Impact of pelvic anteversion on spinopelvic alignment in an asymptomatic population: a dynamic perspective of standing and sitting.

BACKGROUND CONTEXT: A subgroup of patients with pelvic anteversion can present with an unusually large degree of lumbar lordosis (LL), a highly sloped sacrum, and a relatively small pelvic incidence (PI). Prior to lumbar surgery, it can be important to consider such unique sagittal alignment. However, until now, there has been a lack of a predictive model considering different pelvic alignments. Furthermore, the dynamic characteristics of an anteverted pelvis (AP) subgroup have also been unclear. PURPOSE: To build linear predictive formulas for LL that take pelvic anteversion into consideration and to explore the dynamic characteristics of an AP subgroup. STUDY DESIGN: Monocentric, cross-sectional study. PATIENT SAMPLE: Five hundred and sixty-five asymptomatic Chinese men and women between the ages of 18 and 80 years. OUTCOME MEASURES: Sagittal parameters including LL, lumbar lordosis minus thoracic kyphosis (LL-TK), PI, pelvic tilt (PT), pelvic incidence minus lumbar lordosis (PI-LL), sacral slope (SS), sacral slope divided by pelvic incidence (SS/PI), sagittal vertical axis (SVA), thoracic kyphosis (TK), and T1 (first thoracic vertebra) pelvic angle (TPA) were measured on whole spine radiographs obtained with participants in standing and sitting positions. METHODS: All participants underwent radiography in the standing position; 235 of them underwent additional radiography in the sitting position to allow measurement of sagittal parameters. The participants with pelvic anteversion were placed in an AP (anteverted pelvis) group. Sagittal parameters were compared between the AP group and the non-AP group, and predictive formulas for LL based on PI were created in both groups. In addition, changes in sagittal parameters from standing to sitting were compared in the AP group and a PI-matched control group. RESULTS: Of the 565 participants, 171 (30.3%) had pelvic anteversion. In comparison with the non-AP group, the AP group presented with larger LL, a larger SS, and a smaller PT, with relatively small PI. The predictive formulas for LL were LL=0.60° × PI+21.60° (R2=0.268; p<.001) in the whole cohort, LL=0. 83×PI+18.75° (R2=0.427; p<.001) in AP group, and LL=0.79°×PI+9.66° (R2=0.451; p<.001) in the non-AP group. In moving from standing to sitting, the AP group presented with a larger decrease in SS and LL compared with the control group, indicating different patterns of spinopelvic motion. CONCLUSIONS: In the cohort examined, 30.3% present with pelvic anteversion. Those with AP present with unique characteristics of spinopelvic alignment. In moving from standing to sitting, they exhibit different patterns of spinopelvic motion. We found that identifying the degree of anteversion in each person improves the accuracy of linear models for predicting the degree of LL, which in turn can make plans for spine surgery more accurate.

Association between the upper instrumented vertebra screw angles and proximal junctional complications in patients with de novo degenerative lumbar scoliosis.

OBJECTIVE: The aim of this study was to investigate the impact of upper instrumented vertebra (UIV) screw angles on proximal junctional complications in patients with de novo degenerative lumbar scoliosis (DNDLS). METHODS: A total of 120 patients with DNDLS who underwent posterior long-segment instrumentation and fusion were included. Patients were divided into a proximal junctional kyphosis/failure (PJK/PJF) group and a non-PJK/PJF group. Radiographic parameters were measured, including UIV screw angle, UIV slope, UIV screw slope, fixed segmental angle (FSA), and spinopelvic parameters. Clinical and radiographic data were compared between the two groups. Multivariate logistic regression was used to analyze the independent risk factors of PJK/PJF. Receiver operating characteristic (ROC) curve analysis was used to determine the threshold value to predict PJK/PJF. RESULTS: Thirty-six patients (30.0%) developed PJK or PJF during follow-up. Patients in the PJK/PJF group had a larger postoperative UIV screw angle, a larger postoperative UIV screw slope, and a larger postoperative PJA. A significant increase was observed in UIV screw angle from immediately postoperative assessment to the final follow-up in two groups (p < 0.001). Multivariate logistic analysis indicated that a larger positive postoperative UIV screw angle was an independent risk factor for PJK/PJF (OR 1.546, 95% CI 1.274-1.877). ROC curve analysis indicated that a UIV screw angle ≥ 1° is more likely to develop PJK/PJF. Compared with group A patients (UIV screw angle < 1°), group B patients (UIV screw angle ≥ 1°) had a higher incidence of PJK, PJF, UIV screw loosening, and worse functional scores at the final follow-up. CONCLUSIONS: Avoiding insertion of cranially directed UIV pedicle screws may help prevent the development of PJK and PJF in patients with DNDLS.

Risk Factors of Postoperative Coronal Balance Transition in Degenerative Lumbar Scoliosis.

STUDY DESIGN: Retrospective radiographic study. OBJECTIVE: To determine the potential risk factors influencing the transition of postoperative coronal balance in degenerative lumbar scoliosis (DLS) patients. SUMMARY OF BACKGROUND DATA: As time passes after surgery, the spinal sequence of DLS patients may dynamically shift from coronal balance to imbalance, causing clinical symptoms. However, the transition of postoperative coronal balance and its risk factors have not been effectively investigated. MATERIALS AND METHODS: We included 156 DLS patients. The cohort was divided into immediate postoperative coronal balance with follow-up balance (N=73) and follow-up imbalance (N=21), immediate postoperative coronal imbalance (CIB) with follow-up balance (N=23), and follow-up imbalance (N=39). Parameters included age, sex, classification of coronal balance, coronal balance distance, fusion of L5 or S1, location of apical vertebra, apical vertebral translation (AVT), Cobb angle of the main curve and lumbar-sacral curve, tilt and direction of L4/5, tilt and direction of upper instrumented vertebra (UIV), and Cobb angle of T1-UIV. Statistical testing was performed using chi-square/Fisher exact test, t tests or nonparametric tests, correlation testing, and stepwise logistic regression. RESULTS: We identified a significant difference in preoperative AVT, preoperative Cobb angle, and immediate postoperative UIV tilt between patients with and without follow-up balance. Logistic regression analysis demonstrated factors associated with follow-up CIB included preoperative AVT ( P =0.015), preoperative Cobb angle ( P =0.002), and tilt of immediate postoperative UIV ( P =0.018). Factors associated with immediate postoperative CIB in patients with follow-up coronal balance were sex, correction ratio of the main curve, and direction of L4. Logistic regression analysis further identified a correction ratio of main curve ≤0.7 ( P =0.009) as an important predictive factor. CONCLUSION: Patients with immediate postoperative coronal balance and higher preoperative AVT, preoperative Cobb angle, and tilt of immediate postoperative UIV were more likely to experience follow-up CIB. A correction ratio of the main curve ≤0.7 was an independent predictor of follow-up CIB. LEVEL OF EVIDENCE: 3.

Role of the Paraspinal Muscles in the Sagittal Imbalance Cascade: The Effects of Their Endurance and of Their Morphology on Sagittal Spinopelvic Alignment.

BACKGROUND: The role of paraspinal muscle degeneration in the cascade of sagittal imbalance is still unclear. This study aimed to compare paraspinal muscle degeneration in the 4 stages of sagittal imbalance: sagittal balance (SB), compensated sagittal balance (CSB), decompensated sagittal imbalance (DSI), and sagittal imbalance with failure of pelvic compensation (SI-FPC). In addition, it aimed to compare the effects paraspinal muscle endurance and morphology on sagittal spinopelvic alignment in patients with lumbar spinal stenosis. METHODS: A cross-sectional study of 219 patients hospitalized with lumbar spinal stenosis was performed. The isometric paraspinal extensor endurance test and evaluation of atrophy and fat infiltration of the paraspinal extensor muscles and psoas major on magnetic resonance imaging were performed at baseline. Spinopelvic parameters including lumbar lordosis, pelvic tilt, sacral slope, pelvic incidence, and the sagittal vertical axis were measured. RESULTS: The patients with lumbar spinal stenosis were divided into 67 with SB, 85 with CSB, 49 with DSI, and 17 with SI-FPC. There were significant differences in paraspinal muscle endurance and morphology among the 4 groups. Furthermore, the SI-FPC group had poorer paraspinal muscle endurance than either the SB or the CSB group. In multiple linear regression analysis, paraspinal muscle endurance and the relative functional cross-sectional area of the paraspinal extensor muscles were the independent predictors of the sagittal vertical axis, and the relative functional cross-sectional area of the psoas major was the independent predictor of relative pelvic version. CONCLUSIONS: This study indicated that paraspinal muscle degeneration is not only an initiating factor in pelvic retroversion but also a risk factor for progression from a compensated to a decompensated stage. Specifically, the impairment of muscle endurance in the CSB stage may be the reason why patients experience failure of pelvic compensation. In addition, paraspinal muscle endurance and muscle morphology (relative functional cross-sectional area of the paraspinal extensor muscles and psoas major) had different clinical consequences. LEVEL OF EVIDENCE: Prognostic Level II . See Instructions for Authors for a complete description of levels of evidence.

Mini-open Pedicle Subtraction Osteotomy versus Standard Posterior Approach for Ankylosing Spondylitis-related Spinal Kyphosis: A Comparative Study.

OBJECTIVE: Surgical strategy for spinal kyphosis in patients with ankylosing spondylitis (AS) has been challenging. Pedicle subtraction osteotomy (PSO) through a minimally invasive (MI) approach has been developed with promising clinical outcomes. We aimed to compare the effectiveness and safety of PSO via an MI approach and a standard posterior approach (SPA) for treating AS-related spinal kyphosis. METHODS: A total of 41 patients with AS-related spinal kyphosis who underwent PSO through an MI approach (MI surgery [MIS] group: n = 25) or SPA (SPA group: n = 16) between January 2015 and July 2020 were retrospectively included. Spinopelvic parameters were evaluated before the surgery, immediately after the surgery, and at the 2-year follow-up. Clinical data including operative time, estimated blood loss, blood transfusion, level of fusion, incision length, bed rest period, length of hospitalization, and surgical complications were compared between the two groups. The Scoliosis Research Society outcomes instrument-22 (SRS-22) was administered to assess patients' quality of life at the latest follow-up. Comparisons between the two groups were performed using independent sample t-test or Chi-square test. RESULTS: Characteristics and baseline kyphosis of the two groups were matched. At the 2-year follow-up, in the MIS group, the average correction values of the sagittal vertical axis and global kyphosis (GK) were 9.5 cm and 44.3°, respectively. Compared with the SPA group, the MIS group had similar correction values and correction losses after surgery. No obvious differences were observed in any radiographic parameters, except for GK, immediately after surgery and at the 2-year follow-up between the two groups (p > 0.05). The MIS group had a significantly shorter operative time, lesser blood loss, lesser transfusion volume, shorter fusion level, and lesser time to mobilization than did the SPA group. Higher average functional activity scores of SRS-22 were obtained in the MIS group than in the SPA group. CONCLUSION: Mini-open PSO may be an effective alternative to the SPA for treating AS-related spinal kyphosis, with comparable correction effect, lesser surgical trauma and faster recovery. This comparative study may provide valuable guidance for surgical decision-making and patient counseling.

The Role of Thoracic Tilt in Identifying Thoracic Compensation and Predicting Proximal Junctional Kyphosis in Degenerative Lumbar Scoliosis.

STUDY DESIGN: A retrospective cohort study of consecutive patients. OBJECTIVE: To investigate the clinical value of thoracic tilt (TT) in characterizing thoracic compensation and predicting proximal junctional kyphosis (PJK) in degenerative lumbar scoliosis (DLS). SUMMARY OF BACKGROUND DATA: Thoracic compensation has been shown to be associated with the development of PJK, while thoracic shape and morphology in patients with DLS remain understudied. METHODS: Patients with DLS who underwent long-segment fusion were divided into a PJK group and a non-PJK group. Asymptomatic elderly volunteers were recruited as healthy controls. Thoracic parameters were measured in both cohorts, including the TT, T1-L1 pelvic angle (TLPA), T12 slope, thoracic kyphosis (TK, T4-T12), global thoracic kyphosis (GTK, T1-T12), and thoracolumbar kyphosis (TLK, T10-L2). Multivariate logistic regression was used to assess the association between TT and the development of PJK, adjusting for confounders. Multivariate linear regression was used to establish the predictive formula for TT. RESULTS: A total of 126 patients with DLS were enrolled, of which 37 (29.4%) developed PJK. Compared with 110 healthy controls, DLS patients had significantly greater TT, TLPA, T12 slope, and TLK as well as smaller TK and GTK (all P <0.001). Preoperatively, the PJK group showed significantly greater TT ( P =0.013), TLPA ( P <0.001), and TLK ( P =0.034) than the non-PJK group. No significant differences were found in TK and GTK before surgery. Postoperatively, the PJK group showed significantly greater TT ( P <0.001), TLPA ( P <0.001), TLK ( P <0.001), and proximal junctional angle ( P <0.001). Multivariate logistic regression analysis showed that greater postoperative TT was associated with the development of PJK. Multivariate linear regression analysis suggested that the regression formula was postoperative TT=0.675×T12slope+0.412×TK+0.158×TLK-4.808 ( R2 =0.643, P <0.001). CONCLUSIONS: The novel sagittal parameter TT can be used for the evaluation of thoracic compensation. Greater preoperative TT might represent a decompensated state of TK. Rebalancing the TT in a sagittal neutral position might help to prevent PJK in patients with DLS.

Impact of lumbar fusion on spinopelvic sagittal alignment from standing to sitting position: which factor is associated with postoperative functional limitations due to lumbar stiffness?

PURPOSE: To investigate the impact of lumbar fusion on spinopelvic sagittal alignment from standing to sitting position and the influencing factors of postoperative functional limitations due to lumbar stiffness. METHODS: A total of 107 patients who undertook posterior lumbar interbody fusion were included. Patients were divided into two groups: Group A (lumbosacral fusion; n = 43) and Group B (floating fusion; n = 64). Spinopelvic parameters in standing and sitting position including pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), fusion segment lordosis (FSL), upper residual lordosis (URL), lower residual lordosis (LRL), thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), sagittal vertical axis (SVA) and T1 pelvic angle (TPA) were measured before and after lumbar fusion. The Lumbar Stiffness Disability Index (LSDI) was used to assess functional limitations due to lumbar stiffness. RESULTS: Accompanied by increased postoperative LSDI, the values of changes from standing to sitting (∆) were reduced in some parameters compared with the preoperative values. ∆PT and ∆SS significantly decreased in both two groups. In Group A, ∆LL significantly decreased with increased ∆URL. In Group B, ∆LL, ∆URL and ∆LRL showed no significant difference before and after surgery. Multiple linear regression analysis showed that age and ∆PT independently influenced the postoperative LSDI in Group A. CONCLUSION: After lumbar fusion, changes of lumbopelvic sagittal parameters from standing to sitting would be restricted. Adjacent segment lordosis could partially compensate for this restriction. For patients with lumbosacral fusion, postoperative functional limitations due to lumbar stiffness were related to age and the postoperative ∆PT from standing to sitting.

Correlations between paraspinal extensor muscle endurance and clinical outcomes in preoperative LSS patients and clinical value of an endurance classification.

Background: Few study has investigated how paraspinal muscle endurance deteriorates in lumbar spinal stenosis (LSS) patients. In addition, little information is available on the relationship between clinical outcomes and the endurance of paraspinal muscles. Objective: To explore the correlation between paraspinal extensor muscle endurance, quality of life (QOL) and sagittal spinopelvic alignment. Besides, we attempted to propose a paraspinal extensor muscle endurance test (PEMET) classification for identifying the severity of clinical symptoms and sagittal imbalance in LSS patients. Methods: 171 hospitalized LSS patients and 100 healthy controls from the community were prospectively enrolled in this study. The paraspinal extensor endurance test was performed at baseline according to Ito test. The LSS patients were stratified into three groups based on the performance time of endurance test: grade I (<10s); grade II (10-60s); and grade III (>60s). Clinical measures of QOL included the visual analog scale scores (VAS) for back pain and leg pain and the Oswestry Disability Index (ODI). Sagittal alignment was analysed by standing posteroanterior and lateral whole spine X-ray in LSS patients. Results: The LSS group had a significantly shorter performance time of the endurance test than the control group. The paraspinal muscle endurance significantly correlated with VAS-back, VAS-leg, ODI, pelvic tilt, lumbar lordosis and sagittal vertical axis (SVA; all p < 0.05). In binary logistic regression, the performance time of the endurance test was an independent factor of both poor functional status (ODI >40; p = 0.005, OR = 0.985) and global sagittal imbalance (SVA >50 mm; p = 0.019, OR = 0.985). Based on PEMET classification, moving from the grade III group to the grade I group, there was progressive worsening in VAS-back and ODI (all adjusted p < 0.05). Moreover, the grade I group had significantly greater VAS- leg, less LL and greater SVA than the other two groups (all adjusted p < 0.05). Conclusion: Paraspinal muscle endurance was associated with QOL and sagittal spinopelvic alignment in LSS patients. A PEMET classification system has been constructed and has shown a correlation with QOL and sagittal imbalance. Translational potential statement: The PEMET classification system proposed in this study could be available for identifying the severity of clinical symptoms and sagittal imbalance during preoperative evaluation in LSS patients.

Novel application of 3D printed microporous prosthesis to repair humeral nonunion with segmental bone defects: a case report.

Background: Nonunion of the humeral shaft can turn into bone defects. There is no consensus on the optimal treatment of humeral shaft nonunion with bone defects. Herein, we presented a single case of a patient with a 9.5 cm humerus shaft bone defect treated with a 3D printed Ti6Al4V microporous prosthesis after internal fixation failure of a middle-inferior humerus fracture. Case Description: A 53-year-old female who injured her left upper limb by falling was diagnosed with a fracture of the left humeral shaft. The fracture was treated with open reduction and internal fixation. Nine months postoperatively, radiography examination indicated humeral nonunion with a 9.5 cm segmental bone defect. A 3D printing technology was then used to design and fabricate a customized microporous prosthesis with an intramedullary nail and lateral plates. A two-stage surgical strategy was performed, including radical debridement, temporary fixation for the induced membrane formation, and the implantation of the prosthesis. At 18 months of follow-up, encouraging clinical outcomes were observed. The prosthesis remained stable in the original implantation area and callus formation was found at the contact end of the prosthesis and bone stump. The upper limb functions returned to normal with a satisfactory functional score. Also, no complications were found. Conclusions: Reconstruction with a 3D printed microporous prosthesis might be used as an alternative for the repair of large segmental bone defects of limbs.

Mechanical Distribution and New Bone Regeneration After Implanting 3D Printed Prostheses for Repairing Metaphyseal Bone Defects: A Finite Element Analysis and Prospective Clinical Study.

Critical metaphyseal bone defects caused by nonunion and osteomyelitis are intractable to repair in clinical practice owing to the rigorous demanding of structure and performance. Compared with traditional treatment methods, 3D printing of customized porous titanium alloy prostheses offer feasible and safe opportunities in repairing such bone defects. Yet, so far, no standard guidelines for optimal 3D printed prostheses design and fixation mode have been proposed to further promote prosthesis stability as well as ensure the continuous growth of new bone. In this study, we used a finite element analysis (FEA) to explore the biomechanical distribution and observed new bone regeneration in clinical practice after implanting 3D printed prostheses for repairing metaphyseal bone defects. The results reflected that different fixation modes could result in diverse prosthesis mechanical conductions. If an intramedullary (IM) nail was applied, the stress mainly conducted equally along the nail instead of bone and prosthesis structure. While the stress would transfer more to the lateral bone and prosthesis's body when the printed wing and screws are selected to accomplish fixation. All these fixation modes could guarantee the initial and long-term stability of the implanted prosthesis, but new bone regenerated with varying degrees under special biomechanical environments. The fixation mode of IM nail was more conducive to new bone regeneration and remodeling, which conformed to the Wolff's law. Nevertheless, when the prosthesis was fixed by screws alone, no dense new callus could be observed. This fixation mode was optional for defects extremely close to the articular surface. In conclusion, our innovative study could provide valuable references for the fixation mode selection of 3D printed prosthesis to repair metaphyseal bone defect.

Development of Nervilia fordii Extract-Loaded Electrospun PVA/PVP Nanocomposite for Antioxidant Packaging.

An ethyl acetate extract from of Nervilia fordii (NFE) with considerable suppression activity on lipid peroxidation (LPO) was first obtained with total phenolic and flavonoid contents and anti-LPO activity (IC50) of 86.67 ± 2.5 mg GAE/g sample, 334.56 ± 4.7 mg RE/g extract and 0.307 mg/mL, respectively. In order to improve its stability and expand its application in antioxidant packaging, the nano-encapsulation of NFE within poly(vinyl alcohol) (PVA) and polyvinyl(pyrrolidone) (PVP) bio-composite film was then successfully developed using electrospinning. SEM analysis revealed that the NFE-loaded fibers exhibited similar morphology to the neat PVA/PVP fibers with a bead-free and smooth morphology. The encapsulation efficiency of NFE was higher than 90% and the encapsulated NFE still retained its antioxidant capacity. Fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD) analysis confirmed the successful encapsulation of NFE into fibers and their compatibility, and the thermal stability of which was also improved due to the intermolecular interaction demonstrated by thermo gravimetric analysis (TGA). The ability to preserve the fish oil's oxidation and extend its shelf-life was also demonstrated, suggesting the obtained PVA/PVP/NFE fiber mat has the potential as a promising antioxidant food packaging material.