Emmanuelle Ferrero

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 CONTEXT Evaluation 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. PURPOSE This study aimed to validate new clinician-friendly software (Surgimap) in the setting of ASD. STUDY DESIGN/SETTING Accuracy 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. PATIENT SAMPLE Fifty ASD patients drawn from a prospective database were used as the study sample. OUTCOME MEASURES Spinal, 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. METHODS For 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. RESULTS Surgimap 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). CONCLUSIONS Using 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

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.

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.

Clinical and stereoradiographic analysis of adult spinal deformity with and without rotatory subluxation

INTRODUCTION In degenerative adult spinal deformity (ASD), sagittal malalignment and rotatory subluxation (RS) correlate with clinical symptomatology. RS is defined as axial rotation with lateral listhesis. Stereoradiography, recently developed for medical applications, provides full-body standing radiographs and 3D reconstruction of the spine, with low radiation dose. HYPOTHESIS 3D stereoradiography improves analysis of RS and of its relations with transverse plane and spinopelvic parameters and clinical impact. MATERIAL AND METHODS One hundred and thirty adults with lumbar ASD and full-spine EOS® radiographs (EOS Imaging, Paris, France) were included. Spinopelvic sagittal parameters and lateral listhesis in the coronal plane were measured. The transverse plane study parameters were: apical axial vertebral rotation (apex AVR), axial intervertebral rotation (AIR) and torsion index (TI). Two groups were compared: with RS (lateral listhesis>5mm) and without RS (without lateral listhesis exceeding 5mm: non-RS). Correlations between radiologic and clinical data were assessed. RESULTS RS patients were significantly older, with larger Cobb angle (37.4° vs. 26.6°, P=0.0001), more severe sagittal deformity, and greater apex AVR and TI (respectively: 22.9° vs. 11.3°, P<0.001; and 41.0° vs. 19.9°, P<0.001). Ten percent of patients had AIR>10° without visible RS on 2D radiographs. RS patients reported significantly more frequent low back pain and radiculalgia. DISCUSSION In this EOS® study, ASD patients with RS had greater coronal curvature and sagittal and transverse deformity, as well as greater pain. Further transverse plane analysis could allow earlier diagnosis and prognosis to guide management. LEVEL OF EVIDENCE 4, retrospective study.

Geographic and Ethnic Variations in Radiographic Disability Thresholds: Analysis of North American and Japanese Operative Adult Spinal Deformity Populations.

BACKGROUND Thresholds for spinal pelvic parameters in adult spinal deformity (ASD) were previously defined in North American patients and are commonly used to guide surgical planning. However, it is unclear whether these same threshold parameters can be more widely applied in other geographic regions and in other ethnicities. OBJECTIVE To evaluate the variation in the radiographic disability thresholds between North American and Japanese ASD populations and to adjust sagittal modifier thresholds accordingly. METHODS Retrospective case series of 717 patients with ASD who had baseline radiographs and Oswestry Disability Index (ODI) from North America (n = 518) and Japan (n = 199) were studied. Patients were compared at baseline for ODI, ODI offset from age- and ethnic-specific values (ODIni), and radiographic parameters. RESULTS Significant differences in classification were observed: A greater proportion of Japanese patients had marked pelvic tilt deformity, whereas a greater proportion of US patients had marked SVA deformity; no difference in the pelvic incidence-lumbar lordosis mismatch sagittal modifier was observed. Health-related quality-of-life scores also differed, with a greater ODI raw value observed in the US patients but similar ODIni scores between cohorts. Stratifying ODIni scores by sagittal modifier grades revealed similar disability scores corresponding to the 0 to + thresholds for pelvic tilt, pelvic incidence-lumbar lordosis mismatch, and sagittal vertical axis across ethnicities. Finally, linear regression analysis demonstrated that compared with US patients, Japanese patients had a lower estimated ODI corresponding to established thresholds of radiographic deformity. CONCLUSION Our findings demonstrate significant variability in health-related quality-of-life measures and radiographic parameters between North American and Japanese patients, supporting the need for population-adjusted sagittal modifiers to more accurately classify deformity. ABBREVIATIONS ASD, adult spinal deformityHRQOL, health-related quality of lifeLL, lumbar lordosisODI, Oswestry Disability IndexODIni, Oswestry Disability Index need for improvementPCS, physical component summaryPI, pelvic incidencePI-LL, pelvic incidence-lumbar lordosis mismatchPT, pelvic tiltSRS, Scoliosis Research SocietySVA, sagittal vertical axisTK, thoracic kyphosis.

Pedicle Subtraction Osteotomy in the Revision Versus Primary Adult Spinal Deformity Patient: Is There a Difference in Correction and Complications?

Study Design. Multicenter, prospective study of consecutive adult spinal deformity (ASD) patients. Objective. To compare alignment correction and perioperative complications after pedicle subtraction osteotomies (PSO) in the primary versus revision surgery setting for ASD. Summary of Background Data. PSO are performed to correct sagittal plane deformity; however, these are difficult procedures that have potential for large blood loss and risk for intraoperative and postoperative complications. Methods. Inclusion criteria were age at least 18 years, lumbar PSO, and available data on perioperative (up to 6 weeks after surgery) complication data. Patients were classified according to SRS‐Schwab sagittal modifiers: PT (pelvic tilt), SVA (sagittal vertical axis), and lumbo‐pelvic mismatch (pelvic incidence−lumbar lordosis). Patients were divided into primary (P; no previous spine fusion surgery) or revision (R; previous fusion). Baseline and 1‐year demographic, radiographic parameters, complications and revision rates were analyzed. Results. A total of 421 patients were included. P (n = 70) and R (n = 351) were similar for age, body mass index, sex, mean total Posterior Spinal Fusion (PSF) levels (P = 10.0; R = 10.5), PSO angle (P = 27°; R = 25°), estimated blood loss (P = 2.76L; R = 2.92L), and operative time (P = 437 min; R = 434 min). The most common osteotomy site was L3 for both primary (31.8%) and revision groups (43.6%). Both groups demonstrated improvement in sagittal spinopelvic parameters from baseline to 1 year, with similar changes in sagittal modifiers except for the pelvic mismatch that improved to a grade 0 (i.e., less than 10°) more often for primary PSO group (83%) than revision PSO group (57%; P = 0.004). Complication rates were similar (P > 0.05) for the following: new motor deficit (P = 4.2%, R = 9.4%), bowel/bladder deficit (P = 1.4%, R = 2.8%), 1‐year revision rate (P = 4.3%, R = 7.4%), and pseudarthrosis rate (P = 1.4%; R = 2.5%; P < 0.05). Conclusion. PSO may be performed in primary or revision ASD patient with similar sagittal deformity correction and similar complication rates; however, primary PSO patients were more likely to achieve better lumbo‐pelvic mismatch correction. Level of Evidence: 3Study Design.Multicenter, prospective study of consecutive adult spinal deformity (ASD) patients.Objective.To compare alignment correction and perioperative complications after pedicle subtraction osteotomies (PSO) in the primary versus revision surgery setting for ASD.Summary of Background Data.PSO

Sagittal alignment and complications following lumbar 3-column osteotomy: does the level of resection matter?

OBJECTIVE Three-column osteotomy (3CO) is a demanding technique that is performed to correct sagittal spinal malalignment. However, the impact of the 3CO level on pelvic or truncal sagittal correction remains unclear. In this study, the authors assessed the impact of 3CO level and postoperative apex of lumbar lordosis on sagittal alignment correction, complications, and revisions. METHODS In this retrospective study of a multicenter spinal deformity database, radiographic data were analyzed at baseline and at 1- and 2-year follow-up to quantify spinopelvic alignment, apex of lordosis, and resection angle. The impact of 3CO level and apex level of lumbar lordosis on the sagittal correction was assessed. Logistic regression analyses were performed, controlling for cofounders, to investigate the effects of 3CO level and apex level on intraoperative and postoperative complications as well as on the need for subsequent revision surgery. RESULTS A total of 468 patients were included (mean age 60.8 years, mean body mass index 28.1 kg/m2); 70% of patients were female. The average 3CO resection angle was 25.1° and did not significantly differ with regard to 3CO level. There were no significant correlations between the 3CO level and amount of sagittal vertical axis or pelvic tilt correction. The postoperative apex level significantly correlated with greater correction of pelvic tilt (2° per more caudal level, R = -0.2, p = 0.006). Lower-level 3CO significantly correlated with revisions for pseudarthrosis (OR = 3.88, p = 0.001) and postoperative motor deficits (OR = 2.02, p = 0.026). CONCLUSIONS In this study, a more caudal lumbar 3CO level did not lead to greater sagittal vertical axis correction. The postoperative apex of lumbar lordosis significantly impacted pelvic tilt. 3CO levels that were more caudal were associated with more postoperative motor deficits and revisions.

Pedicle subtraction osteotomy in the revision versus primary adult spinal deformity patient

Study Design. Multicenter, prospective study of consecutive adult spinal deformity (ASD) patients. Objective. To compare alignment correction and perioperative complications after pedicle subtraction osteotomies (PSO) in the primary versus revision surgery setting for ASD. Summary of Background Data. PSO are performed to correct sagittal plane deformity; however, these are difficult procedures that have potential for large blood loss and risk for intraoperative and postoperative complications. Methods. Inclusion criteria were age at least 18 years, lumbar PSO, and available data on perioperative (up to 6 weeks after surgery) complication data. Patients were classified according to SRS‐Schwab sagittal modifiers: PT (pelvic tilt), SVA (sagittal vertical axis), and lumbo‐pelvic mismatch (pelvic incidence−lumbar lordosis). Patients were divided into primary (P; no previous spine fusion surgery) or revision (R; previous fusion). Baseline and 1‐year demographic, radiographic parameters, complications and revision rates were analyzed. Results. A total of 421 patients were included. P (n = 70) and R (n = 351) were similar for age, body mass index, sex, mean total Posterior Spinal Fusion (PSF) levels (P = 10.0; R = 10.5), PSO angle (P = 27°; R = 25°), estimated blood loss (P = 2.76L; R = 2.92L), and operative time (P = 437 min; R = 434 min). The most common osteotomy site was L3 for both primary (31.8%) and revision groups (43.6%). Both groups demonstrated improvement in sagittal spinopelvic parameters from baseline to 1 year, with similar changes in sagittal modifiers except for the pelvic mismatch that improved to a grade 0 (i.e., less than 10°) more often for primary PSO group (83%) than revision PSO group (57%; P = 0.004). Complication rates were similar (P > 0.05) for the following: new motor deficit (P = 4.2%, R = 9.4%), bowel/bladder deficit (P = 1.4%, R = 2.8%), 1‐year revision rate (P = 4.3%, R = 7.4%), and pseudarthrosis rate (P = 1.4%; R = 2.5%; P < 0.05). Conclusion. PSO may be performed in primary or revision ASD patient with similar sagittal deformity correction and similar complication rates; however, primary PSO patients were more likely to achieve better lumbo‐pelvic mismatch correction. Level of Evidence: 3Study Design.Multicenter, prospective study of consecutive adult spinal deformity (ASD) patients.Objective.To compare alignment correction and perioperative complications after pedicle subtraction osteotomies (PSO) in the primary versus revision surgery setting for ASD.Summary of Background Data.PSO

Current trends in the management of degenerative lumbar spondylolisthesis

Degenerative spondylolisthesis (DS) is a common disease of the degenerative spine, often associated with lumbar canal stenosis. However, the choice between the different medical or surgical treatments remains under debate. Preference for surgical strategy is based on the functional symptoms, and when surgical treatment is selected, several questions should be posed and the surgical strategy adapted accordingly. One of the main goals of surgery is to improve neurological symptoms. Therefore, radicular decompression may be necessary. Radicular decompression can be performed indirectly through interbody fusion or interspinous spacer. However, indirect decompression has some limits, and the most frequent technique is a posterior decompression with fusion. Indeed, in cases of DS, associated fusion or dynamic stabilization are recommended to improve functional outcomes and prevent future destabilization. Risk factors for destabilization, such as anteroposterior and angular mobility, and significant disc height, have been discussed in the literature. When fusion is performed, osteosynthesis is often associated. It is essential to choose the length and position of the fusion according to the pelvic incidence and global alignment of the patient. It is possible to add interbody fusion to the posterolateral arthrodesis to improve graft area and stability, increase local lordosis and open foramina. The most common surgical treatment for DS is posterior decompression with instrumented fusion. Nevertheless, some cases are more complicated and it is crucial to consider the patient’s general health status, symptoms and alignment when selecting the surgical strategy. Cite this article: EFORT Open Rev 2018;3 DOI: 10.1302/2058-5241.3.170050