Shian Liu

Recruitment of Compensatory Mechanisms in Sagittal Spinal Malalignment Is Age and Regional Deformity Dependent A Full-Standing Axis Analysis of Key Radiographical Parameters

Study Design. Retrospective review, full-body radiographical analysis of adult patients with sagittal spinal malalignment (SSM). Objective. To investigate the compensatory mechanisms involved in the sagittal plane of the body after progressive spinal sagittal malalignment and to study the impact of age on compensatory mechanism recruitment. Summary of Background Data. Patients with SSM recruit compensatory mechanisms to maintain erect posture and horizontal gaze. Mechanisms such as pelvic retroversion, knee flexion, and pelvic shift have been proposed, but how they contribute and how age affects their recruitment are poorly understood. Methods. Retrospective review of adult patients with SSM who underwent full-standing axis stereoradiography (EOS imaging). Radiographical measurements were performed with Surgimap. Patients were categorized on the basis of the mismatch between pelvic incidence (PI) and lumbar lordosis (PI-LL). Compensatory mechanisms were normalized to each patients PI-LL and compared by mismatch groups. In addition, patients were subcategorized into 2 age groups (≥65 and <65 yr) and compared within the same groups of mismatch. Results. A total of 161 patients with a mean age of 62.93 ± 12.8 years. Mean sagittal vertical axis = 62.3 ± 61.5 mm; pelvic tilt (PT) = 29.2° ± 8.4°; and PI-LL = 21.0° ± 14.9°. Mismatch groups were as follows: group 1: PI-LL 0°–10°; group 2: 10°–20°; group 3: 20°–30°; and group 4: >30°. There were significant differences between all groups with regard to thoracic kyphosis (TK), PT, knee flexion angle, and pelvic shift by analysis of variance (P < 0.001). As PI-LL increased, TK and PT contribution to the compensation cascade decreased and knee flexion angle and pelvic shift contribution increased. Patients with PI-LL of more than 30° who were older had significantly less PT and more TK than patients with similar PI-LL who were younger. Conclusion. Spinopelvic mismatch is an important driver in SSM. Pelvic retroversion and flattening of TK (reduction) become exhausted with increasing mismatch, at which point there seems to be a steady transfer of compensation toward significant participation of the lower limbs. Further analysis suggests differential recruitment of these compensatory mechanisms based upon age. Level of Evidence: 3

Osteotomies in the treatment of spinal deformities: indications, classification, and surgical planning.

Abstract The surgical treatment of adult spinal deformity has been shown to offer superior clinical and radiographic outcomes compared with nonoperative approaches; furthermore, osteotomies are increasingly applied for treating spinal deformities. Establishing a plan for a patient suffering from marked spinal deformity is a matter of consideration of certain radiographic parameters which correlate with health-related quality of life scores, adherence to consistent principles of alignment and established formulas, and selecting the appropriate osteotomies. This is a review of the most recent work on vertebral osteotomies and includes a summary of a systematic and anatomically based osteotomy classification. A universal classification will facilitate communication, standardize outcomes research, and establish a framework upon which indications can be properly studied and described. Ongoing multicenter collaboration is certain to drive a more evidence-based approach to the complex clinical scenarios of patients suffering from spinal deformity.

Role of pelvic translation and lower-extremity compensation to maintain gravity line position in spinal deformity

OBJECT Previous forceplate studies analyzing the impact of sagittal-plane spinal deformity on pelvic parameters have demonstrated the compensatory mechanisms of pelvis translation in addition to rotation. However, the mechanisms recruited for this pelvic rotation were not assessed. This study aims to analyze the relationship between spinopelvic and lower-extremity parameters and clarify the role of pelvic translation. METHODS This is a retrospective study of patients with spinal deformity and full-body EOS images. Patients with only stenosis or low-back pain were excluded. Patients were grouped according to T-1 spinopelvic inclination (T1SPi): sagittal forward (forward, > 0.5°), neutral (-6.3° to 0.5°), or backward (< -6.3°). Pelvic translation was quantified by pelvic shift (sagittal offset between the posterosuperior corner of the sacrum and anterior cortex of the distal tibia), hip extension was measured using the sacrofemoral angle (SFA; the angle formed by the middle of the sacral endplate and the bicoxofemoral axis and the line between the bicoxofemoral axis and the femoral axis), and chin-brow vertical angle (CBVA). Univariate and multivariate analyses were used to compare the parameters and correlation with the Oswestry Disability Index (ODI). RESULTS In total, 336 patients (71% female; mean age 57 years; mean body mass index 27 kg/m(2)) had mean T1SPi values of -8.8°, -3.5°, and 5.9° in the backward, neutral, and forward groups, respectively. There were significant differences in the lower-extremity and spinopelvic parameters between T1SPi groups. The backward group had a normal lumbar lordosis (LL), negative SVA and pelvic shift, and the largest hip extension. Forward patients had a small LL and an increased SVA, with a large pelvic shift creating compensatory knee flexion. Significant correlations existed between lower-limb parameter and pelvic shift, pelvic tilt, T-1 pelvic angle, T1SPi, and sagittal vertical axis (0.3 < r < 0.8; p < 0.001). ODI was significantly correlated with knee flexion and pelvic shift. CONCLUSIONS This is the first study to describe full-body alignment in a large population of patients with spinal pathologies. Furthermore, patients categorized based on T1SPi were found to have significant differences in the pelvic shift and lower-limb compensatory mechanisms. Correlations between lower-limb angles, pelvic shift, and ODI were identified. These differences in compensatory mechanisms should be considered when evaluating and planning surgical intervention for adult patients with spinal deformity.

The benefit of nonoperative treatment for adult spinal deformity: identifying predictors for reaching a minimal clinically important difference

BACKGROUND CONTEXT Adult spinal deformity (ASD) patients may gain minimal clinically important difference (MCID) in one or more of the health-related quality-of-life instruments without surgical intervention. The present study identifies the baseline characteristics of this subset of nonoperative patients and proposes predictors of those most likely to benefit. PURPOSE The study aims to determine the factors that affect likelihood of nonoperative patients to reach MCID. STUDY DESIGN/SETTING This is a retrospective review of a prospective, multicenter database. PATIENT SAMPLE The study includes nonoperative ASD patients. OUTCOME MEASURES Health-related quality-of-life measures, including the Scoliosis Research Society (SRS)-22 questionnaire, were used. METHODS The study used a multicenter database of 215 nonoperative patients with ASD and with minimum 2-year follow-up. Using a multivariate analysis, two groups were compared to identify possible predictors: those who reached MCID in the SRS pain or activity (N=86) at 2 years and those who did not reach MCID (N=129). A subgroup multivariate analysis of patients with a deficit (potential improvement) in both SRS pain and activity (N=84) was performed. Data collection was supported by a grant from DePuy for the International Spine Study Group Foundation. RESULTS At baseline, the nonoperative patients who reached MCID had a significantly lower SRS pain score (3.0 vs. 3.6), smaller thoracolumbar Cobb (TL Cobb) angle (29.6° vs. 36.5°; 87 patients with SRS-Schwab classification of lumbar or double), lower sacral slope (33.1° vs. 36.4°), and less lumbar lordosis (46.5° vs. 52.8°) (all p<.05). The SRS pain and TL Cobb were significant predictors for reaching MCID. The pelvic incidence minus lumbar lordosis (PI-LL) was significant on univariate analysis but not on multivariate analysis (7.5° vs. 2.6°; p=.14). In the subset of severely disabled patients, worse vertebral obliquity was a predictor for not achieving MCID (p<.05). CONCLUSIONS Nonoperative ASD patients who achieved MCID in SRS activity or pain had a lower baseline SRS pain score and less coronal deformity in the TL region. Greater baseline pain offers significant room for potential improvement, which may be important in identifying ASD patients who have the potential to reach MCID nonoperatively. Coronal deformities in the TL region and associated vertebral obliquity may negatively impact potential for improvement in nonoperative care.

Global sagittal axis: a step toward full-body assessment of sagittal plane deformity in the human body.

OBJECTIVE Sagittal malalignment requires higher energy expenditure to maintain an erect posture. Because the clinical impact of sagittal alignment is affected by both the severity of the deformity and recruitment of compensatory mechanisms, it is important to investigate new parameters that reflect both disability level and compensatory mechanisms for all patients. This study investigated the clinical relevance of the global sagittal axis (GSA), a novel measure to evaluate the standing axis of the human body. METHODS This is a retrospective review of patients who underwent full-body radiographs and completed health-related quality of life (HRQOL) questionnaires: Oswestry Disability Index (ODI), Scoliosis Research Society-22, EuroQol-5D (EQ-5D), and the visual analog scale for back and leg pain. The GSA was defined as the angle formed by a line from the midpoint of the femoral condyles to the center of C-7, and a line from the midpoint between the femoral condyles to the posterior superior corner of the S-1 sacral endplate. After evaluating the correlation of GSA/HRQOL with sagittal parameters, linear regression models were generated to investigate how ODI and GSA related to radiographic parameters (T-1 pelvic angle, pelvic retroversion, knee flexion, and pelvic posterior translation). RESULTS One hundred forty-three patients (mean age 44 years) were included. The GSA correlated significantly with all HRQOL (up to r = 0.6 with EQ-5D) and radiographic parameters (up to r = 0.962 with sagittal vertical axis). Regression between ODI and sagittal radiographic parameters identified the GSA as an independent predictor (r = 0.517, r2 = 0.267; p < 0.001). Analysis of standardized coefficients revealed that when controlling for deformity, the GSA increased with a concurrent decrease in pelvic retroversion (-0.837) and increases in knee flexion (+0.287) and pelvic posterior translation (+0.193). CONCLUSIONS The GSA is a simple, novel measure to assess the standing axis of the human body in the sagittal plane. The GSA correlated highly with spinopelvic and lower-extremities sagittal parameters and exhibited remarkable correlations with HRQOL, which exceeded other commonly used parameters.

Perioperative Risks Associated with Cervical Spondylotic Myelopathy Based on Surgical Treatment Strategies.

Background Few studies have provided nationwide estimates of patient characteristics and procedure-related complications, or examined postsurgical outcomes for patients with cervical spondylotic myelopathy (CSM) comparatively with respect to surgical approach. The objective of this study is to identify patients at risk for morbidity and mortality directly related with the selected approach, report an overall nation-wide complication rate for each approach against which surgeons can compare themselves, and direct future research to improve patient outcomes. Methods Patients surgically treated for CSM were retrospectively identified using ICD-9-CM codes from the Nationwide Inpatient Sample (NIS) database. Four cohorts were compared for demographics and hospital system-related data: anterior (ACDF, ACCF), posterior decompression without fusion, decompression with posterior fusion, and combined anterior-posterior. Multivariate analysis was also used to determine the odds ratio of morbidity and mortality among the cohorts. Results 54,416 discharges were identified between 2001 and 2010: 34,400 anterior, 9,014 decompression procedures without fusion, 8,741 decompression procedures with posterior fusion, and 2,261 combined anterior-posterior. Groups were statistically different with respect to age, length of hospital stay, mortality, and complications. Groups were statistically different for Deyo score except between posterior decompression only and combined approaches. Using multivariate analysis and adjusting for covariates, the combined (2.74[2.18-3.44]) and laminectomy (1.22[1.04-1.44]) cohorts had an increased risk of mortality when compared to anterior alone. Conclusion These findings are the first to determine the rates and odds of perioperative risks directly related to combined anterior-posterior procedures. This study provides clinically useful data for surgeons to educate patients and direct future research to improve patient outcomes.

Impact of dynamic alignment, motion, and center of rotation on myelopathy grade and regional disability in cervical spondylotic myelopathy

OBJECT Cervical stenosis is a defining feature of cervical spondylotic myelopathy (CSM). Matsunaga et al. proposed that elements of stenosis are both static and dynamic, where the dynamic elements magnify the canal deformation of the static state. For the current study, the authors hypothesized that dynamic changes may be associated with myelopathy severity and neck disability. This goal of this study was to present novel methods of dynamic motion analysis in CSM. METHODS A post hoc analysis was performed of a prospective, multicenter database of patients with CSM from the AOSpine North American study. One hundred ten patients (34%) met inclusion criteria, which were symptomatic CSM, age over 18 years, baseline flexion/extension radiographs, and health-related quality of life (HRQOL) questionnaires (modified Japanese Orthopaedic Association [mJOA] score, Neck Disability Index [NDI], the 36-Item Short Form Health Survey Physical Component Score [SF-36 PCS], and Nurick grade). The mean age was 56.9 ± 12 years, and 42% of patients were women (n = 46). Correlations with HRQOL measures were analyzed for regional (cervical lordosis and cervical sagittal vertical axis) and focal parameters (kyphosis and spondylolisthesis between adjacent vertebrae) in flexion and extension. Baseline dynamic parameters (flexion/extension cone relative to a fixed C-7, center of rotation [COR], and range of motion arc relative to the COR) were also analyzed for correlations with HRQOL measures. RESULTS At baseline, the mean HRQOL measures demonstrated disability and the mean radiographic parameters demonstrated sagittal malalignment. Among regional parameters, there was a significant correlation between decreased neck flexion (increased C2-7 angle in flexion) and worse Nurick grade (R = 0.189, p = 0.048), with no significant correlations in extension. Focal parameters, including increased C-7 sagittal translation overT-1 (slip), were significantly correlated with greater myelopathy severity (mJOA score, Flexion R = -0.377, p = 0.003; mJOA score, Extension R = -0.261, p = 0.027). Sagittal slip at C-2 and C-4 also correlated with worse HRQOL measures. Reduced flexion/extension motion cones, a more posterior COR, and smaller range of motion correlated with worse general health SF-36 PCS and Nurick grade. CONCLUSIONS Dynamic motion analysis may play an important role in understanding CSM. Focal parameters demonstrated a significant correlation with worse HRQOL measures, especially increased C-7 sagittal slip in flexion and extension. Novel methods of motion analysis demonstrating reduced motion cones correlated with worse myelopathy grades. More posterior COR and smaller range of motion were both correlated with worse general health scores (SF-36 PCS and Nurick grade). To our knowledge, this is the first study to demonstrate correlation of dynamic motion and listhesis with disability and myelopathy in CSM.

Clinical and Radiographic Evaluation

Planning for spinal procedures has been utilized throughout history. The first planned and documented fusion surgery was noted by Dr. Fred Albee in 1911, when he reported a tibial bone graft transplantation into the spine to treat Pott’s disease [1]. Decades later, Dr. Francis Denis proposed the three-column theory of spinal stability [2], which led to a better understanding for the anatomical implications of osteotomies. Today, studies continue to reveal the superiority of surgical treatment for spinal deformities [3–7], and the reliability of osteotomies in the setting of rigid coronal and sagittal deformities [8–10]. The widespread use of osteotomies is evident in the statistics from the Agency for Healthcare Research and Quality (AHRQ), which showed a significant increase in the number of patients discharged with osteotomies and fusions within the most recent 14 years of available data in the USA [11, 12].

Novel Method Using Baseline Normalization and Area Under the Curve to Evaluate Differences in Outcome Between Treatment Groups and Application to Patients With Cervical Spondylotic Myelopathy Undergoing Anterior Versus Posterior Surgery.

Study Design.: Retrospective review of a prospective database. Objective.: To describe a novel method that uses baseline normalization and area under the curve (AUC) to compare surgical outcomes between patients surgically treated anteriorly versus posteriorly for cervical spondylotic myelopathy (CSM). Summary and Background Data.: It is important to control for baseline characteristics, especially disease severity, when evaluating differences in outcomes between 2 treatment groups. However, current methods of reporting outcomes are limited perhaps diminish the health impact of the entire postoperative recovery experience. Methods.: In the prospective, multicenter AO Spine North America CSM database, 147 patients had complete modified Japanese Orthopaedic Association (mJOA) data at baseline and at 6-, 12-, and 24-months postoperatively and were either treated anteriorly (n = 94) or posteriorly (n = 53). Each patients follow-up mJOA scores were normalized by dividing them by the patients baseline value. A graph was then plotted with the time point on the x-axis and the normalized score or “recovery index” on the y-axis. The AUC was calculated and then compared between the anterior and posterior surgical approach groups. Results.: The non-normalized recovery profile of the anterior group was better than that of the posterior group, as the patients treated anteriorly had less functional impairment at baseline. After normalization, patients in the anterior and posterior group had similar recovery indices and AUCs at 6-months following surgery. At 24-months, patients treated posteriorly had a significantly higher recovery index (1.32) and a larger AUC (16.3) than those treated anteriorly (1.11, 14.5, P = 0.004 and P = 0.006, respectively). Conclusion.: This is the first study to apply AUC analysis to patients with CSM. In surgical patients with CSM, those treated anteriorly achieved a higher mJOA score at all time points than those treated posteriorly. The recovery indices, however, were not significantly different between approach groups at 6 months. Level of Evidence: 3

Complications in Patients Undergoing Spinal Fusion After THA

Introduction Patients with lumbar spine and hip disorders may, during the course of their treatment, undergo spinal fusion and THA. There is disagreement among prior studies regarding whether patients who undergo THA and spinal fusion are at increased risk of THA dislocation and other hip-related complications. Questions / Purposes Is short or long spinal fusion associated with an increased rate of postoperative complications in patients who underwent a prior THA? Patients and Methods A retrospective study of New York State’s Department of Health database (SPARCS) was performed. SPARCS has a unique identification code for each patient, allowing investigators to track the patient across multiple admissions. The SPARCS dataset spans visit data of patients of all ages and races across urban and rural locations. The SPARCs dataset encompasses all facilities covered under New York State Article 28 and uses measures to further representative reporting of data concerning all races. Owing to the nature of the SPARCS dataset, we are unable to comment on data leakage, as there is no way to discern between a patient who does not subsequently seek care and a patient who seeks care outside New York State. ICD-9-Clinical Modification codes identified adult patients who underwent elective THA from 2009 to 2011. Patients who had subsequent spinal fusion (short: 2-3 levels, or long: ≥ 4 levels) with a diagnosis of adult idiopathic scoliosis or degenerative disc disease were identified. Forty-nine thousand nine hundred twenty patients met the inclusion criteria of the study. In our inclusion and exclusion criteria, there was no variation with respect to the distribution of sex and race across the three groups of interest. Patients who underwent a spinal procedure (short versus long fusion) had comparable age. However, patients who did not undergo a spinal procedure were older than patients who had short fusion (65 ± 12.4 years versus 63 ± 10.7 years; p < 0.001). Multivariate binary logistic regression models that controlled for age, sex, and Deyo/Charlson scores were used to investigate the association between spinal fusion and THA revisions, postoperative dislocation, contralateral THAs, and total surgical complications to the end of 2013. A total of 49,920 patients who had THAs were included in one of three groups (no subsequent spinal fusion: n = 49,209; short fusion: n = 478; long fusion: n = 233). Results Regression models revealed that short and long spinal fusions were associated with increased odds for hip dislocation, with associated odds ratios (ORs) of 2.2 (95% CI, 1.4-3.6; p = 0.002), and 4.4 (95% CI, 2.7-7.3; p < 0.001), respectively. Patients who underwent THA and spinal surgery also had an increased odds for THA revision, with ORs of 2.0 (95% CI, 1.4-2.8; p < 0.001) and 3.2 (95% CI, 2.1-4.8; p < 0.001) for short and long fusion, respectively. However, spinal fusions were not associated with contralateral THAs. Further, short and long spinal fusions were associated with increased surgical complication rates (OR = 2.8, 95% CI, 2.1-3.8, p < 0.001; OR = 5.3, 95% CI, 3.8-7.4, p < 0.001, respectively). Conclusion We showed that spinal fusion in adults is associated with an increased frequency of complications and revisions in patients who have had a prior THA. Specifically, patients who had a long spinal fusion after THA had 340% higher odds of experiencing a hip dislocation and 220% higher odds of having to undergo a revision THA. Further research is necessary to determine whether this relationship is associated with the surgical order, or whether more patient-specific surgical goals of revision THA should be developed for patients with a spinal deformity. Level of Evidence Level III, therapeutic study