Paradoxical spinopelvic motion: does global balance influence spinopelvic motion in total hip arthroplasty?

BACKGROUND: Recent research has proposed a classification of spinopelvic stiffness according to pelvic spatial orientation for risk stratification in patients who undergo total hip arthroplasty (THA). However, the influence of global alignment was not investigated, and this study evaluated the effect of global balance (sagittal vertical axis [SVA]) on spinopelvic motion. METHODS: We conducted a retrospective review of consecutive primary THA patients. We measured SVA, spinopelvic parameters (pelvic tilt [PT], pelvic incidence, and sacral slope), thoracic kyphosis (TK), lumbar lordosis (LL), proximal femur angle (PFA), and cup version using functional radiographs of patients in the standing and upright sitting positions. Linear regression was performed to identify parameters related to global trunk alignment change (∆SVA). Spinopelvic stiffness was defined as PT position change < 10°, and a subset of patients with PT change < 0° was categorized into a paradoxical spinopelvic motion group. RESULTS: One hundred twenty-four patients were analyzed (mean age: 65 years, 61% female). In univariate regression analysis, ∆TK, ∆LL, and ∆PFA were correlated to ∆SVA. In multivariate regression analysis, ΔLL (p < 0.001) and ΔPFA (p < 0.001) were found to be correlated to ΔSVA (ΔSVA = - 11.97 + 0.05ΔTK - 0.23ΔLL - 0.17ΔPFA; adjusted R2 = 0.558). Spinopelvic stiffness was observed in 40 patients (32%), including five (4%) with paradoxical motion (∆PT = - 3° ± 1°, p < 0.001) with characteristics of balanced standing global trunk alignment (standing SVA = - 1.0 ± 5.1 cm), similar stiffness of the lumbosacral spine (∆LL = - 7° ± 5°), higher hip motion (∆PFA = - 78° ± 6°, p = 0.017), and higher anterior trunk shift (∆SVA = 6.2 ± 2.0 cm, p = 0.003) from standing to sitting as compared to the stiffness group. Two of these five patients experienced dislocation events after THA. CONCLUSIONS: The lumbosacral and hip motions were the major contributors to global alignment postural change. Paradoxical motion is a rare but dangerous clinical condition in THA that might be related to a disproportionally large trunk shift in the stiff lumbosacral spine causing excessive hip motion. In paradoxical motion, diminishing functional acetabular clearance during position change might pose the prosthesis at higher risk of impingement and instability than spinopelvic stiffness.

Narrative Review of Clinical Impact of Head-Hip Offset Following Adult Spinal Deformity Surgery.

In adult spinal deformity (ASD) surgery, mechanical failure (MF) has been a significant concern for spine surgeons as well as patients. Despite earnest endeavors to prevent MF, the absence of a definitive consensus persists, owing to the intricate interplay of multifarious factors associated with this complication. Previous approaches centered around global spinal alignment have yielded limited success in entirely forestalling MF. These methodologies, albeit valuable, exhibited limitations by neglecting to encompass global balance and compensatory mechanisms within their purview. In response to this concern, an in-depth comprehension of global balance and compensatory mechanisms emerges as imperative. In this discourse, the center of gravity and the gravity line are gaining attention in recent investigations pertaining to global balance. This narrative review aims to provide an overview of the global balance and a comprehensive understanding of related concepts and knowledge. Moreover, it delves into the clinical ramifications of the contemporary optimal correction paradigm to furnish an encompassing understanding of global balance and the current optimal correction strategies within the context of ASD surgery. By doing so, it endeavors to furnish spine surgeons with a guiding compass, enriching their decision-making process as they navigate the intricate terrain of ASD surgical interventions.

Why does knee flexion in the standing position occur? Spinal deformity or knee osteoarthritis.

Background: The interaction between knee osteoarthritis and spinal deformity and knee flexion (KF) remains unclear. We aimed to clarify the relationship between KF in the standing position and the severity of spinal deformity and knee osteoarthritis. Methods: We analyzed older volunteers aged over 60 years who participated in the musculoskeletal screening program. The participant's characteristics and standing radiographic parameters were assessed. After a preliminary analysis, a propensity score-matched model was established with adjustments for age, sex, and body mass index (BMI). Cases were divided into KF (knee angle [KA] ≥10°) and non-KF (KA <10°) groups. Results: In a preliminary analysis of 252 cases (42 KF and 210 non-KF), there were significant differences in age and BMI between the KF and non-KF groups (all p < 0.05). Using a one-to-one propensity score-matched analysis, 38 pairs of cases were selected. There were significantly higher values of C7 sagittal vertical axis, T1 pelvic angle, pelvic tilt, pelvic incidence minus lumbar lordosis, KA, ankle angle, and pelvic shift in the KF group than in the non-KF group (all p < 0.05). In the KF group, 71.1% of the cases had severe spinal deformity (defined as marked deformity by the SRS-Schwab classification), and 31.6% had severe knee osteoarthritis (defined as a Kellgren Lawrence grade ≥3). Of the 31.6%, 7.9% were attributable to knee osteoarthritis alone, and 23.7% to both knee osteoarthritis and spinal deformity. Conclusions: This study clarified that compensatory changes due to spinopelvic malalignment, not due to knee osteoarthritis alone, mainly affected KF in the standing position.

Systematic Review of Reciprocal Changes after Spinal Reconstruction Surgery : Do Not Miss the Forest for the Trees.

The purpose of this review was to synthesize the research on global spinal alignment and reciprocal changes following cervical or thoracolumbar reconstruction surgery. We carried out a search of PubMed, EMBASE, and Cochrane Library for studies through May 2020, and ultimately included 11 articles. The optimal goal of a truly balanced spine is to maintain the head over the femoral heads. When spinal imbalance occurs, the human body reacts through various compensatory mechanisms to maintain the head over the pelvis and to retain a horizontal gaze. Historically, deformity correction has focused on correcting scoliosis and preventing scoliotic curve progression. Following substantial correction of a spinal deformity, reciprocal changes take place in the flexible segments proximal and distal to the area of correction. Restoration of lumbar lordosis following surgery to correct a thoracolumbar deformity induces reciprocal changes in T1 slope, cervical lordosis, pelvic shift, and lower extremity parameters. Patients with cervical kyphosis exhibit different patterns of reciprocal changes depending on whether they have head-balanced or trunk-balanced kyphosis. These reciprocal changes should be considered to in order to prevent secondary spine disorders. We emphasize the importance of evaluating the global spinal alignment to assess postoperative changes.

Impact of cervical range of motion on the global spinal alignment in ankylosing spondylitis patients with thoracolumbar kyphosis following pedicle subtraction osteotomy.

BACKGROUND CONTEXT: The head's center of gravity (COG) plumb line (PL) and C7 PL could be simultaneously positioned over the pelvis in adult spinal deformity with normal cervical mobility. However, the position of the head in relation to the global spinal alignment has yet to be investigated in ankylosing spondylitis (AS) patients with thoracolumbar kyphosis. PURPOSE: The objective of this study was to analyze the position of head in relation to the global spinal alignment in AS-related thoracolumbar kyphosis. STUDY DESIGN/SETTING: Retrospective single-center study. PATIENT SAMPLE: AS patients who underwent lumbar pedicle subtraction osteotomy for thoracolumbar kyphosis from January 2010 to August 2016 were reviewed. Only patients with a visible ear canal on the preoperative, immediate postoperative, and final follow-up radiographs were included. OUTCOME MEASURES: The chin-brow angle, cervical range of motion (ROM), lumbar lordosis (LL), thoracolumbar angle, thoracic kyphosis (TK), L1 pelvic angle, pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), TK+LL+PI, PI-LL, maximal kyphosis (MK), deformity angular rate, T1 pelvic angle, T1 tilt, spinosacral angle, sagittal vertical axis (SVA) COG-C7, SVA COG-femoral head (FH), and SVA C7-S were evaluated. Data regarding the health-related quality of life, including the Oswestry disability index (ODI) and visual analogue scale (VAS)-back score, were also collected preoperatively, 2 years postoperatively, and at the latest follow-up. METHODS: The cohort was divided into patients with occiput-trunk (OT) concordance or with OT discordance according to the SVA COG-C7 ≤30 mm or >30 mm, respectively. There was no funding in this study and there are no conflict of interest-associated biases. RESULTS: A total of 43 patients (36 males and 7 females) with a mean age of 34.2 years (range, 18-59 years) were identified. There were 17 patients accompanied with OT concordance and 26 patients with OT discordance preoperatively. The cervical ROM was significantly lower (24.0° vs 56.1°, p<.001) and SVA COG-C7 was significantly larger (71.7 mm vs 7.4 mm, p<.001) in patients with OT discordance. Furthermore, the PT was larger (41.0° vs 33.5°, p=.010) in patients with OT discordance. After surgery, the whole cohort showed an improvement in LL (-8.6° vs -52.8°, p<.001). Moreover, the CBVA (25.4° vs 1.3°, p<.001) and SVA COG-C7 (46.2 mm vs 21.6 mm, p<.001) were significantly decreased following lumbar PSO. There were 13 patients accompanied with OT discordance postoperatively, and the cervical ROM was still lower (22.5° vs 42.8°, p=.024) in these patients. Postoperative PT was larger (26.5° vs 20.1°, p=.033) in the patients with OT discordance. At the latest follow-up, there were 17 patients accompanied with OT discordance. In these 17 patients, the cervical ROM was significantly lower (21.0° vs 47.0°, p=.001) and PT was significantly higher (26.2° vs 19.2°, p=.012). The ODI and VAS-back scores demonstrated no significant differences between the two groups preoperatively, 2 years postoperatively, or at the latest follow-up. CONCLUSIONS: OT discordance in AS-related thoracolumbar kyphosis could be caused by the reduced cervical ROM. To maintain global spinal balance, the pelvis rotated further backward in response to the larger SVA COG-C7. Moreover, the larger SVA COG-C7 could be decreased after the lumbar PSO. Although there were radiographic differences between the patients with OT concordance and with OT discordance, there was no difference in clinical outcomes, and that a larger sample size and longer follow-up are needed.

Automatic analysis of global spinal alignment from simple annotation of vertebral bodies.

Purpose: Measurement of global spinal alignment (GSA) is an important aspect of diagnosis and treatment evaluation for spinal deformity but is subject to a high level of inter-reader variability. Approach: Two methods for automatic GSA measurement are proposed to mitigate such variability and reduce the burden of manual measurements. Both approaches use vertebral labels in spine computed tomography (CT) as input: the first (EndSeg) segments vertebral endplates using input labels as seed points; and the second (SpNorm) computes a two-dimensional curvilinear fit to the input labels. Studies were performed to characterize the performance of EndSeg and SpNorm in comparison to manual GSA measurement by five clinicians, including measurements of proximal thoracic kyphosis, main thoracic kyphosis, and lumbar lordosis. Results: For the automatic methods, 93.8% of endplate angle estimates were within the inter-reader 95% confidence interval ( CI 95 ). All GSA measurements for the automatic methods were within the inter-reader CI 95 , and there was no statistically significant difference between automatic and manual methods. The SpNorm method appears particularly robust as it operates without segmentation. Conclusions: Such methods could improve the reproducibility and reliability of GSA measurements and are potentially suitable to applications in large datasets-e.g., for outcome assessment in surgical data science.

Establishment of a novel rehabilitation program for patients with dropped head syndrome: Short and intensive rehabilitation (SHAiR) program.

The pathophysiology of dropped head syndrome (DHS) remains unknown, and its treatment algorithm and indication are not standardized. Here, we established a novel rehabilitation program, short and intensive rehabilitation program for DHS (SHAiR program), consisting of cervical paraspinal muscles exercise, range of motion exercise, cervical and thoracic mobilization, deep cervical flexor muscle exercise, hip lift exercise, anterior pelvic tilt exercise, and walking exercise. The aim of this study was to evaluate the clinical effectiveness of this program. We reviewed clinical outcomes for five consecutive patients with DHS who underwent the SHAiR program (SHAiR group). The outcomes were compared with those of other five patients with DHS who received exercise instruction (control group). Demographic data, the duration from onset of DHS, the apex of sagittal kyphosis on the lateral radiographs, and clinical outcomes including the ability to maintain normal horizontal gaze, chin brow vertical angle, and numerical rating scale (NRS) were evaluated at the initial visit and final follow-up at 7.5 months. There was no significant difference between the two groups in terms of demographic and radiographic data. The ability of horizontal gaze and NRS of cervical pain improved rapidly for all five patients in the SHAiR group as compared to no improvement for all patients in the control group. Rehabilitation for DHS was considered effective not only for localized rehabilitation such as exercise for training cervical extensor muscle function but also exercises for thoracolumbar posture improvement and the psoas muscle.

Effect of thoracic and pelvic anteroposterior diameters on spinal sagittal alignment.

PURPOSE: This study aimed to analyze the effect of the thoracic anteroposterior diameter (TAPD) and pelvic anteroposterior diameter (PAPD) on global sagittal alignment in asymptomatic patients with normal sagittal alignment. PATIENT SAMPLE: The study investigated 2042 adult patients who initially presented at our hospital with a hip and knee problem without history of symptoms related to the entire spine. Only 57 patients with normal global sagittal alignment (C2-7 sagittal vertical axis (SVA) and C7-S1 SVA of <10 mm) were considered. METHODS: The whole-spine standing lateral radiographs were obtained to analyze the following parameters: pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), thoracic inlet angle (TIA), T1 slope, cervical spinal parameters (angle of C0-2, C2-7, and C0-7), TAPD, and PAPD. Statistical analysis was performed using Pearson correlation coefficients and multiple regression analyses. RESULTS: All the parameters showed a normal distribution. TAPD had a significant relationship with thoracic kyphosis (TK; r = 0.458), TIA (r = 0.677), and C0-2 angle (r = 0.294) but no significant relationship with T1 slope and other cervical parameters. PAPD had a significant relationship with PI (r = 0.309) and PT (r = 0.463) but no significant relationship with LL, SS, and TK. The multiple regression analysis showed that TIA = 21.974 + 0.405 (TK) + 0.188 (TAPD) (p < 0.0001). CONCLUSIONS: TAPD and PAPD are associated with TIA, TK, C0-2 angle, PI, and PT, all of which act as key factors in spinal sagittal alignment. Although they did not directly correlate with other cervical parameters, T1 slope, and LL, TAPD and PAPD might have indirect effects on cervical and lumbar spinal sagittal alignment through their relationships with TIA, TK, and PI.

Full-Body Radiographic Analysis of Postoperative Deviations From Age-Adjusted Alignment Goals in Adult Spinal Deformity Correction and Related Compensatory Recruitment.

BACKGROUND: Full-body stereographs for adult spinal deformity (ASD) have enhanced global deformity and lower-limb compensation associations. The advent of age-adjusted goals for classic ASD parameters (sagittal vertical axis, pelvic tilt, spino-pelvic mismatch [PI-LL]) has enabled individualized evaluation of successful versus failed realignment, though these remain to be radiographically assessed postoperatively. This study analyzes pre- and postoperative sagittal alignment to quantify patient-specific correction against age-adjusted goals, and presents differences in compensation in patients whose postoperative profile deviates from targets. METHODS: Single-center retrospective review of ASD patients ≥ 18 years with biplanar full-body stereographic x-rays. Inclusion: ≥ 4 levels fused, complete baseline and early (≤ 6-month) follow-up imaging. Correction groups generated at postoperative visit for actual alignment compared to age-adjusted ideal values for pelvic tilt, PI-LL, and sagittal vertical axis derived from clinically relevant formulas. Patients that matched exact ± 10-year threshold for age-adjusted targets were compared to unmatched cases (undercorrected or overcorrected). Comparison of spinal alignment and compensatory mechanisms (thoracic kyphosis, hip extension, knee flexion, ankle flexion, pelvic shift) across correction groups were performed with ANOVA and paired t tests. RESULTS: The sagittal vertical axis, pelvic tilt, and PI-LL of 122 patients improved at early postoperative visits (P < .001). Of lower-extremity parameters, knee flexion and pelvic shift improved (P < .001), but hip extension and ankle flexion were similar (P > .170); global sagittal angle decreased overall, reflecting global postoperative correction (8.3° versus 4.4°, P < .001). Rates of undercorrection to age-adjusted targets for each spino-pelvic parameter were 30.3% (sagittal vertical axis), 41.0% (pelvic tilt), and 43.6% (PI-LL). Compared to matched/overcorrections, undercorrections recruited increased posterior pelvic shift to compensate (P < .001); knee flexion was recruited in undercorrections for sagittal vertical axis and pelvic tilt; thoracic hypokyphosis was observed in PI-LL undercorrections. All undercorrected groups displayed consequentially larger global sagittal angle (P < .001). CONCLUSIONS: Global alignment cohort improvements were observed, and when comparing actual to age-adjusted alignment, undercorrections recruited pelvic and lower-limb flexion to compensate. LEVEL OF EVIDENCE: 3.

How Cervical Reconstruction Surgery Affects Global Spinal Alignment.

BACKGROUND: There have been no reports describing how cervical reconstruction surgery affects global spinal alignment (GSA). OBJECTIVE: To elucidate the effects of cervical reconstruction for GSA through a retrospective multicenter study. METHODS: Seventy-eight patients who underwent cervical reconstruction surgery for cervical kyphosis were divided into a Head-balanced group (n = 42) and a Trunk-balanced group (n = 36) according to the values of the C7 plumb line (PL). We also divided the patients into a cervical sagittal balanced group (CSB group, n = 18) and a cervical sagittal imbalanced group (CSI group, n = 60) based on the C2 PL-C7 PL distance. Various sagittal Cobb angles and the sagittal vertical axes were measured before and after surgery. RESULTS: Cervical alignment was improved to achieve occiput-trunk concordance (the distance between the center of gravity [COG] PL, which is considered the virtual gravity line of the entire body, and C7 PL < 30 mm) despite the location of COG PL and C7PL. A subsequent significant change in thoracolumbar alignment was observed in Head-balanced and CSI groups. However, no such significant change was observed in Trunk-balanced and CSB groups. We observed 1 case of transient and 1 case of residual neurological worsening. CONCLUSION: The primary goal of cervical reconstruction surgery is to achieve occiput-trunk concordance. Once it is achieved, subsequent thoracolumbar alignment changes occur as needed to harmonize GSA. Cervical reconstruction can restore both cervical deformity and GSA. However, surgeons must consider the risks and benefits in such challenging cases.

Impact of spino-pelvic and global spinal alignment on the risk of osteoporotic vertebral collapse.

INTRODUCTION: Numerous studies have reported the risk factors of osteoporotic vertebral collapse. However, whether spino-pelvic and global spinal alignments are associated with the occurrence of osteoporotic vertebral collapse remains unclear. This study aimed to investigate the association between spino-pelvic and global spinal alignments and the occurrence of osteoporotic vertebral collapse. METHODS: A total of 46 consecutive patients who underwent a nonoperative treatment for a single-level fresh osteoporotic thoracolumbar vertebral compression fracture (T10 to L3) were retrospectively reviewed. The parameters evaluated were the pelvic incidence, anterior deviation of the C7 plumb line, distance between the C7 plumb line and the center of the fractured vertebra, and kyphotic wedge angle of the fractured vertebra in a standing whole-spine radiograph at the beginning of the nonoperative treatment. As an outcome measure, the presence or absence of osteoporotic vertebral collapse was radiographically evaluated at the final follow-up. Multiple logistic regression analysis was used to determine significant risk factors of osteoporotic vertebral collapse. RESULTS: The mean values for each parameter were as follows: pelvic incidence, 58.0 degrees; anterior deviation of the C7 plumb line, 3.0 cm; distance between the C7 plumb line and the center of the fractured vertebra, 5.7 cm; and kyphotic wedge angle of the fractured vertebra, 14.6 degrees. Multiple logistic regression analysis revealed that the distance between the C7 plumb line and center of the fractured vertebra was a significant risk factor of osteoporotic vertebral collapse (p = 0.012; odds ratio, 1.025). The anterior deviation of the C7 plumb line (p = 0.214), pelvic incidence (p = 0.728), and kyphotic wedge angle of the fractured vertebra (p = 0.07) did not affect the occurrence of osteoporotic vertebral collapse. CONCLUSIONS: A large distance between the C7 plumb line and center of the fractured vertebra was a significant risk factor of osteoporotic vertebral collapse. The distance approximately represents that of between gravity center of trunk cranial to the fractured vertebra and the fractured vertebra. Accordingly, the large distance may cause larger flexion moment to the fractured site, leading to stress concentration that results in insufficient bone healing.

Age-related variations in global spinal alignment and sagittal balance in asymptomatic Japanese adults.

OBJECTIVES: The global spinal sagittal alignment varies widely among healthy individuals as it is affected by not only race, but also aging. We investigated age-related changes in the spinal alignment in asymptomatic Japanese individuals. METHODS: The subjects comprised 220 individuals without any spine-related neurological symptoms or treatment history thereof who visited our outpatient clinic. Lateral radiographs of the whole spine were taken for all subjects in the standing position. Based on the images obtained, spino-pelvic parameters were calculated using Jackson's method so as to analyze any correlations with age. RESULTS: TIA, TK, and C2-C7A were found to markedly increase with age from late middle age (P < 0.05). No correlation with aging was found for lumbosacral parameters or sagittal balance (P > 0.05). However, there were 22 subjects (10%) with C7SVA > 50 mm, with those aged 70 years or older accounting for half of this subpopulation. Sagittal balance tended to be retained even in elderly subjects if lumbosacral lordosis was large enough to compensate for thoracic kyphosis. A very strong correlation was found between the L1 slope and whole-spine sagittal balance (P < 0.0001, r = -0.497). CONCLUSIONS: Increases in cervicothoracic curvature occurring along with thoracic deformation underlie age-related changes in the spine. In contrast, the lumbosacral spine compensates in such a manner so as to maintain the sagittal balance. The whole-spine sagittal balance can deteriorate if the compensatory changes in the lumbosacral spine are insufficient. The L1 slope is a central parameter that defines the whole-spine sagittal balance. ABBREVIATIONS: PI; pelvic incidence; SS; sacral slope; PT; pelvic tilt; LL; lumbar lordosis; C7SVA; C7 sagittal vertical axis; SSA; spinosacral angle; TK; thoracic kyphosis; C2-C7SVA; C2-C7 sagittal vertical axis; C2-C7A; C2-C7 Angle; TIA; thoracic inlet angle; NT; neck tilt.