Barthelemy Liabaud

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

Validation of a new computer-assisted tool to measure spino-pelvic parameters

BACKGROUND CONTEXTnEvaluation of sagittal alignment is essential in the operative treatment of spine pathology, particularly adult spinal deformity (ASD). However, software applications for detailed spino-pelvic analysis are usually complex and not applicable to routine clinical use.nnnPURPOSEnThis study aimed to validate new clinician-friendly software (Surgimap) in the setting of ASD.nnnSTUDY DESIGN/SETTINGnAccuracy and inter- and intra-rater reliability of spine measurement software were tested. Five users (two experienced spine surgeons, three novice spine research fellows) independently performed each part of the study in two rounds with 1 week between measurements.nnnPATIENT SAMPLEnFifty ASD patients drawn from a prospective database were used as the study sample.nnnOUTCOME MEASURESnSpinal, pelvic, and cervical measurement parameters (including pelvic tilt [PT], pelvic incidence [PI], lumbar-pelvic mismatch [PI-LL], lumbar lordosis [LL], thoracic kyphosis [TK], T1 spino-pelvic inclination [T1SPI], sagittal vertical axis [SVA], and cervical lordosis [CL]) were the outcome measures.nnnMETHODSnFor the accuracy evaluation, 30 ASD patient radiographs were pre-marked for anatomic landmarks. Each radiograph was measured twice with the new software (Surgimap); measurements were compared to those from previously validated software. For the reliability and reproducibility evaluation, users measured 50 unmarked ASD radiographs in two rounds. Intra-class correlation (ICC) and International Organization for Standardization (ISO) reproducibility values were calculated. Measurement time was recorded.nnnRESULTSnSurgimap demonstrated excellent accuracy as assessed by the mean absolute difference from validated measurements: PT: 0.12°, PI: 0.35°, LL: 0.58°, PI-LL: 0.46°, TK: 5.25°, T1SPI: 0.53°, and SVA: 2.04 mm. The inter- and intra-observer reliability analysis revealed good to excellent agreement for all parameters. The mean difference between rounds was <0.4° for PT, PI, LL, PI-LL, and T1SPI, and <0.3 mm for SVA. For PT, PI, LL, PI-LL, TK, T1SPI, and SVA, the intra-observer ICC values were all >0.93 and the inter-observer ICC values were all >0.87. Parameters based on point landmarks rather than end plate orientation had a better reliability (ICC≥0.95 vs. ICC≥0.84). The average time needed to perform a full spino-pelvic analysis with Surgimap was 75 seconds (+25).nnnCONCLUSIONSnUsing this new software tool, a simple method for full spine analysis can be performed quickly, accurately, and reliably. The proposed list of parameters offers quantitative values of the spine and pelvis, setting the stage for proper preoperative planning. The new software tool provides an important bridge between clinical and research needs.

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

OBJECTnPrevious 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.nnnMETHODSnThis 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).nnnRESULTSnIn 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.nnnCONCLUSIONSnThis 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.

Natural Head Posture in the Setting of Sagittal Spinal Deformity: Validation of Chin-Brow Vertical Angle, Slope of Line of Sight, and McGregor's Slope With Health-Related Quality of Life.

BACKGROUNDnThe maintenance of horizontal gaze is an essential function of upright posture and global sagittal spinal alignment. Horizontal gaze is classically measured by the chin-brow vertical angle (CBVA), which is not readily measured on most lateral spine radiographs.nnnOBJECTIVEnTo evaluate relations between CBVA and the slope of the line of sight, the slope of McGregors line (McGS), and Oswestry Disability Index.nnnMETHODSnPatients were identified from a single center database of 531 spine patients who underwent full-body EOS x-rays. Correlations between CBVA, the slope of the line of sight, and McGS were assessed. Using a quadratic regression with Oswestry Disability Index and CBVA, windows of low disability were identified. Comparison of sagittal spinopelvic parameters was carried out between patients with ascending gaze and neutral position.nnnRESULTSnThree hundred three patients were included (74% female, mean age 54.8 years, body mass index 26.6 ± 6.0 kg/m). CBVA strongly correlated with the slope of the line of sight (r = 0.996) and McGS (r = 0.862). Regression studies between Oswestry Disability Index and CBVA yielded a range of values corresponding to low disability (-4.7 degrees to 17.7 degrees). Similarly, a low disability range for the slope of the line of sight (-5.1 degrees to 18.5 degrees) and McGS (-5.7 degrees to 14.3 degrees) was computed. Patients with ascending gaze had a worse spinopelvic alignment than neutral position patients.nnnCONCLUSIONnThe slope of the line of sight and McGS correlated strongly with CBVA and can be used as surrogate measures. The range of values for these measures corresponding to low disability was identified. These values can be used as a general guideline to assess alignment for diagnostic purposes. Cervical compensatory mechanism may modify the natural head position in sagittally misaligned patients.nnnABBREVIATIONSnCBVA, chin-brow vertical angleHRQoL, health-related quality of lifeMcGS, slope of McGregors lineODI, Oswestry Disability IndexSLs, slope of the line of sight.

Predicting Cervical Alignment Required to Maintain Horizontal Gaze Based on Global Spinal Alignment.

Study Design. A retrospective cohort. Objective. The aim of this study was to investigate the cervical alignment necessary for the maintenance of horizontal gaze that depends on underlying thoracolumbar alignment. Summary of Background Data. Cervical Sagittal Curve (CC) is affected by thoracic and global alignment. Recent studies suggest large variability in normative CC ranging from lordotic to kyphotic alignment. No previous studies have assessed the effect of global spinal alignment on CC in maintenance of horizontal gaze. Methods. Patients without previous history of spinal surgery and able to maintain their horizontal gaze while undergoing full body imaging were included. Patients were stratified on the basis of thoracic kyphosis (TK) into (<30, 30–40, 40–50, and >50) and then by SRS-Schwab sagittal vertical axis (SVA) modifier into (posterior alignment SVA <0, aligned 0–50, and malaligned >50u200amm). Cervical alignment was assessed among SVA grade in TK groups. Stepwise linear regression analysis was applied on random selection of 60% of the population. A simplified formula was developed and validated on the remaining 40%. Results. In each TK group (nu200a=u200a118, 137, 125, 197), lower CC (C2-C7) was significantly more lordotic by increased Schwab SVA grade. T1 slope and cervical SVA significantly increased with increased thoracolumbar (C7-S1) SVA. Upper CC (C0-C2) and mismatch between T1 slope and CC (T1-CL) were similar. Regression analysis revealed LL minus TK (LL-TK) as an independent predictor (ru200a=u200a0.640, r2u200a=u200a0.410) with formula: CCu200a=u200a10- (LL-TK)/2. Validation revealed that the absolute difference between the predicted CC and the actual CC was 8.5°. Moreover, 64.2% of patients had their predicted C2-C7 values within 10° of the actual CC. Conclusion. Cervical kyphosis may represent normal alignment in a significant number of patients. However, in patients with SVA >50 and greater thoracic kyphosis, cervical lordosis is needed to maintain the gaze. Cervical alignment can be predicted from underlying TK and lumbar lordosis, which may be clinically relevant when considering correction for thoracolumbar or cervical deformity Level of Evidence: 3

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.

Complication rates associated with 3-column osteotomy in 82 adult spinal deformity patients: retrospective review of a prospectively collected multicenter consecutive series with 2-year follow-up

OBJECTIVE Although 3-column osteotomy (3CO) can provide powerful alignment correction in adult spinal deformity (ASD), these procedures are complex and associated with high complication rates. The authors objective was to assess complications associated with ASD surgery that included 3CO based on a prospectively collected multicenter database. METHODS This study is a retrospective review of a prospectively collected multicenter consecutive case registry. ASD patients treated with 3CO and eligible for 2-year follow-up were identified from a prospectively collected multicenter ASD database. Early (≤ 6 weeks after surgery) and delayed (> 6 weeks after surgery) complications were collected using standardized forms and on-site coordinators. RESULTS Of 106 ASD patients treated with 3CO, 82 (77%; 68 treated with pedicle subtraction osteotomy [PSO] and 14 treated with vertebral column resection [VCR]) had 2-year follow-up (76% women, mean age 60.7 years, previous spine fusion in 80%). The mean number of posterior fusion levels was 12.9, and 17% also had an anterior fusion. A total of 76 early (44 minor, 32 major) and 66 delayed (13 minor, 53 major) complications were reported, with 41 patients (50.0%) and 45 patients (54.9%) affected, respectively. Overall, 64 patients (78.0%) had at least 1 complication, and 50 (61.0%) had at least 1 major complication. The most common complications were rod breakage (31.7%), dural tear (20.7%), radiculopathy (9.8%), motor deficit (9.8%), proximal junctional kyphosis (PJK, 9.8%), pleural effusion (8.5%), and deep wound infection (7.3%). Compared with patients who did not experience early or delayed complications, those who had these complications did not differ significantly with regard to age, sex, body mass index, Charlson Comorbidity Index, American Society of Anesthesiologists score, smoking status, history of previous spine surgery or spine fusion, or whether the 3CO performed was a PSO or VCR (p ≥ 0.06). Twenty-seven (33%) patients had 1-11 reoperations (total of 44 reoperations). The most common indications for reoperation were rod breakage (n = 14), deep wound infection (n = 15), and PJK (n = 6). The 24 patients who did not achieve 2-year follow-up had a mean of 0.85 years of follow-up, and the types of early and delayed complications encountered in these 24 patients were comparable to those encountered in the patients that achieved 2-year follow-up. CONCLUSIONS Among 82 ASD patients treated with 3CO, 64 (78.0%) had at least 1 early or delayed complication (57 minor, 85 major). The most common complications were instrumentation failure, dural tear, new neurological deficit, PJK, pleural effusion, and deep wound infection. None of the assessed demographic or surgical parameters were significantly associated with the occurrence of complications. These data may prove useful for surgical planning, patient counseling, and efforts to improve the safety and cost-effectiveness of these procedures.

When is compensation for lumbar spinal stenosis a clinical sagittal plane deformity

BACKGROUND CONTEXTnDegenerative lumbar stenosis (DLS) patients have been reported to lean forward in an attempt to provide neural decompression. Spinal alignment in patients with DLS may resemble that of adult spinal deformity (ASD). No previous studies have compared and contrasted the compensatory mechanisms of DLS and ASD patients.nnnPURPOSEnThis study aimed to determine the differences in compensatory mechanisms between DLS and ASD patients with increasing severity of sagittal spinopelvic malalignment. Contrasting these compensatory mechanisms may help determine at what severity sagittal malalignment represents a clinical sagittal deformity rather than a compensation for neural compression.nnnSTUDY DESIGN/SETTINGnThis is a retrospective clinical and radiological review.nnnPATIENT SAMPLEnBaseline x-rays in patients without spinal instrumentation, with the clinical radiological and diagnoses of DLS or ASD, were assessed for patterns of spinopelvic compensatory mechanisms. Patients were stratified by sagittal vertical axis (SVA) according to the Scoliosis Research Society-Schwab [SRS-Schwab] classification.nnnOUTCOME MEASURESnRadiographic spinopelvic parameters were measured in the DLS and ASD groups, including SVA, pelvic incidence-lumbar lordosis mismatch (PI-LL), T1 spinopelvic inclination (T1SPi), T1 pelvic angle (TPA), and pelvic tilt (PT).nnnMETHODSnThe two diagnosis cohorts were propensity-matched for PI and age. Each group contained 125 patients and was stratified according to the SRS-Schwab classification. Regional spinopelvic,lower limb, and global alignment parameters were assessed to identify differences in compensatory mechanisms between the two groups with differing degrees of deformity. No funding was provided by any third party in relation to carrying out this study or preparing the manuscript.nnnRESULTSnWith mild to moderate malalignment (SRS-Schwab groups 0, or + for PT, PI-LL, or SVA), DLS patients permit anterior truncal inclination and recruit posterior pelvic shift instead of pelvic tilt to maintain balance, while providing relief of neurologic symptoms. Adult spinal deformity patients with mild to moderate deformity recruit pelvic tilt earlier than DLS patients. With moderate to severe malalignment, no significant difference was found in compensatory mechanisms between DLS and ASD patients.nnnCONCLUSIONSnPatients with DLS permit mild to moderate deformity without recruiting compensatory mechanisms of PT, reducing truncal inclination and thoracic hypokyphosis to achieve neural decompression. However, with moderate to severe deformity, their desire for upright posture overrides the desire for neural decompression, evident by the adaptation of compensatory mechanisms similar to that of ASD patients.

Dedicated Spine Measurement Software Quantifies Key Spino-Pelvic Parameters More Reliably Than Traditional Picture Archiving and Communication Systems Tools.

Study Design. Measurement reliability study of adult spinal deformity (ASD) patient radiographs using intraclass correlation coefficients (ICC) and variance. Objective. The aim of the study was to compare picture archiving and communication systems (PACS) to dedicated spine measurement software (SMS). Summary of Background Data. Accurate radiographic measurement of sagittal alignment is essential for evaluating ASD. PACS measurements often necessitate rudimentary techniques and estimations of anatomic landmarks and angles. Though SMS has been studied and validated, no studies directly compare PACS to SMS. Methods. Eleven independent observers (7 spine surgeons, 4 researchers) digitally measured 20 ASD radiographs for pelvic incidence (PI), pelvic tilt (PT), lumbar lordosis (LL), PI-LL, thoracic kyphosis (TK), and sagittal vertical axis (SVA). Round 1 used PACS basic line/angle tools; Round 2 used a validated SMS that automatically calculates spino-pelvic parameters from 6 user-identified landmarks. Means, coefficient of variance (CV), and intraclass correlation coefficients (ICC) were analyzed. Results. PACS measurements were significantly greater than SMS (PI, PT, PI-LL: Pu200a<u200a0.0001), though within clinical and measurement margins of error. Excluding TK, the variations in measurement (CV) were significantly greater for PACS (14–34%) vs. SMS (11–23%). Reliability was greater in SMS than PACS for PI, PT, PI-LL, LL, and SVA. The greatest differences in intraclass correlation coefficients (ICC) between PACS and SMS were in PI (PACS: 0.647; SMS: 0.810) and PI-LL (PACS: 0.921; SMS: 0.970). Among surgeons, the differences between PACS and SMS were augmented, and SMS had higher intraclass correlation coefficients (ICC) than PACS for all parameters (mean intraclass correlation coefficients [ICC] 0.931 vs. 0.861). Among surgeons, PI had the lowest reliability (PACS: 0.505; SMS: 0.752) and SVA had the highest (PACS: 0.985; SMS: 0.994). Conclusion. SMS provides significantly more reliable measurements than PACS, especially among surgeons. Consistent use of SMS in the evaluation and surgical planning of ASD patients appears necessary given the significant differences in values, variance, and reliability between PACS and SMS. Level of Evidence: 3

A comparative analysis of the prevalence and characteristics of cervical malalignment in adults presenting with thoracolumbar spine deformity based on variations in treatment approach over 2 years

PurposeCharacteristics specific to cervical deformity (CD) concomitant with adult thoracolumbar deformity (TLD) remains uncertain, particularly regarding treatment. This study identifies cervical malalignment prevalence following surgical and conservative TLD treatment through 2xa0years.MethodsRetrospective analysis of a prospective, multicenter adult spinal deformity (ASD) database. CD was defined in operative and non-operative ASD patients according to the following criteria: T1 Slope minus Cervical Lordosis (T1S-CL) ≥20°, C2–C7 Cervical Sagittal Vertical Axis (cSVA) ≥40xa0mm, C2–C7 kyphosis >10°. Differences in rates, demographics, health-related quality of life (HRQoL) scores for Oswestry Disability Index (ODI) and Scoliosis Research Society Questionnaire (SRS-22r), and radiographic variables were assessed between treatment groups (Op vs. Non-Op) and follow-up periods (baseline, 1-year, 2-year).ResultsThree hundred and nineteen (200 Op, 199 Non-Op) ASD patients were analyzed. Op patients’ CD rates at 1 and 2xa0years were 78.9, and 63.0xa0%, respectively. Non-Op CD rates were 21.1 and 37.0xa0% at 1 and 2xa0years, respectively. T1S-CL mismatch and cSVA malalignment characterized Op CD at 1 and 2xa0years (pxa0<xa00.05). Op and Non-Op CD groups had similar cervical/global alignment at 1xa0year (pxa0>xa00.05 for all), but at 2xa0years, Op CD patients had worse thoracic kyphosis (TK), T1S-CL, CL, cSVA, C2–T3 SVA, and global SVA compared to Non-Ops (pxa0<xa00.05). Op CD patients had worse ODI, and SRS Activity at 1 and 2xa0years post-operative (pxa0<xa00.05), but had greater 2-year SRS Satisfaction scores (pxa0=xa00.019).ConclusionsIn the first study to compare cervical malalignment at extended follow-up between ASD treatments, CD rates rose overall through 2xa0years. TLD surgery, resulting in higher CD rates characterized by T1S-CL and cSVA malalignment, produced poorer HRQoL. This information can aid in treatment method decision-making when cervical deformity is present concomitant with TLD.