Patient-specific 3D-printed Brace for Adolescent Idiopathic Scoliosis: A Prospective Cohort Study.

OBJECTIVE: To evaluate the efficacy, safety of patient-tailored 3D printed brace in the treatment of adolescent idiopathic scoliosis (AIS), and to compare the health-related quality of life (HRQoL) of patients treated with two different types of brace. MATERIALS AND METHODS: From September 2017 to August 2020, 103 AIS patients requiring non-operative management were prospectively recruited in this study. All patients were followed up every 6 months, clinical and radiological examination were assessed at each follow-up time. Full-length anteroposterior X-ray of the spine in the standing position was performed obtained. At the last follow-up, each patient completed a standardized HRQoL questionnaire. Compliance is defined as that the patient insists on wearing the brace for ≥ 23h every day (full-time wearing) and follow-up every 6 months until bone maturity.The rate of major curve Cobb progression was defined that maximum Cobb Angle of major curve greater than 6° compared with that at the initial diagnosis, or aggravated to more than 45° so that orthopedic surgery was recommended during treatment, which was defined as the rate of conversion to surgery. The effects of these two types of braces on the rate of major curve Cobb progression and HRQoL were analyzed by independent sample t-test ad Chi-square test. RESULTS: The thickness was 4 mm for thoracolumbosacral orthosis (TLSO) and 3 mm for 3D-printed brace (3DPB). In addition, compared with the material used in TLSO, the weight (600-800 grams) of the 3DPB materials with the same area is reduced by about 25-30%. 55 patients (49.1%) and 48 patients (33.1%) were respectively included in the 3DPB cohort and the TLSO cohort.The maximum Cobb angle of major curve in the 3DPB cohort was significantly lower than those in the TLSO cohort at 6 months, 12 months and the last follow-up (p < 0.01). The thoracic kyphosis (TK) and lumbar lordosis (LL) of the two cohorts at the last follow-up were lower than those before brace treatment, in addition, there was a significant difference in TK (p = 0.001) and LL (p = 0.004) between the two cohorts at the follow-up. The scores of physical function, pain, self-image, mental health and treatment satisfaction in the Chinese version of SRS-22 in the 3DPB cohort were higher than those in the TLSO cohort (p < 0.01 and p < 0.05, respectively). The scores of the 3DPB cohort were significantly higher than those of the TLSO group in the four dimensions (p = 0.008, 0.013, 0.015, and 0.002, respectively) of the EuroQol-5D health description system except for mobility, and the overall health status of EuroQol-5D was higher for the 3DPB cohort (p < 0.001). At the last follow-up, One patient in the 3DPB cohort and ten patients in the TLSO cohort had major curve Cobb progression of greater than 6°, and the rate of major curve Cobb progression in 3DPB cohort was significantly lower than that in the TLSO cohort (OR 14.2, 95% CI 1.7∼115.8, p < 0.01). One patient in the 3DPB and seven patients in the TLSO cohorts received subsequent surgery or was recommended for surgery, and the rate of conversion to surgery was significantly lower than in the 3DPB cohort (OR 9.2, 95% CI 1.1∼77.9, p < 0.05). CONCLUSIONS: Patient-tailored 3D-printed brace is lighter, thinner, and more comfortable than conventional braces in the treatment of AIS. It can substantially improve the HRQoL of patients and can significantly reduce the progression of major curve Cobb progression and rate of conversion of surgery.

Paraspinal Muscle Endurance and Morphology (PMEM) Score: A New Method for Prediction of Postoperative Mechanical Complications After Lumbar Fusion.

BACKGROUND CONTEXT: Although the relationships between paraspinal muscles and lumbar degenerative disorders have been acknowledged, paraspinal muscle evaluation has not been incorporated into clinical therapies. PURPOSE: We aimed to establish a novel paraspinal muscle endurance and morphology (PMEM) score to better predict mechanical complications after lumbar fusion. STUDY DESIGN: Prospective cohort study. PATIENT SAMPLE: A total of 212 patients undergoing posterior lumbar interbody fusion with at least one year of follow-up were finally included. OUTCOME MEASURES: Mechanical complications including screw loosening, pseudarthrosis and other complications like cage subsidence, and patient-reported outcomes were evaluated at last follow-up. METHODS: The PMEM score comprised one functional muscular parameter (the performance time of the endurance test) and two imaging muscular parameters (relative functional cross-sectional area [rFCSA] of paraspinal extensor muscles [PEM] and psoas major [PS] on magnetic resonance imaging). The score was established based on a weighted scoring system created by rounding ß regression coefficients to the nearest integer in univariate logistic regression. The diagnostic performance of the PMEM score was determined by binary logistic regression model and receiver operating characteristic (ROC) curve with the area under the curve (AUC). Additionally, pairwise comparisons of ROC curves were conducted to compare the diagnostic performance of the PMEM score with conventional methods based on a single muscular parameter. Moreover, differences of mechanical complications and patient-reported outcomes among the PMEM categories were analyzed using Chi-square test with Bonferroni correction. RESULTS: The PMEM score, calculated by adding the scores for each parameter, ranges from 0 to 5 points. Patients with higher PMEM scores exhibited higher rates of mechanical complications (p < 0.001). Binary logistic regression revealed that the PMEM score was an independent factor of mechanical complications (p < 0.001, OR = 2.002). Moreover, the AUC of the PMEM score (AUC = 0.756) was significantly greater than those of the conventional methods including the endurance test (AUC = 0.691, Z = 2.036, p < 0.05), PEM rFCSA (AUC = 0.690, Z = 2.016, p < 0.05) and PS rFCSA (AUC = 0.640, Z = 2.771, p < 0.01). In terms of the PMEM categories, a score of 0 to 1 was categorized as low-risk muscular state of mechanical complications; 2 to 3, as moderate; and 4 to 5, as high-risk state. Moving from the low-risk state to the high-risk state, there was a progressive increase in the rates of mechanical complications (13.8% vs 32.1% vs 72.7%; p < 0.001), and a decrease in the rates of clinically significant improvement of patient-reported outcomes (all p < 0.05). CONCLUSIONS: The PMEM score might comprehensively evaluate paraspinal muscle degeneration and exhibit greater ability in predicting mechanical complications than the conventional evaluations after lumbar fusion. Surgeons might develop individualized treatment strategy tailored to different muscle degeneration statuses reflected by the PMEM score for decreasing the risk of mechanical complications.

Preoperative and follow-up variations of psoas major muscle are related to S1 screw loosening in patients with degenerative lumbar spinal stenosis.

BACKGROUND: It was reported the paraspinal muscle played an important role in spinal stability. The preoperative paraspinal muscle was related to S1 screw loosening. But the relationship between preoperative and postoperative change of psoas major muscle (PS) and S1 pedicle screw loosening in degenerative lumbar spinal stenosis (DLSS) patients has not been reported. This study investigated the effects of preoperative and follow-up variations in the psoas major muscle (PS) on the first sacral vertebra (S1) screw loosening in patients with DLSS. METHODS: 212 patients with DLSS who underwent lumbar surgery were included. The patients were divided into the S1 screw loosening group and the S1 screw non-loosening group. Muscle parameters were measured preoperatively and at last follow-up magnetic resonance imaging. A logistic regression analysis was performed to investigate the risk factors for S1 screw loosening. RESULTS: The S1 screw loosening rate was 36.32% (77/212). The relative total cross-sectional areas and relative functional cross-sectional areas (rfCSAs) of the PS at L2-S1 were significantly higher after surgery. The increased rfCSA values of the PS at L3-S1 in the S1 screw non-loosening group were significantly higher than those in the S1 screw loosening group. The regression analysis showed male, lower CT value of L1 and longer segment fusion were independent risk factors for S1 screw loosening, and postoperative hypertrophy of the PS was a protective factor for S1 screw loosening. CONCLUSIONS: Compared to the preoperative muscle, the PS size increased and fatty infiltration decreased after surgery from L2-3 to L5-S1 in patients with DLSS after short-segment lumbar fusion surgery. Postoperative hypertrophy of the PS might be considered as a protective factor for S1 screw loosening. MRI morphometric parameters and postoperative selected exercise of PS for DLSS patients after posterior lumbar fusion surgery might contribute to improvement of surgical outcome.

Mimicking the mechanical properties of cortical bone with an additively manufactured biodegradable Zn-3Mg alloy.

Additively manufactured (AM) biodegradable zinc (Zn) alloys have recently emerged as promising porous bone-substituting materials, due to their moderate degradation rates, good biocompatibility, geometrically ordered microarchitectures, and bone-mimicking mechanical properties. While AM Zn alloy porous scaffolds mimicking the mechanical properties of trabecular bone have been previously reported, mimicking the mechanical properties of cortical bone remains a formidable challenge. To overcome this challenge, we developed the AM Zn-3Mg alloy. We used laser powder bed fusion to process Zn-3Mg and compared it with pure Zn. The AM Zn-3Mg alloy exhibited significantly refined grains and a unique microstructure with interlaced α-Zn/Mg2Zn11 phases. The compressive properties of the solid Zn-3Mg specimens greatly exceeded their tensile properties, with a compressive yield strength of up to 601 MPa and an ultimate strain of >60 %. We then designed and fabricated functionally graded porous structures with a solid core and achieved cortical bone-mimicking mechanical properties, including a compressive yield strength of >120 MPa and an elastic modulus of ≈20 GPa. The biodegradation rates of the Zn-3Mg specimens were lower than those of pure Zn and could be adjusted by tuning the AM process parameters. The Zn-3Mg specimens also exhibited improved biocompatibility as compared to pure Zn, including higher metabolic activity and enhanced osteogenic behavior of MC3T3 cells cultured with the extracts from the Zn-3Mg alloy specimens. Altogether, these results marked major progress in developing AM porous biodegradable metallic bone substitutes, which paved the way toward clinical adoption of Zn-based scaffolds for the treatment of load-bearing bony defects. STATEMENT OF SIGNIFICANCE: Our study presents a significant advancement in the realm of biodegradable metallic bone substitutes through the development of an additively manufactured Zn-3Mg alloy. This novel alloy showcases refined grains and a distinctive microstructure, enabling the fabrication of functionally graded porous structures with mechanical properties resembling cortical bone. The achieved compressive yield strength and elastic modulus signify a critical leap toward mimicking the mechanical behavior of load-bearing bone. Moreover, our findings reveal tunable biodegradation rates and enhanced biocompatibility compared to pure Zn, emphasizing the potential clinical utility of Zn-based scaffolds for treating load-bearing bony defects. This breakthrough opens doors for the wider adoption of zinc-based materials in regenerative orthopedics.

Deep Learning Model Coupling Wearable Bioelectric and Mechanical Sensors for Refined Muscle Strength Assessment.

Muscle strength (MS) is related to our neural and muscle systems, essential for clinical diagnosis and rehabilitation evaluation. Although emerging wearable technology seems promising for MS assessment, problems still exist, including inaccuracy, spatiotemporal differences, and analyzing methods. In this study, we propose a wearable device consisting of myoelectric and strain sensors, synchronously acquiring surface electromyography and mechanical signals at the same spot during muscle activities, and then employ a deep learning model based on temporal convolutional network (TCN) + Transformer (Tcnformer), achieving accurate grading and prediction of MS. Moreover, by combining with deep clustering, named Tcnformer deep cluster (TDC), we further obtain a 25-level classification for MS assessment, refining the conventional 5 levels. Quantification and validation showcase a patient's postoperative recovery from level 3.2 to level 3.6 in the first few days after surgery. We anticipate that this system will importantly advance precise MS assessment, potentially improving relevant clinical diagnosis and rehabilitation outcomes.

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.

Time trends in the burden of low back pain and its associated risk factors in China from 1990 to 2019.

Background: From 1990 to 2019, low back pain (LBP) was the leading cause of years lived with disability (YLDs) in China. However, the change patterns of LBP and its risk factors in China remain unclear. Methods: Data from the Global Burden of Disease Study 2019 were used. We used the join-point regression model and age-period-cohort analysis to evaluate the time trends of attributable risk factors on the burden of LBP. Results: In 2019, the risk factors included in this analysis accounted for 4.36 million YLDs of LBP, representing 42.2% of all YLDs of LBP in China, with 2.86 million due to occupational ergonomic factors, 1.74 million due to smoking, and 0.46 million due to high body mass index (BMI). The age-standardized YLD rates of LBP showed downward trends during 1990-2019, while there was a faster decline between 1990 and 1994. The curves of local drifts, which reflected the average annual percentage change across age groups, showed an increasing trend with age for high BMI and smoking, and a downward trend for occupational ergonomic factors. The YLD rates for LBP increased dramatically with age for high BMI, while it reached a peak at 40-60 years old for occupational ergonomic factors, and 65-80 years old for smoking. The period and cohort rate ratios of LBP YLD decreased in the past 3 decades for occupational ergonomic factors and smoking, while increased for high BMI. Conclusions: Our results provided strong evidence that there were diverse changing patterns for different risk factors, highlighting the need for risk-specific strategies. The translational potential of this article: China has the largest senior population and the fastest aging population in the world. Given that LBP typically occurs in the senior population, there would be an increasing LBP burden on China's health system. This suggests that effective strategies for LBP prevention should be strictly implemented in China, particularly in the senior population, which is of crucial translational potential.

Involvement of DJ-1 in the pathogenesis of intervertebral disc degeneration via hexokinase 2-mediated mitophagy.

Intervertebral disc degeneration (IDD) is an important pathological basis for degenerative spinal diseases and is involved in mitophagy dysfunction. However, the molecular mechanisms underlying mitophagy regulation in IDD remain unclear. This study aimed to clarify the role of DJ-1 in regulating mitophagy during IDD pathogenesis. Here, we showed that the mitochondrial localization of DJ-1 in nucleus pulposus cells (NPCs) first increased and then decreased in response to oxidative stress. Subsequently, loss- and gain-of-function experiments revealed that overexpression of DJ-1 in NPCs inhibited oxidative stress-induced mitochondrial dysfunction and mitochondria-dependent apoptosis, whereas knockdown of DJ-1 had the opposite effect. Mechanistically, mitochondrial translocation of DJ-1 promoted the recruitment of hexokinase 2 (HK2) to damaged mitochondria by activating Akt and subsequently Parkin-dependent mitophagy to inhibit oxidative stress-induced apoptosis in NPCs. However, silencing Parkin, reducing mitochondrial recruitment of HK2, or inhibiting Akt activation suppressed DJ-1-mediated mitophagy. Furthermore, overexpression of DJ-1 ameliorated IDD in rats through HK2-mediated mitophagy. Taken together, these findings indicate that DJ-1 promotes HK2-mediated mitophagy under oxidative stress conditions to inhibit mitochondria-dependent apoptosis in NPCs and could be a therapeutic target for IDD.

Distal Junctional Failures in Degenerative Thoracolumbar Hyperkyphosis.

OBJECTIVE: Degenerative thoracolumbar hyperkyphosis (DTH) is a disease that negatively affects individual health and requires surgical intervention, yet the ideal surgical approach and complications, especially distal junctional failures (DJF), remain poorly understood. This study aims to investigate DJF in DTH and to identify the risk factors for DJF so that we can improve surgical decision-making, and advance our knowledge in the field of spinal surgery to enhance patient outcomes. METHODS: This study retrospectively reviewed 78 cases (late osteoporotic vertebral compression fracture [OVCF], 51; Scheuermann's kyphosis [SK], 17; and degenerative disc diseases [DDD], 10) who underwent corrective surgery in our institute from 2008 to 2019. Clinical outcomes were assessed using health-related quality of life (HRQOL) measures, including the visual analogue scale (VAS) scores for back and leg pain, the Oswestry disability index (ODI), and the Japanese Orthopaedic Association (JOA) scoring system. Multiple radiographic parameters, such as global kyphosis (GK) and thoracolumbar kyphosis (TLK), were assessed to determine radiographic outcomes. Multivariate logistic regression analysis was employed to identify the risk factors associated with DJF. RESULTS: HRQOL improved, and GK, TLK decreased at the final follow-up, with a correction rate of 67.7% and 68.5%, respectively. DJF was found in 13 of 78 cases (16.7%), two cases had wedging in the disc (L3-4) below the instrumentation, one case had a fracture of the lowest instrumented vertebrae (LIV), one case had osteoporotic fracture below the fixation, nine cases had pull-out or loosening of the screws at the LIV and three cases (23.1%) required revision surgery. The DJF group had older age, lower computed tomography Hounsfield unit (CT HU), longer follow-up, more blood loss, greater preoperative sagittal vertical axis (SVA), and poorer postoperative JOA and VAS scores (back). The change in TLK level was larger in the non-DJF group. Post-sagittal stable vertebrae (SSV) moved cranially compared with pre-SSV. CONCLUSION: Age, CT HU, length of follow-up, estimated blood loss, and preoperative SVA were independent risk factors for DJF. We recommend fixation of the two vertebrae below the apex vertebrae for DTH to minimize surgical trauma.

Factors associated with non-fusion after direct pars repair of lumbar spondylolysis with pedicle screw and lamina hook: a clinical and CT-assessed study.

BACKGROUND: Pedicle screw and lamina hook (PSLH) technique is an effective and popular method for direct pars repair of lumbar spondylolysis. There is a lack of studies to explore factors that may influence the healing of spondylolysis after direct pars repair surgery. The present study aimed to investigate the factors associated with non-fusion after direct pars repair of lumbar spondylolysis with PSLH technique. METHODS: A total of 55 subjects (average age 21.1 ± 6.3 years, a total of 120 pars defects) diagnosed with symptomatic spondylolysis and underwent pars repair surgery with PSLH were followed up and their clinical data were analyzed. Subjects were divided into a non-fusion group and fusion group according to whether the pars defect had bony fusion at last follow-up assessed by CT. Radiographic data, data related to spondylolysis and clinical outcomes were collected and compared between groups. RESULTS: The mean follow-up time of the 55 patients was 24.8 ± 12.0 (12-64) months. Among the 120 pars defects, 101 defects were successfully fused and 19 were not fused according to CT. The fusion rate was 84.2%. Multivariable logistic regression analysis showed the factors correlated with non-fusion after pars repair surgery: whether the spondylolysis segment was associated with spina bifida occulta (SBO) (P = 0.001), stage of the defect (P = 0.047), width of the defect (P = 0.002), and disc degeneration (P = 0.014). CONCLUSION: Direct pars repair by PSHL is a reliable treatment for lumbar spondylolysis with a fusion rate of 84.2%. Association with SBO of the spondylolysis segment, a terminal stage of the defect, a wider defect gap, and grade III disc degeneration may be factors associated with non-fusion after direct pars repair of lumbar spondylolysis with PLSH. Non-fusion patients after pars repair appear to have worse clinical results compared to fusion patients.

How surface-to-volume ratio affects degradation of magnesium: in vitro and in vivo studies.

Despite the many studies carried out over the past decade to determine the biodegradation performance of magnesium and its alloys, few studies focused on the effect of altered surface area to volume ratio on in vitro and in vivo degradation rate and osteogenesis. Here, high purity magnesium cylindrical rods with gradient of surface area to volume ratio were processed by excavating different numbers of grooves on the side surface. The immersion test in SBF solution and the rat femoral condylar bone defect model were used to evaluate the degradation of magnesium rods in vitro and in vivo, respectively. We demonstrated that, the increased number of grooves on the HP magnesium surface represented a decrease in the percentage of residual volume over time, not necessarily an increase in absolute degradation volume or a regular change in corrosion rate. Furthermore, there were strong linear correlations between the relative degradation volume and the initial surface-to-volume ratio of HP magnesium rods both in vitro and in vivo. The difference in the slope of this relationship in vitro and in vivo might help to determine the possible range of in vivo degradation rates via in vitro data. In addition, the corrosion rate is more suitable for evaluating bone formation surrounding the different HP magnesium rods. Our findings in this work may facilitate adjusting the in vivo degradation and osteogenesis of different kinds of orthopedic implants made of the same magnesium-based material, and thus, accelerate the clinical popularization and application.

Imaging signs for preoperative diagnosis of dural ossification in patients with thoracic ossification of the ligamentum flavum: a blind, randomized diagnostic accuracy study.

Background: Dural ossification (DO) is the leading cause of surgery-related dural tear in patients with ossification of the ligamentum flavum (OLF). An accurate preoperative diagnosis of DO is conducive to the selection of appropriate surgical methods. Although several imaging signs, such as Banner cloud sign (BCs), tram-track sign (TTs), and comma sign (Cs) have been proposed for the preoperative diagnosis of DO, their diagnostic value has not been well studied. The aim of this study was to explore the diagnostic value of BCs, TTs, and Cs, and provide evidence-based data for their clinical application. Methods: This is a blind, randomized diagnostic study using retrospectively collected data from 102 consecutive patients who were diagnosed with OLF and underwent decompression surgery between January 2018 and June 2019. A total of 8 surgeons with different qualifications were recruited to read these imaging signs to identify the presence of DO. Surgical records were used as the reference standard. Sensitivity, specificity, and the area under the receiver operating characteristic (ROC) curve (AUC) were used to evaluate the diagnostic accuracy of each imaging sign and their different combinations. Results: Of the 102 patients, 21 were diagnosed with DO. BCs had a significantly higher diagnostic accuracy than TTs and Cs, with the AUC of 0.704, 0.607, and 0.593, respectively. The specificity of BCs, Cs, TTs, and their combination in diagnosing DO was 91.5%, 92.1%, 68.3%, and 62.2%, respectively. In the combined diagnostic test, the results showed that the combined diagnosis accuracy of BCs and Cs was the highest, and the AUC was 0.738. The combination of BCs, Cs, and TTs increased the sensitivity of diagnosing DO (77.5%), but did not improve the diagnostic accuracy, and the AUC was 0.699. Conclusions: BCs had higher diagnostic accuracy than TTs and Cs. BCs and Cs were highly specific for DO, whereas TTs could be confusing due to their non-specific presentations. The combination of BCs, TTs, and Cs improved the sensitivity of DO diagnosis, but not the specificity and accuracy.

Relationship between the postoperative variations of paraspinal muscles and adjacent-segment degeneration in patients with degenerative lumbar spinal stenosis after posterior instrumented lumbar fusion.

OBJECTIVE: This study aimed to quantify pre- and postoperative paraspinal muscular variation following posterior lumbar interbody fusion (PLIF) in patients with degenerative lumbar spinal stenosis (DLSS) and measure the association of this variation with adjacent-segment degeneration (ASD). METHODS: Data from 149 patients who underwent L4-S1 PLIF for DLSS were collected. Patients were divided into radiologically confirmed ASD and control groups according to follow-up radiological findings. MRI was performed before surgery and at the last follow-up. Muscular parameters including the relative cross-sectional area (rCSA), relative functional cross-sectional area (rFCSA), relative total cross-sectional area (rTCSA), and fatty infiltration (FI) of the multifidus (MF), erector spinae (ES), and psoas major (PM) muscles were measured on preoperative and follow-up L2-S1 MR images. Logistic regression was used to investigate risk factors for ASD. RESULTS: The rate of radiological ASD was 42.3% at the final follow-up (mean 25.71 ± 8.35 months). At surgical levels, the rFCSA and rTCSA of the MF and ES muscles decreased. The FI of the MF from L2-3 to L5-S1 and ES muscles at L5-S1 significantly increased after surgery, while the rFCSA and rTCSA of the PM muscle increased and its FI decreased. At adjacent levels, the rFCSA and rTCSA of the MF muscle and rTCSA of the ES muscle decreased and the FI of the MF muscle increased postoperatively (p < 0.05), but the rFCSA and rTCSA of the PM muscle increased and its FI decreased (p < 0.05). The FIs of the MF, ES, and PM muscles at adjacent levels significantly differed between the ASD and control groups. Logistic regression analysis indicated that higher BMI (p = 0.002) and FI of the PM muscle at adjacent levels (p = 0.025) were significant risk factors for ASD. CONCLUSIONS: The functional area decreased in the MF and ES muscles and increased in the PM muscle after L4-S1 PLIF. A compensatory postoperative decrease in FI of the PM muscle at the adjacent level was a protective factor for ASD in DLSS patients after PLIF.

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.

In vivo segmental vertebral kinematics in patients with degenerative lumbar scoliosis.

PURPOSE: This study aimed to find a standard of the vertebra kinematics during functional weight-bearing activities in degenerative lumbar scoliosis (DLS) patients. METHODS: Fifty-four patients were involved into this study with forty-two in DLS group and twelve in the control group. The three-dimensional (3D) vertebral models from L1 to S1 of each participant were reconstructed by computed tomography (CT). Dual-orthogonal fluoroscopic imaging, along with FluoMotion and Rhinoceros software, was used to record segmental vertebral kinematics during functional weight-bearing activities. The primary and coupled motions of each vertebra were analyzed in patients with DLS. RESULTS: During flexion-extension of the trunk, anteroposterior (AP) translation and craniocaudal (CC) translation at L5-S1 were higher than those at L2-3 (9.3 ± 5.1 mm vs. 6.4 ± 3.5 mm; P < 0.05). The coupled mediolateral (ML) translation at L5-S1 in patients with DLS was approximately three times greater than that in the control group. During left-right bending of the trunk, the coupled ML rotation at L5-S1 was higher in patients with DLS than that in the control group (17.7 ± 10.3° vs. 8.4 ± 4.4°; P < 0.05). The AP and CC translations at L5-S1 were higher than those at L1-2, L2-3, and L3-4. During left-right torsion of the trunk, the AP translation at L5-S1 was higher as compared to other levels. CONCLUSIONS: The greatest coupled translation was observed at L5-S1 in patients with DLS. Coupled AP and ML translations at L5-S1 were higher than those in healthy participants. These data improved the understanding of DLS motion characteristics.

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.

Impact of preoperative clinical state on 2-year clinical outcomes following degenerative lumbar scoliosis surgery.

To assess the preoperative clinical state's impact on clinical outcomes after surgery for degenerative lumbar scoliosis (DLS) based on the minimal clinically important difference (MCID). Preoperative and follow-up (FU) scores in each Scoliosis Research Society-22 (SRS-22) domain were compared with age- and sex-matched normative references. At baseline, patients were classified by differences from normative values in four groups: Worst, Severe, Poor, and Moderate. At 2 years postoperative FU, patients were divided into four groups (Worst Severe Poor Asymptomatic) based on the difference in MCID between postoperative and normal values. The changes in MCID were considered as the criterion for surgical efficacy. In addition, we calculated the classification of preoperative and FU clinical symptom severity in each domain in same patient. The distinction among curve types was also performed based on the SRS-Schwab classification. A total of 123 patients were included. During FU, patients with more severe preoperative clinical symptoms were more likely to achieve clinical changes (>1 MCID, p < 0.05), but the rate of reaching "asymptomatic" was lower (p < 0.05). Kendall's tau-b correlation analysis found that preoperative clinical severity was correlated with clinical changes category in Activity (Tau-b = 0.252; p = 0.002), Pain (Tau-b = 0.230; p = 0.005), Appearance (Tau-b = 0.307; p < 0.001), and Mental (Tau-b = 0.199; p = 0.016), and it also was correlated with FU clinical severity in Activity (Tau-b = 0.173; p = 0.023), Pain (Tau-b = 0.280; p < 0.001), and Mental (Tau-b = 0.349; p < 0.001). There was a correlation between preoperative clinical severity and FU SRS-22 score outcomes. Patients with severe preoperative clinical symptoms can experience better treatment outcomes during FU, but it is also more difficult to recover to the normal reference.

Upper instrumented vertebrae selection criteria for degenerative lumbar scoliosis based on the hounsfield unit asymmetry of the first coronal reverse vertebrae: an observational study.

BACKGROUND: Selection of the upper instrumented vertebra (UIV) is crucial for surgical treatment of degenerative lumbar scoliosis (DLS), given the relevance of UIV in postoperative proximal adjacent segment degeneration (pASD). Our previous research found that selection of UIV not lower than (≤) the first coronal reverse vertebra (FCRV), which marks the turning point of Hounsfield unit (HU) asymmetry, could significantly reduce pASD. However, the degree of HU asymmetry can vary among patients, suggesting a demand for more individualized UIV selection criteria, which we aimed to develop using quantitative HU measurement in the current study. METHODS: We included 153 consecutive patients with DLS. Quantitative measurement of HU of both sides of the vertebrae of these patients was performed on three planes of CT reconstruction for average values and determination of FCRV. Pre- and postoperative X-ray plain films were examined for radiological measurements and determination of pASD. Further, 35 patients with lumbar disc herniation and without significant scoliosis were also included as the reference group, and their bilateral HU was measured. RESULTS: In all 153 patients, those with UIV ≤ FCRV had a significantly lower rate of pASD (9.4% vs. 24.6%, P = 0.011). The difference between HU of the left and right sides of the FCRV (dF) could range from close to 0-59.4. The difference between HU of the left and right sides of the vertebrae in the reference group had an average value of 5.21. In 101 dF ≥ 5 DLS patients, those with UIV ≤ FCRV had a significantly lower rate of pASD (7.6% vs. 28.6%, P = 0.005), while this rate was insignificant in the other 52 dF < 5 patients (13.3% vs. 18.2%, P = 0.708). No other general, radiological, or operative parameter was found to have significant influence on the occurrence of pASD. CONCLUSIONS: Selection of UIV ≤ FCRV can significantly reduce the risk of pASD for patients with DLS with dF ≥ 5. Trial Registration Not applicable, since this is an observational study.

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.