The role of the fractional lumbosacral curve in persistent coronal malalignment following adult thoracolumbar deformity surgery: a radiographic analysis

The Lumbosacral Fractional Curve vs Maximum Coronal Cobb Angle in Adult Spinal Deformity Patients with Coronal Malalignment: Which Matters More?

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

In patients undergoing adult spinal deformity (ASD) surgery we sought to: 1) report preoperative and postoperative lumbosacral fractional (LSF) curve and maximum coronal Cobb angles and 2) determine their impact on radiographic, clinical, and patient-reported outcomes (PROs).

METHODS

A single-institution cohort study was undertaken. The LSF curve was the cobb angle between the sacrum and most tilted lower lumbar vertebra. Coronal/sagittal vertical axis (CVA/SVA) were collected. Patients were compared between 4 groups: 1) Neutral Alignment (NA); 2) coronal malalignment only (CM); 3) Sagittal malalignment only (SM); and 4) Combined-Coronal-Sagittal-Malalignment (CCSM). Outcomes including postoperative CM, postoperative coronal vertical axis, complications, readmissions, reoperation, and PROs.

RESULTS

A total of 243 patients underwent ASD surgery with mean total instrumented levels of 13.5. Mean LSF curve was 12.1±9.9°(0.2-62.3) and mean max Cobb angle was 43.0±26.5° (0.0-134.3). The largest mean LSF curves were seen in patients with CM (14.6°) and CCSM (13.1°) compared to NA (12.1°) and SM (9.5°) (p=0.100). A higher LSF curve was seen in patients with fusion to the sacrum and instrumentation to the pelvis (p=0.009), and a higher LSF curve was associated with more TLIFs (p=0.031). Postoperatively, more TLIFs were associated with greater amount of LSF curve correction (p<0.001). Comparing the LSF and the max Cob angle among Qiu types, the highest mean max Cobb angle was in Qiu Type B patients (p=0.025), whereas the highest mean LSF curve was in Qiu Type C patients (p=0.037). Moreover, 82.7% of patients had a LSF curve opposite the max Cobb angle. The LSF curve was larger than the max Cobb angle in 22/243 (9.1%) patients, and most of these 22 patients were Qiu Type A (59.1%). Regarding correction, the max Cobb angle achieved more correction than the LSF curve, judged by the percent improved from preop (54.5% Cobb vs. 46.5% LSF, p=0.025) in patients with max cobb>20° and LSF curve >5°. The LSF curve underwent greater correction in Qiu Type C patients (9.2°) compared to Type A (5.7°) and Type B (5.1°) (p=0.023); however, the max Cobb angle was similarly corrected among Qiu Types: Type A 21.8°, Type B 24.6°, and Type C 25.4° (p=0.602). Minimal differences were seen comparing the preop/postop/change in LSF curve and max Cobb angle regarding postop CM, postop CVA, complications, readmissions, reoperation, and PROs.

CONCLUSIONS

The LSF curve was highest in patients with CM, CCSM, and Qiu Type C curves. Most patients had a LSF curve opposite the max Cobb angle. The max Cobb angle was more often corrected than the LSF curve. The LSF curve underwent greater correction among Qiu Type C patients, whereas the max Cobb angle was similarly corrected among all Qiu Types. No clear trend was seen regarding postoperative complications and PROs between the LSF curve and max Cobb angle.

Coronal Alignment in Adult Spine Surgery

Coronal realignment is an important goal in adult spine surgery that has been overshadowed by emphasis on the sagittal plane. As coronal malalignment drives considerable functional disability, a fundamental understanding of its clinical and radiographic evaluation and surgical techniques to prevent its development is of utmost importance. In this study, we review etiologies of coronal malalignment and their radiographic and clinical assessments, risk factors for and functional implications of postoperative coronal malalignment, and surgical strategies to optimize appropriate coronal realignment in adult spine surgery.

Anterior lumbar interbody fusion versus transforaminal lumbar interbody fusion for correction of lumbosacral fractional curves in adult (thoraco)lumbar scoliosis: A systematic review

Background

Anterior lumbar interbody fusion (ALIF) or transforaminal lumbar interbody fusion (TLIF) may be used to correct the lumbosacral fractional curve (LsFC) in de novo adult (thoraco) lumbar scoliosis. Yet, the relative benefits of ALIF and TLIF for LsFC correction remain largely undetermined.

Purpose

To compare the currently available data comparing radiographic correction of the LsFC provided by ALIF and TLIF of LsFC in adult (thoraco)lumbar scoliosis.

Methods

A systematic review was performed on original articles discussing fractional curve correction of lumbosacral spinal deformity (using search criteria: "lumbar" and "fractional curve"). Articles which discussed TLIF or ALIF for LsFC correction were presented and radiographic results for TLIF and ALIF were compared.

Results

Thirty-one articles were returned in the original search criteria, with 7 articles included in the systematic review criteria. All 7 articles presented radiographic results using TLIF for LsFC correction. Three of these articles also discussed results for patients whose LsFC were treated with ALIFs; 2 articles directly compared TLIF and ALIF for LsFC correction. Level III and level IV evidence indicated ALIF as advantageous for reducing the coronal Cobb angle of the LsFC. There were mixed results on relative efficacy of ALIF and TLIF in the LsFC for restoration of adequate global coronal alignment.

Conclusions

Limited level III and IV evidence suggests ALIF as advantageous for reducing the coronal Cobb angle of the LsFC in de novo adult (thoraco) lumbar scoliosis. Relative efficacy of ALIF and TLIF in the LsFC for restoration of global coronal alignment may be dictated by several factors, including directionality and magnitude of preoperative coronal deformity. Given the limited and low-quality evidence, additional research is warranted to determine the ideal interbody support strategies to address the LsFC in adult (thoraco) lumbar scoliosis.

Oblique lateral interbody fusion for lumbosacral fractional curve correction in degenerative lumbar scoliosis

PURPOSE

In combined anterior-posterior adult spinal deformity surgery, the optimal combination of anterior and posterior procedures remains unclear. We aimed to demonstrate the radiological outcomes and relevant factors in oblique lateral interbody fusion (OLIF) for lumbosacral fractional curve (FC) correction combined with open posterior surgery in degenerative lumbar scoliosis (DLS).

METHODS

This study involved 42 consecutive patients with DLS who had a major curve (MC) ≥ 20° and an FC (L4 to S1) ≥ 10°, and underwent a combined anterior-posterior surgery Changes in the MC, FC, coronal balance distance, type of coronal imbalance, coronal/sagittal disc angle at L4-5 and L5-S1, L4 and L5 tilt, and sagittal parameters were examined. The associations between FC correction and demographic, surgical, and radiological factors were analysed.

RESULTS

The FC decreased from 16.9 ± 7.3° preoperatively to 6.6 ± 4.4° at the last follow-up (P < 0.001). The coronal disc angle at L4-5 and L5-S1 were, respectively, 6.8 ± 2.2° and 6.0 ± 4.1° preoperatively and decreased to 2.2 ± 2.1 and 1.2 ± 1.3° at the last follow-up (both P < 0.001). The changes in FC were greater in uppermost instrumented level > T10 (P < 0.001), and associated with the preoperative FC (r = 0.820, P < 0.001), L4 tilt (r = 0.434, P = 0.007), and L5 tilt (r = 0.462, P = 0.003).

CONCLUSION

OLIF at the FC combined with open posterior surgery is an effective combined anterior-posterior correction strategy in DLS.

Adherence to the Obeid coronal malalignment classification and a residual malalignment below 20 mm can improve surgical outcomes in adult spine deformity surgery

PURPOSE

Coronal balance is a major factor impacting the surgical outcomes in adult spinal deformity (ASD). The Obeid coronal malalignment (O-CM) classification has been proposed to improve the coronal alignment in ASD surgery. Aim of this study was to investigate whether a postoperative CM < 20 mm and adherence to the O-CM classification could improve surgical outcomes and decrease the rate of mechanical failure in a cohort of ASD patients.

METHODS

Multicenter retrospective analysis of prospectively collected data on all ASD patients who underwent surgical management and had a preoperative CM > 20 mm and a 2-year follow-up. Patients were divided in two groups according to whether or not surgery had been performed in adherence to the guidelines of the O-CM classification and according to whether or not the residual CM was < 20 mm. The outcomes of interest were radiographic data, rate of mechanical complications and Patient-Reported Outcome Measures.

RESULTS

At 2 years, adherence to the O-CM classification led to a lower rate of mechanical complications (40 vs. 60%). A coronal correction of the CM < 20 mm allowed for a significant improvement in SRS-22 and SF-36 scores and was associated with a 3.5 times greater odd of achieving the minimal clinical important difference for the SRS-22.

CONCLUSION

Adherence to the O-CM classification could reduce the risk of mechanic complications 2 years after ASD surgery. Patients with a residual CM < 20 mm showed better functional outcomes and a 3.5 times greater odd of achieving the MCID for the SRS-22 score.

Independent Risk Factors of Postoperative Coronal Imbalance after Adult Spinal Deformity Surgery

The aim of the present study is to elucidate preoperative risk factors for inadequate correction of coronal imbalance and/or creation of new postoperative coronal imbalance (iatrogenic CIB) in patients who undergo surgery for Adult Spinal Deformity (ASD). A retrospective review of adults who underwent posterior spinal fusion (>5 levels) for ASD was performed. Patients were divided into groups according to the Nanjing classification: type A (CSVL < 3 cm), type B (CSVL > 3 cm and C7 plumb line shifted to major curve concavity), and type C (CSVL > 3 cm and C7 plumb line shifted to major curve convexity). They were also divided according to postoperative coronal balance in balanced (CB) vs. imbalanced (CIB) and according to iatrogenic coronal imbalance (iCIB). Preoperative, postoperative, and last follow-up radiographical parameters and intraoperative data were recorded. A multivariate analysis was performed to identify independent risk factors for CIB. A total of 127 patients were included (85 type A, 30 type B, 12 type C). They all underwent long (average levels fused 13.3 ± 2.7) all-posterior fusion. Type C patients were more at risk of developing postoperative CIB (p = 0.04). Multivariate regression analysis indicated L5 tilt angle as a preoperative risk factor for CIB (p = 0.007) and indicated L5 tilt angle and age as a preoperative independent risk factors for iatrogenic CIB (p = 0.01 and p = 0.008). Patients with a preoperative trunk shift towards the convexity of the main curve (type C) are more prone to postoperative CIB and leveling the L4 and L5 vertebrae is the key to achieve coronal alignment preventing the "takeoff phenomenon".

Risk factors for coronal oblique take-off following adult spinal deformity surgery using lateral lumbar interbody fusion and open posterior corrective fusion

PURPOSE

To evaluate risk factors associated with oblique take-off (OT) following lateral lumbar interbody fusion (LLIF) for adult spinal deformity.

METHODS

Thirty-nine consecutive patients (mean age 67.9 years) with scoliosis of the lumbar curve (> 30°) were evaluated. Multilevel LLIF, followed by open thoraco-pelvic posterior corrective fusion after 1 week, was performed. We defined OT as a distance of > 25 mm between the C7 plumb line and the central sacral vertical line and examined risk factors by dividing the patients into the OT and non-OT groups.

RESULTS

OT occurred in 11 patients (28%), all showing a tilt to the convex side. The correction rate of the lumbar curve was approximately 70% range for both groups, which indicated good correction. Preoperative radiographs showed a high L1-central sacral vertical line in the standing position; high L5 tilt in the supine position; high L3, L4, and L5 tilts to the convex side in the supine-bending position; and a high L4 vertebral wedge on the convex side in OT cases. Multiple logistic regression analysis showed that an L4 tilt to the concave side in the bending position was the most effective predictor of OT (odds ratio = 1.104, P = 0.047). For a cutoff value of 16°, the sensitivity and specificity were 73% and 61%, respectively, according to the receiver operating characteristic curve analysis (area under the curve = 0.73).

CONCLUSION

OT occurred in 28% of adult scoliosis patients following LLIF. An L4 tilt > 16° to the concave side in the bending position was the most valuable risk factor.

LEVEL OF EVIDENCE

IV.

Incidence and risk factors of iatrogenic coronal malalignment after adult spinal deformity surgery: a single-center experience

OBJECTIVE

The authors' objectives were: 1) to evaluate the incidence and risk factors of iatrogenic coronal malalignment (CM), and 2) to assess the outcomes of patients with all three types of postoperative CM (iatrogenic vs unchanged/worsened vs improved but persistent).

METHODS

A single-institution, retrospective cohort study was performed on adult spinal deformity (ASD) patients who underwent > 6-level fusion from 2015 to 2019. Iatrogenic CM was defined as immediate postoperative C7 coronal vertical axis (CVA) ≥ 3 cm in patients with preoperative CVA < 3 cm. Additional subcategories of postoperative CM were unchanged/worsened CM, which was defined as immediate postoperative CVA within 0.5 cm of or worse than preoperative CVA, and improved but persistent CM, which was defined as immediate postoperative CVA that was at least 0.5 cm better than preoperative CVA but still ≥ 3 cm; both groups included only patients with preoperative CM. Immediate postoperative radiographs were obtained when the patient was discharged from the hospital after surgery. Demographic, radiographic, and operative variables were collected. Outcomes included major complications, readmissions, reoperations, and patient-reported outcomes (PROs). The t-test, Kruskal-Wallis test, and univariate logistic regression were performed for statistical analysis.

RESULTS

In this study, 243 patients were included, and the mean ± SD age was 49.3 ± 18.3 years and the mean number of instrumented levels was 13.5 ± 3.9. The mean preoperative CVA was 2.9 ± 2.7 cm. Of 153/243 patients without preoperative CM (CVA < 3 cm), 13/153 (8.5%) had postoperative iatrogenic CM. In total, 43/243 patients (17.7%) had postoperative CM: iatrogenic CM (13/43 [30.2%]), unchanged/worsened CM (19/43 [44.2%]), and improved but persistent CM (11/43 [25.6%]). Significant risk factors associated with iatrogenic CM were anxiety/depression (OR 3.54, p = 0.04), greater preoperative sagittal vertical axis (SVA) (OR 1.13, p = 0.007), greater preoperative pelvic obliquity (OR 1.41, p = 0.019), lumbosacral fractional (LSF) curve concavity to the same side of the CVA (OR 11.67, p = 0.020), maximum Cobb concavity opposite the CVA (OR 3.85, p = 0.048), and three-column osteotomy (OR 4.34, p = 0.028). In total, 12/13 (92%) iatrogenic CM patients had an LSF curve concavity to the same side as the CVA. Among iatrogenic CM patients, mean pelvic obliquity was 3.1°, 4 (31%) patients had pelvic obliquity > 3°, mean preoperative absolute SVA was 8.0 cm, and 7 (54%) patients had preoperative sagittal malalignment. Patients with iatrogenic CM were more likely to sustain a major complication during the 2-year postoperative period than patients without iatrogenic CM (12% vs 33%, p = 0.046), yet readmission, reoperation, and PROs were similar.

CONCLUSIONS

Postoperative iatrogenic CM occurred in 9% of ASD patients with preoperative normal coronal alignment (CVA < 3 cm). ASD patients who were most at risk for iatrogenic CM included those with preoperative sagittal malalignment, increased pelvic obliquity, LSF curve concavity to the same side as the CVA, and maximum Cobb angle concavity opposite the CVA, as well as those who underwent a three-column osteotomy. Despite sustaining more major complications, iatrogenic CM patients did not have increased risk of readmission, reoperation, or worse PROs.