BACKGROUND: Previous research has identified a specific subtype known as failure of pelvic compensation (FPC) in patients with adult spinal deformity (ASD). However, the criteria for assessing FPC remain inconsistent, and its impacts on spinal sagittal alignment and health-related quality-of-life (HRQoL) scores remain unclear.
OBJECTIVE: To propose a novel criterion for identifying FPC based on variations in spinopelvic alignment during the transition from the supine to upright position and to evaluate the effects of FPC on patients\' spinal sagittal alignment and HRQoL scores.
METHODS: Retrospective cross-sectional study.
METHODS: Patients with ASD from a monocenter database.
METHODS: Radiographic measures, including thoracic kyphosis (TK), lumbar lordosis (LL), sacral slope (SS), pelvic tilt, pelvic incidence (PI), and sagittal vertical axis (SVA), were measured on lateral whole-spine radiographs. LL and SS were also measured on reconstructed lumbar computed tomography images in the sagittal view taken in the supine position. The relative functional cross-sectional area (rFCSA) of paraspinal muscles was evaluated via lumbar magnetic resonance imaging. HRQoL measures, encompassing visual analog scale for back pain (VAS-BP), Oswestry Disability Index (ODI), and Scoliosis Research Society-22R (SRS-22R), were collected.
METHODS: A total of 154 patients were enrolled. Based on the calculated minimum detectable change of SS, FPC was defined as the change in SS of less than 3.4° between supine and upright positions. Patients were divided into 3 groups: sagittal balance with pelvic compensation (SI-PC), sagittal imbalance with pelvic compensation (SI-PC), and sagittal imbalance with failure of pelvic compensation (SI-FPC). Radiographic parameters and HRQoL scores were compared among the groups.
RESULTS: Thirty-six patients were categorized into the SB-PC group, 87 into the SI-PC group, and 31 into the SI-FPC group. Patients with low PI and small paraspinal muscles rFCSA were more prone to experiencing FPC accompanied by severe sagittal imbalance. The SI-FPC group exhibited less TK and a larger SS than the SI-PC group exhibited and had a similar SVA as that of the SI-PC group. Additionally, they displayed worse VAS-BP, ODI, SRS-function, and SRS-22 total scores than the SB-PC group displayed.
CONCLUSIONS: In patients with ASD, an inherently low pelvic compensatory reserve and a high fatty infiltration in paraspinal muscles are pivotal factors contributing to FPC. Compared with SI-PC patients, SI-FPC patients demonstrate a thoracic-dominant compensatory pattern for sagittal malalignment. In addition, these patients experienced more severe pain and functional decline than the SB-PC patients experienced.

OBJECTIVE: Robot-assisted total knee arthroplasty (TKA) was developed to improve the precision and accuracy of implant placement in conventional TKA. However, the angular differences between referenced axes in robot-assisted TKA and conventional TKA remain unclear. The aim of this study was to investigate the angular differences in sagittal alignment between robot-assisted TKA and conventional TKA for both the femur and the tibia and to discuss their clinical implications.
METHODS: We conducted a retrospective analysis of data from 100 patients (97 patients) who underwent computed tomography (CT) for Mako TKA. We measured the angle between the robot femoral axis (RFA) and conventional femoral axis (CFA) in the sagittal plane and the angle between the robot tibial axis (RTA) and the conventional tibial axis (CTA). Angles were compared between the sexes. Correlation analysis was conducted between the angles and height.
RESULTS: In the sagittal plane, the mean RFA-CFA angle was 2.2° ± 1.6°, and the mean RTA-CTA angle was 2.3° ± 1.6°. There were no significant differences between the two angles among males and females (p > 0.05). There was a correlation between the RFA-CFA angle and RTA-CTA angle (p < 0.001, r = 0.33), and there was a correlation between height and the combination of the RFA-CFA angle and RTA-CTA angle (p = 0.03, r = 0.22).
CONCLUSIONS: There are angular differences between the axes referenced by robot-assisted TKA and those referenced by conventional TKA, which may be influenced by patient height. Correctly understanding these differences is crucial when evaluating the implant position and surgical outcomes after robot-assisted TKA. Furthermore, caution should be taken when assessing the flexion-extension angle of the knee since the angles displayed in the Mako system are different from the angles measured with intramedullary anatomical axes. After all, sagittal alignment principles differ between robot-assisted and conventional TKA; however, further studies are required to determine which principle is more appropriate or to modify these principles.

BACKGROUND: Understanding spinal sagittal balance is crucial for assessing and treating spinal deformities in pediatric populations.
OBJECTIVE: The aim of the present observational study is to examine the parameters of sagittal alignment of the regional spine and spinopelvic region in asymptomatic pediatric populations and the characteristics of these parameters with age and sex.
METHODS: We enrolled 217 participants, consisting of 112 males (51.6%) and 105 females (48.4%), aged between 4 and 15 years, with an average age of 12.19 years. Pelvic incidence, pelvic tilt, sacral slope, lumbar lordosis, thoracic kyphosis, T1 slope, C7 slope, cervical sagittal vertical axis, and C2-7 Cobb angle were measured. Three spine surgeons conducted radiographic measurements utilizing the PACS software. The measurement reliability was assessed through ICCs.
RESULTS: Our results show significant age-related changes in pelvic tilt and cervical sagittal vertical axis, with notable gender differences in pelvic tilt, lumbar lordosis, and thoracic kyphosis. Girls have larger PT, boys have larger cSVA. PI, PT, and cSVA also differ among different age groups. Correlation analysis shows that a series of relationships that align with adult population patterns between pelvic incidence, pelvic tilt, sacral slope, lumbar lordosis, and thoracic kyphosis.
CONCLUSIONS: Significant variations in PT and cSVA across diverse age cohorts highlights notable disparities in the distribution of PT and cSVA values within the pediatric population. Gender-based differences in PT, LL, and TK and correlation in spinopelvic parameter could enhances our understanding of compensatory mechanisms.

OBJECTIVE: This study aimed to compare cervical sagittal parameters and clinical outcomes between patients undergoing cervical laminoplasty(CL) and those undergoing lateral mass screw fixation(LMS).
METHODS: We retrospectively studied 67 patients with multilevel ossification of the posterior longitudinal ligament (OPLL) of the cervical spine who underwent lateral mass screw fixation (LMS = 36) and cervical laminoplasty (CL = 31). We analyzed cervical sagittal parameters (C2-7 sagittal vertical axis (C2-7 SVA), C0-2 Cobb angle, C2-7 Cobb angle, C7 slope (C7s), T1 slope (T1s), and spino-cranial angle (SCA)) and clinical outcomes (visual analog scale [VAS], neck disability index [NDI], Japanese Orthopaedic Association [JOA] scores, recovery rate (RR), and minimum clinically significant difference [MCID]). The cervical sagittal parameters at the last follow-up were analyzed by binary logistic regression. Finally, we analyzed the correlation between the cervical sagittal parameters and each clinical outcome at the last follow-up after surgery in both groups.
RESULTS: At the follow-up after posterior decompression in both groups, the mean values of C2-C7 SVA, C7s, and T1s in the LMS group were more significant than those in the CL group (P ≤ 0.05). Compared with the preoperative period, C2-C7 SVA, T1s, and SCA gradually increased, and the C2-C7 Cobb angle gradually decreased after surgery (P < 0.05). The improvement in the JOA score and the recovery rate was similar between the two groups, while the improvement in the VAS-N score and NDI score was more significant in the CL group (P = 0.001; P = 0.043). More patients reached MCID in the CL group than in the LMS group (P = 0.036). Binary logistic regression analysis showed that SCA was independently associated with whether patients reached MCID at NDI postoperatively. SCA was positively correlated with cervical NDI and negatively correlated with cervical JOA score at postoperative follow-up in both groups (P < 0.05); C2-7 Cobb angle was negatively correlated with cervical JOA score at postoperative follow-up (P < 0.05).
CONCLUSIONS: CL may be superior to LMS in treating cervical spondylotic myelopathy caused by OPLL. In addition, smaller cervical SCA after posterior decompression may suggest better postoperative outcomes.

BACKGROUND: 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.
OBJECTIVE: To build linear predictive formulas for LL that take pelvic anteversion into consideration and to explore the dynamic characteristics of an AP subgroup.
METHODS: Monocentric, cross-sectional study.
METHODS: Five hundred and sixty-five asymptomatic Chinese men and women between the ages of 18 and 80 years.
METHODS: 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.

BACKGROUND: There is an increasing number of different brands of robotic total knee arthroplasty (TKA) systems. Most robotic TKA systems share the same coronal alignment, while the definitions of sagittal alignment vary. The purpose of this study was to investigate whether these discrepancies impact the sagittal alignment of the lower extremity.
METHODS: A total of 72 lower extremity computed tomography scans were included in our study, and 3-dimensional models were obtained using software. A total of 7 brands of robotic TKA systems were included in the study. The lower extremity axes were defined based on the surgical guide for each implant. We also set the intramedullary axis as a reference to evaluate the discrepancies in sagittal alignment of each brand of robotic system.
RESULTS: On the femoral side, the axis definition was the same for all 7 robotic TKA systems. The robotic TKA axes showed a 2.41° (1.58°, 3.38°) deviation from the intramedullary axis. On the tibial side, the 7 robots had different axis definitions. The tibial mechanical axis of 6 of the TKA systems was more flexed than that of the intramedullary axis, which means the posterior tibial slope was decreased while the tibial mechanical axis of the remaining system was more extended.
CONCLUSIONS: The sagittal alignment of the lower extremity for 7 different brands of robotic TKA systems differed from each other and all deviated from the intramedullary axis. Surgeons should be aware of this discrepancy when using different brands of robotic TKA systems to avoid unexpected sagittal alignment and corresponding adverse clinical outcomes.
METHODS: Level IV, Therapeutic Study.

The impact of cervical sagittal alignment on cervical facet joint degeneration (CFD) and the risk factors for CFD in patients with degenerative cervical myelopathy (DCM) were investigated in the current study.
A total of 250 surgical patients with DCM were recruited. The clinical data and radiographical characteristics, including CFD, cervical sagittal balance parameters, Hounsfield unit (HU) values, disc degeneration (DD), and modic change, were collected. The detailed correlation between these characteristics and CFD was analyzed. Characteristics, including CFD, were compared among the various cervical alignment types and different CFD groups. Finally, the risk factors for CFD were revealed via logistic regression.
CFD was prevalent in DCM patients. Age, cervical sagittal vertical axis (cSVA), range of motion, T1 slope, thoracic inlet angle, DD, HU value, and modic change correlated with CFD segmentally and globally (P < 0.05). The lordosis and sigmoid types had a significantly higher CFD prevalence (P < 0.05). Furthermore, the average CFD threshold for the severe CFD group was 1.625 (area under the curve, 0.958). Additionally, 167 patients with average CFD <1.625 and 83 patients with CFD of ≥1.625 were classified into the mild CFD group and severe CFD group, respectively. Finally, multivariate analysis was performed, and age, cSVA, HU value, modic change, and DD were determined to be independent risk factors for CFD.
The load distribution tends to shift to a more shear-like pattern in the sigmoid and kyphosis types and in those with a higher cSVA, thereby promoting CFD. Aging, cervical malalignment, low bone mineral density, DD, and modic change were revealed to result in high risks of CFD.

暂无摘要。

OBJECTIVE: To compare the sagittal alignment of patients with diverse mechanical complications (MCs) following adult spinal deformity (ASD) surgery with that of patients without MCs.
METHODS: A total of 371 patients who underwent ASD surgery were enrolled. The sagittal spinopelvic parameters were measured preoperatively and at the 6-month and last follow-up, and the global alignment and proportion (GAP) score was calculated. The subjects were divided into non-MC and MCs groups, and the MCs group was further divided into rod fracture (RF), screw breakage (SB), screw dislodgement (SD) and proximal junctional kyphosis (PJK) subgroups.
RESULTS: Preoperatively, the RF group had greater thoracolumbar kyphosis (TLK) and relative upper lumbar lordosis (RULL); the SB group had the largest pelvic incidence (PI) and lumbar lordosis (LL); the SD group had the least global sagittal imbalance; and the PJK group had the highest thoracic kyphosis (TK), TLK and RULL. At the last follow-up, the RF and SB groups featured a large PI minus LL (PI-LL), while the PJK group featured a prominent TK; all the MCs subgroups had sagittal malalignment and a higher GAP score, and the SB group had the most severe cases. Logistic regressions showed that the relative spinopelvic alignment (RSA) score was correlated with RF, SB and SD, while the RSA and age scores were associated with PJK.
CONCLUSIONS: Each patient with MCs had individual characteristics in the sagittal plane following ASD surgery, which may be helpful to understand the pathophysiology of poor sagittal alignment with its subsequent MCs and guide an eventual revision strategy.

OBJECTIVE: Isthmic spondylolisthesis (IS) is distinguished by a congenital defect or acquired fracture of the pars interarticularis. Numerous studies on L5 low-grade IS have been carried out; however, there is a paucity of data regarding the condition of L5 IS concomitant with L4/5 disc herniation. This study aimed to identify the incidence rate and to illustrate the possible risk factors for L4/5 disc herniation in L5 low-grade IS patients.
METHODS: A total of 268 consecutive patients diagnosed as L5/S1 low-grade IS between May 2017 and May 2022 were retrospectively enrolled in this study. Depending on the presence of L4/5 disc herniation or not, patients were divided into an L4/5 disc herniation group (L4/5 DH) and an L4/5 non-disc herniation group (L4/5 non-DH). Radiographic parameters were measured, and the ratios of L4-S1 segmental lordosis (SL) to lumbar lordosis (LDI), L4 inferior endplate (IEP) to L5 superior endplate (SEP) (L4 IEP/L5 SEP), and L5 IEP to S1 SEP (L5 IEP/S1 SEP) were compared between groups. The Pfirrmann grade of the L4/5 disc and the L5/S1 disc, and Roussouly classifications of each patient were also recorded. Univariate analysis (including independent-samples t-test and χ2 -test) and multiple logistic regression analysis were performed to analyze the data.
RESULTS: There were 40 patients (14.9%) in the L4/5 DH group. The Roussouly classification differed significantly between groups. As demonstrated by the Pfirrmann grade, the L4/5 DH group showed more advanced disc degeneration at L4/5 than the L4/5 non-DH group. In contrast to the L4/5 non-DH group, the L4/5 DH group had a significantly larger L4 IEP, L4 IEP/L5 SEP, S1 SEP, and LDI while smaller L4/5 disc angle, L4/5 disc height, slip percentage, lumbar lordosis, and sacral slope. Multivariate logistic regression analysis revealed that higher L4/5 disc Pfirrmann grade (p = 0.004), decreased L4/5 disc height (p < 0.001), and lower L5 slip percentage (p = 0.022) were significantly associated with the occurrence of L4/5 DH.
CONCLUSIONS: L4/5 disc herniation is not unusually accompanied by L5/S1 low-grade IS. Advanced L4/5 disc degeneration, decreased L4/5 disc height, and lower L5 slip percentage might be significantly associated with L4/5 disc herniation.