What factors are associated with a better restoration of pelvic version after adult spinal deformity surgery?

INTRODUCTION

Poor restoration of pelvic version after adult spinal deformity (ASD) surgery is associated with an increased risk of mechanical complications and worse quality of life. We studied the factors linked to the improvement of postoperative pelvic version.

MATERIALS AND METHODS

This is a retrospective analysis of a prospective multicenter ASD database. Selection criteria were: operated patients having preoperative severe pelvic retroversion as per GAP score (Relative Pelvic Version-RPV < - 15°); panlumbar fusions to the pelvis; 2-year follow-up. Group A comprised patients with any postoperative improvement of RPV score, and group B had no improvement. Groups were compared regarding baseline characteristics, surgical factors, and postoperative sagittal parameters. Parametric and non-parametric analyses were employed.

RESULTS

177 patients were studied, median age 67 years (61; 72.5), 83.6% female. Groups were homogeneous in baseline demographics, comorbidities, and preoperative sagittal parameters (p > 0.05). The difference in RPV improvement was 11.56º. Group A (137 patients) underwent a higher percentage of ALIF procedures (OR = 6.66; p = 0.049), and posterior osteotomies (OR = 4.96; p < 0.001) especially tricolumnar (OR = 2.31; p = 0.041). It also showed a lower percentage of TLIF procedures (OR = 0.45; p = 0.028), and posterior decompression (OR = 0.44; p = 0.024). Group A displayed better postoperative L4-S1 angle and relative lumbar lordosis (RLL), leading to improved sacral slope (and RPV), and global alignment (RSA). Group A patients had longer instrumentations (11.45 vs 10; p = 0.047) and hospitalization time (13 vs 11; p = 0.045). All postoperative sagittal parameters remained significantly better in group A through follow-up. However, differences between the groups narrowed over time.

CONCLUSIONS

ALIF procedures and posterior column osteotomies improved pelvic version postoperatively, and associated better L4-S1 and lumbar lordosis restoration, indirectly improving all other sagittal parameters. However, these improvements seemed to fade during the 2-year follow-up.

The influence of pelvic tilt on sacral insufficiency fracture occurrence: Insights into the prevalence of high pelvic tilt among patients affected

INTRODUCTION

Fragility fractures without significant trauma of the pelvic ring in older patients have an increasing incidence due to demographic change. Influencing factors other than osteoporotic bone quality that lead to an insufficiency fracture are not yet known. However, it is suspected that the pelvic tilt (PT) has an effect on the development of such an insufficiency fracture. This study explores the influence of the PTs in patients with insufficiency fractures of the posterior pelvic ring.

MATERIALS AND METHODS

A total of 49 geriatric patients with fragility fractures of the pelvic ring were treated at a university hospital level-1 trauma center during a period between February and December 2023, and their fractures were classified according to the FFP classification of Rommens and Hofmann. Complete sets of computer tomography (CT) and radiological images were available to determine the PT angle of the patients.

RESULTS

34 FFP type 2 and 15 FFP type 3 classified patients were included in the study. Significant difference was seen in the pelvic tilt (PT) angle between the patient group with insufficiency fractures (n= 49; mean age: 78.02 ± 11.80) and the control group with lumbago patients (n= 53; mean age: 69.23 ± 11.23). The PT was significantly higher in the patients with insufficiency fractures (25.74° ± 4.76; p⁎⁎⁎⁎ ≤ 0.0001).

CONCLUSIONS

The study demonstrates a significant extension of the PT angle of individuals with insufficiency fractures when compared to those with lumbago. The result suggests a potential association between pelvic tilt and fracture susceptibility.

TRIAL REGISTRATION

A retrospective study about the influence of sagittal balance of the spine on insufficiency fractures of the posterior pelvic ring measured by the "pelvic tilt angle", DRKS00032120. Registered 20th June 2023 - Prospectively registered. Trial registration number DRKS00032120.

Relationship between spinal structural damage and sagittal balance in axial spondyloarthritis: Is the thoracic spine the starting point?

OBJECTIVES

To assess the relationship between spinal structural damage, sagittal balance parameters and spine curvatures in patients with axial spondyloarthritis (axSpA).

MATERIAL AND METHODS

In this cross-sectional study, the pelvic and sagittal balance parameters were obtained through EOS® (Biospace, Paris, France). Patients were divided into three groups according to the modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS) tertiles (G1 ≤6, n = 36; G2: 6.1-31, n = 36; G3 >31, n = 35) and pelvic and sagittal parameters were compared across them. Multivariable regression analysis was performed to analyze the impact of spinal structural damage and of other factors on sagittal vertical axis (SVA), an important sagittal balance parameter.

RESULTS

A total of 107 patients was included. G2 and 3 exhibited higher mean values of thoracic kyphosis T1-T12 when compared to G1 (10.5°(12.3) vs. 22.3°(17.3) vs. 35.2°(14.6), p < 0.001), and G3 demonstrated lumbar L1-S1 straightening compared to the other groups (55.7°(9) and 50.7°(19.8), G1 and G2, respectively, vs. 35.7°(13.2), p < 0.001). Mean SVA values showed an increasing gradient from G1 to G3 (21.6(25.1) vs. 41(44.3) vs. 84.3(47.2)mm, p < 0.001). In the multivariable regression, a one-unit increase in total mSASSS was associated with an average 0.8 mm higher SVA.

CONCLUSIONS

Our data showed that more spinal structural damage is associated with a higher SVA, reflecting poorer sagittal balance. Patients with increasing spinal damage have an important increase in thoracic kyphosis suggesting that postural modifications in patients with axSpA might have their origin in the thoracic spine.

Correlation between sagittal parameters and disability of patients with nonspecific chronic low back pain: a cross-sectional study of 435 subjects

BACKGROUND CONTEXT

Sagittal parameters are significantly correlated with health-related quality of life (HRQoL) in adult spinal deformity patients. Their association with HRQoL in patients with nonspecific chronic low back pain (NSCLBP) is unclear.

PURPOSE

To analyze the correlation between sagittal parameters and disability in NSCLBP patients.

DESIGN

A cross-sectional study.

PATIENT SAMPLE

Subjects included 435 patients with NSCLBP divided into low disability and high disability groups.

OUTCOME MEASURES

Function was measured using the Oswestry Disability Index (ODI). Pain intensity was measured using the Numeric Rating Scale (NRS) and HRQoL was measured using 36-item Short Form Health Survey (SF-36).

METHODS

Sagittal parameters, demographic data, ODI, SF-36 eight-dimensional scores and NRS scores of patients with NSCLBP were collected. Taking ODI=20 as the cut-off value, patients were divided into low disability group (ODI≤20) and high disability group (ODI>20), and ODI were converted to Ranked ODI (RODI) accordingly. Univariate analysis of the correlation among age, gender, body mass index (BMI), sagittal parameters, RODI, SF-36 eight-dimensional scores, NRS scores were then conducted. The variables related to RODI were analyzed by logistic regression to discover their independent influence on RODI. p<.05 was considered to indicate statistical significance.

RESULTS

A total of 435 patients with NSCLBP were included. Univariate correlation analysis showed that the correlation coefficients between age, sacral slope-pelvic tilt (SS-PT), spinosacral angle (SSA) and RODI were (r=0.126, p<.01), (r=-0.115, p<.05), (r=-0.116, p<.05), respectively. The logistic regression analysis indicated that the regression coefficients of age and SSA were 0.030 (p=.001), -0.044 (p=.002), respectively, and the odds ratio and 95% confidence interval (CI) were 1.031 (1.012, 1.050), 0.957 (0.930, 0.985).

CONCLUSIONS

Age and SSA are independent factors for disability of NSCLBP. SSA can comprehensively reflect the sagittal balance of the spine of patients with NSCLBP. Decreased SSA represents poor sagittal balance, which will increase the disability of NSCLBP.

Defining threshold for sagittal correction in lumbar fractures

PURPOSE

Surgical indications for thoraco-lumbar fractures are driven both by neurological status, fractures instability and kyphotic deformity. Regarding kyphotic deformity, an angulation superior to 20° is considered by many surgeons as a surgical indication to reduce the disability induced by post-traumatic kyphosis. However, there is a lack of data reporting the ideal or theoretical lordosis that one must have in a particular lumbar segment on CT-scan. The main goal of this study was to determine the mean value for segmental lumbar lordosis according to pelvic incidence (PI) on a cohort of normal subjects.

METHODS

The consecutive CT-scan of 171 normal adult subjects were retrospectively analyzed. The PI and the segmental lordosis (L4S1, L3L5, L2L4, L3L1, L2T12 and T11-L1) were measured on all CT-scan. The mean values were calculated for the global cohort and a sub-group analysis according to IP ranges (< 45°, 45 < IP < 60° and > 60°) was performed.

RESULTS

The mean angular values for the whole cohort were IP: 54, 9°; L4S1: - 38, 1°; L3L5: - 30, 6°; L2L4: - 14, 1°; L1L3: - 4, 9°; T12L2: + 1, 9° and T11L1: + 5, 4°. The segmental values vary significatively with PI ranges, as for L3L5: - 26, 8° (PI < 45°); - 30° (45 < PI < 60°) and - 35, 1° (PI > 60°).

CONCLUSION

These results provide a referential of theoretical values of segmental lordosis according to PI. This abacus may help spinal surgeon in their decision-making process regarding lumbar fractures, to determine the amount of sagittal correction needed, according to the PI range, to be adapted to the sagittal morphology of the patient.

LEVEL OF EVIDENCE

III.

Microendoscopic Tailored Spine Decompression as a Less-Invasive, Stability-Preserving Surgical Option to Instrumented Correction in Complex Spine Deformities: A Preliminary Multicenter Experience

OBJECTIVES

The aim of this study was to explore the effectiveness of a less-invasive posterior spine decompression in complex deformities. We studied the potential advantages of the microendoscopic approach, supplemented by the piezoelectric technique, to decompress both sides of the vertebral canal from a one-sided approach to preserve spine stability, ensuring adequate neural decompression.

METHODS

A series of 32 patients who underwent a tailored stability-preserving microendoscopic decompression for lumbar spine degenerative disease was retrospectively analyzed. The patients underwent selective bilateral decompression via a monolateral approach, without the skeletonization of the opposite side. For omo- and the contralateral decompression, we used a microscopic endoscopy-assisted approach, with the assistance of piezosurgery, to work safely near the exposed dura mater. Piezoelectric osteotomy is extremely effective in bone removal while sparing soft tissues.

RESULTS

In all patients, adequate decompression was achieved with a high rate of spine stability preservation. The approach was essential in minimizing the opening, therefore reducing the risk of spine instability. Piezoelectric osteotomy was useful to safely perform the undercutting of the base of the spinous process for better contralateral vision and decompression without damaging the exposed dura. In all patients, a various degree of neurologic improvement was observed, with no immediate spine decompensation.

CONCLUSIONS

In selected cases, the tailored microendoscopic monolateral approach for bilateral spine decompression with the assistance of piezosurgery is adequate and safe and shows excellent results in terms of spine decompression and stability preservation.

Analysis of Spinopelvic Parameters and Lumbar Lordosis in Patients with Transitional Lumbosacral Vertebrae, with Special Reference to Sacralization and Lumbarization

BACKGROUND

Transitional lumbosacral vertebra presents in 2 forms based on its origin: sacralization and lumbarization. These patients have 2 options for sacral endplates (upper and lower) and consequently, 2 sets of values for spinopelvic parameters and lumbar lordosis (LL). This study aimed to evaluate these parameters in asymptomatic patients with sacralization and lumbarization and compare them with each other and normative values.

METHODS

Spinopelvic parameters and LL according to upper and lower endplate were measured using abdominal computed tomography in 1420 asymptomatic patients, of which 108 had Transitional lumbosacral vertebra. These parameters were compared among patients with lumbarization and sacralization and with normal controls. In addition, correlations between the upper and lower endplate parameters were determined.

RESULTS

As compared to the control group, upper endplate measurements yielded lower spinopelvic parameters and LL values while lower endplate values yielded higher values. While these values were significantly different from normative values, these parameters were similar in both lumbarization and sacralization groups. Furthermore, most spinopelvic parameters of both upper and lower endplates were strongly correlated, and the differences between the upper and lower PI and LL values are relatively constant (27° and 14°, respectively.

CONCLUSIONS

Upper and lower endplate parameters are comparable in patients with sacralization and lumbarization; therefore, the average spatial position of a sacralized L5 and a lumbarized S1 within the pelvis is similar and either parameter can be used for radiological measurements. Further studies with symptomatic patients are warranted to confirm these results.

Lumbar reconstruction with hyperlordotic cages: Prediction of neuroforaminal height in comparison to established age and sex dependent reference values

Interbody cages are routinely used in lumbar reconstruction surgery of deformity cases for restoration of lordosis and sagittal balance of the spine. However, if hyperlordotic implants are inserted into the intervertebral space, special consideration has to be taken concerning the height of the neural foramen during cage implantation. The greater the lordotic angle of the cage is, the higher the posterior size of the cage needs to be in order to avoid neuroforaminal nerve root impingement. In this technical communication, we propose and clinically validate a stepwise mathematic model to predict neuroforaminal height in patients undergoing lumbar reconstruction with hyperlordotic cages. The length of the superior and inferior vertebral end plates including the height of the neural foramen are measured before implantation of the cage in standing sagittal view x-rays. By assumption of an isosceles triangle in combination with the posterior height and the lordotic angle of the cage, the neuroforaminal height after cage implantation can be estimated. By comparison of the predicted neuroforaminal height with age and sex dependent reference values, nerve root impingement can be avoided by selection of the necessary posterior height of the hyperlordotic cage while still gaining sufficient lumbar lordosis.

Knee flexion compensation in postoperative adult spinal deformity patients: implications for sagittal balance and clinical outcomes

PURPOSE

To determine whether maintaining good sagittal balance with significant knee flexion (KF) constitutes a suboptimal outcome after adult spinal deformity (ASD) correction.

METHODS

This single-center, single-surgeon retrospective study, assessed ASD patients who underwent posterior spinal fusion between 2014 and 2020. Inclusion criteria included meeting at least one of the following: PI-LL ≥ 25°, T1PA ≥ 20°, or CrSVA-H ≥ 2 cm. Those with lower-extremity contractures were excluded. Patients were classified into four groups based on their 6-week postoperative cranio-hip balance and KF angle, and followed for at least 2 years: Malaligned with Knee Flexion (MKF+) (CrSVA-H > 20 mm + KFA > 10), Malaligned without Knee Flexion (MKF-) (CrSVA-H > 20 mm + KFA < 10), Aligned without Knee Flexion (AKF-) (CrSVA-H < 20 mm + KFA < 10), and Aligned with Knee Flexion (AKF+) (CrSVA-H < 20 mm + KFA > 10). The primary outcomes of this study included one and two year reoperation rates. Secondy outcomes included clinical and patient reported outcomes.

RESULTS

263 patients (mean age 60.0 ± 0.9 years, 74.5% female, and mean Edmonton Frailty Score 3.3 ± 0.2) were included. 60.8% (160/263 patients) exhibited good sagittal alignment at 6-week postop without KF. Significant differences were observed in 1-year (p = 0.0482) and 2-year reoperation rates (p = 0.0374) across sub-cohorts, with the lowest and highest rates in the AKF- cohort (5%, n = 8) and MKF + cohort (16.7%, n = 4), respectively. Multivariable Cox regression demonstrated the AKF- cohort exhibited significantly better reoperation outcomes compared to other groups: AKF + (HR: 5.24, p = 0.025), MKF + (HR: 31.7, p < 0.0001), and MKF- (HR: 11.8, p < 0.0001).

CONCLUSION

Our findings demonstrate that patients relying on knee flexion compensation in the early postoperative period have inferior outcomes compared to those achieving sagittal balance without knee flexion. When compared to malaligned patients, those with CrSVA-H < 20 mm and KFA > 10 degrees experience fewer early reoperations but similar delayed reoperation rates. This insight emphasizes the importance of considering knee compensation perioperatively when managing sagittal imbalance in clinical practice.

How the hip-spine relationship influences total hip arthroplasty

INTRODUCTION

Motion in the spine, pelvis and hips which make up the spinopelvic femoral complex (SPFC) implies mechanical relationships that help maintain trunk balance and optimize hip functionThe aim of this study was to understand the physiology of the SPFC and evaluate the dysfunctions of the SPFC and their implications for total hip arthroplasty considering the hip-spine relationship.

METHODS

A review of relevant and comprehensive studies on this subject is reported in order to highlight a pathophysiology that integrates the description of the evaluations of the spine-pelvic and hip parameters and recommendations for the kinematic planning of the THA procedure. The primary objective was to determine which type of hip-spine relationship has the highest risk for THA complications and to become proficient in selecting the priority surgical intervention when both the hip and spine are affected. Finally, this review attempted to assist hip surgeons with surgical technique, tools, implant selection, and goals of planning a THA that requires personalized kinematic alignment. Determine the influence of THA on these kinematics and the effect of stiffness of the lumbopelvic complex on the risk of THA failure.

RESULTS

When a person sits, the pelvis goes into retroversion and the acetabulum opens forward. This frees the femoral head and neck to allow hip flexion. The opposite - pelvic anteversion - occurs when a person stands. When pelvic mobility is limited, the hip must increase its range of motion to accommodate these posture changes. Disturbances in spinal and pelvic kinematics lead to abnormal hip function, which may contribute to complications following total hip arthroplasty (THA).

CONCLUSION

A precise evaluation of the parameters governing the SPFC must be taken into account in order to best optimize the placement and choice of THA implants.

LEVEL OF EVIDENCE

IV.

Adult spinal deformity correction surgery using age-adjusted alignment thresholds: clinical outcomes and mechanical complication rates. A systematic review of the literature

PURPOSE

Adult spinal deformity (ASD) surgery gives good clinical outcomes but has a high rate of mechanical complications (MC). In 2016, Lafage described the age-adjusted alignment thresholds (AAAT) to adapt the correction in relation to patient's age proposing less aggressive corrections for the elderly population. The aim of this review was to clarify the effectiveness of AAAT to achieve good health-related quality of life (HRQoL) and their relationship with post-operative MC.

MATERIALS AND METHODS

We performed a review of the literature, including articles reporting data on post-operative HRQoL and MC rates in relation to the AAAT. Data were stratified according to whether they matched the AAAT, dividing the population in undercorrected (U), matched (M) and overcorrected (O). The quality of the included studies was assessed using the GRADE and MINORS systems.

RESULTS

Six articles reporting data from 1,825 patients were included. The different categories (U, M and O) had homogeneous pre-operative sagittal parameters (p > 0.05) that became statistically different after surgeries (p < 0.05). Proximal junctional kyphosis (PJK) was more frequent in the O group compared to U (p = 0.05). Post-operative HRQoL parameters were similar in the 3 groups (p > 0.05). The quality of the included studies was generally low with a high bias risk.

CONCLUSION

The results extrapolated from this review are interesting, as for the same HRQoL the U group had a lower MC rate. Unfortunately, the results are inconsistent, mainly because of the low quality of the included studies and the lack of reporting of some important patient- and surgery-related factors.

Deep learning algorithm for fully automated measurement of sagittal balance in adult spinal deformity

AIM

Deep learning (DL) algorithms can be used for automated analysis of medical imaging. The aim of this study was to assess the accuracy of an innovative, fully automated DL algorithm for analysis of sagittal balance in adult spinal deformity (ASD).

MATERIAL AND METHODS

Sagittal balance (sacral slope, pelvic tilt, pelvic incidence, lumbar lordosis and sagittal vertical axis) was evaluated in 141 preoperative and postoperative radiographs of patients with ASD. The DL, landmark-based measurements, were compared with the ground truth values from validated manual measurements.

RESULTS

The DL algorithm showed an excellent consistency with the ground truth measurements. The intra-class correlation coefficient between the DL and ground truth measurements was 0.71-0.99 for preoperative and 0.72-0.96 for postoperative measurements. The DL detection rate was 91.5% and 84% for preoperative and postoperative images, respectively.

CONCLUSION

This is the first study evaluating a complete automated DL algorithm for analysis of sagittal balance with high accuracy for all evaluated parameters. The excellent accuracy in the challenging pathology of ASD with long construct instrumentation demonstrates the eligibility and possibility for implementation in clinical routine.

Impact of deep brain stimulation therapy on the vertebral sagittal balance in Parkinson's disease patients

Parkinson's disease (PD) is characterized by cardinal motor signs: 4-6 Hz resting tremor, rigidity, and bradykinesia. In addition, 3-18% of PD patients have camptocormia, an abnormal forward flexion of the thoracolumbar spine, which may have a negative impact on patients' quality of life. Different possible treatments have been suggested for such a condition, but no one is resolutive. This study aims to define the possible impact of DBS, with selective targeting on the dorsal-lateral region of the STN, on the sagittal balance of patients affected by PD. Among all patients that have undergone DBS procedures in our institution, we selected eight subjects, four females and four males, with selective targeting on the dorsal-lateral region of the subthalamic nucleus (STN) because of camptocormia and other severe postural changes. Radiological assessments of spinal balance parameters before surgery and at 6 and 12 months postoperatively were carried out. Comparison of preoperative and postoperative spine X-ray data showed a statistically significant improvement in dorsal kyphosis angle (D-Cobb) 12 months after the operation. Deep brain stimulation with selective targeting of the dorsal lateral part of the STN may induce changes of the posture in patients with Parkinson's disease 12 months after the operation, which appears to improve in this small sample size, but larger observational and controlled trials would be required to confirm this observation.

Effect of lumbosacral transitional vertebrae on sagittal balance of lumbo-pelvic complexity assessed by quantitative whole-body CT imaging

Background

The variation at the lumbosacral junction certainly results in occult alignment changes in the lumbo-pelvic complexity (LPC). This retrospective case-control study aims to investigate the influences of lumbosacral transitional vertebrae (LSTV) on sagittal lumbo-pelvic balance assessment and provide some recommendations for preoperative imaging evaluation.

Methods

Based on whole-body computed tomography (CT) images, a total of 210 individuals with complete segmentation anomalies of LSTV were included and divided into 23 presacral vertebrae (PSV) (sacralization, n=102), 25 PSV (lumbarization, n=108). The control group with 24 PSV (normal, n=100) was matched by age and gender. Sagittal lumbo-pelvic parameters including pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), sacral table angle (STA), sacral kyphosis (SK), and pelvic radius (PR) were measured at the ontogenetical S1 (Ontog S1) level and the morphological S1 (Morph S1), respectively. These parameters were compared using t-test, Kruskal-Wallis H test and post hoc test. Spearman's rank correlation coefficient and linear regression were used to investigate the association of lumbo-pelvic parameters with LSTV types and measurement levels.

Results

All the parameters at the Ontog S1 differed significantly from those at the Morph S1 (all P<0.001). At the Ontog S1 level, PI, PT, SS, and LL were negatively correlated with vertebrae counts; SK and PR were positively correlated with vertebrae counts (all P<0.001). Instead, reverse results were obtained at the Morph S1 level. The measurement level and vertebrae counts were independent influence factors for the measurement of PI, PT, SS, SK, and PR (all P<0.05). Compared with the measured values of the matched controls, the variability of most lumbo-pelvic parameters (PI, SS, LL, STA, SK, PR values of 25 PSV subgroup, and PI, PT, SS, LL, STA values of 23 PSV subgroup) at the Morph S1 level were significantly smaller than that at the Ontog S1. The measurements of PT, SS, LL, and PR were less influenced by the measurement level and vertebrae counts than those of PI and SK.

Conclusions

Morph S1 is more recommended for the measurements of most lumbo-pelvic parameters in patients with LSTV. The parameters (PT, SS, LL, STA, PR) are shown more stable and recommended to help reduce the effects caused by LSTV.

Correction of Spinal Sagittal Alignment after Posterior Lumbar Decompression: Does Severity of Central Canal Stenosis Matter?

STUDY DESIGN

This study adopted a retrospective study design.

PURPOSE

Our study aimed to investigate the impact of central canal stenosis severity on surgical outcomes and lumbar sagittal correction after lumbar decompression.

OVERVIEW OF LITERATURE

Studies have evaluated sagittal correction in patients with central canal stenosis after lumbar decompression and the association of stenosis severity with worse preoperative sagittal alignment. However, none have evaluated the impact of spinal stenosis severity on sagittal correction.

METHODS

Patients undergoing posterior lumbar decompression (PLD) of ≤4 levels were divided into severe and non-severe central canal stenosis groups based on the Lee magnetic resonance imaging (MRI) grading system. Patients without preoperative MRI or inadequate visualization on radiographs were excluded. Surgical characteristics, clinical outcomes, and sagittal measurements were compared. Multivariate logistic regression was performed to determine the predictors of pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), and pelvic incidence minus lumbar lordosis (PI-LL).

RESULTS

Of the 142 patients included, 39 had severe stenosis, and 103 had non-severe stenosis. The mean follow-up duration for the cohort was 4.72 months. Patients with severe stenosis were older, had higher comorbidity indices and levels decompressed, and longer lengths of stay and operative times (p <0.001). Although those with severe stenosis had lower lordosis, lower SS, and higher PI-LL mismatch preoperatively, no differences in Delta LL, SS, PT, or PI-LL were observed between the two groups (p >0.05). On multivariate regression, severe stenosis was a significant predictor of a lower preoperative LL (estimate=-5.243, p =0.045) and a higher preoperative PI-LL mismatch (estimate=6.192, p =0.039). No differences in surgical or clinical outcomes were observed (p >0.05).

CONCLUSION

Severe central lumbar stenosis was associated with greater spinopelvic mismatch preoperatively. Sagittal balance improved in both patients with severe and non-severe stenosis after PLD to a similar degree, with differences in sagittal parameters remaining after surgery. We also found no differences in postoperative outcomes associated with stenosis severity.

Prone Transpsoas Lateral Interbody Fusion (PTP LIF) with Anterior Docking: Preliminary functional and radiographic outcomes

Background

Disadvantages of lateral interbody fusion (LIF) through a direct, transpsoas approach include difficulties associated with lateral decubitus positioning and limited sagittal correction without anterior longitudinal ligament release or posterior osteotomy. Prior technical descriptions advocate anchoring or docking the retractor into the posterior to middle aspect of the disc space.

Methods

72 patients who underwent 116 total levels of Prone Transpsoas (PTP) LIF with anterior docking with a single surgeon between December 2021 and May 2023 were included. Patient characteristics, perioperative data, as well as postoperative functional and radiographic outcomes were recorded. Subgroup analysis was performed for patients who underwent single-level PTP LIF with single-level percutaneous fixation (SLP). Patients in the SLP subgroup did not undergo direct decompression, release, or osteotomy.

Results

N=41 (56.9%) of cases included the L4-5 level. No vascular, bowel, or other visceral complications occurred. No patients developed a permanent motor deficit. Both the total cohort and the SLP group demonstrated statistically significant improvements in functional outcomes including Oswestry Disability Index (ODI) and Visual Analog Scale (VAS) as well as all radiographic parameters measured. Mean total operative time (incision to completion of closure for lateral and posterior fusion) in the SLP group was 104.3 minutes with a significant downward trend with increasing surgeon experience. The SLP group demonstrated a 9.9° increase in segmental lordosis (SL), a 7.5° increase in lumbar lordosis (LL), 5.3° reduction in pelvic tilt (PT), and a decrease in pelvic incidence - lumbar lordosis mismatch (PI-LL) from 11.0° preoperatively to 3.9°, postoperatively (p<.01).

Conclusions

PTP LIF with anterior docking may address shortcomings associated with traditional lateral interbody fusion by producing safe and reproducible access with improved restoration of segmental lordosis and optimization of spinopelvic parameters.

Functional outcomes correlate with sagittal spinal balance in degenerative lumbar spondylolisthesis surgery

BACKGROUND CONTEXT

Degenerative lumbar spondylolisthesis (DLS) is a debilitating condition associated with poor preoperative functional status. Surgical intervention has been shown to improve functional outcomes in this population though the optimal surgical procedure remains controversial. The importance of maintaining and/or improving sagittal and pelvic spinal balance parameters has received increasing interest in the recent DLS literature. However, little is known about the radiographic parameters most associated with improved functional outcomes among patients undergoing surgery for DLS.

PURPOSE

To identify the effect of postoperative sagittal spinal alignment on functional outcome after DLS surgery.

STUDY DESIGN

Retrospective cohort study.

PATIENT SAMPLE

Two-hundred forty-three patients in the Canadian Spine Outcomes and Research Network (CSORN) prospective DLS study database.

OUTCOME MEASURES

Baseline and 1-year postoperative leg and back pain on the 10-point Numeric Rating Scale and baseline and 1-year postoperative disability on the Oswestry Disability Index (ODI).

METHODS

All enrolled study patients had a DLS diagnosis and underwent decompression in isolation or with posterolateral or interbody fusion. Global and regional radiographic alignment parameters were measured at baseline and 1-year postoperatively including sagittal vertical axis (SVA), pelvic incidence and lumbar lordosis (LL). Both univariate and multiple linear regression was used to assess for the association between radiographic parameters and patient-reported functional outcomes with adjustment for possible confounding baseline patient factors.

RESULTS

Two-hundred forty-three patients were available for analysis. Among participants, the mean age was 66 with 63% (153/243) female with the primary surgical indication of neurogenic claudication in 197/243 (81%) of patients. Worse pelvic incidence-LL mismatch was correlated with more severe disability [ODI, 0.134, p<.05), worse leg pain (0.143, p<.05) and worse back pain (0.189, p<.001) 1-year postoperatively. These associations were maintained after adjusting for age, BMI, gender, and preoperative presence of depression (ODI, R2 0.179, β, 0.25, 95% CI 0.08, 0.42, p=.004; back pain R2 0.152 (β, 0.05, 95% CI 0.022, 0.07, p<.001; leg pain score R2 0.059, β, 0.04, 95% CI 0.008, 0.07, p=.014). Likewise, reduction of LL was associated with worse disability (ODI, R2 0.168, β, 0.04, 95% CI -0.39, -0.02, p=.027) and worse back pain (R2 0.135, β, -0.04, 95% CI -0.06, -0.01, p=.007). Worsened SVA correlated with worse patient reported functional outcomes (ODI, R2 0.236, β, 0.12, 95% CI 0.05, 0.20, p=.001). Similarly, an increase (worsening) in SVA resulted in a worse NRS back pain (R2 0.136, β, 0.01, 95% CI .001, 0.02, p=.029) and worse NRS leg pain (R2 0.065, β, 0.02, 95% CI 0.002, 0.02, p=.018) scores regardless of surgery type.

CONCLUSIONS

Preoperative emphasis on regional and global spinal alignment parameters should be considered in order to optimize functional outcome in lumbar degenerative spondylolisthesis treatment.

Variation of cervical sagittal alignment parameters according to age and pelvic incidence in degenerative spinal deformity patients

INTRODUCTION

In asymptomatic subjects, variations of cervical sagittal alignment parameters according to age and spinopelvic organization have been reported. A large range of compensation phenomena has been observed in degenerative spinal deformity in order to maintain horizontal gaze, but it remains unclear how age and spinopelvic morphology could additionally influence cervical alignment. The aim of this observational retrospective study was to describe the distribution of cervical sagittal alignment parameters according to age and pelvic incidence in subjects with and without degenerative spinal deformity in order to precisely evaluate cervical compensation phenomena in adult spinal deformity (ASD).

MATERIAL AND METHODS

Radiographs of 478 subjects (327 females and 151 males) were distributed into 235 asymptomatic and 243 deformed subjects. Occipito-cervical parameters were McGregor-C1, McGregor-C2, C1-C2 and occipito-C2 angles. The cervicothoracic inflection point (CTIP) was determined. Caudal cervical sagittal alignment parameters were: C2-C7 lordosis, C2-apex (superior arch), apex-CTIP (inferior arch), occipito-C3 and occipito-C4 angles, C7-slope and T1-slope. The distribution of parameters was analyzed using a Bayesian inference (significant when Pr > 0.975 or Pr < 0.025). Comparisons between asymptomatic and deformed subjects were done after matching on age (40-60 years; > 60 years) and on PI (< 45°; 45-60°; > 60°).

RESULTS

Among occipito-cervical parameters, there was no significant change in McGregor-C1 angle. However, McGregor-C2 angle was significantly higher in the ASD group (Pr = 0.0029), with influence of age (Pr = 0.023), but PI influence. C1-C2 lordosis was significantly higher in the ASD group compared to the asymptomatic group (Pr < 0.0007), without influence of age or PI noticed. C2-C7 lordosis was also higher in the ASD group (Pr < 0.025) with a role of age and PI (Pr < 0.025). Cervical lordosis in the superior arch was significantly higher in the ASD group (Pr > 0.999), without influence of age or PI. In the inferior arch, the lordosis angle was not modified according to the group, but there was an influence of age (Pr < 0.0007). C7-slope and T1-slope were higher according the age group (Pr < 0.0012), without influence of the group or PI.

CONCLUSION

This observational study highlights cervical sagittal alignment adaptations in degenerative spinal deformity, matched on age and pelvic incidence. The inferior cervical spine seemed to be modified with a higher lordosis, increasing with age responding to the age-related thoracic kyphosis increase. In addition to that, the superior cervical spine hyperextends more in adult degenerative deformity to maintain horizontal gaze.

LEVEL OF EVIDENCE

III.

Sagittal balance parameters in achondroplasia

Introduction

Lumbar spinal stenosis (LSS) is the main problem for adult achondroplasia (Ach). Sagittal imbalance of the spine may play a role in LSS causing neurogenic claudication in Ach patients.

Research question

The purpose of this study is to describe the sagittal balance parameters in Ach patients.

Methods

A single-centre retrospective study of Ach patients that visited the Neurosurgery outpatient clinic of the Leiden University Medical Centre (LUMC) between 2019 and 2022 was performed. We defined sagittal imbalance by a C7 sagittal vertical axis (SVA) of more than 10 mm.

Results

There were 13 patients with a spinal sagittal imbalance and 15 patients with a balanced spine. In both groups, the sacral slope (SS) was comparable (45.0° and 49.0°, p = 0.305), but exceeding the mean SS in non achondroplasts (38.0°). Lumbar lordosis (LL) was more pronounced in the balanced group (55.5° versus 41.7°, p = 0.019), and positively correlated to SS in contrast to the absence of a correlation in the imbalanced group. Thoracolumbar kyphosis (TLK) was increased comparably in both groups (19.6° and 24.6°), and far exceeding the TLK in non achondroplasts (circa 0°), and in both groups negatively correlated with the LL, although not enough to compensate for the smaller LL in the imbalanced group.

Conclusion

Only if the LL compensates for both a larger SS and TLK, the Ach spine can maintain sagittal balance. An explanation for the current data can be the failure of the lumbar spine to give sufficient lordosis due to degenerative processes.

Degenerative lumbar spondylolisthesis: review of current classifications and proposal of a novel classification system

PURPOSE

To review existing classification systems for degenerative spondylolisthesis (DS), propose a novel classification designed to better address clinically relevant radiographic and clinical features of disease, and determine the inter- and intraobserver reliability of this new system for classifying DS.

METHODS

The proposed classification system includes four components: 1) segmental dynamic instability, 2) location of spinal stenosis, 3) sagittal alignment, and 4) primary clinical presentation. To establish the reliability of this system, 12 observers graded 10 premarked test cases twice each. Kappa values were calculated to assess the inter- and intraobserver reliability for each of the four components separately.

RESULTS

Interobserver reliability for dynamic instability, location of stenosis, sagittal alignment, and clinical presentation was 0.94, 0.80, 0.87, and 1.00, respectively. Intraobserver reliability for dynamic instability, location of stenosis, sagittal alignment, and clinical presentation were 0.91, 0.88, 0.87, and 0.97, respectively.

CONCLUSION

The UCSF DS classification system provides a novel framework for assessing DS based on radiographic and clinical parameters with established implications for surgical treatment. The almost perfect interobserver and intraobserver reliability observed for all components of this system demonstrates that it is simple and easy to use. In clinical practice, this classification may allow subclassification of similar patients into groups that may benefit from distinct treatment strategies, leading to the development of algorithms to help guide selection of an optimal surgical approach. Future work will focus on the clinical validation of this system, with the goal of providing for more evidence-based, standardized approaches to treatment and improved outcomes for patients with DS.

Validation of a preoperative formula to estimate postoperative pelvic sagittal alignment and mobility before performing total hip arthroplasty for patients with hip osteoarthritis

BACKGROUND

Although it is important to consider pelvic alignment and mobility in the standing and sitting positions before THA, it is not known how to preoperatively predict individual postoperative pelvic alignment and mobility. The purpose of this study was to investigate the pelvic alignment and mobility before and after THA, and to develop a predictive formula using preoperative factors to calculate postoperative sagittal alignment and mobility.

METHODS

One hundred seventy patients were assessed. The 170 patients were randomly divided into a prediction model analysis group (n = 85) and an external validation group (n = 85). In the prediction model analysis group, preoperative spinopelvic parameters were used to develop the predictive formulas to predict the postoperative sacral slope (SS) in standing and sitting positions and ΔSS. These were applied to the external validation group and assessed.

RESULTS

R² in multiple linear regression models for postoperative SS in standing, SS in sitting and ΔSS were 0.810, 0.672, and 0.423, respectively. The values of predicted and postoperative parameters were very close with no significant difference: SS in standing (33.87 vs. 34.23, P = 0.834), SS in sitting (18.86 vs. 19.51, P = 0.228), and ΔSS (15.38 vs. 14.72, P = 0.619).

CONCLUSION

The present study showed that the pelvic alignment and mobility after THA can be predicted using preoperative factors. Although a model with higher accuracy is needed, it is important to use a predictive formula to estimate the postoperative condition before performing THA.

Sagittal realignment: surgical restoration of the global alignment and proportion score parameters: a subgroup analysis. What are the consequences of failing to realign?

INTRODUCTION

The Global Alignment and Proportion (GAP) score incorporates three domains directly modified with surgery (relative pelvic version-RPV, relative lumbar lordosis-RLL, lumbar distribution index-LDI) and one indirectly restored (relative spinopelvic alignment-RSA). We analyzed our surgical realignment performance and the consequences of domain-specific realignment failure on mechanical complications and PROMs.

MATERIALS AND METHODS

From an adult spinal deformity prospective multicenter database, we selected patients: fused to pelvis, upper instrumented vertebra at or above L1, and 2 years of follow-up. Descriptive, univariate and multivariate analyses were employed.

RESULTS

The sample included 333 patients. RLL-6w showed the highest success rate (58.3% aligned), but 16.5% of patients were classified in the "Severe hypolordosis" and "Hyperlordosis" subgroups. RPV-6w was the most challenging to realign, with 51.6% moderate or severe retroversion. Regarding RSA-6w, 21.9% had severe positive malalignment. Correct alignment of RPV-6w (p = 0.025) and RSA-6w (p = 0.002) proved to be protective factors against the development of mechanical complications. Severe pelvic retroversion (p = 0.026) and severe positive malalignment (p = 0.007) were risk factors for mechanical complications. RSA-6w "Severe positive malalignment" was associated with less improvement in PROMs: ∆ODI (8.83 vs 17.2; p = 0.011), ∆SRS-22 total (0.54 vs 0.87; p = 0.007), and ∆SF-36PCS (3.47 vs 7.76; p = 0.04); MCID for ODI (37.0 vs 55.5%; p = 0.023), and SRS-22 (40.8 vs 60.1%; p = 0.015); and PASS for ODI (17.6 vs 31.7%; p = 0.047).

CONCLUSIONS

RPV was the most underperformed modifiable parameter. Severe pelvic retroversion and severe positive malalignment influenced the occurrence of mechanical complications. Severe positive malalignment affected PROMs improvement.

Analysis of Components of Upper Cervical Lordosis in Asymptomatic Lordotic and Kyphotic Subjects

BACKGROUND

Upper cervical lordosis (CL) can be divided into 2 components: C2 slope (C2S) and McGregor slope (MGS) or C0-1 and C1-2 angles. The aim of this study was to investigate the components of upper CL in asymptomatic kyphotic and lordotic subjects.

METHODS

CL, C0-2 Cobb angle, MGS, C2S, C1 Slope, C0-1 Cobb angle, C1-2 Cobb angle, T1 slope angular parameters, and the C2-7 sagittal vertical axis distance of 78 asymptomatic subjects were measured.

RESULTS

Sixty subjects had lordotic curvature and 18 had kyphotic curvature. There was a significant difference between the kyphotic and lordotic groups in all parameters, except for C0-1 Cobb angle and C2-7 sagittal vertical axis. In lordotic subjects, MGS and C2S accounted for 58% and 42% of the C0-2 angle, whereas in kyphotic subjects, 86% of C0-2 was accounted for by C2S. There was a strong negative correlation between C2S and MGS.

CONCLUSIONS

In asymptomatic subjects, as CL decreases, MGS decreases, C2S increases, and the C0-2 angle turns down on the horizontal plane to maintain the horizontal gaze. Turning down the C0-2 angle is more important than its value for maintaining horizontal gaze; thus, the slopes (MGS and C2S) can better represent the upper and lower cervical alignment than angle values can. The relationship between upper and lower cervical alignment should be evaluated in terms of slope angles rather than simple angles. The lack of significant difference between the C0-1 angles in the kyphotic and lordotic groups suggests that only the C1-2 angle is involved in the compensatory mechanism for the horizontal gaze.

The ratio of cervical lordosis to C7 slope represents the reciprocal change between cervical sagittal alignment and global spinal alignment

PURPOSE

This retrospective cross-sectional study investigated variations in the ratio of cervical lordosis to C7 slope (CL/C7S) at different stages of global sagittal balance to better understand how global sagittal alignment affects cervical alignment.

METHODS

A total of 255 patients with the degenerative lumbar disease were retrospectively studied within a single medical center. Whole spine radiographs were used to evaluate sagittal parameters, mainly including occiput-C2 lordosis (OC2), cervical lordosis (CL), C7 slope (C7S), the ratio of cervical lordosis to C7 slope (CL/C7S), cervical sagittal vertical axis (CSVA), thoracic kyphosis (TK), lumbar lordosis (LL), pelvic tilt (PT), pelvic incidence (PI), PI minus LL mismatch (PI-LL), and sagittal vertical axis (SVA). Patients were divided into the balance group (SVA < 50 mm, PI-LL ≤ 10°), hidden imbalance group (SVA < 50 mm, PI-LL > 10°), and imbalance group (SVA > 50 mm).

RESULTS

Significant correlations were found between CL/C7S and OC2 (r = - 0.334), CSVA (r = - 0.504), PI-LL (r = 0.189), and SVA (r = 0.309). Multivariable linear regression analysis indicated that patients in the hidden imbalance group had lower CL/C7S than those in the balance group (B = - 0.234, P < 0.001), whereas the value of CL/C7S in patients with imbalanced sagittal alignment was higher than those with balanced alignment (B = 0.164, P = 0.011). The mean value of CL/C7S was 0.71, 0.51, and 0.97 in the balance, hidden imbalance, and imbalance groups, respectively. The global spine tended to tilt forward as the LL decreased, while TK, PT, PI-LL, and SVA increased (all, P < 0.001) from the balance stage to the imbalance stage.

CONCLUSIONS

CL/C7S tended to be lower when the thoracic extension increased to maintain global sagittal balance at the hidden imbalance stage. Inversely, CL/C7S increased significantly when the global spine showed severe anterior malalignment.

Using Lordotic Cages at the L5-S1 Level Does Not Guarantee the Improvement of Sagittal Alignment in Patients Who Underwent Posterior Lumbar Interbody Fusion

Study Design

Retrospective comparative study.

Purpose

This study aimed to investigate the effects of the lordotic angle of cages on sagittal alignment in patients who underwent 1- or 2-level posterior lumbar interbody fusion (PLIF), including the L5-S1 level.

Overview of Literature

Few studies have addressed the effects of the lordotic angle of cages on regional and global sagittal balance in patients undergoing PLIF at the L5-S1 level.

Methods

Sixty-one patients who underwent 1- or 2-level PLIF, including the L5-S1 level, were divided into two groups based on the lordotic angle of cages (4° and 8° in 41 and 20 patients, respectively). Clinical and radiological parameters were compared. Correlation analyzes were performed to reveal the effect of flexibility and position of cages on the regional sagittal parameters.

Results

Pre- and postoperative clinical and radiological parameters were not different between the two groups. Although clinical outcomes improved postoperatively, sagittal parameters did not improve postoperatively in both groups. Patients who underwent 1-level PLIF at the L5-S1 level with the use of 8° cages showed no postoperative improvement (segmental angle: 16.1°-15.9°, p =0.140; lumbar lordosis: 44.8°-47.8°, p =0.740) of regional sagittal parameters. The degree of anterior location of cages showed a positive correlation with the postoperative restoration of the segmental angle (p =0.012 and p =0.050 at 1 and 2 years postoperatively, respectively).

Conclusions

Clinical and radiological outcomes based on the lordotic angle of cages were not different. Even with the use of 8° cages and regardless of the more anterior position of cages, sagittal alignment did not improve in cases involving the L5-S1 level. PLIF at the L5-S1 level should be used with caution because improvement in sagittal alignment did not occur.

The age-specific normative values of standing whole-body sagittal alignment parameters in healthy adults: based on international multicenter data

PURPOSE

To investigate the age-specific normative values of whole-body sagittal alignment (WBSA) including global balance parameters in healthy adults and to clarify the correlations among parameters based on the data from three international multicenter.

METHODS

Three hundred and seventeen healthy subjects (range: 20-84 y.o., mean: 43.8 ± 14.7 y.o.) were included and underwent whole-body biplanar X-ray imaging system. Spinopelvic parameters and knee flexion (KF), the center of acoustic meatus (CAM)-hip axis (HA), and C2 dentiform apophyse (OD)-HA, the cranial center (Cr)-HA were evaluated radiologically. Sub-analysis for correlation analysis between age and parameters and among parameters was performed to investigate age-specific change and compensatory mechanisms.

RESULTS

For age-related change, C2-7 angle (r = .326 for male/.355 for female), KF (r = .427/.429), and SVA (r = .234/.507) increased with age in both male and female group. For global parameters related to the center of the gravity, correlations with age were not significant (r = .120/.161 for OD-HA, r = .163/.275 for Cr-HA, r = .149/.262 for CAM-HA). Knee flexion (KF) has correlation with global parameters (i.e., SVA, OD-HA, Cr-HA, CAM-HA) and does not have correlations with local spinopelvic alignment.

CONCLUSION

While several local alignment changes with age were found, changes in global parameters related to the center of gravity were kept relatively mild by the chain of compensation mechanisms including the lower limbs. We showed the normative values for a comprehensive WBSA in standing posture from large international healthy subjects' database.

Influence of spinal lordosis correction location on proximal junctional failure: a biomechanical study

STUDY DESIGN

Assessment of sagittal lordosis distribution on mechanical proximal junctional failure-related risks through computer-based biomechanical models.

OBJECTIVE

To biomechanically assess how lordosis distribution influences radiographical and biomechanical indices related to Proximal Junctional Failure (PJF). The "optimal" patient-specific targets to restore the sagittal balance in posterior spinal fusion are still not known. Among these, the effect of the lumbar lordosis correction strategy on complications such as PJF remain uncertain.

METHODS

In this computational biomechanical study, five adult spinal deformity patients who underwent posterior spinal fixation were retrospectively reviewed. Their surgery, first erect posture and flexion movement were simulated with a patient-specific multibody model. Three pedicle subtraction osteotomy (PSO) levels (L3, L4, and L5) were simulated, with consistent global lordosis for a given patient and pelvic tilt adjusted accordingly to the actual surgery. Computed loads on the anterior spine and instrumentation were analyzed and compared using Kruskal-Wallis statistical tests and Spearman correlations.

RESULTS

In these models, no significant correlations were found between the lordosis distribution index (LDI), PSO level and biomechanical PJF-related indices. However, increasing the sagittal vertical axis (SVA) and thoracolumbar junction angle (TLJ) and decreasing the sacral slope (SS) increased the bending moment sustained by the rods at the proximal instrumented level (r = 0.52, 0.57, - 0.56, respectively, p < 0.05). There was a negative correlation between SS and the bending moment held by the adjacent proximal segment (r = - 0.71, p < 0.05).

CONCLUSION

Based on these biomechanical simulations, there was no correlation between the lordosis distribution and PJF-associated biomechanical factors. However, increasing SS and flattening the TLJ, as postural adjustment strategies required by a more distal PSO, did decrease such PJF-related factors. Sagittal restoration and PJF risks remain multifactorial, and the use of patient-specific biomechanical models may help to better understand the complex interrelated mechanisms.

A biomechanical study shows the direction of compression influences the amount of lordosis gained in lumbar fusion

STUDY DESIGN

Biomechanical model study.

BACKGROUND

Lumbar lordosis is usually lost in the degenerative process, and when lumbar fusion is required, its restoration is one of the modern metrics of a successful operation. We sought to investigate the hypothesis that changing direction of compression during surgical fusion, would gain more lordosis.

METHODS

Using a biomechanical Sawbones™ model we inserted polyaxial pedicle screws from S1 to L4. A rod was placed in the screws without requiring reduction. Markers were attached to the spinous processes to allow photographic analysis of lordosis. Two methods were compared. Method A - caudal screws were locked first and compression proceeded in a cranial direction prior to locking. Method B - cranial screws were locked first and compression proceeded caudally. Increasing levels of surgical invasiveness were tested; intact, interbody cage, inferior facet resection, and Ponte resection and using different rods including: lordotic, hyperlordotic and straight.

FINDINGS

Method B demonstrated to be consistently superior to Method A, regardless of the type of rod used and for every level of surgical invasiveness performed. (P < 0.001).

INTERPRETATION

locking the top screws first was a consistently superior method of compression, gaining more lordosis. To explain this finding we suggest the following: During posterior compression of pedicle screws along a fixed rod, screw motion is limited by the conflict between the fixed lordotic rod position, and the need for the moving screw to move in a kyphotic arc which is determined by the cage which acts as a pivot point.

Does the anterior column realignment technique influences the stresses on posterior instrumentation in sagittal imbalance correction? A biomechanical, finite-element analysis of L5-S1 ALIF and L3-4 lateral ACR

STUDY DESIGN

Biomechanical finite-element study.

OBJECTIVE

To directly compare the biomechanical effects of two different techniques for sagittal plane correction of adult spine deformity based on the anterior longitudinal ligament (ALL) resection and use of hyperlordotic cages, namely, the anterior column realignment (ACR) in L3-4, and ALIF in L5-S1 in terms of primary stability and rod stresses using finite-element models.

METHODS

A finite-element model of the thoracolumbar spine was used to perform the analysis. Starting from this "intact" model, three further models were constructed through the insertion of spinal instrumentation, i.e., pedicle screws, rods and cages: 1) posterior instrumentation between T9 and S1 (referred to as "T9-S1"); 2) posterior instrumentation T9-S1 + Hyperlordotic (26°) ALIF cage in L5-S1 ("ALIF"); 3) posterior instrumentation T9-S1 + Hyperlordotic (30°) ACR cage in L3-4 ("ACR"). These models were studied by simulations applying, alternately, a pure moment of 7.5 Nm between the three planes of motion (flexion, extension, lateral bending, and bilateral axial rotation), uniformly distributed over the upper surface of the T9 thoracic vertebra. A total of 24 simulations were performed (6 per models).

RESULTS

All models presented a significant reduced ROM when compared to the intact model; the ROM reduction was higher both at L3-4 in the ACR model and at L5-S1 in the ALIF model. At L3-4, the ACR model had, in all cases, the lowest maximum values of Von Mises stresses on the rods, especially in flexion-extension. At L4-5, the ALIF model had the lowest stresses during flexion-extension and axial rotation, while the ACR model had the lowest stresses during lateral bending. At L5-S1, the ALIF model had, in all cases, the lowest stresses on the rods.

CONCLUSIONS

This finite-element study showed how both ACR at L3-4 and ALIF-ACR at L5-S1 are effective in restoring lumbar lordosis (LL), stabilizing the spine and reducing stress on posterior rods at the index level when compared to a simple fixation model. Interestingly, ALIF-ACR reduces rod stress even at L4-5 in flexion-extension and axial rotation, possibly due to a better distribution of LL, especially on the lower arch, while ACR reduces the stress at L4-5 in lateral bending, possibly thanks to the larger footprint of the cage that increases the area of contact with the lateral side of the endplates.

Does Laminectomy Affect Spino-Pelvic Balance in Lumbar Spinal Stenosis? A Study Based on the EOS X-Ray Imaging System

PURPOSE

Lumbar spinal stenosis (LSS) is a degenerative disorder causing the forward bending of the trunk and pelvic retroversion with the consequent loss of lumbar lordosis; surgical treatment is intended to enlarge the canal and foramina and decompress the nerve roots. The purpose of our study is to determine whether and to what extent facet-sparing laminectomy affects the spino-pelvic balance.

METHODS

The spino-pelvic balance of 26 patients was analysed before and after surgery through the EOS X-ray Imaging System. The following parameters were considered: thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT) and sacral slope (SS). Clinical data were expressed in numeric values according to the Oswestry Disability Index (ODI), the visual analogue scale (VAS) and the modified Japanese Orthopaedic Association (mJOA) scoring system.

RESULTS

Significant SS decreases and PT increases were noticed after surgery, without modification in LL, axial vertebral rotation (AVR) and the general alignment. Pain and disability had a significant improvement, as represented by a decrease in scores on the VAS and ODI scales and an increase in scores on the mJOA functional scale.

CONCLUSION

The most important parameter seems to be a congruence between pelvic and spinal parameters, which achieves an economic posture with the physiologic position of the axis of gravity. According to the literature, a standard sagittal balance (SB) has not been defined.

Functional outcome of surgical management of low mid-grade lumbar spondylolisthesis when considering the sagittal balance parameters preoperatively: a prospective study

BACKGROUND

Prospective study objectives. A sagittal balance is a good tool to improve the functional outcome of spine spondylolisthesis surgeries, primarily noted that it has a good impact in deformity surgery and then applied to every spine surgery and the aim of this study is to evaluate its functional outcome when considered in preoperative planning for non-dysplastic low- and mid-grade spondylolisthesis surgeries.

METHOD

Forty patients diagnosed as low- or mid-grade non-dysplastic spondylolisthesis had undergone surgery at Cairo University after failed medical treatment had been evaluated preoperatively by measuring the sagittal balance parameters which include SVA, spinopelvic angles, lumbar lordosis, pelvic tilt, sacral slope, and pelvic incidence and then measure it along a follow-up period of 1 year postoperatively started from February 2018 and correlate it with functional outcome using Oswestry score (ODI)and VAS. Correction of parameters has been estimated preoperatively by manual estimation and Surgimap application then applied during the operation.

RESULTS

All patients were treated by surgical treatment through posterior transpedicular screw fixation with conventional or reduction screws and fusion ± TLIF cages. The mean of lumbar lordosis and mean spinopelvic angles were increased in a statistically significant manner. Pelvis tilt was decreased in a statistically insignificant manner. The mean of pelvic incidence was not changed and statistically insignificant, and this is matching the fact that pelvic incidence is a constant parameter. The sacral slope was increased in a statistically insignificant manner. Final results showed that 37 had a statistically significant improvement in their ODI >20% at the last visit. Three patients had a poor clinical outcome with ODI scorFinal results showed that 37 had a statistically significant improvement in their ODI >20% at the last visit. Three patients had a poor clinical outcome with ODI score of >20% improvement, and we noticed that the level of pathology was at the level of L4L5, SVA was positive and worsen postoperatively, and also, it is accompanied by decreased lumbar lordosis. Change in ODI means statistically significant improvement when considering sagittal parameters preoperation and during operation.

CONCLUSION

Sagittal balance parameters should be considered in the surgical management of low-grade spondylolisthesis cases to improve their functional outcome.

Sagittal Imbalance May Lead to Higher Risks of Vertebral Compression Fractures and Disc Degeneration-A Finite Element Analysis

BACKGROUND

Sagittal balance is an important clinical parameter of the spine for its normal function. Maintenance of the sagittal balance is crucial in the clinical management of spinal problems.

METHODS

Three different finite element models with spinal alignments based on Schwab's classification were developed: (1) Balanced/Normal model (sagittal vertical axis [SVA] = 0 mm, lumbar lordosis [LL] = 50°, thoracic kyphosis [TK] = 25°, pelvic incidence [PI] = 45°, pelvic tilt [PT] = 10°, sacral slope [SS] = 35°); (2) Balanced with compensatory mechanisms/Flatback model (SVA = 50 mm, LL = 20°, TK = 20°, PI = 45°, PT = 30°, SS = 15°); and (3) Imbalanced/Hyperkyphotic model (SVA = 150 mm, LL = -5°, TK = 25°, PI = 45°, PT = 40°, SS = 5°). All 3 models were subjected to the follower loads simulating bodyweight/muscular contractions along with the moments to simulate flexion, extension, lateral bending, and axial rotation. The maximum cortical vertebral stress, annular stress, and intradiscal pressure (IDP) were calculated and compared.

RESULTS

The results showed that the hyperkyphotic model had higher stresses in the vertebrae (25% higher), the annulus fibrosus (48% higher) and the IDP (8% higher) than the normal models in flexion. The segments near the thoracolumbar junction (T10-L1) showed the highest increase in the vertebral body stress, the annulus fibrosus stress, and the IDP.

CONCLUSIONS

This study showed that the imbalance in sagittal alignment might be responsible for disc degeneration and atraumatic vertebral fractures at the thoracolumbar regions, supporting clinical findings.

Lordosis loss in degenerative spinal conditions

PURPOSE

To establish whether common degenerative lumbar spine conditions have a predictable sagittal profile and associated range of lordosis. The spinopelvic balance of a normal population and normal ranges are well described in the literature. There is also evidence that certain degenerative conditions can lead to a preponderance of loss of lordosis at specific spinal levels. There is limited literature on the range and magnitude of loss of lordosis for known degenerative lumbar spine pathologies.

METHODS

A retrospective analysis of prospectively obtained radiographs from a dual surgeon database was performed and imaging analysed for spinopelvic parameters. Degenerative conditions studied were; Lumbar degenerative spondylolisthesis (L3/4 and L4/5 analysed separately), L5/S1 degenerative disc disease, L5/S1 isthmic spondylolisthesis. Pelvic incidence, sacral slope, pelvic tilt, segmental and global lumbar lordosis, vertebral lordosis and lumbar vertical axis were measured.

RESULTS

The range of change in segmental lordosis was normally distributed for all studied degenerative spinal conditions except L5/S1 isthmic spondylolisthesis. L5/S1 degenerative disc disease affected younger adults (mean age 37), whilst degenerative spondylolisthesis at L3/4 and L4/5 affected older adults (mean ages 69.5 and 68.9 respectively). Removing an outlying high-grade L5/S1 isthmic spondylolisthesis made the data distribution approach a normal distribution.

CONCLUSION

Most degenerative spinal pathologies cause a normally distributed spectrum of deformity which should be addressed and corrected with a tailored, individualised surgical plan for each patient. Universal treatment recommendations should be interpreted with caution.

Should adjacent asymptomatic lumbar disc herniation of L5-S1 isthmic spondylolisthesis be simultaneously rectified? Evaluation of postoperative spino-pelvic sagittal balance and functional outcomes

Background

This study aimed to analyze the efficacy of the simultaneous rectification of adjacent asymptomatic lumbar disc herniation (asLDH) of L5-S1 isthmic spondylolisthesis (IS).

Methods

One hundred and forty-eight patients with L5-S1 IS, and simultaneous L4-5 asLDH, were recruited between January 2012 and December 2017, for this study. Group A: seventy-two patients received PLIF at L5-S1. Group B: seventy-six patients received PLIF at L4-S1. The radiographic outcomes were assessed via the lumbar lordosis (LL), segmental lordosis (SL), sacral slope (SS), pelvic incidence (PI), pelvic tilt (PT), PI-LL and slip degree (SD). The functional outcomes were evaluated via the visual analog scale (VAS), Oswestry disability index (ODI), and reoperation rate. The potential risk hazards for reoperation were identified using both uni- and multivariate logistic regression analyses.

Results

The postoperative LL, SL, PT, SS, SD, VAS, and ODI exhibited vast improvements (P < 0.05). Relative to Group A, Group B exhibited markedly better LL, SL, PT, PI-LL,VAS and ODI scores at the final follow-up (P < 0.05). Group B also achieved better SD values post surgery than Group A (P < 0.05). The reoperation rate was remarkably elevated in Group A, compared to Group B (P < 0.05). The multivariate logistic regression analysis showed the L4-5 asLDH grade was a stand-alone risk hazard for reoperation, whereas, pre-SL and pre-LL offered protection against reoperation (P < 0.05).

Conclusions

L4-S1 PLIF is recommended to correct asLDH in L5-S1 IS patients, with high-grade disc herniation and abnormal sagittal alignment.

Can artificial intelligence support or even replace physicians in measuring sagittal balance? A validation study on preoperative and postoperative full spine images of 170 patients

PURPOSE

Sagittal balance (SB) plays an important role in the surgical treatment of spinal disorders. The aim of this research study is to provide a detailed evaluation of a new, fully automated algorithm based on artificial intelligence (AI) for the determination of SB parameters on a large number of patients with and without instrumentation.

METHODS

Pre- and postoperative sagittal full body radiographs of 170 patients were measured by two human raters, twice by one rater and by the AI algorithm which determined: pelvic incidence, pelvic tilt, sacral slope, L1-S1 lordosis, T4-T12 thoracic kyphosis (TK) and the spino-sacral angle (SSA). To evaluate the agreement between human raters and AI, the mean error (95% confidence interval (CI)), standard deviation and an intra- and inter-rater reliability was conducted using intra-class correlation (ICC) coefficients.

RESULTS

ICC values for the assessment of the intra- (range: 0.88-0.97) and inter-rater (0.86-0.97) reliability of human raters are excellent. The algorithm is able to determine all parameters in 95% of all pre- and in 91% of all postoperative images with excellent ICC values (PreOP-range: 0.83-0.91, PostOP: 0.72-0.89). Mean errors are smallest for the SSA (PreOP: -0.1° (95%-CI: -0.9°-0.6°); PostOP: -0.5° (-1.4°-0.4°)) and largest for TK (7.0° (6.1°-7.8°); 7.1° (6.1°-8.1°)).

CONCLUSION

A new, fully automated algorithm that determines SB parameters has excellent reliability and agreement with human raters, particularly on preoperative full spine images. The presented solution will relieve physicians from time-consuming routine work of measuring SB parameters and allow the analysis of large databases efficiently.

Spinopelvic measurements of sagittal balance with deep learning: systematic review and critical evaluation

PURPOSE

To summarize and critically evaluate the existing studies for spinopelvic measurements of sagittal balance that are based on deep learning (DL).

METHODS

Three databases (PubMed, WoS and Scopus) were queried for records using keywords related to DL and measurement of sagittal balance. After screening the resulting 529 records that were augmented with specific web search, 34 studies published between 2017 and 2022 were included in the final review, and evaluated from the perspective of the observed sagittal spinopelvic parameters, properties of spine image datasets, applied DL methodology and resulting measurement performance.

RESULTS

Studies reported DL measurement of up to 18 different spinopelvic parameters, but the actual number depended on the image field of view. Image datasets were composed of lateral lumbar spine and whole spine X-rays, biplanar whole spine X-rays and lumbar spine magnetic resonance cross sections, and were increasing in size or enriched by augmentation techniques. Spinopelvic parameter measurement was approached either by landmark detection or structure segmentation, and U-Net was the most frequently applied DL architecture. The latest DL methods achieved excellent performance in terms of mean absolute error against reference manual measurements (~ 2° or ~ 1 mm).

CONCLUSION

Although the application of relatively complex DL architectures resulted in an improved measurement accuracy of sagittal spinopelvic parameters, future methods should focus on multi-institution and multi-observer analyses as well as uncertainty estimation and error handling implementations for integration into the clinical workflow. Further advances will enhance the predictive analytics of DL methods for spinopelvic parameter measurement.

LEVEL OF EVIDENCE I

Diagnostic: individual cross-sectional studies with the consistently applied reference standard and blinding.

Correlation analysis of the PI-LL mismatch according to the pelvic incidence from a database of 468 asymptomatic volunteers

PURPOSE

Previous studies on adults with degenerative scoliosis (ADS) have been fixed the threshold of PI-LL mismatch less than 10° for achieving good clinical outcomes. Recent studies discussed that PI-LL mismatch should consider individual pelvic incidence (PI) and should be set first in a normal population. The purpose of this study is to assess the variability of PI-LL mismatch according to PI in an asymptomatic population.

METHODS

Full-body low dose stereoradiographic evaluation was done in a multi-ethnic cohort of 468 asymptomatic adult volunteers. Patients were clustered in three groups depending on individual PI values: PI < 45°, 45° < PI < 60° and PI > 60°. 3D measurements were performed using a commercially available 2D/3D modeling software to establish a correlation of PI with other spinopelvic parameters. ANOVA and Tukey's HSD for post-hoc analysis were used to determine the differences between the three groups.

RESULTS

In our asymptomatic population, the mean value of PI-LL mismatch is - 5.4° ± 10.7°. Clusterization of the population reveals significant differences in the distribution of L1S1 lordosis, pelvic tilt and PI-LL with positive linear correlation according to PI values. As an interestingly result, PI-LL mismatch is equal to 0° when PI is around 64°.

CONCLUSIONS

The present study demonstrated that PI-LL mismatch is negative in an asymptomatic population (- 5.4° ± 10.7°) and the value should be customized to each patient to be able to restore the appropriate lordosis in ADS. The PI-LL mismatch is given by the formula PI-LL = - 28.5 + 0.44 × PI.

How does magnetically controlled growing rods insertion affect sagittal alignment in ambulatory early onset scoliosis patients?

PURPOSE

The importance of sagittal alignment restoration in early onset scoliosis (EOS) management has rarely been investigated to date. The aim was to report the influence of magnetically controlled growing rods (MCGR) insertion on the sagittal alignment of EOS patients.

METHODS

All consecutive ambulatory patients operated with MCGR rods between 2011 and 2018 were retrospectively included in four institutions. Standing biplanar radiographs were performed preoperatively, in the early postoperative period and at latest follow-up. Global and local sagittal parameters, spinal global shape and harmony were investigated.

RESULTS

A total of 37 ambulatory EOS patients were included (mean age at surgery 8.5 (± 2) years). 70% had a balanced construct postoperatively. Both MaxTK (- 17°, p = 0.02) and MaxLL (- 15°, p = 0.001) were significantly reduced, particularly at the instrumented levels. The number of vertebrae included in the lumbar lordosis significantly increased (+ 2 levels, p = 0.02), as well as the thoraco-lumbar inflexion point (+ 2 levels, p < 0.001) and the kyphosis apex (+ 1 level, p < 0.001). Overall mechanical failure rate was 40.5%, and radiological PJK was observed in 43% of the patients, with 11 remaining asymptomatic. Patients with initial hyperkyphosis (> 50°) developed more complications (62% vs. 28%, p = 0.04).

CONCLUSION

MCGR insertion flattened the spine in EOS, at both instrumented and non-instrumented levels. Overall spinal harmony was modified, with a cranial shift of the thoraco-lumbar inflexion point and the thoracic kyphosis apex, associated with a lengthening of the lumbar lordosis. The rate of complication remained high, some explanations being found in the radiological changes reported such as the preoperative location of the TK apex.

LEVEL OF EVIDENCE

IV.

Pelvic and spinal postural changes between standing-sitting positions following lumbosacral fusion: a pilot study

Purpose

Prospective pre-operative and post-operative comparative analysis of radiographic spino-pelvic parameters between sitting versus standing positions of patients with LS fusion, to detect adaptation mechanisms around fused spinal segments.

Methods

Sixteen patients aged 53.9 ± 15.9 who underwent LS fusion between L3 and S1 were extracted from the database of an ongoing prospective study. Different spino-pelvic parameters were evaluated on full spine X-rays, standing, then sitting straight. Parameters were compared pre-operative versus post-operative, and on standing versus sitting X-rays.

Results

Preliminary results revealed a significantly greater pre-operative pelvic tilt (PT) in sitting than standing posture, (p = 0.020) but not in post-operative (p = 0.087). After surgery, PT was lower in sitting compared to pre-operative (p = 0.034) but not in standing (p = 0.245). L4–S1 lordosis was lower in sitting than standing in pre-operative (p = 0.014) and post-operative (p = 0.021). Surgery decreased segmental lordosis above the fusion (PSL, proximal sagittal lordosis) in sitting (p = 0.039) but not in standing (p = 0.193). No significant differences in thoracic kyphosis (TK) were observed. Fusions down to L5 versus S1 showed no significant differences for PT and PSL, neither in sitting versus standing, nor pre-operative versus post-operative.

Conclusion

Before fusion, compared to standing, PT increases in sitting straight posture (pelvic retroversion), and the lumbar spine adapts by decreasing its lordosis, mainly at L4–S1. After fusion, the segments adjacent to the instrumented section, adapt in flexion at lumbosacral and thoracolumbar junctions, i.e. just below and above (PSL). This might have mechanical implications for the occurrence of adjacent segment disease.

Maximizing mechanical advantage: surgical technique increases stiffness in spinal instrumentation

PURPOSE

While there has been a great improvement in the treatment of adolescent idiopathic scoliosis, sagittal deformity correction has remained challenging. Increased rod stiffness has been shown to reduce thoracic flattening. We propose that the surgical technique can increase rod stiffness. A mechanical study was created to quantify the effect this has on construct stiffness.

METHODS

The sagittal bending stiffness of a constrained over contoured rod was measured using four different commonly used instrumentation systems. Pedicle screws were secured into custom printed blocks. One block was completely immobilized, while the other block was subject to four levels of constraint. This includes no constraint, mild constraint, moderate constraint, and maximal constraint with both blocks immobilized. The rod apex was loaded until 1 cm of displacement occurred. The stiffness was then calculated and compared between groups.

RESULTS

All four rod types showed increased bending stiffness as the construct became more constrained. The moderately constrained and the maximally constrained groups had a significantly higher stiffness compared to the unconstrained groups in all rod types (p < 0.05). The 6.0 mm titanium circular rods showed the highest increase in stiffness between maximal and no constraint, which became 3.02 × stiffer.

CONCLUSIONS

Rod stiffness is not only determined by size, shape, and metal alloy, but also by surgical technique. Constraining the spinal instrumentation by first locking the rod to the proximal and distal anchors significantly increases the sagittal bending stiffness. In a mechanical model this technique increases rod bending stiffness regardless of the material or shape.

The challenge of measuring spinopelvic parameters: inter-rater reliability before and after minimally invasive lumbar spondylodesis

BACKGROUND

The common manual measurement technique of spinal sagittal alignment on X-rays is susceptible to rater-dependent variability, which has not been adequately considered in previous publications. This study investigates the effect of those variations in the characterization of patients receiving lumbar spondylodesis.

METHODS

General alignment parameters on pre- and postoperative X-rays were evaluated by four raters in 43 prospectively sampled patients undergoing monolevel spondylodesis. The Intra-class Correlation Coefficient (ICC) for each rater pair and all raters together was calculated for inter-rater reliability. For the operation-induced change of the sagittal alignment in every patient the Wilcoxon test was applied to compare for each rater separately.

RESULTS

The ICCs were "good" (>0.75) to "excellent" (>0.9) for all raters together and for 45 of the 48 single rater pairs (93.75%). All revealed a significant increase of the addressed segmental lordosis and disc height and no significant change for spinopelvic parameters and sagittal vertical axis from pre- to postoperative. The lumbar lordosis showed a significant increase through the operation of +2.5° (p = 0.014) and +3.7° (p = 0.015) in two raters and no difference for the other ones (+2.1°, p = 0.171; -2.2°, p = 0.522).

CONCLUSIONS

The pre- to postoperative change of lumbar lordosis revealed different significance levels for different raters, although the ICCs were formally good. Accordingly, the evaluation by only one rater would lead to different conclusions. Due to this susceptibility of alignment measurements to rater-dependent variability, the exact evaluation process should be described in every publication and the consistency of significant results be validated through multiple raters.

TRIALS REGISTRATION

The trial was approved by the local ethics committee and listed at the national clinical trials register ( DRKS00004514 , date of registration: 08/11/2012).

Clinical outcome after lumbar spinal fusion surgery in degenerative spondylolisthesis: a 3-year follow-up

INTRODUCTION

Lumbar spinal fusion surgery is a widely accepted surgical treatment in degenerative causes of lumbar spondylolisthesis. The benefit of reduction of anterior displacement and restoration of sagittal parameters is still controversially debated. Purpose of the underlying publication was to analyze the influence of radiographic sagittal parameters of the spine in aspects of changes in postoperative clinical outcome.

MATERIALS AND METHODS

By prospective analysis, we included patients with low-grade degenerative lumbar spondylolisthesis (Meyerding grades I and II) with mono- or bisegmental fusion surgery with a minimum follow-up data of 3 years. For clinical outcome measures, COMI, ODI and EQ-5D were used. Spinopelvic parameters (sacral inclination, pelvic tilt, sacral slope and pelvic incidence, lumbar lordosis and lumbar index as well as anterior displacement and sagittal rotation) were measured on plain radiographs.

RESULTS

We could observe a significant benefit in clinical outcome after lumbar fusion surgery in low-grade spondylolisthesis in our mid-term follow-up data including 32 patients. By surgical reduction, we could see significant restoration of anterior displacement and sagittal rotation. Interestingly, a significant correlation between restoration of both sagittal rotation and sacral inclination and clinical outcome score was observed in the 3-year follow-up.

CONCLUSION

In low-grade spondylolisthesis, spinal fusion surgery is a well-established surgical procedure; however, the impact of sagittal parameters and reduction of anterior displacement remains controversial. Within our findings, restoration of sagittal parameters showed significant correlation to improvement in clinical outcome in our mid-term follow-up data.

[Lumbo-pelvino-acetabular alignment-basics and clinical consequences]

The spinal shape and the pelvic ante-/retroversion of an individual are determined by its innate, genetically fixed lumbosacral angulation. This can be measured with little effort in the lateral standing radiograph of the patient. In spinal surgery, there are a lot of original papers on the topic. In hip surgery, however, the individual pelvic version and its consequences for the acetabular orientation have not received the same attention so far.This review focuses on previous data on the relationship between lumbosacral angulation and pelvic ante-/retroversion. Four anatomically definable pelvic types can be distinguished; three of those have to be considered as facultatively pathogenetic. Clinical consequences arise for the clinical pictures of spondylolisthesis, non-specific lower back pain, acetabular retroversion and developmental dysplasia of the hip, as well as for acetabular cup positioning in total hip arthroplasty.

Optoelectronic Study of Gait Kinematics in Sagittal Spinopelvic Imbalance

OBJECTIVE

Degenerative processes induce loss of lumbar lordosis and anterior sagittal imbalance (ASI). Optoelectronic study provides kinematic analysis of movement and can also detect ASI. The aim of the present study was to assess gait kinematic modifications induced by ASI.

METHODS

Thirty-five healthy male volunteers were subjected to reversible ASI induced by wearing a kyphotic thermoformed thoracolumbar corset. The deformation was assessed by C7 tilt on EOS (EOS Imaging, Paris, France) full-spine views. Ten optoelectronic gait recordings were made with corset and 10 without. Gait kinematic parameters (stride length, walking speed, rhythm), gait balance parameters (center of mass braking index, stride width, double support time) and spinal sagittal balance parameters (C7T10S1, C7´S1' and spinal angles) were averaged. Adjusted analysis distinguished direct ASI impact from locomotor factors.

RESULTS

The corset-induced ASI produced +15° change in C7 tilt (P < 0.0001), -7.4° in C7T10S1 (P < 0.0001), +66.2 mm in C7´S1' (P < 0.0001), and +13.1° in spinal angle (P < 0.0001). Radiographic and optoelectronic data correlated significantly. Stride length (P < 0.0001) and rhythm (P = 0.0003) were significantly reduced, contributing to a reduction in walking speed (P < 0.0001), and strongly influencing double support time (β = -0.38; 95% confidence interval [CI]: -0.69; -0.06). Center of mass braking index was significantly reduced (P < 0.0001) and significantly influenced by ASI (β = -0.51; 95% CI: -0.78; -0.28). Stride width was significantly increased by ASI (P < 0.0001), independently of rhythm and stride length.

CONCLUSIONS

ASI induced by a kyphotic corset was detectable on the optoelectronic system, leading to significant changes in gait kinematics. Locomotor parameters were significantly reduced. Balance parameters were significantly and directly altered by ASI.

Compensatory mechanisms recruited against proximal junctional kyphosis by patients instrumented from the thoracolumbar junction to the iliac

PURPOSE

The compensatory mechanisms recruited by un-instrumented patients against sagittal imbalance are well documented. However, there is a lack of information regarding instrumented patients.

MATERIAL AND METHODS

We performed a retrospective analysis of data collected prospectively in a multicenter adult spinal deformity database. We included patients suffering PJK/PJF after (T8-L2) to iliac instrumentation with minimum two-year follow-up. We measured quantitative sagittal spinopelvic and qualitative sagittal distribution parameters in the immediate postoperative period (6w) and at the time of PJK/PJF appearance. We analyzed how these parameters changed comparing these two time points with univariate and multivariate logistic regression analyses.

RESULTS

A total of 69 patients were included. Two different patterns at PJK/PJF were found: 36 patients activated compensation (defined as an increase in pelvic retroversion (ΔRPV > 5º), and 33 did not (ΔRPV < 5º). The difference in behavior relied mostly on the amount of not surgically restored pelvic rotation at 6w (OR: 0.6; CI95%: 0.4-9.2; P = 0.017). Non-compensators had less rotation reserve (PTx100/PI = 33.9% vs 47.8%;P < 0.001) associated with worse 6w relative pelvic version and lower lumbar arc restoration, worse 6w relative sagittal alignment and GAP-score, compared with compensators (P < 0.001). Compensators' response was based on pelvic retroversion, causing lower lumbar arc decrease, lumbar apex caudal migration, and upper lumbar arc posterior inclination. Despite compensation, a thoracic kyphosis increase in both upper and lower arches gradually evolved into a PJK/PJF. Non-compensators did not react to PJK/PJF, which forced them into kyphosis from the lumbar apex and extending cranially, mainly throughout the upper thoracic arc.

CONCLUSIONS

In patients fused from the TL junction to the iliac, those having greater postoperative pelvic rotation reserve showed greater capacity to recruit compensatory mechanisms against PJK/PJF.

Rationale and techniques for Posterior Opening Wedge Osteotomy (POWO) in proximal junctional failure due to iatrogenic lumbar hyperlordosis

Proximal junctional kyphosis (PJK) is a compensatory phenomenon in reaction to pathologic lumbar hyperlordosis. Inappropriate spinal curve harmony incurs risk of PJK. Postoperative failure of posterior instrumentation, with kyphosis resistant to revision surgery at the proximal junction, may be caused by excessive iatrogenic lumbar lordosis. The surgical attitude should be to decrease lumbar lordosis by posterior opening wedge osteotomy (POWO). We describe the rationale for POWO and surgical techniques at L3. The technique is illustrated by a case report at 24 months' follow-up. Based on rational analysis of the distribution of lordosis along the lumbar spine and of adaptation of the sitting position, POWO may be indicated to avoid PJK after revision surgery in adult spinal Deformation revision surgery.

Analysis of factors associated with sagittal alignment deterioration after correction of degenerative scoliosis by in situ contouring

INTRODUCTION

In situ contouring is one of the surgical techniques used for scoliosis reduction. The initial correction could change over time, with deterioration of the sagittal balance. The purpose of this study was to analyze the loss of correction after degenerative lumbar scoliosis surgery using in situ contouring.

MATERIALS AND METHODS

Full spine radiographs of 73 patients (mean age 63.3 years, mean follow-up 27 months) were analyzed before surgery, after surgery, and at the final follow-up. The following radiographic parameters were measured: C2-C7 lordosis, T4-T12 kyphosis, L1-S1 lordosis, pelvic tilt, pelvic incidence, sacral slope, SVA C7, SVA C2, Cobb angle. Bayesian inference was used to compare the changes in these parameters. A probability>0.95 was considered as a significant change.

RESULTS

After surgery, lumbar lordosis increased from -28.4° to -37.8° (probability 0.999), then decreased to -32.1° at the final follow-up (probability 0.953). Thoracic kyphosis increased from 29.6° to 37.4° after surgery (probability 1.00) and continued to increase to 41.6° at the final follow-up (probability 0.999). SVA C7 increased from 38.5mm to 62.3mm (probability 0.999) and pelvic tilt from 19.4° to 25.1° (probability 1.00) during the follow-up period. Ten patients had to be reoperated because of a surgical site infection. Infection (14%) was associated with an increase of SVA C7 (probability 0.989) and thoracic kyphosis (probability 0.987). Nonunion (16%) was associated with a decrease in lumbar lordosis (probability 0.756).

CONCLUSION

Correction of degenerative lumbar scoliosis by in situ contouring resulted in sagittal balance correction; however, some of this correction was lost during the follow-up period. The main risk factors were deep wound infection and nonunion.

LEVEL OF EVIDENCE

IV, Retrospective study.

Treatment of lumbar canal stenosis in patients with compensated sagittal balance

INTRODUCTION

The need to combine fusion with decompression in patients with lumbar canal stenosis is still controversial. The aim of this study was to show that isolated decompression leads to the same outcomes as decompression plus fusion in patients who have preserved global sagittal balance.

MATERIALS AND METHODS

A single-center retrospective cohort of 110 patients who were operated for a single-level lumbar stenosis was divided into two groups based on the treatment: isolated decompression or fusion-decompression. These patients had a normal odontoid-hip axis angle (ODHA) (-5° to +2°) and had no spondylolisthesis or frontal deformity. We compared the clinical outcome scores and spinal-pelvic parameters preoperatively and at 1 year of follow-up. We evaluated the minimal clinically important difference (MCID) corresponding to a 12.8-point difference in the Owestry Disability Index (ODI). The analysis in each group was based on the MCID.

RESULTS

The clinical outcome scores improved significantly in both groups. There was a 77% decrease in the ODI>12.8 points with no significant difference between groups. The analysis based on the MCID showed that patients with a poor clinical result at 1 year in the isolated decompression group were more likely to have lumbar pain, while the ones in the fusion-decompression group were more likely to have radicular pain.

CONCLUSION

The clinical and radiological results of fusion-decompression are not superior at 1 year relative to isolated decompression for treating single-level lumbar canal stenosis in patients with compensated sagittal balance. Full-spine weight bearing radiographs are key to determining the patient's sagittal balance and to ensuring there are no radiological instability factors that may require a stabilizing procedure.

LEVEL OF EVIDENCE

IV Retrospective study of data collected prospectively.

The Impact of Single-Level Anterior Cervical Discectomy and Fusion on Cervical Sagittal Parameters and Its Correlation With Pain and Functional Outcome of Patients With Neck Pain

BACKGROUND

This study examines the changes in segmental and global cervical sagittal parameters after single-level anterior cervical discectomy and fusion (ACDF) in patients with cervical radiculopathy or myelopathy. We also investigate whether these changes have any relation with postoperative pain and functional outcome of the patients.

METHODS

Sixty patients (37 females and 23 males) with a mean age of 45.9 ± 9.5 years who were candidates of single-level ACDF due to cervical myelopathy or radiculopathy participated in the study. At baseline, 1 month, and 6 months after ACDF, outcomes of the study including sagittal balance parameters, pain intensity, and Neck Disability Index (NDI) were measured among the patients. Intensity of pain and neck disability were measured using the visual analog scale (VAS) and validated version of NDI, respectively. Using a standard lateral cervical radiography, the Cobb angle for occiput-C2, C1-C2, and C2-C7 as well as operation-level angle (OA; Cobb's angle at the level of discopathy), the thoracic inlet angle, and C7 and T1 slope angles were measured.

RESULTS

The intensity of pain and neck disability of patients improved significantly during the follow up of the study comparing with baseline measurements (P < .001). There was a significant correlation between the increase of C2-C7 angle, C1-C2 angle, and OA and improvement in neck pain and NDI at 1- and 6-month follow ups.

CONCLUSIONS

We found that changes at C2-C7 angle, C1-C2 angle, and OA have positive significant correlation with clinical outcome including pain improvement and decrease of disability in patients who undergo ACDF.

LEVEL OF EVIDENCE

3.

CLINICAL RELEVANCE

The results of this study might be beneficial in selection of cervical cages with appropriate size during ACDF surgery, as our findinds showed that larger cages could lead to better functional outcome in patients.

The Relationship Between Preoperative Cervical Sagittal Balance and Clinical Outcome of Patients With Hirayama Disease Treated With Anterior Cervical Discectomy and Fusion

OBJECTIVE

Anterior cervical discectomy and fusion (ACDF) is a common surgical method used to treat patients with Hirayama disease. And sagittal balance indexes have been revealed to be predictors of clinical outcomes in patients with cervical diseases, but their relationships with ACDF-treated Hirayama disease outcomes remain unknown. The purpose of this study is to evaluate the relationship of preoperative cervical sagittal balance indexes and clinical outcomes in ACDF-treated Hirayama disease patients.

METHODS

Eighty patients with Hirayama disease treated by ACDF were reviewed retrospectively. Six cervical sagittal balance parameters were collected including Cobb angle, T1 slope, C1-7 sagittal vertical axis (SVA), C2-7 SVA, center of gravity of the head (CGH)-C7 SVA, range of motion. The recovery outcomes of the patients were divided into 2 groups by Odom score and the differences in recovery between the 2 groups were confirmed by electromyography. The correlation between imaging parameters and postoperative outcome was evaluated with logistic regression. The receiver operating characteristic (ROC) curve and area under the ROC curve (AUC) were used to evaluate the significant result of logistic regression and the optimal diagnostic value.

RESULTS

Only 2 parameters, Cobb angle and CGH-C7 SVA, showed statistical correlation with the postoperative outcome assessment by logistic regression. AUC of Cobb angle and CGH-C7 SVA were 0.559 and 0.702 respectively. The optimal predictive threshold was 1.50° and 5.40 mm, respectively.

CONCLUSION

A larger Cobb angle and smaller CGH-C7 SVA seemed to correlate with a better postoperative outcome. These 2 factors could be used to predict the outcome of surgical treatment of Hirayama disease preoperatively.