Pelvic parameters and global spine balance for spine degenerative disease: the importance of containing for the well being of content

Corrective Long Spinal Fusion to the Ilium for Patients with Adult Spinal Deformity Results in Good Physical Function after Mid- to Long-Term Postoperative Follow-Up

Introduction

This study investigated the mid- to long-term postoperative outcomes of patients with adult spinal deformity (ASD), focusing on physical function and quality of life (QOL). We also compared age-related changes between patients aged 75 years or older (high elderly) and those younger than 75 years (low elderly).

Methods

A total of 47 patients with ASD underwent thoracic-iliac long spinal fusion between August 2013 and September 2014. The study spanned from the preoperative period to at least 5 years postoperatively. Physical function was assessed using isometric hip flexion and knee extension muscle strength, the 6-min walk distance test, the 10-m walk test, and the timed up and go test. QOL was assessed using the Scoliosis Research Society-22 and Oswestry Disability Index. Repeated-measures analysis of variance with a mixed model approach, corrected for multiple comparisons using Bonferroni, was performed.

Results

Of the 47 patients, 21 participated in the study. Patients with ASD showed improved gait ability postoperatively. Hip flexor strength decreased at more than 5 years postoperatively compared with the preoperative strength. Patient-reported outcome (PRO) scores showed continuous improvement postoperatively, regardless of age. Although older patients had lower preoperative and postoperative physical function, their PRO scores significantly improved and remained favorable for more than 5 years postoperatively.

Conclusions

Patients with ASD experienced sustained improvements in walking ability and PRO for more than 5 years postoperatively. The results of this study showed that even among the elderly, PRO scores consistently improved after surgery and remained positive for an extended period.

Landet: an efficient physics-informed deep learning approach for automatic detection of anatomical landmarks and measurement of spinopelvic alignment

PURPOSE

An efficient physics-informed deep learning approach for extracting spinopelvic measures from X-ray images is introduced and its performance is evaluated against manual annotations.

METHODS

Two datasets, comprising a total of 1470 images, were collected to evaluate the model's performance. We propose a novel method of detecting landmarks as objects, incorporating their relationships as constraints (LanDet). Using this approach, we trained our deep learning model to extract five spine and pelvis measures: Sacrum Slope (SS), Pelvic Tilt (PT), Pelvic Incidence (PI), Lumbar Lordosis (LL), and Sagittal Vertical Axis (SVA). The results were compared to manually labelled test dataset (GT) as well as measures annotated separately by three surgeons.

RESULTS

The LanDet model was evaluated on the two datasets separately and on an extended dataset combining both. The final accuracy for each measure is reported in terms of Mean Absolute Error (MAE), Standard Deviation (SD), and R Pearson correlation coefficient as follows: [ S S ∘ : 3.7 ( 2.7 ) , R = 0.89 ] ,[ P T ∘ : 1.3 ( 1.1 ) , R = 0.98 ] , [ P I ∘ : 4.2 ( 3.1 ) , R = 0.93 ] , [ L L ∘ : 5.1 ( 6.4 ) , R = 0.83 ] , [ S V A ( m m ) : 2.1 ( 1.9 ) , R = 0.96 ] . To assess model reliability and compare it against surgeons, the intraclass correlation coefficient (ICC) metric is used. The model demonstrated better consistency with surgeons with all values over 0.88 compared to what was previously reported in the literature.

CONCLUSION

The LanDet model exhibits competitive performance compared to existing literature. The effectiveness of the physics-informed constraint method, utilized in our landmark detection as object algorithm, is highlighted. Furthermore, we addressed the limitations of heatmap-based methods for anatomical landmark detection and tackled issues related to mis-identifying of similar or adjacent landmarks instead of intended landmark using this novel approach.

Factors related to T1 slope: spinopelvic balance and thoracic compensation

OBJECTIVE

To identify factors associated with T1 slope (T1S).

METHODS

A total of 215 patients over 18 years old who underwent whole-spine X-rays to evaluate lower back pain were enrolled in this study. T1S, pelvic tilt (PT), sacral slope (SS), pelvic incidence (PI), thoracic kyphosis (TK), lumbar lordosis (LL), cervical lordosis (CL), thoracolumbar kyphosis (TLK), and sagittal vertical axis (SVA) were measured. Patients were divided into balance, compensatory balance, thoracic compensation, and thoracic decompensation groups.

RESULTS

TK (p < 0.001), SVA (p < 0.001), and CL (p = 0.020) were significantly related to high T1S. The balance group had the smallest PT, largest SS and largest LL of the four groups (p < 0.001). The thoracic compensation group had the smallest TK of all groups (p < 0.001). There was no significant difference in T1S between the balance and thoracic compensation groups (p = 0.099). The thoracic decompensation group had a larger T1S than the balance group (p = 0.023).

CONCLUSIONS

Caudal spine segments had a sequential effect on cranial spine segments. T1S reflected the compensation ability of the spine. The absence of balance tended to increase the T1S. Pelvic posterior rotation and thoracic compensation were two crucial factors protecting against increased T1S in patients with ASD.

T1 pelvic angle is associated with rapid progression of hip arthrosis

PURPOSE

To evaluate the association between global spinal malalignment and rapid progression of hip arthrosis.

METHODS

This was a retrospective, case-control study including 90 patients, contributing 90 hips, who underwent hemi- or total hip arthroplasty at our institution. For analysis, hips were classified into a rapid progression group, defined as ≥ 2 mm destruction of the femoral head or loss of the hip joint space within a 12-month period (n = 30), and a non-rapid progression group, defined by no observable hip disease progression over a period more than 12 months (n = 60). Logistic regression analysis identified factors that predicted rapid progression, with a receiver operating characteristic curve analysis used to confirm factors.

RESULTS

Significant between-group differences were identified for the following parameters: pelvic tilt (P = 0.002, PT), sagittal vertical axis (P = 0.002, SVA), and T1 pelvic angle (P < 0.001, TPA). On multiple logistic regression, PT (P = 0.002), SVA (P = 0.002), and TPA (P < 0.001) were predictive of a rapid progression on hip arthrosis, with the area under the curve being greater for TPA than PT (P = 0.035).

CONCLUSION

Global spinal alignment is associated with rapid progression of hip arthrosis. TPA could assist in identifying patients at risk for rapid progression of hip arthrosis, allowing for time management.

Compensatory classification in spine sagittal malalignment with lumbar degeneration

Objective

To generate a compensatory classification to evaluate sagittal spinal malalignment with lumbar degeneration.

Methods

We included 162 patients with low back pain who underwent full-length spinal radiography in our hospital from August 2019 to October 2021. Using full-length spine X-rays, we measured pelvic tilt (PT), sacral slope (SS), pelvic incidence (PI), thoracic kyphosis (TK), lumbar lordosis (LL), C7 slope (C7S), thoracolumbar kyphosis (TLK), and C7 sagittal vertical axis (SVA). We also recorded the Oswestry Disability Index (ODI) and visual analog scale (VAS). Patients were divided into four groups based on the SRS-Schwab classification and four other groups based on the compensatory classification.

Results

ODI correlated with age, SS, LL, TK, C7-SVA, SRS-Schwab classification, and compensatory classification. Lumbar VAS score correlated with LL, TK, C7-SVA, SRS-Schwab classification, and compensatory classification. Leg VAS score only correlated with LL. Hidden imbalance and imbalance with compensation had more significant PT and larger TK than balance patients. The symptoms of the four compensatory classification groups gradually worsened.

Conclusion

The spinal-pelvic sagittal balance in patients with lumbar degeneration based on pelvic and thoracic compensation can reflect spinal balance and symptoms. This parameter might help evaluate spine sagittal alignment in elderly patients with lumbar degeneration.

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.

Four types of global spine sagittal alignment and compensation mechanism in adult patients with lumbar degenerative disease

BACKGROUND

The objective of this study was to describe and classify common variations and compensation mechanisms in the sagittal alignment of the spine with lumbar degenerative disease.

METHODS

A total of 230 patients over 18 years old who underwent whole-spine X-rays to evaluate lower back pain were enrolled in this study. C7 slope, pelvic tilt (PT), sacral slope (SS), pelvic incidence (PI), thoracic kyphosis (TK), lumbar lordosis (LL), cervical lordosis (CL), thoracolumbar kyphosis (TLK), and sagittal vertical axis (SVA) were measured. Patients were divided into Group A (balance without compensation), B (balance with compensation), C (unbalance with compensation), and D (unbalance without compensation) according to spinopelvic balance and thoracic compensation.

RESULTS

Group A had the largest LL, smallest PT, largest SS, and best clinical parameters of the four groups (p < 0.001, p < 0.001, p < 0.001, p < 0.001). The age increased gradually from Group B to Group D. Group B had an increased TK compared with Group A (p < 0.001). Group C had an increased TK compared with Group A (p < 0.001). Group D had an increased C7 slope compared with Group A (p = 0.022).

CONCLUSIONS

This classification is shown four different regional and global alignments of the spine. Compensation took place to keep the balance of the spine. Classification types were consistent with age, compensation abilities, and clinical parameters. This classification potentially represents a valuable tool for comprehensive analysis of lumbar degenerative before surgical treatment considering sagittal balance.

Impact of cervical and global spine sagittal alignment on cervical curvature changes after posterior cervical laminoplasty

OBJECTIVE

To analyze the correlation between the changes in cervical curvature and the sagittal parameters of spino-pelvic and clinical efficacy after posterior laminoplasty (LP).

METHODS

The patients with cervical spondylosis treated with LP from June 2018 to December 2020 were reviewed. The preoperative and follow-up spine full-length films were measured. The measured data included C2-C7 Cobb angle, C2-7 sagittal vertical axis (SVA), T1 slope (T1S), pelvic incidence, sacral slope (SS), pelvic tilt (PT), lumbar lordosis (LL), thoracic kyphosis (TK), and C7-SVA. Japanese Orthopaedic Association (JOA) score and neck disability index (NDI) score were recorded before surgery and follow-up.

RESULTS

There were 56 patients in this study. There were no significant differences in spino-pelvic sagittal parameters before and after surgery; however, the JOA score significantly improved. The changes in postoperative cervical lordosis correlated with SS, PT, LL, T1S, and C7-SVA (P < 0.05). Regression analysis showed that T1S and C7-SVA were associated with reducing cervical lordosis (P = 0.021 and P = 0.001, respectively). Patients with larger T1S combined with larger C7-SVA had more cervical lordosis loss, poor JOA improvement, and high postoperative NDI scores (P < 0.001, P = 0.018, and P < 0.001, respectively).

CONCLUSION

Patients should be examined with full-length spine film before surgery to evaluate the cervical and spino-pelvic sagittal balance. T1S and C7-SVA correlated with changes in cervical sagittal alignment after LP.

LEVEL OF EVIDENCE

III.

Knee Extension Is Related to the Posteriorly Deviated Gravity Line to the Pelvis in Young Adults: Radiographic Analysis Using Low-Dose Biplanar X-ray

PURPOSE

We sought to compare the radiographic parameters concerning the sagittal alignment of the standing whole-body skeletons between the knee extension group and control group using the low-dose biplanar X-ray system in a young adult population without knee pain, and to investigate the associated variables for the sagittal knee angle (sagKA) among the radiographic parameters of global sagittal alignment.

MATERIALS AND METHODS

We reviewed whole-body standing sagittal radiographs of 124 young adults taken from December 2018 to May 2020 in a single institution. We compared the radiographic parameters concerning the lower extremity sagittal alignment and global sagittal alignment between the knee extension group and control group. The factors correlated with sagKA were evaluated using multiple linear regression analysis.

RESULTS

The sagittal vertical axis (SVA), the horizontal offset between the gravity line (GL) and the posterior edge of S1 endplate (GL-S), and the horizontal offset between the GL and the hip center (GL-H) were -11.6±21.3 mm, 5.1±23.8 mm, and -25.1±27.1 mm in the knee extension group, respectively, which were significantly smaller than those in the control group. The C7 plumb line (C7PL) and GL were deviated posterior to the sacrum and the hip center in the knee extension group, with the mean sagKA of -5.6° in young adults.

CONCLUSION

The GL-H using GL, not the SVA using C7PL, was a significant radiographic factor associated with the sagKA.

Change in sagittal alignment after decompression alone in patients with lumbar spinal stenosis without significant deformity: a prospective cohort study

OBJECTIVE

The authors' objective was to investigate whether sagittal balance improves in patients with spinal stenosis after decompression alone.

METHODS

This prospective longitudinal cohort study compared preoperative and 6-month postoperative 36-inch full-length radiographs in patients aged older than 60 years. Patients underwent decompression alone for central lumbar spinal stenosis with either a minimally invasive bilateral laminotomy for central decompression, unilateral laminectomy as an over-the-top procedure for bilateral decompression, or traditional wide laminectomy with removal of the spinous processes on both sides. The following radiographic parameters were measured: sagittal vertical axis (SVA), lumbar lordosis (LL), pelvic tilt (PT), pelvic incidence (PI), PI-LL mismatch, coronal Cobb angle, and sacral slope (SS). Patient-reported outcome measures (PROMs) were collected, including scores on the Oswestry Disability Index (ODI), visual analog scale (VAS) for leg and back pain, and EQ-5D.

RESULTS

Forty-five patients (24 males) with a mean ± SD age of 71.8 ± 5.6 years were included. Sagittal balance showed statistically significant improvement, with the mean SVA decreasing from 52.3 mm preoperatively to 33.9 mm postoperatively (p = 0.0001). The authors found an increase in LL, from mean -41.5° preoperatively to -43.9° postoperatively, but this was not statistically significant (p = 0.055). A statistically significant decrease in PI-LL mismatch from mean 8.4° preoperatively to 5.8° postoperatively was found (p = 0.002). All PROM scores showed significant improvement after spinal decompression surgery. The correlations between SVA and all PROMs were statistically significant at both preoperative and postoperative time points, although most correlations were weak except for those between preoperative SVA and ODI (r = 0.55) and between SVA and VAS for leg pain (r = 0.58).

CONCLUSIONS

Sagittal balance and PROMs show improvement at short-term follow-up evaluations in patients who have undergone decompression alone for lumbar spinal stenosis.

Perioperative Predictive Factors for Positive Outcomes in Spine Fusion for Adult Deformity Correction

Purpose: Identifying perioperative factors that may influence the outcomes of long spine fusion for the treatment of adult deformity is key for tailored surgical planning and targeted informed consent. The aim of this study was to analyze the association between demographic or perioperative factors and clinical outcomes 2 years after long spine fusion for the treatment of adult deformity. Methods: This study is a multivariate analysis of retrospectively collected data. All patients who underwent long fusion of the lumbar spine for adult spinal deformity (January 2016–June 2019) were included. The outcomes of interest were the Oswestry disability index (ODI), visual analogic scale (VAS) preoperatively and at 1 and 2 years’ follow up, age, body mass index, American Society of Anaesthesiologists (ASA) score, upper and lowest instrumented vertebrae (UIV and LIV, respectively), length of surgery, estimated blood loss, and length of hospital stay. Results: Data from 192 patients were available. The ODI at 2 years correlated weakly to moderately with age (r = 0.4), BMI (r = 0.2), ASA (r = 0.3), and LIV (r = 0.2), and strongly with preoperative ODI (r = 0.6). The leg VAS at 2 years moderately correlated with age (r = 0.3) and BMI (r = 0.3). Conclusion: ODI and VAS at 2 years’ follow-up had no to little association to preoperative age, health status, LIV, or other peroperative data, but showed a strong correlation with preoperative ODI and pain level.

Relationship Between Muscle Mass of the Lower Limbs and Falls Caused by Spinal Misalignment in Women Aged 70 Years: A Retrospective Study

STUDY DESIGN

This retrospective study was conducted from 2015 to 2016 at the osteoporosis outpatient clinic of Showa University School of Medicine.

OBJECTIVE

This study aimed to investigate the association between lower-limb muscle mass and spinal misalignment-related falls in elderly women.

SUMMARY OF BACKGROUND DATA

Poor spinal alignment affects gait and balance, reducing the quality of life. Negative correlations between age-associated skeletal muscle loss and spinal sagittal alignment have been reported.

MATERIALS AND METHODS

This study included 127 women with osteoporosis aged more than 70 years. The correlation between lower-limb skeletal muscle index (SMI) and sagittal vertical axis (SVA) was calculated using radiographic measurements. Spinopelvic parameters, including SVA, sacral slope, pelvic tilt (PT), pelvic incidence, and lumbar lordosis, were measured. Lower-limb SMI was measured using whole-body dual-energy x-ray absorptiometry and calculated as SMI=nonfat mass/height2. The balance function was evaluated using the single-leg stance test. Data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests; significance level was set at P<0.05. Bivariate and multivariate logistic regression analyses were used to determine correlations.

RESULTS

Participants were classified into the balance and mismatch groups on the basis of a threshold SVA value of 50 mm. The groups did not differ significantly in age, height, weight, pelvic incidence, or sacral slope. Lumbar lordosis significantly decreased and PT and lower-limb SMI significantly increased in the mismatch group compared with the balance group. Lower-limb SMI was significantly correlated with increased SVA in bivariate and multivariate regression analyses. Patients with PT ≥20 degrees and SVA ≥50 mm had significantly increased lower-limb SMI.

CONCLUSIONS

Increased SVA is associated with increased lower-limb SMI, which negatively affects standing balance. An increased lower-limb SMI may represent a novel compensatory mechanism for poor spinal alignment in elderly women with osteoporosis.

LEVEL OF EVIDENCE

Level III.

Factors related to length of hospital stay after two-stage corrective surgery for adult spinal deformity in elderly Japanese

BACKGROUND

Postoperative recovery of activities of daily living after surgery in elderly patients often takes a longer time because of their frailty. However, it is unclear how long it takes for patients with adult spinal deformity (ASD) to recover their abilities to live their daily lives in their home after corrective fusion surgery. This study aimed to investigate the length of hospital stay required to perform activities of daily living (ADL) in patients undergoing two-stage corrective fusion surgery for ASD in our institution and to detect factors associated with the length of hospital stay.

METHODS

Thirty-four consecutive female ASD patients (median age, 70 years) who underwent two-stage corrective fusion surgery (lateral lumbar interbody fusion at the first stage and posterior corrective fusion at the second stage) from T9 or T10 to the pelvis were included. The length of hospital stay from admission to return home was determined, and correlations between length of hospital stay and demographics, skeletal muscle mass, operative invasion and perioperative complications, and spino-pelvic alignment were investigated.

RESULTS

The median length of hospital stay was 51 days, exceeding 100 days in 25% of cases. Age at surgery (ρ = 0.545, p = 0.001), estimated glomerular filtration rate (ρ = -0.603, p < 0.001), age-adjusted Charlson comorbidity index (ρ = 0.437, p = 0.01), and preoperative pelvic incidence (ρ = 0.356, p = 0.04) were correlated with length of hospital stay. Preoperative skeletal muscle mass, preoperative spinal imbalance, perioperative changes in spino-pelvic alignment, operative invasion, and perioperative complications were not correlated with length of hospital stay.

CONCLUSIONS

After >50 days, ADL performance of each patient reached the extent required for daily living to return home after two-stage corrective fusion surgery for ASD. Factors related to length of hospital stay were age and indices related to frailty.

Higher incidence of aseptic loosening caused by a lower canal filling ratio with a modified modular stem in total hip arthroplasty

Purpose

Although a cementless modular prosthesis has shown reliable results, cases of unstable fixation and revision due to aseptic loosening were observed in our institute. The purpose of this study was to clarify the causes of unstable fixation of the prosthesis.

Methods

A total of 144 patients (154 hips) who underwent total hip arthroplasty using the modular prosthesis were retrospectively investigated. For the cohort study, 97 patients (104 hips) were included. The femoral component survival rate and sleeve fixation were assessed at a minimum follow-up of 5 years. Patients were divided into 2 groups, including stable and unstable fixation groups, by sleeve fixation. Clinical and radiographic outcomes were compared.

Results

The Kaplan-Meier survival rate at 9 years was 93% with revision for any reason as the endpoint in study cohort. The reasons for revision were recurrent dislocation (1 hip) and aseptic loosening of the stem (5 hips). A total of 88 hips (84.6%) showed stable fixation, and 16 hips (15.4%) showed unstable fixation at final follow-up. There was no significant difference in clinical outcomes between the 2 groups at final follow-up. The canal flare index was significantly higher, and the canal filling ratio was significantly lower in the unstable fixation group.

Conclusion

Although the modified modular prosthesis was useful for treating anatomically difficult patients, we need to pay attention to both proximal/distal mismatch of the intramedullary canal and the canal filling ratio to achieve stable fixation and good long-term results.

Inframalleolar Varus Deformity: Role of Calcaneal Osteotomies

The cavo varus foot is a complex pathology due to skeletal deformity and neuro-muscular unbalance. The key concept for a successful treatment is to consider the whole foot and ankle complex from a bone and soft tissue perspective. Undercorrection is the main issue in cavo varus foot management, which may be attributed to intrinsic correction defects of the described calcaneal osteotomies or to a lack of understanding about the pathology and the subsequent algorithm of treatment. The authors disclose their daily algorithm of treatment, considering the foot and ankle complex and the role of calcaneal osteotomies in ankle inframalleolar deformities.

Pedicle screw insertion with patient-specific 3D-printed guides based on low-dose CT scan is more accurate than free-hand technique in spine deformity patients: a prospective, randomized clinical trial

BACKGROUND

Screw misplacement incidence can be as high as 15-30% in spine deformity surgery, with possible devastating consequences. Some technical solutions to prevent misplacement require expensive devices. MySpine^TM comprises a low-dose CT scan of the patient's spine to build a virtual model of the spine to plan the screw trajectories and a 3D-printed patient-specific guide system to prepare the screw trajectories and to implant the screws in the vertebrae in order to increase reproducibility and safety of the implants. The aim of this open-label, single-center, prospective randomized clinical trial with independent evaluation of outcomes was to compare the accuracy of free-hand insertion of pedicle screws to MySpine^TM 3D-printed patient-specific guides.

METHODS

Twenty-nine patients undergoing surgical correction for spinal deformity were randomized to Group A (pedicle screws implantation with MySpine^TM) or Group B (free-hand implantation). Group A received 297 pedicle screws, and Group B 243 screws. Forty-three screws in Group A crossed over to free-hand implantation. Screw position was graded according to Gertzbein in grades 0, A, B or C, with grades 0 or A considered as "safe area." Total fluoroscopy dose and time were compared in six patients of each group.

RESULTS

Comparing the two study groups, we observed a statistically significant difference between the two groups (p < 0.05), with 96.1% of screws in the "safe area" in Group A versus a 82.9% in Group B. Group-A patients had a mean effective dose of 0.23 mSv compared to 0.82 mSv in Group B. Patient-specific, 3D-printed pedicle screw guides increase safety in a wide spectrum of deformity conditions. In addition, the total radiation dose is reduced, even considering the need of a low-dose preoperative CT for surgical planning.

LEVEL OF EVIDENCE

I. These slides can be retrieved under Electronic Supplementary Material.

The Large Individual Differences in the Range of Hip Joint Motion Rather Than Lumbar Spine Motion Affect Dynamic Spinopelvic Rhythm

INTRODUCTION

Global spinal balance and its relationship to the pelvis have received much attention, and various formulae have been used to predict postoperative spinopelvic alignment for spinal surgery. However, previous studies had limitations because no consideration was given to the dynamic factor.

METHODS

Fifteen healthy adults without any lumbar disorder (group A) and 9 L4-spondylolisthesis patients (Group B) volunteered to participate in the study. Sequential images were captured with the subjects in the standing position with maximal forward bending followed by backward bending using a dynamic flat panel detector system. Spinopelvic parameters (LL: lumbar lordosis, SA: sacrofemoral angle, SS: sacral slope, PI: pelvic incidence, DP: distance of the horizontal movement of the pelvis) were evaluated. We also investigated the relationship between LL and SA (lumbar/hip [L/H] ratio) as the spinopelvic rhythm.

RESULTS

In group A, the mean change in LL was 83.2 ± 9.5°; change in SA, 45.4 ± 16.6°; SS, 42.6 ± 8.9°; PI, 43.2 ± 7.7°; DP, 15.7 ± 3.4 cm, and L/H ratio, 3.6 ± 2.7. However, spinopelvic rhythm changed over time, because the change in LL was larger than the change in SA from the middle of the rising motion to the upright position. In group B, the mean change in LL was 50.3 ± 8.0°; SA, 56.9 ± 16.0°; SS, 27.5 ± 13.5°; PI, 47.4 ± 10.4°; DP, 12.7 ± 6.8 cm; and L/H ratio, 1.0 ± 0.5.

CONCLUSIONS

When compared with the change in LL, individual differences were largely noted in the change in SA. These results demonstrated that the range of hip joint motion under physiological conditions, unlike anatomical motion, differed substantially between individuals. Therefore, spinopelvic rhythm is dependent on the change in SA.

S1 Pedicle Subtraction Osteotomy in Sagittal Balance Correction. A Feasibility Study on Human Cadaveric Specimens

BACKGROUND

A cadaveric feasibility study was carried out. Osteotomies to correct fixed sagittal imbalance are usually performed at L₃/ L₄.

OBJECTIVE

To investigate the feasibility of S₁ pedicle subtraction osteotomy to correct spinal deformity and spinopelvic parameters, achieving better results with more limited exposure. The data obtained will allow a fixation construct specific for this osteotomy to be designed.

METHODS

S₁ pedicle subtraction osteotomy was performed on 12 cadaveric specimens. Baseline and postprocedural computed tomography and biomechanical studies were performed. Data were analyzed with a fixation system SolidWorks model, and the redesigned fixation construct was described and analyzed with an ANSYS model.

RESULTS

S₁ pedicle subtraction osteotomy is technically feasible. The fixation can be achieved with L₄, L₅, and iliac screws connected with bars. The system can be reinforced with a polyetheretherketone cage placed anteriorly in the S₁ body osteotomy site, a cross-connecting bar, a double iliac screw, or an anterior interbody cage placed at the L₅-S₁ disc. The fixation strength is improved by angulating the iliac rod channel 10°, adding a semi-sphere to the locking screw contact surface and 2 fins to its saddle. The redesigned construct showed suitable stress and deformation levels, achieving the expected biomechanical requirements.

DISCUSSION

Compared with surgery on higher levels, S₁ pedicle subtraction osteotomy allows greater correction with shorter fixation, because the osteotomy is performed at a more caudal level, modifying the spinopelvic parameters.

CONCLUSIONS

S₁ pedicle subtraction osteotomy is technically feasible. Finite element analysis results indicate that it has appropriate biomechanical properties.

What is the Current Evidence on Vertebral Body Osteonecrosis?: A Systematic Review of the Literature

Osteonecrosis (ON) is a clinical entity characterized by a pattern of cell death and complex process of bone resorption and formation. Studies related to ON have largely focused on certain anatomical sites; however, the evidence on vertebral body ON (VBON) is largely inconsistent and fragmented. The aim of this study was to clarify the pathophysiology, risk factors, imaging findings, and available treatment modalities for VBON. A systematic review of the relevant articles published in English was performed using PubMed, Embase, Medline, Google Scholar, Cochrane Central Register of Controlled Trials (CENTRAL), and CINAHL databases. A total of 81 articles were included in this study. Three main topics about VBON were identified: (1) pathophysiology and risk factors, (2) diagnosis, and (3) treatment. Forty-five studies were based on the pathophysiology, 52 on diagnosis, and 38 on the treatment options for VBON. The literature on VBON was limited and mainly focused on post-traumatic cases with a considerable overlap with nonunion and pseudoarthrosis.

Vertebral body osteonecrosis: proposal of a treatment-oriented classification system

PURPOSE

To present a classification system for vertebral body osteonecrosis (VBON) based on imaging findings and sagittal alignment and consequently to propose treatment guidelines.

METHODS

Chart review and classification of imaging and clinical findings. An analysis of literature about VBON has been evaluated to conceive the classification. The current data allows to correlate radiological findings with different stages of the pathophysiological process and consequently to propose a patient-tailored treatment plan.

RESULTS

The classification identifies 4 stages: stage 0 (theoretical phase), stage 1 (early phase), stage 2 (instability phase) and stage 3 (fixed deformity phase). Local (angular kyphosis expressed as anterior-posterior wall height ratio) and global (sagittal vertical axis and pelvic tilt) sagittal alignment are considered as complementary modifiers to tailor the most suitable treatment. Stage 1 is generally managed conservatively. Stage 2 and 3 often require different surgical approaches according to local and global sagittal alignment.

CONCLUSIONS

The classification allows a systematic staging of this disease and can help establish a proper and patient-oriented treatment plan. Further researches are advocated to fully validate the proposed classification system. These slides can be retrieved under Electronic Supplementary Material.

Hypercomplex pedicle subtraction osteotomies: definition, early clinical and radiological results and complications

PURPOSE

To describe hypercomplex pedicle subtraction osteotomies (HyC-PSO) for adult spine deformity with sagittal imbalance in terms of preoperative, intraoperative and postoperative outcomes and complications.

METHODS

From a prospective single centre database, patients undergoing PSO between January 2016 and May 2017 were reviewed. HyC-PSO were defined as those in patients with one of the following conditions: sagittal correction > 45° needed at a single level or at 1-3 consecutive vertebrae, more than 60° of total sagittal correction needed and PSO on segments of the spine with congenital deformities.

RESULTS

22 patients were included, 14 had standard PSO (group A) and 8 had HyC-PSO (group B). Significant correction of lumbar lordosis (LL) and pelvic (PT) was noted in both groups (p < 0.01). Operative time was longer in HyC-PSO, 604 min compared to standard PSO, 478 min. A trend versus greater intraoperative blood loss (3837 vs 2285 ml) and greater intraoperative blood infusion (from cell saver plus homologous, 2306 vs 1280 ml) was recorded in HyC-PSO (ns). Patients in group B received significantly more blood units intra and postoperatively (8.25 vs 4.71 units, p = 0.006). Sagittal correction at the PSO level (54.7°-30° to 85°-vs 26.8°-8° to 39°-, p = 0.000) and total sagittal correction (64.5°-50 to 95°-vs 39.8°-20° to 51°-, p = 0.000) were greater in HyC-PSO. PROMs at the last available follow-up did not show significant differences between groups for any of the outcomes analyzed. Complications were similar in both groups.

CONCLUSION

This is the first report on hypercomplex pedicle subtraction osteotomies. Hypercomplex PSO describes a subset of clinical scenarios with increased surgical effort that can be measured as longer surgical time and greater blood transfusion requirements. Successful correction of misalignment can be achieved in this specific group of patients, and clinical results and complications profile could be similar to standard PSO procedures.

Xipho-pubic angle (XPA) correlates with patient's reported outcomes in a population of adult spinal deformity: results from a multi-center cohort study

STUDY DESIGN

Retrospective multi-center cohort study.

PURPOSE

Sagittal misalignment causes changes in the abdominal shape. Xipho-pubic angle (XPA) has been previously described to radiographically evaluate the shape of the abdominal cavity in patients with spine deformity. The aims of this study are to evaluate the correlation of XPA-to-spinopelvic sagittal parameters and to patients' health-related quality-of-life (HRQoL) scores.

METHODS

278 patients from a multi-center database with diagnosis adult spinal deformity (ASD) (one or more of: coronal Cobb angle > 20°, sagittal vertical axis (SVA) > 50 mm, pelvic tilt (PT) > 25°, and thoracic kyphosis > 60°) were included. Cut-off values for moderate and severe disability (ODI-Oswestry Disability Index-20 and 40%) were calculated. Pearson's correlation was tested between XPA and spinopelvic parameters and between XPA and HRQoL scores.

RESULTS

The cut-off value of XPA to identify ODI severe disability (40/100) was identified with XPA smaller than 103°; minimal (20/100) disability was identified by XPA greater than 113°. XPA showed strong correlation to sagittal spinopelvic parameters-PT, SVA, lumbar lordosis (LL), pelvic incidence (PI) minus LL-and to HRQoL scores-ODI, SF-36 PCS and SRS-22 activity and pain. XPA was the parameter with the strongest correlation to HRQoL scores.

CONCLUSIONS

Xipho-pubic angle reflects changes in spinal changes and has strong correlation to HRQoL and spinopelvic parameters. It can discriminate between patients with minimal, moderate, and severe disability as measured by ODI scores. These slides can be retrieved under Electronic Supplementary Material.

Thoracic hyperkyphosis non invasively measured by general practitioners is associated with chronic low back pain: A cross-sectional study of 1364 subjects

OBJECTIVE

The aim of this study was to examine the association between trunk sagittal posture and nonspecific chronic low back pain (CLBP) by evaluating plumb-line distances in subjects recruited in an everyday clinical setting.

METHODS

Of the 1364 subjects recruited, 63.1% were female (mean age ± SD: 56.2 ± 16.8 years). Subjects were categorized into CLBP and control groups and were prospectively assessed over a 3-month period. They provided information about their daily activities and their history of CLBP. Prognostic factors were analysed using univariate and multivariate logistic regression analyses. A physical examination was performed to record demographic (i.e. age, height and weight) and pain characteristics, and the intensity of pain was assessed using a numerical visual analogue scale. Disability was assessed using the Roland-Morris Disability Questionnaire (RMDQ). A simple measure generally used for sagittal plane screening purposes during growth was also utilized.

RESULTS

Multivariate logistic regression analysis revealed that gender (OR = 1.70), RMDQ score (OR = 0.51) and thoracic hyperkyphosis (C7 + L3 at the plumb-line distance) (OR = 1.57) were associated with CLBP. The final regression model explained 85.6% (R² = 0.56; P < 0.001) of the variability.

CONCLUSIONS

General practitioners can clinically and easily assess trunk posture in subjects with low back pain to identify subjects at higher risk of CLBP.

Predictive Accuracy of Surgimap Surgical Planning for Sagittal Imbalance: A Cohort Study

MINI: Surgical planning in sagittal imbalance is recognized as a key step of treatment to ensure good clinical results. Surgimap is a reliable tool to predict satisfactory postoperative sagittal alignment. Setting by default pelvic tilt to 20° improves predictive value during surgical planning.

STUDY DESIGN

A cohort study.

OBJECTIVE

To evaluate the predictive value of surgical planning using Surgimap regarding postoperative sagittal alignment.

SUMMARY OF BACKGROUND DATA

Surgical planning in sagittal imbalance is recognized as a key step of treatment to ensure results.

METHODS

The study involved 40 nonconsecutive patients who underwent surgery for sagittal misalignment. Postoperative alignment measured by sagittal vertical axis (SVA) and pelvic tilt was considered the gold standard. Surgimap prediction of final alignment was considered the test. Planning and postoperative films were classified as properly and improperly aligned. Sensitivity, specificity, and positive and negative predictive values of Surgimap planning [using two different methods: direct simulation (method A) and simulation after correction of pelvic tilt to 20° (method B)] to detect postoperative improper alignment were calculated.

RESULTS

Seventeen (42.5%) of 40 patients had proper postoperative alignment. According to method A, a proper alignment was achieved in 13 patients [S = 76.5%, Sp = 73.9%, RR = 2.93 (95% confidence interval, CI 1.40; 6.12), P < 0.001]; According to method B, a proper alignment was achieved in 15 patients [S = 88.2%, Sp = 60.9%, RR = 2.25 (95% CI 1.32; 23.86), P < 0.001]. Kappa statistics indicate moderate agreement between actual postoperative alignment and computer prediction.

CONCLUSION

The ability of Surgimap to predict proper postoperative sagittal alignment was excellent in this cohort. Its ability to predict proper alignment was improved by correction of pelvic tilt to 20° during planning.

LEVEL OF EVIDENCE

2.

Evaluation of Global Sagittal Balance in Koreans Adults

OBJECTVIE

The global sagittal postural patterns as characterized by Roussouly classification have been previously described in various ethnicities, there were no studies investigated in Koreans. To analyze the distribution of the global sagittal postural patterns in Korean adults using Roussouly classification, the author prospectively studied.

METHODS

252 asymptomatic Korean adults was recruited. Data was obtained by reviewing the films for each subject. Spinopelvic parameters were measured and sagittal postural patterns were then determined according to Roussouly classification. We compared the data across different ethnicities from our study and a previous study to further characterize Korean sagittal postures.

RESULTS

The subject included 151 males and 101 females, with mean age of 33.2±8.2 years. The average descriptive results were as below: thoracic kyphosis 28.6±7.7°, lumbar lordosis 48.3±10.2°, sacral slope 37.8±5.8°, pelvic incidence 45.1±7.5°, pelvic tilt 9.4±6.7°, spinosacral angle 130.1±5.4°, and sagittal vertical axis 16.25±22.5 mm. 125 subjects among 252 (49.6%) belonged to Roussouly type 3 (namely neutral). There were also 58 (23%), 33 (13.1%), and 36 (14.3) subjects in type 1, 2, and 4 (namely non-neutral), respectively.

CONCLUSION

Enrolling 252 asymptomatic Korean adults, this prospective study found that 49.6% of asymptomatic Korean adults possessed a sagittal posture of Roussouly type 3. All radiologic parameters follows general concept of spinal sagittal balance pattern. Overall, this study might be a basis for further investigation of spinal sagittal balance.

The Human Pelvis: Variation in Structure and Function During Gait

The shift to habitual bipedalism 4-6 million years ago in the hominin lineage created a morphologically and functionally different human pelvis compared to our closest living relatives, the chimpanzees. Evolutionary changes to the shape of the pelvis were necessary for the transition to habitual bipedalism in humans. These changes in the bony anatomy resulted in an altered role of muscle function, influencing bipedal gait. Additionally, there are normal sex-specific variations in the pelvis as well as abnormal variations in the acetabulum. During gait, the pelvis moves in the three planes to produce smooth and efficient motion. Subtle sex-specific differences in these motions may facilitate economical gait despite differences in pelvic structure. The motions of the pelvis and hip may also be altered in the presence of abnormal acetabular structure, especially with acetabular dysplasia. Anat Rec, 300:633-642, 2017. © 2017 Wiley Periodicals, Inc.

Influence of Sacral Slope on the Loading of Pedicle Screws in Postoperative L5/S1 Isthmic Spondylolisthesis Patient: A Finite Element Analysis

STUDY DESIGN

A finite element analysis.

OBJECTIVE

To evaluate the influence of sacral slope (SS) on the loading of pedicle screws in postoperative isthmic spondylolisthesis (IS).

SUMMARY OF BACKGROUND DATA

The spinopelvic anatomy was important for the biomechanics in spondylolisthesis. To our knowledge, no study concentrated on the postoperative biomechanics of the IS with the different SS.

METHODS

Based on the computed tomography images, a finite model of L5/S1 IS was constructed. Posterolateral fusion (PLF) and posterior lumbar interbody fusion (PLIF) models were simulated with different sacral slope (35°, 40°, 45°, 50°, and 55°). Moreover, 500N preload was imposed on the L5 superior endplate and 15 Nm was given to simulate flexion, extension, lateral flexion, and rotation of the body. The maximum stress on the instrumentation was recorded in different model with different sacral slope.

RESULT

The model of the L5/S1 IS was verified to be valid. The maximum stress on the internal fixation system of each model was always at the posterior part of the sacral screw or connection point between screw and rod. Except for the SS of 35° in PLIF model, all the maximum stress occurred in flexion loading, which was 535.47 MPa for PLF and 339.49 MPa for PLIF with SS of 55°. The stress on the sacral screw of the PLF was higher than that of the PLIF model with same sacral slope, for example, 453.38 MPa for PLF, 282.64 MPa for PLIF under flexion with SS of 45°. With the increase of the SS, the maximum stress on the sacral screws increased in both the PLF and PLIF models.

CONCLUSION

The maximum stress on the internal fixation system of the PLF and PLIF concentrated at the posterior part of sacral screw or the connection point between the screw and rod. With the same SS, the stress on the screw of PLF was higher than that of PLIF. PLIF may be a better choice for IS with a high SS.

LEVEL OF EVIDENCE

N/A.

Clinical, physical, and radiographic analyses of lumbar degenerative kyphosis and spondylolisthesis among community-based cohort

PURPOSE

To investigate longitudinal radiographic changes, and physical characteristics of lumbar degenerative kyphosis (LDK) and spondylolisthesis (DS).

METHODS

Two-hundred eighty nine community-based female subjects were recruited from population register and studied longitudinally for a mean 12.3 years. Upright entire spine radiographs were used to evaluate spinopelvic parameters, including lumbar lordosis (LL), pelvic incidence (PI), and vertebral slip (% slip). Physical measurements included lumbar range of motion (ROM), isometric trunk muscle strength, and photometric gait posture using change in trunk inclination angle (dTIA).

RESULTS

Subjects' mean age (standard deviation: SD) was 56.9 (10.0) years at baseline and 68.5 (9.2) years at the final follow-up. Among 202 subjects who could perform instructed physical measurements, DS, defined as more than 5 % slip, was found in 50 subjects (24.8 %), and LDK, defined as LL of less than 1SD of mean value (<24.4°), was found in 24 subjects (11.9 %). DS subjects showed a significant weakness in trunk flexor strength (normal 282.5 ± 73.0 N vs. DS 245.5 ± 75.5 N, p = 0.0219), and LDK subjects showed significant differences in: trunk extensor strength (normal 493.4 ± 172.8 N vs. LDK 386.3 ± 167.6 N, p = 0.0066), ROM, and dTIA (normal 3.5° ± 2.7° vs. LDK 7.6° ± 4.8°, p < 0.0001). PI was significantly larger in DS and smaller in LDK than normal subjects (normal 53.8° ± 9.9° vs. DS 58.2° ± 10.6°, p = 0.0111; normal vs. LDK 48.4° ± 9.2°, p = 0.0191).

CONCLUSIONS

Current study showed that DS was associated with reduced trunk flexor strength, which might increase pelvic anteversion, and LDK was associated with reduced extensor strength, ROM, and ambulatory kyphosis. Physical characteristics should be evaluated for the successful management of adult spinal deformity.

Stand-alone anterior lumbar interbody fusion for treatment of degenerative spondylolisthesis

We sought to evaluate the clinical and radiologic efficacy of stand-alone anterior lumbar interbody fusion (ALIF) for low grade degenerative spondylolisthesis, the favoured surgical management approach at our institution. The optimal approach for surgical management of spondylolisthesis remains contentious. We performed a prospective analysis of all consecutive patients with low grade lumbar spondylolisthesis who underwent ALIF between 2009 and 2013 by a single surgeon (n=27). The mean age was 64.9 years with a male to female ratio of 14:13. There were 32 levels operated and the average preoperative spondylolisthesis was 14.8%, which reduced to 6.4% postoperatively and 9.4% at the latest follow-up (p=0001). Postoperative disc height was increased to 175% of preoperative values and was statistically significant (p<0.001) and remained improved with an overall change of 139% at the latest follow-up. The radiological fusion rate was 91%. The 12-Item Short Form Health Survey (SF-12) mental and physical component summary improved from 31.7 to 43.0 (p=0.007) and from 35.4 to 51.7 (p=0.0026), respectively. The mean visual analogue scale pain score improved from 7.6 to 2.2 (p<0.001), and the mean Oswestry disability index improved from 56.9 to 17.8% (p<0.0001). The overall clinical success rate was 93%. The posterior disc height correlated with spondylolisthesis reduction (p=0.04) and the only clinical factor affecting reduction was body mass index (p=0.04). The present study provides encouraging short term results for stand-alone ALIF as a procedure for low grade lumbar degenerative spondylolisthesis. Future studies should include adequately powered, prospective, multicentre registry studies with long term follow-up to allow a better assessment of the relative benefits and risks.