Overcorrection of lumbar lordosis for adult spinal deformity with sagittal imbalance: comparison of radiographic outcomes between overcorrection and undercorrection

Radiographic severity of knee osteoarthritis in adult spinal deformity: the effect on rod fracture after long spinal fusion in deformity correction

BACKGROUND CONTEXT

Instrumentation failure, notably rod fracture (RF), may occur even after ideal spinal deformity correction in adult spinal deformity (ASD). As RF is the major reason behind a revision surgery, various risk factors of RF are reported in literature, including pedicle subtraction osteotomy (PSO) technique itself. However, whether hip and knee joint diseases serve as another risk factor for RF remains unexplored.

PURPOSE

To investigate the effects of lower-extremity joint diseases on RF in ASD patients who underwent deformity correction through long-segment fixation with PSO.

STUDY DESIGN

Retrospective study.

PATIENT SAMPLE

About 96 consecutive ASD patients (mean age, 71.2 years) who underwent deformity correction through PSO and long-segment fixation from T10 to S1 between 2008 and 2019 were included. Those with radiographic data less than 2 years were excluded.

OUTCOME MEASURES

RF was confirmed on radiograph, computed tomography (CT) and bone scan or SPECT images. Coronal and sagittal spinopelvic parameters, lower-extremity osteoarthritis (OA) parameters and clinical outcomes (Oswestry Disability Index [ODI] and Visual Analog Scale [VAS]) were analyzed.

METHODS

Radiographic measurements were performed at preoperative, postoperative, and last follow-up visits. Patients were divided into 2 groups: non-RF (n=60) and RF (n=36). Radiographic factors were assessed, correlations between parameters were examined, and multivariate logistic regression analysis was performed to evaluate risk factors for RF.

RESULTS

Structural and functional leg length discrepancies (LLDs), pelvic obliquity (PO), and the differences of mechanical axis (MAD) between both extremities had significantly differed between the groups (p<.05). The between-knee differences in the extent of OA, clinically significant MAD and PO, and the incidences of both structural and functional LLD were significantly greater in the RF group than in the non-RF group (p<.05). On correlation analysis, PO was not correlated with coronal radiographic parameters but was correlated with structural and functional LLDs and MAD (p<.05). Logistic analysis revealed that the difference in OA grade between the knee joints, functional LLD, and preoperative lower extremity surgery were significantly associated with RF (p<.05).

CONCLUSION

ASD in the elderly often presents alongside degenerative changes in the lower-extremities, and even with ideal spinal deformity correction, RF may still occur if preexisting joint pathologies are not resolved. In the deformity correction of ASD, it is essential that we not only pursue the restoration of spinopelvic harmony, but also apply perioperative measures for lower-extremity degenerative joint diseases.

Comparison of Revision Techniques for Rod Fracture after Adult Spinal Deformity Surgery: Rod Replacement Alone or Coupled with Lateral Lumbar Interbody Fusions or Accessory Rods

Background: Rod fracture (RF) is the most common cause of revision in adult spinal deformity (ASD) surgery, and various treatment strategies for preventing RF are reported in the literature. This retrospective study, involving 139 ASD patients (aged ≥65 years and a minimum 2-year follow-up) who underwent long-segment fixation from T10 to sacrum with pedicle subtraction osteotomy (PSO), analyzed long-term results, including radiographical parameters and the incidence of recurrent RF (re-RF), to determine the most effective revision method for preventing RF. Methods: Patients were classified into three groups according to the revision method performed for RF: simple rod replacement (RR group, n = 17), lateral lumbar interbody fusion around the PSO site (RR + LLIF group, n = 8), and accessory rod insertion (RR + AR group, n = 22). Baseline characteristics and radiographical and clinical parameters were analyzed. Results: RF occurred in 47 patients (34%) at an average of 28 months following primary deformity correction. Re-RF occurred in six patients (13%) at an average of 37 months. Re-RF occurred most commonly in the RR group (p = 0.048). Every re-RF in the RR group occurred at the PSO site; none occurred in the RR + LLIF group, and one in the RR + AR group occurred near the L4-5. After both primary deformity correction and revision surgery, spinopelvic parameters had shown favorable results, and clinical outcomes had improved in all three groups without significant intergroup differences. Conclusions: Accessory rod insertion or an additional LLIF around the PSO site seems to provide greater strength and stability to the previously fused segments than a simple rod replacement, which demonstrates the need for additional support in revision surgery for RF after a PSO.

Incidence and risk factors of new-onset sacroiliac joint pain after spinal surgery: a systematic review and meta-analysis

Purpose

A systematic review and meta-analysis for incidence and risk factors of new-onset sacroiliac joint pain (SIJP) after spinal surgery aimed to provide evidence-based medical references for its early prevention, timely intervention, and appropriate treatment.

Methodology

The protocol of the systematic review and meta-analysis was registered in the International Prospective Register of Systematic Review (PROSPERO) with the PROSPERO ID (CRD42023463177). Relevant studies were searched to January 2024 from the databases of PubMed, Embase, Cochrane Library, and Web of Science, and the types of studies were cohort studies, case-control studies, and cross-sectional studies. Study quality was assessed using the Newcastle-Ottawa Scale (NOS) and the Cross-Sectional/Prevalence Study Quality recommended by the Agency for Healthcare Research and Quality (AHRQ). Two authors conducted studies search, data extraction, and quality assessment independently. Meta-analyses were done using Stata 14.0 software.

Results

Twelve observational studies with 3,570 spinal surgery patients were included. Ten were case-control studies, one was a cross-sectional study, and another was a cohort study, all of which were of moderate quality and above. The results of the meta-analysis showed that the incidence of new-onset SIJP after spinal surgery was 9.40%; females, no. of surgical segments, fusion to the sacrum, and postoperative pelvic tilt (PT) were significantly associated with the new-onset SIJP after spinal surgery. Meta-analyses for preoperative and postoperative controls of spondylopelvic parameters showed that postoperative lumbar lordosis (LL) in the SIJP group and postoperative LL and sacral slope (SS) of patients in the NoSIJP group had significant differences from preoperative.

Conclusion

Available evidence suggests that an increased risk of new-onset SIJP after spinal surgery is associated with sex, multi-segmental surgery, fusion to the sacrum, and greater postoperative PT.

Focusing on the amount of immediate changes in spinopelvic radiographic parameters to predict the amount of mid-term improvement of quality of life in adult degenerative scoliosis patients with surgery

INTRODUCTION

Surgery is still an effective treatment option for adult degenerative scoliosis (ADS), but how to predict patients' significant amount of the improvement in quality of life remains unclear. The previous studies included an inhomogeneous population. This study aimed to report the results about concentrating on the amount of immediate changes in spinopelvic radiographic parameters to predict the amount of mid-term improvement in quality of life in ADS patients.

MATERIALS AND METHODS

Pre-operative and immediately post-operative radiographic parameters included Cobb angle, coronal vertical axis (CVA), sagittal vertical axis (SVA), lumbar lordosis (LL), thoracic kyphosis (TK), pelvic tilt (PT), sacral slope (SS), pelvic incidence (PI) and LL/PI matching (PI-LL). Quality of life scores were evaluated pre-operatively and at the final follow-up using Oswestry Disability Index (ODI) and visual analogue scale (VAS). The amount of immediate changes in spinopelvic radiographic parameters (Δ) and the amount of mid-term improvement in quality of life (Δ) were defined, respectively.

RESULTS

Patients showed significant change in radiographic parameters, ODI and VAS pre- and post-surgery, except CVA and PI. Univariate analysis showed a significant correlation between ΔTK, ΔLL, ΔCVA and the amount of mid-term improvement in quality of life, but multivariate analysis did not get a significant result. Univariate and multivariate analyses showed that ΔSVA was still a significant predictor of ΔVAS and ΔODI. The changes in the other radiographic parameters were not significant. The equations were developed by linear regression: ΔODI = 0.162 × ΔSVA - 21.592, ΔVAS = 0.034 × ΔSVA - 2.828. In the ROC curve for ΔSVA in the detection of a strong ΔODI or ΔVAS, the cut-off value of ΔSVA was - 19.855 mm and - 15.405 mm, respectively.

CONCLUSIONS

This study shows that ΔSVA can predict the amount of mid-term improvement in quality of life in ADS patients. The changes in the other radiographic parameters were not significant. Two equations were yielded to estimate ΔODI and ΔVAS. ΔSVA has respective cut-off value to predict ΔODI and ΔVAS.

The Impact of Upper Instrumented Vertebra Orientation on Proximal Junctional Kyphosis: A Novel and Fixed Parameter, Fused Spinopelvic Angle

STUDY DESIGN

A retrospective study.

OBJECTIVES

To evaluate the impact of upper instrumented vertebra (UIV) orientation including the fused spinopelvic angle (FSPA) on proximal junctional kyphosis (PJK).

SUMMARY OF BACKGROUND DATA

PJK is a challenging complication after adult spinal deformity (ASD) surgery. Some studies proposed UIV orientation act as a risk factor of PJK, but there remain debates because UIV orientation is changed by position. Therefore, we investigated the relationship between the FSPA, a novel parameter for the relationship between UIV and pelvis which did not change by position, and PJK.

MATERIALS AND METHODS

ASD patients who underwent long-segment fusion to the pelvis and followed up for more than two years were included. Comparative analysis was performed on spinopelvic parameters including UIV orientation parameters (UIV slope angle and FSPA) between PJK and non-PJK group. Binary regression analysis was conducted to find out the risk factors for PJK. And correlation analysis was conducted to find out the parameters that affect the FSPA.

RESULTS

A total of 190 patients were included. PJK incidence was 13.2% (25/190). PJK group showed a significantly greater postoperative UIV slope (21.3° vs. 18.8°, P =0.041) and significantly lesser postoperative FSPA (-0.9° vs. 4.5°, P <0.001). In binary regression analysis, only FSPA acted as a risk factor of PJK (odds ratio=0.920, P =0.004). The FSPA has strong positive correlation with pelvic incidence (PI)-lumbar lordosis (LL) ( r =0.666, P <0.001) and negative correlation with lordosis distribution index (LDI) ( r =-0.228, P =0.004).

CONCLUSION

The FSPA is a fixed parameter which is not dependent on position. A reduction of the FSPA increases the risk for PJK. The FSPA can be adjusted through PI-LL and LDI. Thus, surgeons should increase the FSPA by adjusting the PI-LL and LDI during ASD surgery to prevent PJK.

Biomechanical study of rod stress in lumbopelvic fixation with lateral interbody fusion: an in vitro experimental study using synthetic bone models

OBJECTIVE

Despite improvements in surgical techniques and instruments, high rates of rod fracture following a long spinal fusion in the treatment of adult spinal deformity (ASD) remain a concern. Thus, an improved understanding of rod fracture may be valuable for better surgical planning. The authors aimed to investigate mechanical stress on posterior rods in lumbopelvic fixation for the treatment of ASD.

METHODS

Synthetic lumbopelvic bone models were instrumented with intervertebral cages, pedicle screws, S2-alar-iliac screws, and rods. The construct was then placed in a testing device, and compressive loads were applied. Subsequently, the strain on the rods was measured using strain gauges on the dorsal aspect of each rod.

RESULTS

When the models were instrumented using titanium alloy rods at 30° lumbar lordosis and with lateral interbody fusion cages, posterior rod strain was highest at the lowest segment (L5-S1) and significantly higher than that at the upper segment (L2-3) (p = 0.002). Changing the rod contour from 30° to 50° caused a 36% increase in strain at L5-S1 (p = 0.009). Changing the rod material from titanium alloy to cobalt-chromium caused a 140% increase in strain at L2-3 (p = 0.009) and a 28% decrease in strain at L5-S1 (p = 0.016). The rod strain at L5-S1 using a flat bender for contouring was 23% less than that obtained using a French bender (p = 0.016).

CONCLUSIONS

In lumbopelvic fixation in which currently available surgical techniques for ASD are used, the posterior rod strain was highest at the lumbosacral junction, and depended on the contour and material of the rods.

Effect of gluteal muscle strengthening exercise on sagittal balance and muscle volume in adult spinal deformity following long-segment fixation surgery

This study aimed to investigate the changes in gluteal muscle volume and the effects of such changes in spinal alignment as a result of postoperative gluteal muscle strengthening exercise (GMSE) in patients following long-segment fixation for adult spinal deformity (ASD). Eighty-three consecutive patients (average age, 70.1 years) were analyzed. Three-dimensional CT scans were conducted to obtain serial axial gluteus muscle image slices. The size of each muscle area in every image slice was measured by Computer Aided Design and the sum of each muscle area was calculated. At the last follow-up, the sagittal vertical axis was significantly greater in the basic postoperative exercise group (1.49 mm vs. 17.94 mm), and the percentage of optimal sagittal alignment was significantly higher in the GMSE group (97.8% vs. 84.2%). At the last follow-up, the gluteus maximus volume was significantly higher in the GMSE group (900,107.1 cm³ vs. 825,714.2 cm³, p = 0.036). For the increase in muscle volume after 1 year, gluteus maximus and medius volumes showed a significant intergroup difference (+ 6.8% vs. + 2.4% and + 6.9% vs. + 3.6%). The GMSE protocol developed in this study could effectively increase gluteal muscle volume and maintain the optimal sagittal balance in patients with ASD.

The Impact of Radiographic Lower Limb-Spinal Length Proportion on Whole-Body Sagittal Alignment

STUDY DESIGN

A radiographic comparative study.

OBJECTIVE

To investigate the influence of radiographic lower limb-spinal length proportion on sagittal radiographic parameters.

SUMMARY OF BACKGROUND DATA

Although lordotic realignment of the lumbar spine is a well-established surgical strategy, its ideal target has not been fully understood. The widely used pelvic incidence-lumbar lordosis discrepancy (PI-LL) method to guide lordotic restoration of the lumber spine in the standing posture, may be further refined using the novel, radiographic lower limb-spinal length proportion parameter in selected subjects.

METHODS

A 100 healthy subjects were imaged in the standing posture using EOS imaging to obtain whole-body lateral radiographs for the measurement of sagittal radiographic parameters. Univariate analyses were performed to compare radiographic parameters between groups with different radiographic lower limb-spinal length proportion. Multivariate analyses were performed to identify the associations between lower limb-spinal length proportions and other radiographic parameters.

RESULTS

Regardless of lower limb-spinal length proportion (mean = 1.4), global lumbar angle (GLA) differed from spinal lordosis (SL), with the absolute means of SL and GLA larger and smaller than pelvic incidence (PI) respectively. Univariate analysis showed that patients with proportionately larger lower limb-spinal length proportion are more likely to have larger mean T1-slope, global thoracic angle (GTA), spinal kyphosis (SK), GLA, and SL. Multivariate analysis showed that a larger lower limb length-spinal length proportion is predictive of larger GLA is less than -47.69° (Odds Ratio (OR) 2.660, P = 0.026), and larger T1-slope of more than 18.84° (OR 3.695, P = 0.012).

CONCLUSION

Larger radiographic lower limb-spinal length proportion results in naturally accentuated spinal curves. These patients balance with a larger lumbar lordosis that is closer to the PI and a higher T1-slope which should be considered for spinal realignment. SL differs from GLA and should be separately assessed.Level of Evidence: 3.

Optimal Lumbar Lordosis Correction for Adult Spinal Deformity with Severe Sagittal Imbalance in Patients Over Age 60: Role of Pelvic Tilt and Pelvic Tilt Ratio

STUDY DESIGN

A retrospective study.

OBJECTIVES

The purpose of this study was to evaluate optimal and ideal target values of the spine balance correction in elderly patients with adult spinal deformity who were over the age of 60 years.

SUMMARY OF BACKGROUND DATA

The target values of the Scoliosis Research Society -Schwab classification to obtain satisfactory alignment and favorable outcomes are used in many spinal reconstruction surgeries. However, uniformly applying the Scoliosis Research Society-Schwab classification to all elderly patients aged 60 years or older showing sagittal malalignment may lead to several inconsistencies.

METHODS

This study included 121 patients (average age 70.5 yr and a minimum 2-yr follow-up) with adult spinal deformity who underwent long-segment fusion from T10 to sacrum. We used Pearson's correlation coefficient to analyze the relationship between clinical and radiographic parameters, and multilinear regression analysis and multivariate logistic regression model (backward elimination method) were conducted using the correlation factors of postoperative (Post) and last follow-up (Last) sagittal vertical axis to find the risk factors of Post sagittal imbalance.

RESULTS

Logistic regression analysis with the correlation factors of Post and Last sagittal vertical axis led to risk factors of Post sagittal imbalance, and after confirming the significance of each path, it was confirmed that the effects of pelvic incidence (PI)- lumbar lordosis (LL) and Post pelvic tilt ratio (PTr) were valid (P < 0.05). After using ROC curve, target value of PI-LL was 1.33, and that of PTr was 25.95%.

CONCLUSION

Through our study, the risk factors of Post sagittal imbalance were the Post value of PI-LL and that of PTr, and target value of PI-LL was <1.33 and that of PTr was <25.95%. These target values can be effective guidelines for spine surgeons who perform spine reconstruction surgeries for elderly patients with a pure sagittal imbalance based on Schwab's formula.Level of Evidence: 4.

Comparative radiological outcomes and complications of sacral-2-alar iliac screw versus iliac screw for sacropelvic fixation

PURPOSE

To compare the outcomes of sacropelvic fixation (SPF) using sacral-2-alar iliac (S2AI) screw with SPF using iliac screw (IS).

METHODS

A comprehensive search of PubMed, EMBASE, Cochrane Central Register of Controlled Trials and Scopus was performed for comparative studies between S2AI and IS for SPF. Two independent investigators selected qualified studies and extracted data indispensably. With 95% confidence intervals (CI), the odds ratio (OR) was applied to dichotomous outcomes and standardized mean difference (SMD) was applied to continuous outcomes for each item.

RESULTS

We included data from thirteen studies involving 722 patients (S2AI, 357 patients; IS, 365 patients). In the pediatric population, the S2AI group had a smaller pelvic obliquity (PO) than the IS group at final follow-up (SMD, - 0.38; 95% CI, - 0.72 to - 0.04). Patients who underwent S2AI screws showed reduced rates of re-operation (S2AI, 13%; IS, 28%), implant failure (S2AI, 12%; IS, 26%) [screw loosening (S2AI, 8%; IS, 20%); screw breakage (S2AI, 2%; IS, 12%)], implant prominence (S2AI, 2%; IS, 14%), pseudarthrosis (S2AI, 3%; IS, 15%), wound infection (S2AI, 8%; IS, 22%) and less blood loss (S2AI, 2035.4 ml; IS, 2708.4 ml).

CONCLUSION

Radiological outcomes indicate an effective maintenance of the correction and arrest of progression of deformity by S2AI, which is equal or better than IS. SPF with S2AI screw has obviously lower incidence of postoperative complications and less blood loss. Given these advantages, the S2AI screw seems to be a beneficial alternative to IS.

Strategies for prevention of rod fracture in adult spinal deformity: cobalt chrome rod, accessory rod technique, and lateral lumbar interbody fusion

OBJECTIVE

Restoring the proper sagittal alignment in adult spinal deformity (ASD) can improve radiological and clinical outcomes, but pseudarthrosis including rod fracture (RF) is a common problematic complication. The purpose of this study was to analyze the methods for reducing the incidence of RF in deformity correction of ASD.

METHODS

The authors retrospectively selected 178 consecutive patients (mean age 70.8 years) with lumbar degenerative kyphosis (LDK) who underwent deformity correction with a minimum 2-year follow-up. Patients were classified into the non-RF group (n = 131) and the RF group (n = 47). For predicting the crucial factors of RF, patient factors, radiographic parameters, and surgical factors were analyzed.

RESULTS

The overall incidence of RF was 26% (47/178 cases), occurring in 42% (42/100 cases) of pedicle subtraction osteotomy (PSO), 7% (5/67 cases) of lateral lumbar interbody fusion (LLIF) with posterior column osteotomy, 18% (23/129 cases) of cobalt chrome rods, 49% (24/49 cases) of titanium alloy rods, 6% (2/36 cases) placed with the accessory rod technique, and 32% (45/142 cases) placed with the 2-rod technique. There were no significant differences in the incidence of RF regarding patient factors between two groups. While both groups showed severe sagittal imbalance before operation, lumbar lordosis (LL) was more kyphotic and pelvic incidence (PI) minus LL (PI-LL) mismatch was greater in the RF group (p < 0.05). Postoperatively, while LL and PI-LL did not show significant differences between the two groups, LL and sagittal vertical axis correction were greater in the RF group (p < 0.05). Nonetheless, at the last follow-up, the two groups did not show significant differences in radiographic parameters except thoracolumbar junctional angles. As for surgical factors, use of the cobalt chrome rod and the accessory rod technique was significantly greater in the non-RF group (p < 0.05). As for the correction method, PSO was associated with more RFs than the other correction methods, including LLIF (p < 0.05). By logistic regression analysis, PSO, preoperative PI-LL mismatch, and the accessory rod technique were crucial factors for RF.

CONCLUSIONS

Greater preoperative sagittal spinopelvic malalignment including preoperative PI-LL mismatch was the crucial risk factor for RF in LDK patients 65 years or older. For restoring and maintaining sagittal alignment, use of the cobalt chrome rod, accessory rod technique, or LLIF was shown to be effective for reducing RF in ASD surgery.

Optimized Surgical Strategy for Adult Spinal Deformity: Quantitative Lordosis Correction versus Lordosis Morphology

BACKGROUND

In surgical correction of adult spinal deformity (ASD), pelvic incidence (PI)-lumbar lordosis (LL) plays a key role to restore normal sagittal alignment. Recently, it has been found that postoperative lordosis morphology act as an important factor in preventing mechanical complications. However, there have been no studies on the effect of postoperative lordosis morphology on the restoration of sagittal alignment. The primary objective of this study was to evaluate the effect of postoperative lordosis morphology on achievement of optimal sagittal alignment. The secondary objective was to find out which radiographic or morphologic parameter affects sagittal alignment in surgical correction of ASD.

METHODS

228 consecutive patients with lumbar degenerative kyphosis who underwent deformity correction and long-segment fixation from T10 to S1 with sacropelvic fixation and follow-up over 2 years were enrolled. Patients were divided according to whether optimal alignment was achieved (balanced group) or not (non-balanced group) at last follow-up. We analyzed the differences of postoperative radiographic parameters and morphologic parameters between two groups. Correlation analysis and stepwise multiple linear regression analysis was performed to predict the effect of PI-LL and morphologic parameters on the sagittal vertical axis (SVA).

RESULTS

Of 228 patients, 195 (85.5%) achieved optimal alignment at last follow-up. Two groups significantly differed in postoperative and last follow-up LL (p < 0.001 and p = 0.028, respectively) and postoperative and last follow-up PI-LL (p < 0.001 and p = 0.001, respectively). Morphologic parameters did not significantly differ between the two groups except lower lordosis arc angle (=postoperative sacral slope). In correlation analysis and stepwise multiple linear regression analysis, postoperative PI-LL was the only parameter which had significant association with last follow-up SVA (R² = 0.134, p < 0.001). Morphologic parameters did not have any association with last follow-up SVA.

CONCLUSIONS

When planning spine reconstruction surgery, although considering postoperative lordosis morphology is necessary, it is still very important considering proportional lordosis correction based on individual spinopelvic alignment (PI-LL) to achieve optimal sagittal alignment.

Risk Factors Predicting C- Versus S-shaped Sagittal Spine Profiles in Natural, Relaxed Sitting: An Important Aspect in Spinal Realignment Surgery

STUDY DESIGN

A cross-sectional study on a randomly selected prospective cohort of patients presenting to a single tertiary spine center.

OBJECTIVE

The aim of this study was to describe the clinical and radiographic parameters of patients with S- and C-shaped thoracolumbar sagittal spinal profiles, and to identify predictors of these profiles in a natural, relaxed sitting posture.

SUMMARY OF BACKGROUND DATA

Sagittal realignment in adult spinal deformity surgery has to consider the sitting profile to minimize the risks of junctional failure. Persistence of an S-shaped sagittal profile in the natural, relaxed sitting posture may reflect a lesser need to accommodate for this posture during surgical realignment.

METHODS

Consecutive patients with low back pain underwent whole body anteroposterior and lateral radiographs in both standing and sitting. Baseline clinical data of patients and radiographic parameters of both standing and sitting sagittal profiles were compared using χ, unpaired t tests, and Wilcoxon rank-sum test. Subsequently, using stepwise multivariate logistic regression analysis, predictors of S-shaped curves were identified while adjusting for confounders.

RESULTS

Of the 120 patients included, 54.2% had S-shaped curves when sitting. The most common diagnoses were lumbar spondylosis (26.7%) and degenerative spondylolisthesis (26.7%). When comparing between patients with S- and C-shaped spines in the sitting posture, only diagnoses of degenerative spondylolisthesis (odds ratio [OR], 5.44; P = 0.01) and degenerative scoliosis (OR, 2.00; P = 0.039), and pelvic incidence (PI) >52.5° (OR, 5.48; P = 0.008), were predictive of an S-shaped sitting sagittal spinal alignment on multivariate analysis.

CONCLUSION

Stiffer lumbar curves (eg, patients with degenerative spondylolisthesis and degenerative scoliosis) or those who have a predilection for an S-shaped standing sagittal profile when sitting (eg, high PI) may be more amenable to fusion in accordance with previously studied sagittal realignment targets. In contrast, more flexible curves may benefit from less aggressive lordotic realignment to prevent potential junctional failures.

LEVEL OF EVIDENCE

3.

Spino-Pelvic Thresholds for Prevention of Proximal Junctional Kyphosis Following Combined Anterior Column Realignment and Short Posterior Spinal Fusion in Degenerative Lumbar Kyphosis

Objective

To analyze ideal indication for combined anterior column realignment (ACR) with short posterior spinal fusion (PSF) and posterior column osteotomy (PCO) for preventing proximal junctional kyphosis (PJK) in adult spinal deformity (ASD) patients with lower lumbar kyphosis and compensatory thoracolumbar lordosis.

Methods

A retrospective study was conducted. This study included 27 ASD patients (average age of 66.6 years; one male and 26 females) with lower lumbar kyphosis and compensated thoracolumbar lordosis who underwent short PSF with PCO following ACR from 2006 to 2010. The minimum follow‐up period was 5 years. The patients were divided into two groups based on the sagittal vertical axis (SVA) of the last follow‐up radiographs, and a comparative analysis was performed evaluating spino‐pelvic parameters and clinical outcomes including the Oswestry Disability Index (ODI), Visual Analog Scale (VAS), and complications.

Results

The mean follow‐up time of included patients was 109.7 months, and the mean number of fused segments was 3.7. The uppermost instrumented vertebra was L₂ in 18 patients or L₃ in nine patients, and lowermost instrumented vertebra was sacrum in all patients. The mean lumbar lordosis (LL) values in the optimal SVA and suboptimal SVA groups were 4.4° and 4.2° preoperatively (P = 0.639), −48.1° and −35° postoperatively (P = 0.007), and −45.2° and −20.7° at the last follow‐up (P < 0.05). Overcorrection was seen in seven patients in the optimal SVA group, whereas all of the patients of the suboptimal SVA group were in the category of undercorrection (P = 0.021). Pelvic incidence (PI) of optimal SVA group (<50 mm, n = 16) and suboptimal SVA group (≥50 mm, n = 11) was 44.1° and 53.8° (P = 0.009). The prevalence of PJK was significantly higher in the suboptimal SVA group (P = 0.008), and last follow‐up VAS for back pain (P < 0.05), and postoperative and last follow‐up ODI (P = 0.002 and P < 0.05) were statistically larger for the suboptimal group than the optimal group.

Conclusions

Combined ACR with short PSF and PCO could effectively prevent sagittal decompensation of PJK and help achieve sagittal balance in the treatment of ASD patients with lower lumbar kyphosis, compensatory thoracolumbar lordosis, and especially low PI (<50°).

Strategy for obtaining solid fusion at L5-S1 in adult spinal deformity: risk factor analysis for nonunion at L5-S1

OBJECTIVE

Maintaining lumbosacral (LS) arthrodesis and global sagittal balance after long fusion to the sacrum remains an important issue in the surgical treatment for adult spinal deformity (ASD). The importance and usefulness of LS fixation have been documented, but the optimal surgical long fusion to the sacrum remains a matter for debate. Therefore, the authors performed a retrospective study to evaluate fusion on CT scans and the risk factors for LS pseudarthrosis (nonunion) after long fusion to the sacrum in ASD.

METHODS

The authors performed a retrospective study of 59 patients with lumbar degenerative kyphosis (mean age 69.6 years) who underwent surgical correction, including an interbody fusion of the L5-S1, with a minimum 2-year follow-up. Achievement of LS fusion was evaluated by analyzing 3D-CT scans at 3 months, 6 months, 9 months, 1 year, and 2 years after surgery. Patients were classified into a union group (n = 36) and nonunion group (n = 23). Risk factors for nonunion were analyzed, including patient and surgical factors.

RESULTS

The overall fusion rate was 61% (36/59). Regarding radiological factors, optimal sagittal balance at the final follow-up significantly differed between two groups. There were no significant differences in terms of patient factors, and no significant differences with respect to the use of pedicle subtraction osteotomy, the number of fused segments, the proportion of anterior versus posterior interbody fusion, S2 alar iliac fixation versus conventional iliac fixation, or loosening of sacral or iliac screws. However, the proportion of metal cages to polyetheretherketone cages and the proportion of sacropelvic fixation were significantly higher in the union group (p = 0.022 and p < 0.05, respectively).

CONCLUSIONS

LS junction fusion is crucial for global sagittal balance, and the use of iliac screws in addition to LS interbody fusion using a metal cage improves the outcomes of long fusion surgery for ASD patients.

Proximal Junctional Kyphosis in Degenerative Sagittal Deformity After Under- and Overcorrection of Lumbar Lordosis: Does Overcorrection of Lumbar Lordosis Instigate PJK?

STUDY DESIGN

Retrospective study.

OBJECTIVE

To analyze proximal junctional kyphosis (PJK) occurrence and surgical outcomes according to degree of lumbar lordosis (LL) correction relative to pelvic incidence (PI). In addition, risk factors of PJK including LL and sagittal vertical axis (SVA) correction were investigated.

SUMMARY OF BACKGROUND DATA

PJK is a common complication after adult spinal deformity surgery, and many factors are known to be associated with PJK. However, the effect of degree of LL correction on PJK occurrence is not fully understood.

METHODS

Eighty-three degenerative sagittal imbalance patients treated with deformity correction and long instrumented fusion to the sacrum with a minimum follow-up of 2 years were studied. Patients were divided into three groups according to their postoperative LL angle relative to PI using the SRS-Schwab classification: Group A (undercorrection, PI-LL> 10°), Group B (ideal correction, -10°

RESULTS

Overall PJK prevalence was 36.1% (30/83), and ratio of optimal SVA at postoperative and last follow-up were significantly higher in Group C (P < 0.001, P < 0.001). Nevertheless, there was no significant difference in PJK prevalence among three groups (40% vs. 37.5% vs. 34.1%; P = 0.907). Group C had better clinical outcomes (last follow-up ODI, VAS of LBP) than Group A (10.0 vs. 18.4; P < 0.001 and 1.5 vs. 4.0; P < 0.001). The increases in LL or SVA correction degree were not associated with PJK occurrence (P = 0.304, P = 0.201).

CONCLUSION

Overcorrection showed good surgical outcomes without increasing PJK prevalence. Degrees of LL and SVA correction do not act as risk factors for PJK. Therefore, in adult spinal deformity patients, LL correction greater than PI may be a good choice that can result in better clinical outcomes without increasing risk of PJK.

LEVEL OF EVIDENCE

4.

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MESH Headings

• Adult
• Aged
• Animals
• Female
• Humans
• Kyphosis/diagnostic imaging
• Kyphosis/etiology
• Lordosis/diagnostic imaging
• Lordosis/surgery
• Lumbar Vertebrae/diagnostic imaging
• Lumbar Vertebrae/surgery
• Male
• Middle Aged
• Neurodegenerative Diseases/diagnostic imaging
• Neurodegenerative Diseases/etiology
• Neurosurgical Procedures/adverse effects
• Neurosurgical Procedures/trends
• Retrospective Studies
• Risk Factors

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Affiliation(s)

Sang-Kyu Im Department of Orthopedic Surgery, Graduate School, College of Medicine, Kyung Hee University, Seoul, Korea
Jung-Hee Lee
Kyung-Chung Kang
Sung Joon Shin
Ki Young Lee
Jong Jun Park
Man Ho Kim

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Estimation of the ideal correction of lumbar lordosis to prevent reoperation for symptomatic adjacent segment disease after lumbar fusion in older people

Background

Symptomatic adjacent segment disease (ASDis) is a major complication following spinal fusion. Sagittal spinopelvic imbalance may contribute to the development of ASDis. However, the exact ideal correction of lumbar lordosis (LL) is unknown for different ages of people to prevent ASDis. The purpose of this study was to estimate the ideal correction of LL required to prevent symptomatic ASDis requiring revision surgery in patients of various ages, and to determine the radiographic risk factors for ASDis.

Methods

468 patients who underwent lumbar fusion between January 2014 and December 2016, were enrolled in the present study. The patients were classified into the ASDis and N-ASD group. These two matched groups were compared regarding surgery-related factors and radiographic features. Multivariate logistic regression analysis was used to evaluate the risk factors for ASDis.

Results

Sixty-two patients (13.25%) underwent reoperation for ASDis during a mean follow-up duration of 38.07 months. Receiver operating characteristic curve analysis showed that the postoperative LL - preoperative LL (△LL) cutoff value was 11.7°for the development of ASDis. Logistic regression analysis revealed that the risk factors for symptomatic ASDis were a smaller LL angle, △LL > 12°, and PI-LL > 10° (p <  0.05). For patients > 60 years, the incidence of ASDis was higher in patients with a LL correction of ≥10° and a lumbar-pelvic mismatch (PI-LL) of > 20°.

Conclusions

The significant predictors of the occurrence of ASDis were a smaller LL angle, △LL > 12°, and PI-LL > 10°. However, in patients older than 60 years, the incidence of ASDis after lumbar fusion was higher in those with a LL correction of ≥10° and PI-LL of > 20°. More attention should be paid to patient age and the angle of correction of LL before lumbar fusion.

Rod Fracture Causing Relief of Back Pain That Developed After Adult Lumbar Degenerative Flat-Back Correction Surgery: A Case Report

A 73-year-old woman underwent deformity correction surgery (anterior lumbar interbody fusion of L2-L3-L4-L5-S1, pedicle subtraction osteotomy at L4, and posterior screw fixation from T10 to the pelvis) due to lumbar degenerative flat-back. Following the operation, the patient experienced pain in her back and buttocks, for which she regularly took medications. She reported frequently feeling a heavy and stretched sensation of pain after the operation in those areas, which made her regret undergoing the operation. However, at 33 months postoperatively, she reported that one day, while getting up from a chair, she felt a crack in her back, which was followed by an improvement in her back and buttock pain; thereafter, she stopped taking pain medications. Follow-up radiography revealed a bilateral rod fracture at the L4–5 level on the right side and at the L3–4 level on the left side. The overall pelvic parameters, except pelvic incidence, slightly changed after the rod fracture. Therefore, the broken rod was replaced and another rod was added to the broken rod area; however, the changed pelvic parameters were not corrected further during the reoperation. Following the reoperation, the patient showed improvements and she no longer required pain medication.

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.

Preliminary report on the flexible rod technique for prevention of proximal junctional kyphosis following long-segment fusion to the sacrum in adult spinal deformity

OBJECTIVE

The incidence of proximal junctional kyphosis (PJK) after long-segment fixation in patients with adult spinal deformity (ASD) has been reported to range from 17% to 61.7%. Recent studies have reported using "hybrid" techniques in which semirigid fixation is introduced between the fused and flexible segments at the proximal level to allow a more gradual transition. The authors used these hybrid techniques in a clinical setting and analyzed PJK to evaluate the usefulness of the flexible rod (FR) technique.

METHODS

The authors retrospectively selected 77 patients with lumbar degenerative kyphosis (LDK) who underwent sagittal correction and long-segment fixation and had follow-up for > 1 year. An FR was used in 30 of the 77 patients. PJK development and spinal sagittal changes were analyzed in the FR and non-FR groups, and the predictive factors of PJK between a PJK group and a non-PJK group were compared.

RESULTS

The patient population comprised 77 patients (75 females and 2 males) with a mean (± SD) follow-up of 32.0 ± 12.7 months (36.7 ± 9.8 months in the non-FR group and 16.8 ± 4.7 months in the FR group) and mean (± SD) age of 71.7 ± 5.1 years. Sagittal balance was well maintained at final follow-up (10.5 and 1.5 mm) in the non-FR and FR groups, respectively. Thoracic kyphosis (TK) and lumbar lordosis (LL) were improved in both groups, without significant differences between the two (p > 0.05). PJK occurred in 28 cases (36.4%) in total, 3 (10%) in the FR and 25 (53.2%) in the non-FR group (p < 0.001). Postoperatively, PJK was observed at an average of 8.9 months in the non-FR group and 1 month in the FR group. No significant differences in the incidence of PJK regarding patient factors or radiological parameters were found between the PJK group and non-PJK group (p > 0.05). However, FR (vs non-FR) and interbody fusion except L5-S1 using oblique lumbar interbody fusion (vs non-oblique lumbar interbody fusion), demonstrated a significantly lower PJK prevalence (p < 0.001 and p = 0.044) among the surgical factors.

CONCLUSIONS

PJK was reduced after surgical treatment with the FR in the patients with LDK. Solid long-segment fixation and the use of the FR may become another surgical option for spine surgeons who plan and make decisions regarding spine reconstruction surgery for patients with ASD.

Relationship Between Lumbar Lordosis and Pelvic Incidence in the Adolescent Patient: Normal Cohort Analysis and Literature Comparison

STUDY DESIGN

Retrospective review; literature comparison.

OBJECTIVES

To review the literature on the relationship between lumbar lordosis (LL) and pelvic incidence (PI) and evaluate this relationship in asymptomatic adolescents while testing the validity of previously reported adult correlation models between LL and PI in an adolescent population.

SUMMARY OF BACKGROUND DATA

Accurate understanding of the normal spinopelvic relationship is critical when considering surgical fusion of the lumbar spine. Many studies have reported relationships between pelvic measurements and LL in adult populations, but data in pediatric populations is lacking.

METHODS

A literature search was performed to identify previously reported relationships between pelvic parameters and LL in adults and pediatric patients. A cohort of 125 asymptomatic adolescent patients evaluated at our institution was evenly split into two cohorts for model development and validation. Linear regression between LL and PI was performed. The resultant regression model was tested in the validation cohort along with previously reported formulae with LL as a function of PI. Mean absolute error (MAE) was calculated and compared between prior models and the newly developed adolescent model using analysis of variance and post-hoc testing.

RESULTS

In our adolescent cohort (mean age: 13 ± 2), there was a strong correlation between PI and LL (r = 0.53). Regression analysis in the development cohort produced the following predictive model: LL = 0.66(PI) + 24.2. Testing in the validation cohort revealed a good correlation between predicted and actual LL (r = 0.51) and an MAE of 8.3. All but three previously reported models functioned with similar accuracy in the adolescent population, with only two methods having an MAE over 10.

CONCLUSIONS

The majority of previously published formulae for predicting LL as a function of PI developed in adults can be extrapolated to adolescent populations. These relationships are important in understanding how to surgically restore the sagittal alignment in adolescents with spinal deformity.

LEVEL OF EVIDENCE

Level IV.

Functional Limitations Due to Stiffness After Long-Level Spinal Instrumented Fusion Surgery to Correct Lumbar Degenerative Flat Back

STUDY DESIGN

A retrospective analysis of functional limitations due to stiffness after long-level spinal instrumented fusion surgery to correct lumbar degenerative flat back was performed.

OBJECTIVE

To analysis the functional limitations in patients treated surgically for adult lumbar degenerative flat back (ALDFB) with long-level instrumented fusion to the sacrum or pelvis.

SUMMARY OF BACKGROUND DATA

Long-level instrumented fusion for ALDFB decreases back pain and spinal deformity. On the contrary, this surgery considerably eliminates spinal range of motion. This may have the potential to impair function and ability to perform activities of daily living (ADLs).

METHODS

Consecutive 44 patients who underwent long-level instrumented fusion to the sacrum or pelvis for ALDFB were retrospectively included in this study. All patients were followed up for a minimum of 13 months. The Lumbar Stiffness Disability Index for Korean Lifestyle and Oswestry Disability Index were administered and analyzed to assess the impact of spinal stiffness on daily living. Cohorts were defined based on the upper instrumented vertebrae (above T10 [group 1] or below L1 [group 2]) and lower instrumented vertebrae (S1 pedicle screw [group S] or iliac bolt screw [group I]).

RESULTS

All patients showed deteriorated postoperative ADLs compared to preoperative values. Group 1 showed deterioration postoperatively compared to group 2. Group 1 showed deteriorated postoperative ADLs compared to preoperative values. In group 2, question 5 and 7 showed deterioration postoperatively compared to preoperative values, and question 2 and 10 showed improvement postoperatively compared to preoperative values. Group I showed deterioration postoperatively compared to group S.

CONCLUSION

This study will hopefully allow surgeons to provide patients with ALDFB with a more informed explanation of expected surgery effects on specific ADLs.

LEVEL OF EVIDENCE

3.

Recurrent Hip Dislocation Following Total Hip Arthroplasty: Treatment with Sagittal Spinal Deformity Correction: A Case Report

CASE

A 63-year-old woman with lumbar degenerative kyphosis who had undergone total hip arthroplasty 34 months previously presented after having multiple episodes of anterior hip dislocation; evaluation also revealed progressive osteoarthritis in the contralateral hip joint. The patient was managed with sagittal correction with pedicle subtraction osteotomy, which resulted in optimal positioning of the acetabular component and an upright posture. The patient had had no additional dislocation events in the involved hip and had reduced pain in the contralateral hip at the time of the 2-year follow-up.

CONCLUSION

It is important to evaluate and address preexisting sagittal imbalance before performing total hip arthroplasty. However, for patients with neglected sagittal imbalance resulting in recurrent hip dislocation after total hip arthroplasty, sagittal deformity correction may be beneficial.

Radiologically defining horizontal gaze using EOS imaging-a prospective study of healthy subjects and a retrospective audit

BACKGROUND CONTEXT

As sagittal alignment of the cervical spine is important for maintaining horizontal gaze, it is important to determine the former for surgical correction. However, horizontal gaze remains poorly-defined from a radiological point of view.

PURPOSE

The objective of this study was to establish radiological criteria to define horizontal gaze.

STUDY DESIGN/SETTING

This study was conducted at a tertiary health-care institution over a 1-month period.

PATIENT SAMPLE

A prospective cohort of healthy patients was used to determine the best radiological criteria for defining horizontal gaze. A retrospective cohort of patients without rigid spinal deformities was used to audit the incidence of horizontal gaze.

OUTCOME MEASURES

Two categories of radiological parameters for determining horizontal gaze were tested: (1) the vertical offset distances of key identifiable structures from the horizontal gaze axis and (2) imaginary lines convergent with the horizontal gaze axis.

MATERIALS AND METHODS

Sixty-seven healthy subjects underwent whole-body EOS radiographs taken in a directed standing posture. Horizontal gaze was radiologically defined using each parameter, as represented by their means, 95% confidence intervals (CIs), and associated 2 standard deviations (SDs). Subsequently, applying the radiological criteria, we conducted a retrospective audit of such radiographs (before the implementation of a strict radioimaging standardization).

RESULTS

The mean age of our prospective cohort was 46.8 years, whereas that of our retrospective cohort was 37.2 years. Gender was evenly distributed across both cohorts. The four parameters with the lowest 95% CI and 2 SD were the distance offsets of the midpoint of the hard palate (A) and the base of the sella turcica (B), the horizontal convergents formed by the tangential line to the hard palate (C), and the line joining the center of the orbital orifice with the internal occipital protuberance (D). In the prospective cohort, good sensitivity (>98%) was attained when two or more parameters were used. Audit using Criterion B+D yielded compliance rates of 76.7%, a figure much closer to that of A+B+C+D (74.8%). From a practical viewpoint, Criterion B+D were most suitable for clinical use and could be simplified to the "3-6-12 rule" as a form of cursory assessment. Verbal instructions in the absence of stringent postural checks only ensured that ~75% of subjects achieved horizontal gaze.

CONCLUSIONS

Fulfillment of Criterion B+D is sufficient to evaluate for horizontal gaze. Further criteria can be added to increase sensitivity. Verbal instructions alone yield high rates of inaccuracy when attempting to image patients in horizontal gaze. Apart from improving methods for obtaining radiographs, a radiological definition of horizontal gaze should be routinely applied for better evaluation of sagittal spinal alignment.

Predictors of Deterioration in Sagittal Balance Following Long Fusion Arthrodesis to L5 in Patients with Adult Scoliosis

Background

The aim of this study was to identify the predictors of deterioration in sagittal balance in patients with adult scoliosis following long fusion arthrodesis to L5.

Material/Methods

A retrospective clinical study included 63 patients with adult scoliosis who underwent long fusion arthrodesis to L5, between February 2005 and May 2015. Radiological imaging values included the angle of lumbar lordosis (LL), and the angle of pelvic incidence (PI). The patients were divided into two cohorts, according to the threshold of average loss of sagittal vertical axis (SVA): a cohort with stable sagittal balance (SSB) and a cohort with deteriorated sagittal balance (DSB). Multivariate logistic regression analysis and the receiver operating characteristic (ROC) curve were used to identify the predictors of clinical outcome.

Results

There were significant differences between the SSB and DSB cohorts in age (p<0.001), preoperative SVA (p<0.001), last follow-up SVA (p<0.001), preoperative LL (p=0.001), last follow-up LL (p<0.001), subsequent L5–S1 disc degeneration (p<0.001) and PI (p=0.028). Patient age >61.5 years (OR=1.251, 95% CI, 1.055–1.484) (P=0.010), preoperative SVA >3.54 cm (OR=1.844, 95% CI, 1.249–2.732) (P=0.002) and preoperative LL <19.0 degrees (OR=0.922, 95% CI, 0.869–0.979) (P=0.008) were identified as predictors of deterioration in sagittal balance.

Conclusions

Deterioration in sagittal balance following long fusion arthrodesis to L5 in patients with adult scoliosis was associated with subsequent L5–S1 disc degeneration and loss of LL, age >61.5 years, preoperative SVA >3.54 cm, and preoperative LL <19.0 degrees.

Predictors for Postoperative Loss of Lumbar Lordosis After Long Fusions Arthrodesis in Patients with Adult Scoliosis

Background

Loss of lumbar lordosis (LL) is closely related to clinical symptoms and operative complications, however, few studies have identified its predictors. The purpose of our study was to identify the predictors for loss of LL in patients with adult scoliosis and provided evidence for surgical decision-making.

Material/Methods

There were 69 patients with adult scoliosis who underwent long fusions arthrodesis from January 2006 to March 2015 included in this retrospectively study. The patients were divided into two cohorts according the average loss of LL: cohort LL (loss of LL below the average) and cohort GL (loss of LL above the average). Multivariate logistic regression analysis and the receiver operating characteristic curve were used to identify the predictors.

Results

There were statistically significant differences between the two cohorts in preoperative LL (p=0.002), postoperative LL (p=0.036), last follow-up LL (p<0.001), postoperative loss LL (p<0.001), preoperative SVA (p=0.007), last follow-up SVA (p=0.018), and pelvic incidence (p=0.016). Preoperative LL <23.5 (OR=0.920, 95% CI=0.870–0.973, p=0.003) and preoperative sagittal vertical axis >4.28 (OR=1.199, 95% CI=1.007–1.429, p=0.041) had good accuracy to predict postoperative loss of LL.

Conclusions

Loss of LL commonly occurred after long fusions arthrodesis in patients with adult scoliosis. Postoperative deteriorated sagittal balance was more frequently than deteriorated coronal balance. Preoperative LL <23.5 and preoperative SVA >4.28 were the predictors for postoperative greater loss of LL in patients after long fusions arthrodesis. More attention should be paid to how to maintain the LL in patients with preoperative predictors, especially if both the identified predictors are present.

Supra-acetabular line is better than supra-iliac line for coronal balance referencing-a study of perioperative whole spine X-rays in degenerative lumbar scoliosis and ankylosing spondylitis patients

BACKGROUND CONTEXT

The aim of spinal deformity correction is to restore the spine's functional alignment by balancing it in both the sagittal and coronal planes. Regardless of posture, the ideal coronal profile is straight, and therefore readily assessable.

PURPOSE

This study compares two radiological methods to determine which better predicts postoperative standing coronal balance.

STUDY DESIGN/SETTING

We conducted a single-center, radiographic comparative study between 2011 and 2015.

PATIENT SAMPLE

A total of 199 patients with a mean age of 55.1 years were studied. Ninety patients with degenerative lumbar scoliosis (DLS) and 109 ankylosing spondylitis (AS) were treated with posterior surgery during this period.

OUTCOME MEASURES

Baseline clinical and radiographic parameters (sagittal and coronal) were recorded. Comparison was performed between the new supra-acetabular line (central sacral vertical line [CSVL1]) and conventional supra-iliac line (CSVL2) perpendicular methods of coronal balance assessment. These methods were also compared with the gold standard standing C7 plumb line.

METHODS

Each patient underwent standardized operative procedures and had perioperative spine X-rays obtained for assessment of spinal balance. Adjusted multivariate analysis was used to determine predictors of coronal balance.

RESULTS

Significant differences in baseline characteristics (age, gender, and radiographic parameters) were found between patients with DLS and AS. CSVL1, CSVL2, and C7 plumb line differed in all the perioperative measurements. These three radiological methods showed a mean right coronal imbalance for both diagnoses in all pre-, intra-, and postoperative radiographs. The magnitude of imbalance was the greatest for CSVL2 followed by CSVL1 and subsequently the C7 plumb line. A larger discrepancy between CSVL and C7 plumb line measurements intraoperatively than those postoperatively suggests a postural effect on these parameters, which is greater for CSVL2. Multivariate analysis identified that in DLS, the preoperative C7 plumb line was predictive of its postoperative value. CSVL1, but not CSVL2, was predictive of the postoperative C7 plumb line in patients with AS.

CONCLUSIONS

The supra-acetabular line (CSVL1) is better, although not ideal, as compared with the supra-iliac line (CSVL2) in determining coronal balance. Because CSVL1 still cannot be relied on with a high predictive value, it is imperative that future studies continue to identify better intraoperative markers for achieving coronal balance.

Effectiveness of deformity-correction surgery for primary degenerative sagittal imbalance: a meta-analysis

OBJECTIVE

As life expectancy continues to increase, primary degenerative sagittal imbalance (PDSI) is diagnosed in an increasing number of elderly people. Although corrective surgery for this sagittal deformity is becoming more popular, the effectiveness of the procedure remains unclear. The authors aimed to collate the available evidence on the effectiveness and complications of deformity-correction surgery in patients with PDSI.

METHODS

The authors carried out a meta-analysis of clinical studies regarding deformity correction in patients with PDSI. The studies were identified through searches of the PubMed, Embase, Web of Science, and Cochrane databases. Surgery outcomes were evaluated and overall treatment effectiveness was assessed in terms of the minimum clinically important difference (MCID) in Oswestry Disability Index (ODI) values and pain levels according to visual analog scale (VAS) scores and in terms of restoration of spinopelvic parameters to within a normal range. Data are expressed as mean differences with 95% CIs.

RESULTS

Ten studies comprising 327 patients were included. The VAS and ODI values improved after deformity-correction surgery. The smallest treatment effect exceeded the MCID for VAS values (4.15 [95% CI 3.48–4.82]) but not for ODI values (18.11 [95% CI 10.99–25.23]). At the final follow-up visit, the mean lumbar lordosis angle (−38.60° [95% CI −44.19° to −33.01°]), thoracic kyphosis angle (31.10° [95% CI 24.67°–37.53°]), C-7 sagittal vertical axis (65.00 mm [95% CI 35.27–94.72 mm]), and pelvic tilt angle (30.82° [95% CI 24.41°–37.23°]) remained outside their normal ranges. Meta-regression analyses revealed a significant effect of ODI change in relation to lumbar lordosis change (p = 0.004). After a mean of 2 years after deformity correction, the mean lumbar lordosis angle and C-7 sagittal vertical axis decreased by 5.82° and 38.91 mm, respectively, and the mean thoracic kyphosis angle increased by 4.7°. The incidences of proximal junctional kyphosis and pseudarthrosis were 23.7% and 12.8%, respectively.

CONCLUSIONS

Deformity correction substantially relieves back pain for about 2 years in adult patients with PDSI. Sufficient surgical restoration of lumbar lordosis can lead to substantial improvement in patient disability and reduced decompensation. Deformity correction represents a viable therapeutic option for patients with PDSI, but further technical advancements are necessary to achieve sufficient lumbar lordosis and reduce complication rates.

'Lumbar Degenerative Kyphosis' Is Not Byword for Degenerative Sagittal Imbalance: Time to Replace a Misconception

Lumbar degenerative kyphosis (LDK) is a subgroup of the flat-back syndrome and is most commonly caused by unique life styles, such as a prolonged crouched posture during agricultural work and performing activities of daily living on the floor. Unfortunately, LDK has been used as a byword for degenerative sagittal imbalance, and this sometimes causes confusion. The aim of this review was to evaluate the exact territory of LDK, and to introduce another appropriate term for degenerative sagittal deformity. Unlike what its name suggests, LDK does not only include sagittal balance disorder of the lumbar spine and kyphosis, but also sagittal balance disorder of the whole spine and little lordosis of the lumbar spine. Moreover, this disease is closely related to the occupation of female farmers and an outdated Asian life style. These reasons necessitate a change in the nomenclature of this disorder to prevent misunderstanding. We suggest the name “primary degenerative sagittal imbalance” (PDSI), which encompasses degenerative sagittal misalignments of unknown origin in the whole spine in older-age patients, and is associated with back muscle wasting. LDK may be regarded as a subgroup of PDSI related to an occupation in agriculture. Conservative treatments such as exercise and physiotherapy are recommended as first-line treatments for patients with PDSI, and surgical treatment is considered only if conservative treatments failed. The measurement of spinopelvic parameters for sagittal balance is important prior to deformity corrective surgery. LDK can be considered a subtype of PDSI that is more likely to occur in female farmers, and hence the use of LDK as a global term for all degenerative sagittal imbalance disorders is better avoided. To avoid confusion, we recommend PDSI as a newer, more accurate diagnostic term instead of LDK.