Passias CD modifiers, sagittal morphotypes as described by Kim et al., and the head versus trunk balance system proposed by Mizutani et al. Mean comparison tests and multivariable binary logistic regression analyses were performed to assess the impact of these deformity classifications on PJK and PJF rates up to 3 years following surgery. RESULTS:A total of 712 patients with concurrent ASD and CD met the inclusion criteria (mean age 61.7 years, 71% female, mean BMI 28.2 kg/m2, and mean Charlson Comorbidity Index 1.90) and underwent surgery (mean number of levels fused 10.1, mean estimated blood loss 1542 mL, and mean operative time 365 minutes; 70% underwent osteotomy). By approach, 59% of the patients underwent a posterior-only approach and 41% underwent a combined approach. Overall, 277 patients (39.1%) had PJK by 1 year postoperatively, and an additional 189 patients (26.7%) developed PJK by 3 years postoperatively. Overall, 65 patients (9.2%) had PJF by 3 years postoperatively. Patients classified as having a cervicothoracic deformity morphotype had higher rates of early PJK than flat neck deformity and cervicothoracic deformity patients (p = 0.020). Compared with the head-balanced patients, trunk-balanced patients had higher rates of PJK and PJF (both p < 0.05). Examining Ames modifier severity showed that patients with moderate and severe deformity by the horizontal gaze modifier had higher rates of PJK (p < 0.001). CONCLUSIONS:In patients with concurrent cervical and thoracolumbar deformities undergoing isolated thoracolumbar correction, the use of CD classifications allows for preoperative assessment of the potential for PJK and PJF that may aid in determining the correction of extending fusion levels.

OBJECTIVE:The objective of this study was to explore the rate of proximal junctional failure (PJF) and functional outcomes of normative alignment goals compared with alignment targets based on age-appropriate physical function. METHODS:Baseline relationships between age, pelvic incidence (PI), and a component of the T1 pelvic angle (TPA) within the fusion were analyzed in adult spinal deformity (ASD) patients and compared with those of asymptomatic patients. Linear regression modeling was used to determine alignment based on PI and age in asymptomatic patients (normative alignment), and in ASD patients, alignment corresponding to age-appropriate functional status (functional alignment). A cohort of 288 ASD patients was split into two groups based on whether the patient was closer to their normative or functional alignment goal at their 6-week postoperative radiographic follow-up. The rates of proximal junctional kyphosis (PJK) and PJF were determined for each cohort. RESULTS:In the 288 ASD patients included in this pre- to postoperative analysis, there was no difference in baseline alignment or health-related quality of life (HRQOL) between the normative alignment and functional alignment groups. At 6 weeks, patients with normative alignment had a smaller TPA (4.45° vs 14.1°) and PI minus lumbar lordosis (-7.24° vs 7.4°) (both p < 0.0001) and higher PJK (40% vs 27.2%, p = 0.03) and PJF (17% vs 6.8%, p = 0.008) rates than patients with functional alignment. CONCLUSIONS:Correction in ASD patients to normative alignment resulted in higher rates of PJK and PJF without improvements in HRQOL. Correction in ASD patients to functional alignment that mirrors the physical function of their age-matched asymptomatic peers is recommended.

OBJECTIVE:The authors of this study sought to evaluate the predictive role of global sagittal alignment and upper instrumented vertebra (UIV) level in symptomatic proximal junctional kyphosis (PJK) among patients with adult spinal deformity (ASD). METHODS:Data on ASD patients who had undergone fusion of ≥ 5 vertebrae from 2008 to 2018 and with a minimum follow-up of 1 year were obtained from a prospectively collected multicenter database and evaluated (n = 1312). Radiographs were obtained preoperatively and at 6 weeks, 6 months, 1 year, 2 years, and 3 years postoperatively. The 22-Item Scoliosis Research Society Patient Questionnaire Revised (SRS-22r) scores were collected preoperatively, 1 year postoperatively, and 2 years postoperatively. Symptomatic PJK was defined as a kyphotic increase > 20° in the Cobb angle from the UIV to the UIV+2. At 6 weeks postoperatively, sagittal parameters were evaluated and patients were categorized by global alignment and proportion (GAP) score/category and SRS-Schwab sagittal modifiers. Patients were stratified by UIV level: upper thoracic (UT) UIV ≥ T8 or lower thoracic (LT) UIV ≤ T9. RESULTS:Patients who developed symptomatic PJK (n = 260) had worse 1-year postoperative SRS-22r mental health (3.70 vs 3.86) and total (3.56 vs 3.67) scores, as well as worse 2-year postoperative self-image (3.45 vs 3.65) and satisfaction (4.03 vs 4.22) scores (all p ≤ 0.04). In the whole study cohort, patients with PJK had less pelvic incidence-lumbar lordosis (PI-LL) mismatch (-0.24° vs 3.29°, p < 0.001) but no difference in their GAP score/category or SRS-Schwab sagittal modifiers compared with the patients without PJK. Regression showed a higher risk of PJK with a pelvic tilt (PT) grade ++ (OR 2.35) and less risk with a PI-LL grade ++ (OR 0.35; both p < 0.01). When specifically analyzing the LT UIV cohort, patients with PJK had a higher GAP score (5.66 vs 4.79), greater PT (23.02° vs 20.90°), and less PI-LL mismatch (1.61° vs 4.45°; all p ≤ 0.02). PJK patients were less likely to be proportioned postoperatively (17.6% vs 30.0%, p = 0.015), and regression demonstrated a greater PJK risk with severe disproportion (OR 1.98) and a PT grade ++ (OR 3.15) but less risk with a PI-LL grade ++ (OR 0.45; all p ≤ 0.01). When specifically evaluating the UT UIV cohort, the PJK patients had less PI-LL mismatch (-2.11° vs 1.45°) but no difference in their GAP score/category. Regression showed a greater PJK risk with a PT grade + (OR 1.58) and a decreased risk with a PI-LL grade ++ (OR 0.21; both p < 0.05). CONCLUSIONS:Symptomatic PJK leads to worse patient-reported outcomes and is associated with less postoperative PI-LL mismatch and greater postoperative PT. A worse postoperative GAP score and disproportion are only predictive of symptomatic PJK in patients with an LT UIV.