Relationships between radiographic parameters and spinopelvic muscles in adult spinal deformity patients

Relationship between global muscle atrophy and sagittal imbalance in patients with degenerative lumbar scoliosis: a study based on three-dimensional reconstruction

PURPOSE

To explore the three-dimensional (3D) characteristics of the paraspinal muscle (PSM) and the risk factors associated with sagittal imbalance (SI) in degenerative lumbar scoliosis (DLS) patients.

METHODS

168 patients with DLS were included in this study. We evaluated radiographic parameters, including spinopelvic parameters, apical intervertebral height, mean osteophyte formation score, apical vertebral rotation, mean facet degeneration, vertebral bone quality, mean intervertebral disc degeneration, mean modic changes, and relative muscle volume (rMV) of the PSM, including the paraspinal extensor muscle (PEM) and psoas major (PS), and fat infiltration (FI) of the PSM.

RESULTS

Significant differences were found in the rMV of PEM, PS, and FI of PEM between the concave and convex sides of the spine (p < 0.001). Seventy-two patients comprised the SI group, and 96 comprised the sagittal balance (SB) group. All the rMV of the PSM of the patients with SI were smaller than those of those with SB (p < 0.05). The patients with SI were older than those with SB (p = 0.001). Additionally, in comparison to those with SB, the patients with SI had less LL and SS (p < 0.05), as well as an increased SVA and PT (p < 0.05). Furthermore, logistic regression revealed that age, LL, and the rMV of PS on the concave side influenced sagittal imbalance.

CONCLUSIONS

This study revealed that the degeneration of the PSM on both sides was asymmetric and that aging, loss of LL, and global atrophy of the PSM, especially the concave side of PS, were significantly correlated with SI in patients with DLS.

Automated quantification of the anatomic accuracy of muscle paths and its application in an image-based subject-specific modeling workflow for adult spinal deformity

BACKGROUND

Musculoskeletal models (MSKM) can non-invasively evaluate the effect of altered muscle geometry and physiology on locomotor function. Nevertheless, this requires anatomically accurate muscle paths throughout functional ranges of motion. However, reference data to evaluate such muscle paths is rarely available, including in adult spinal deformity (ASD). Although this degenerative disorder alters muscle geometry and physiology, these parameters are not available to inform clinical decision-making as generic MSKM cannot account for these alterations, and reliable ASD-specific modeling workflows do not currently exist.

RESEARCH QUESTION

Can an efficient workflow be developed for evaluating and optimizing the anatomic accuracy of dynamic muscle paths in personalized MSKM and applied for reliable spinal motion simulations in ASD?

METHODS

A workflow was developed to automatically analyze anatomic muscle accuracy throughout predefined ranges of motion in terms of muscle-bone penetration, muscle action, moment arm magnitude, and discontinuities. Erector spinae, multifidus, and psoas muscles were semi-automatically segmented in magnetic resonance images of one healthy and two ASD subjects. Next, their muscle representation, insertion sites, and complexity were iteratively refined with the above workflow to generate subject-specific MSKM and compare them against state-of-the-art generic MSKM.

RESULTS

All muscles in the subject-specific MSKM were anatomically accurate, except for discontinuities in 3.81 % (psoas) and 0.37 % (multifidus) of moment arm curves across motions and subjects. In contrast, scaled generic MSKM were consistently associated with muscle-bone penetration, decreased moment arm magnitude, and opposite muscle actions.

SIGNIFICANCE

This novel workflow is the first to allow for an efficient evaluation of the anatomic accuracy of dynamic muscle paths. Its application in MSKM of ASD patients resulted in subject-specific muscle paths, with an anatomically correct muscle geometry, while preventing bone penetration during the representative range of motions. The workflow is promising to enable biomechanical analyses of ASD with an accuracy beyond that of scaled generic models.

Weak trunk extensors in adult spinal deformity patients are related to sagittal malalignment and kinematic limitations

BACKGROUND

Adult spinal deformity (ASD) is associated with muscles' degeneration that affects postural control and outcomes of an eventual corrective surgery. Evaluation of ASD is usually based on static radiographs and more recently on functional assessment. However, there has been limited exploration of muscle strength weakness in ASD. The aim was to investigate the relationship between trunk muscles' strength in ASD and its relationship with radiographic and kinematic alterations and quality-of-life decline.

METHODS

28 ASD and 18 asymptomatic subjects underwent biplanar radiographs with 3D calculation of spino-pelvic and global postural parameters. 3D movement analysis of gait, sitting to standing and stair ascent, was studied allowing the calculation of head, trunk and lower limbs 3D kinematics. Participants filled out health related quality of life questionnaires. A single operator measured 4 times the strength of the trunk muscles, using a hand-held dynamometer, to assess measurements' reliability. ASD population was divided into two groups based on the strength of trunk extensors: ASD-weak extensors (N = 11 patients having trunk extensors strength

RESULTS

Measurements of muscle strengths using the hand-held dynamometer were reliable (ICC>0.94). On standing radiographs, the ASD-weak extensors group showed an increased positive sagittal malalignment compared to the other groups (SVA=61 mm vs ASD-normal extensors: 18 mm, controls: -4 mm, p < 0.001). This sagittal malalignment remained during movement (kinematic-SVA=223 mm vs ASD-normal extensors:178 mm, controls:138 mm, p < 0.001). Muscle strength weakness was correlated to the decline of quality-of-life scores (PCS-SF36: r = 0.48, VAS for pain: ρ=-0.39).

CONCLUSIONS

This study showed that weak trunk extensors are associated with sagittal malalignment in static position, kinematic limitations during daily life activities and reduced quality of life scores. Future studies will investigate the effect of muscle strengthening on both static and dynamic alignment in ASD and their quality of life.

Collapse

Key Words

• 3D movement analysis
• Adult spinal deformity
• Functional assessment
• Muscle strength
• Trunk extensors

Collapse

MESH Headings

• Humans
• Male
• Female
• Biomechanical Phenomena
• Adult
• Quality of Life
• Torso/physiopathology
• Middle Aged
• Muscle Strength/physiology
• Case-Control Studies
• Radiography
• Spinal Curvatures/physiopathology
• Spinal Curvatures/diagnostic imaging
• Muscle Weakness/physiopathology
• Muscle, Skeletal/physiopathology
• Gait/physiology
• Young Adult

Collapse

Grants Collapse

Affiliation(s)

Maria Saadé Laboratory of Biomechanics and Medical Imaging, Faculty of Medicine, Saint-Joseph University of Beirut, Beirut, Lebanon
Rami Rachkidi Laboratory of Biomechanics and Medical Imaging, Faculty of Medicine, Saint-Joseph University of Beirut, Beirut, Lebanon
Ali Rteil Laboratory of Biomechanics and Medical Imaging, Faculty of Medicine, Saint-Joseph University of Beirut, Beirut, Lebanon
Elma Ayoub Laboratory of Biomechanics and Medical Imaging, Faculty of Medicine, Saint-Joseph University of Beirut, Beirut, Lebanon
Elena Jaber Laboratory of Biomechanics and Medical Imaging, Faculty of Medicine, Saint-Joseph University of Beirut, Beirut, Lebanon
Celine Chaaya Laboratory of Biomechanics and Medical Imaging, Faculty of Medicine, Saint-Joseph University of Beirut, Beirut, Lebanon
Nabil Nassim Laboratory of Biomechanics and Medical Imaging, Faculty of Medicine, Saint-Joseph University of Beirut, Beirut, Lebanon
Elio Mekhael Laboratory of Biomechanics and Medical Imaging, Faculty of Medicine, Saint-Joseph University of Beirut, Beirut, Lebanon
Rami Rehayem Laboratory of Biomechanics and Medical Imaging, Faculty of Medicine, Saint-Joseph University of Beirut, Beirut, Lebanon
Julien Abi Nahed Technology Innovation Unit, Hamad Medical Corporation, Doha, Qatar
Bilal Ramadan Laboratory of Biomechanics and Medical Imaging, Faculty of Medicine, Saint-Joseph University of Beirut, Beirut, Lebanon
Mohamad Karam Laboratory of Biomechanics and Medical Imaging, Faculty of Medicine, Saint-Joseph University of Beirut, Beirut, Lebanon
Ismat Ghanem Laboratory of Biomechanics and Medical Imaging, Faculty of Medicine, Saint-Joseph University of Beirut, Beirut, Lebanon
Abir Massaad Laboratory of Biomechanics and Medical Imaging, Faculty of Medicine, Saint-Joseph University of Beirut, Beirut, Lebanon
Ayman Assi Laboratory of Biomechanics and Medical Imaging, Faculty of Medicine, Saint-Joseph University of Beirut, Beirut, Lebanon; Institut de Biomécanique Humaine Georges Charpak, Arts et Métiers, Paris, France.

Collapse

Collaborators Collapse

Determining the risk factors for postoperative mechanical complication in degenerative scoliosis: a machine learning approach based on musculoskeletal metrics

OBJECTIVE

To determine the risk factors for mechanical complications (MC) following corrective surgery for degenerative scoliosis through a machine learning (ML) algorithm.

METHODS

Patients with degenerative scoliosis who received corrective surgery were enrolled. A total of 213 cases were ultimately included and randomized into the training set (70%) and test set (30%) to develop the machine learning-based algorithm. The demographic data, comorbidities, regional and global radiographic parameters, paraspinal muscle (PSM) fat infiltration rate (FI%), and vertebral bone quality (VBQ) score were analyzed.

RESULTS

A total of 101 patients (47.4%) had MC, including 46 patients with proximal junctional kyphosis or failure (PJK/PJF), 7 patients with distal junctional kyphosis or failure (DJK/DJF), and 25 patients with rod or screw breakage. In the testing set, Gaussian Naive Bayes (GNB) exhibited the highest AUC at 0.77, while Random Forest (RF) exhibited the highest PRC at 0.63. GNB, RF, and Logistic Regression (LR) models all achieved an accuracy of 0.69, while RF exhibited the highest sensitivity at 0.60 and lowest Brier score of 0.20. Shapley Additive Explanation (SHAP) analysis identified higher FI% of PSM, elevated VBQ score, higher preoperative T1-pelvic angle (T1PA), and postoperative lordosis maldistribution as major risk factors for MC. Based on RF model, local interpretable model-agnostic explanations (LIME) visualization was successfully developed for individual risk calculation.

CONCLUSION

The RF and GNB models showed the best overall performance. Both RF and GNB models identified top-ranked/major risk factors including higher paraspinal muscle fat infiltration, elevated VBQ score, higher preoperative T1PA angle, and postoperative lordosis maldistribution providing valuable insights for surgical decision-making.

Proximal junctional kyphosis above long spinal fusions

INTRODUCTION

Spinal deformity in adults is a major public health problem. After failure of conservative treatment, correction and fusion surgery leads to clinical and radiological improvement. However, mechanical complications and more particularly - proximal junctional kyphosis (PJK) - are common with an incidence of 10%-40% depending on the studies.

ANALYSIS

Several risk factors have been identified and can be grouped into three categories. Among the patient-related factors, advanced age, comorbidities, osteoporosis and sarcopenia play a determining role. Among the radiological factors, changes in sagittal alignment (cranial migration of thoracolumbar inflection point, over-correction of lumbar hyperlordosis, preoperative thoracolumbar kyphosis) play a key role. Finally, the fusion technique itself may increase the risk of PJK (use of screws instead of hooks) as a surgical factor.

PREVENTION

Prevention happens at each phase of treatment. A patient assessment is done preoperatively to identify those at risk of PJK. Treating osteoporosis is beneficial. The surgical strategy must also be adapted: the choice of transitional implants such as sublaminar links or hooks and the use of ligament reinforcement techniques can help minimize the risk of PJK. Finally, methodical clinical and radiological follow-up will help to detect early signs of PJK and allow a surgeon to reoperate right away.

TREATMENT

Not all PJK requires surgical revision. Radiological monitoring and functional treatment is sometimes sufficient. However, if the patient develops pain, neurological complications or instability detected by imaging (unstable fracture, spondylolisthesis, spinal cord compression), revision surgery is necessary. It may consist of proximal extension of the fusion combined with decompression of the stenosis levels at a minimum.

CONCLUSION

PJK is a major challenge for surgeons. The best treatment is prevention, with a thorough analysis of risk factors leading to a well-planned and personalized surgery. Regular postoperative follow-up is essential.

LEVEL OF EVIDENCE

Expert opinion.

Alignment considerations in degenerative spinal conditions: A narrative review

Background

With an aging population, degenerative spinal diseases are contributing significantly to the healthcare's burden. Spinal alignment in the context of adult spinal deformities has become an important domain of research.

Methods

We conducted a narrative review of the latest considerations in spinal alignment within the context of degenerative spinal conditions, discussed current strategies for morphological assessment and finally identified potential areas for future research.

Results

This review reported that degenerative spinal conditions lead to a complex disruption of spinal alignment. It also highlighted the importance of spino-pelvic alignment with specific attention to compensatory mechanisms that occur in response to spinal deformities. Emerging technologies including Artificial Intelligence and epigenetics are showing promises in terms of patient care.

Conclusions

Understanding spinal alignment in degenerative conditions underscores the importance of dynamic and individualized assessments. Future research should integrate emerging technologies along with traditional clinical practices in order to optimize patient outcomes and minimize complications for patients suffering from degenerative spinal diseases.

Evaluation of lumbar paraspinal muscles degeneration and fatty infiltration in dynamic sagittal imbalance based on magnetic resonance imaging

PURPOSE

To explore degeneration and fatty infiltration (FI) of lumbar paraspinal muscles in patients with dynamic sagittal imbalance (DSI) and the relationship between lumbar paraspinal muscles degeneration, fatty infiltration and severity of the disease.

METHODS

We recruited 41 DSI patients and selected 22 lumbar spinal stenosis (LSS) patients without osphyalgia as controls. All patients received magnetic resonance imaging (MRI) scan and DSI patients also received pre-walk and post-walk X-rays. DSI patients were divided into 2 subgroups according to their symptom improvement after conservative treatment. We calculated rmCSA and FI of the lumbar paraspinal muscles. The rmCSA and FI between DSI and control and between DSI subgroups were compared by t test. The regression analysis was used to explore the risk factors influencing disease severity. Receiver operating characteristic (ROC) curves and area under curves (AUCs) were used to evaluate the severity of the disease.

RESULTS

In comparison of rmCSA and FI between DSI and control, there are significant differences of most muscles. In comparison of rmCSA between two subgroups, there are significant differences of most muscles, while in comparison of FI, only muscles in L4 segment have significant different. In logistic regression analysis, total rmCSA and total FI are risk factors influencing disease severity. ROC curves shows that total rmCSA and total FI both achieve an AUC greater than 0.7.

CONCLUSION

Compared with control, DSI patients have degeneration and fatty infiltration of the lumbar paraspinal muscles. The degeneration and fatty infiltration are risk factors influencing disease severity. The total rmCSA and total FI can be used as an indicator to determine whether a patient has severe DSI.

MRI quantitative muscle characterization in children with X-linked hypophosphatemia

INTRODUCTION

Children with X Linked Hypophosphatemia (XLH) suffer from carential ricket, bone deformities and lameness. No previous study demonstrated a morphological distinction in muscles in these patients. The aim of this prospective study was to characterize, using Magnetic Resonance Imaging (MRI), the muscle morphology of pelvis, thigh and leg in children with XLH and to compare it with typically developed (TD) children.

HYPOTHESIS

We hypothesized that lower limbs muscles in children with XLH are different from TD children and could explain limp walking.

MATERIAL AND METHODS

Three-dimensional reconstructions of the muscles were performed in 11 patients with XLH and 15 TD children. Muscle lengths, sections and volumes were calculated and normalized with height and weight. Mean age was 10.

RESULTS

Lengths were all smaller in children with XLH except for the Medius/minimus gluteus muscles (p=0.64). The difference seemed higher in muscles with a long tendinous part as semitendinosus (0.139 vs 0,164; p<0.01). All volumes were significantly inferior in children with XLH. This preliminary study showed significant differences in muscle structures between patients with XLH and TD children.

DISCUSSION

Medius/minimus gluteus seemed to be particularly developed in children with XLH. Nevertheless it is not possible to conclude if it is related to XLH or a consequence of bone deformities.

LEVEL OF PROOF

IV.

What patient parameters influence lumbar stiffness in patients with hip pathology?

Lumbar stiffness leads to greater hip dependence to achieve sagittal motion and increases instability after total hip arthroplasty (THA). We aimed to determine parameters that influence lumbar stiffness among patients with hip pathology. We hypothesized that modifiable (degenerative changes, spinal canal stenosis, facet orientation) and nonmodifiable factors (muscle condition) would be associated with lumbar spine stiffness. In this retrospective case-cohort study from a tertiary referral center, consecutive patients presenting at a hip specialist clinic underwent standing and deep-seated radiographic assessment to measure lumbar lordosis (∆LL) (stiffness: ∆LL < 20°), hip flexion (∆PFA: pelvic femoral angle), and degree of degenerative-disc-disease (DDD) (facet osteoarthritis, disc height, endplate proliferative changes). Of these, 65 patients were selected with previous lumbar spine magnetic resonance imaging, allowing to determine lumbar facet orientation, spinal canal stenosis (Schizas classification), and flexor- and extensor-muscle atrophy (Goutallier classification). Mean ∆LL was 45° (range: 11°-72°) and four patients (6%) exhibited spine stiffness. Patients with multilevel DDD (n = 22) had less ∆LL than those with no/single level (n = 43) DDD (34° [range: 11°-53°] vs. 51° [21°-72°]; p < 0.001). Number of DDD levels correlated strongly with ∆LL (ρ = -0.642; p < 0.001). Spinal stiffness was only seen in patients with ≥4 DDD levels. There was no correlation between ∆LL and facet orientation (p > 0.05). ∆LL correlated strongly with extensor atrophy at L3-L4 (ρ = -0.473), L4-L5 (ρ = -0.520), and L5-S1 (ρ = -0.473) and poorly with flexors at L4-L5 (ρ = -0.134) and L5-S1 (ρ = -0.227). Lumbar stiffness is dependent on modifiable (muscle atrophy) and nonmodifiable (extend of DDD) factors. This can guide nonoperative management of hip pathology, emphasizing the relevance of core muscle rehabilitation to improve posture and stiffness. Identification ≥4 DDD levels should alert surgeons of increased THA instability risk. Level of evidence: level IV, cohort series.

Preoperative Body Composition Correlates with Postoperative Muscle Volume and Degeneration after Total Hip Arthroplasty

Impaired muscle recovery after total hip arthroplasty (THA) may affect gait and activities of daily living. Bioelectrical impedance analysis (BIA) can assess body composition and muscle volume, and computed tomography (CT) can assess muscle volume and the fatty degeneration of muscle. This study aimed to explore the effectiveness of BIA, and the correlation between preoperative body composition and postoperative muscle volume and degeneration after THA using BIA and CT. Thirty-eight patients who underwent THA and had BIA and CT performed pre- and postoperatively were retrospectively assessed. The BIA-derived measurements of preoperative body composition (fat mass index, fat-free mass index, and phase angle) were correlated with the CT-derived measurements (pre- and postoperative muscle volume and gluteus maximus and quadriceps Hounsfield Units of the affected hip). The preoperative fat mass index negatively correlated with the postoperative muscle volume of the gluteus maximus (p = 0.02) and quadriceps (p < 0.001) and the Hounsfield Units of the gluteus maximus (p = 0.03) and quadriceps (p = 0.03). The preoperative fat-free mass index positively correlated with the postoperative muscle volume of the quadriceps (p = 0.02). The preoperative phase angle positively correlated with the postoperative muscle volume of the quadriceps (p = 0.001) and the Hounsfield Units of the gluteus maximus (p = 0.03) and quadriceps (p = 0.001). In patients who underwent THA, preoperative body composition correlated with postoperative muscle volume and the fatty degeneration of the affected lower limb. Preoperative body composition may help predict postoperative muscle volume and fatty degeneration and thus, postoperative recovery.

The effects of back extensor strength in different body positions on health-related quality of life in patients with degenerative spinal deformity

BACKGROUND

Degenerative spinal deformity (DSD) is believed to originate from degeneration of the discs and facet joints and vertebral wedging. Currently, the nosogeny of DSD is not yet fully clarified and there has been no systematic study on the impact of their lower back muscle strength on quality of life.

OBJECTIVE

To determine the characteristics of back extensor strength (BES) in different body positions and examine their correlations with health-related quality of life (HQOL) in degenerative spinal deformity (DSD) patients.

METHODS

Participants comprised 60 DSD patients and 40 healthy volunteers. Maximal isometric BES was evaluated by dynamometers with the subject in three different positions (standing, prone, sitting). The visual analogue scale (VAS) score, Oswestry Disability Index (ODI), Roland-Morris Disability Questionnaire (RMQ), and 36-item Short Form Health Survey (SF-36) score were used to evaluate patient HQOL. Correlations between the BES in different body positions and HQOL were analysed.

RESULTS

The BES values in three body positions were significantly smaller in DSD patients than healthy subjects (P< 0.05). The standing BES was found to be negatively associated with ODI and RMQ (R= 0.313, p< 0.05 and R= 0.422, p< 0.01, respectively). A negative relationship between sitting BES and RMQ was also seen (R= 0.271, p< 0.05). In addition, the standing and prone BES were positively correlated with the physical functioning score of the SF-36 (R= 0.471, p< 0.01 and R= 0.289, p< 0.05, respectively), and the sitting BES was positively correlated with the role-physical score of the SF-36 (R= 0.436, p< 0.01).

CONCLUSION

The results indicate that the back extensor muscle is compromised in DSD patients and there are differences in predicting the severity of disability and physical HQOL scores with BES in different positions. Standing BES was the most reliable contributor to HQOL among three body positions.

Bioinformatics analysis of paravertebral muscles atrophy in adult degenerative scoliosis

Paravertebral muscles (PVM) act as one of the major dynamic factors to maintain human upright activities and play a remarkable role in maintaining the balance of the trunk. Adult degenerative scoliosis (ADS) has become one of the important causes of disability in the elderly population owing to the changes in spinal biomechanics, atrophy and degeneration of PVM, and imbalance of the spine. Previously, many studies focused on the physical evaluation of PVM degeneration. However, the molecular biological changes are still not completely known. In this study, we established a rat model of scoliosis and performed the proteomic analysis of the PVM of ADS. The results showed that the degree of atrophy, muscle fat deposition, and fibrosis of the PVM of rats positively correlated with the angle of scoliosis. The proteomic results showed that 177 differentially expressed proteins were present in the ADS group, which included 105 upregulated proteins and 72 downregulated proteins compared with the PVM in individuals without spinal deformities. Through the construction of a protein-protein interaction network, 18 core differentially expressed proteins were obtained, which included fibrinogen beta chain, apolipoprotein E, fibrinogen gamma chain, thrombospondin-1, integrin alpha-6, fibronectin-1, platelet factor 4, coagulation factor XIII A chain, ras-related protein Rap-1b, platelet endothelial cell adhesion molecule 1, complement C1q subcomponent subunit A, cathepsin G, myeloperoxidase, von Willebrand factor, integrin beta-1, integrin alpha-1, leukocyte surface antigen CD47, and complement C1q subcomponent subunit B. Further analysis of the Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) and immunofluorescence showed that the neutrophil extracellular traps (NETs) formation signaling pathway plays a major role in the pathogenesis of PVM degeneration in ADS. The results of the present study preliminarily laid the molecular biological foundation of PVM atrophy in ADS, which will provide a new therapeutic target for alleviating PVM atrophy and decreasing the occurrence of scoliosis.

Characteristics of paraspinal muscle degeneration in patients with adult degenerative scoliosis

INTRODUCTION

Adult degenerative scoliosis (ADS) is a 3D deformity that greatly affects the quality of life of patients and is closely related to the quality of paraspinal muscles (PSMs), but the specific degenerative characteristics have not been described.

METHODS

This study included ADS patients who were first diagnosed in our hospital from 2018 to 2022. Muscle volume (MV) and fat infiltration (FI) of PSM were measured by 3D reconstruction, and spinal parameters were assessed by X-ray. The values of convex side (CV) and concave side (CC) were compared.

RESULTS

Fifty patients were enrolled with a mean age of 64.1 ± 5.8 years old. There were significant differences in MV, FI, and Cobb angle between male and female groups. The MV of MF and PS on the CC was significantly larger than that on the CV. In the apex and the segments above the apex, the FI of the MF on the CC is greater than the CV, and in the CV of the segment below the apex, the FI of the MF is greater than the CC. Besides, there was a significant positive correlation between the FI and Cobb angle in the MF of the CC-CV.

CONCLUSION

There were significant differences in the MV and FI of PSM on both sides of the spine in ADS patients. It was determined that the PSM of ADS showed different degrees of degeneration in different levels of the lumbar spine and were positively correlated with Cobb angle.

Scoliosis

Scoliosis is a three-dimensional spinal deformity that can occur at any age. It may be idiopathic or secondary in children, idiopathic and degenerative in adults. Management of patients with scoliosis is multidisciplinary, involving rheumatologists, radiologists, orthopaedic surgeons, and prosthetists. Imaging plays a central role in diagnosis, including the search for secondary causes, follow-up, and preoperative work-up if surgery is required. Evaluating scoliosis involves obtaining frontal and lateral full-spine radiographs in the standing position, with analysis of coronal and sagittal alignment. For adolescent idiopathic scoliosis, imaging follow-up is often required, accomplished using low-dose stereoradiography such as EOS imaging. For adult degenerative scoliosis, the crucial characteristic is rotatory subluxation, also well detected on radiographs. Magnetic resonance imaging is usually more informative than computed tomography for visualizing associated canal and foraminal stenoses. Radiologists must also have a thorough understanding of postoperative features and complications of scoliosis surgery because aspects can be misleading.

Spinal Cord Alignment in Patients with Thoracolumbar Burst Fracture

Objective  To evaluate the spinopelvic alignment in patients with thoracolumbar burst fracture (TBF) without neurological deficit treated nonsurgically and surgically in a tertiary reference trauma hospital. Method  Retrospective cross-sectional study of patients with single level, type A3 and A4 AOSpine TBF only of the thoracolumbar region. Analysis of clinical data, low back pain (visual analogue scale [VAS]), Denis Pain Scale, quality of life (SF-36), sagittal (TC, TLC, LL, SVA) and spinopelvic (IP, PV, SI, PI-LL) radiographic parameters of patients treated surgically and nonsurgically. Results A total of 50 individuals with an average age of 50 years old with a mean follow-up of 109 months (minimum of 19 and maximum of 306 months) were evaluated. There was a significant difference between treatments for the Denis Work Scale ( p  = 0.046) in favor of nonsurgical treatment. There was no significant difference between the treatments for lower back pain VAS and Denis Pain Scale ( p  = 0.468 and p  = 0.623). There was no significant difference between treatments in any of the domains evaluated with the SF-36 ( p  > 0.05). Radiographic parameters were not different between the analyzed groups; however, all radiographic parameters showed significant difference between the population considered asymptomatic, except for pelvic incidence ( p  < 0.005). Conclusions  The spinopelvic alignment was normal in patients with TBF without neurological deficit treated nonsurgically and surgically after a minimum follow-up of 19 months. However, they presented a higher mean pelvic version and discrepancy between lumbar lordosis and pelvic incidence when compared with the reference values of the Brazilian population.

Physical and radiographic features of degenerative retrolisthesis in Japanese female volunteers: an observational cohort study

Hundred and twenty four females with spondylolisthesis were divided into three groups (A group: anterolisthesis; P group: retrolisthesis; and AP group: antero-retrolisthesis), We reviewed their whole-spine radiographs and measured their standard sagittal parameters, including thoracic kyphosis (TK), pelvic incidence (PI), lumbar lordosis (LL), pelvic tilt (PT), and sacral slope (SS). The muscle strengths of the trunk flexor, trunk extensor, iliopsoas, and quadriceps were measured. Health-related quality of life was assessed using the Short Form 36-item Health Survey-physical component summary (SF-36 PCS). PI, SS, and LL-TK of participants in the P group were significantly lower than those in the A and AP groups (PI: P group vs. A group, p < 0.001, P group vs. AP group, p = 0.01), (SS: P group vs. A group, p = 0.001, P group vs. AP group, p = 0.003), (LL-TK: P group vs. A group, p < 0.001, P group vs. AP group, p = 0.049). TK of participants in the P and AP groups was greater than that of those in the A group. (P group vs. A group, p = 0.04, AP group vs. A group, p = 0.0025). The SF-36 PCS score in the P group was lower than that in the A and AP groups. (P group vs. A group, p = 0.004, P group vs. AP group, p = 0.012). The muscle strengths of the trunk flexor and trunk extensor and quadriceps in the P group were lower than those in the A groups. (Trunk flexor: P group vs. A group, p = 0.012), (Trunk extensor: P group vs. A group, p = 0.018), (Quadriceps: P group vs. A group, p = 0.011). In conclusion, female participants with degenerative retrolisthesis had a smaller PI and SS and a larger TK, along with decreased physical function and QoL scores than those with anterolisthesis.

The relationship between spinal alignment and activity of paravertebral muscle during gait in patients with adult spinal deformity: a retrospective study

BACKGROUND

Spinal alignment in patients with adult spinal deformity (ASD) changes between rest and during gait. However, it remains unclear at which point the compensated walking posture breaks down and how muscles respond. This study used time-synchronized electromyography (EMG) to investigate the relationship between dynamic spinal alignment and muscle activity during maximum walking duration to reveal compensation mechanisms.

METHODS

This study collected preoperative three-dimensional gait analysis data from patients who were candidates for corrective surgery for ASD from April 2015 to May 2019. We preoperatively obtained dynamic spinal alignment parameters from initiation to cessation of gait using a motion capture system with time-synchronized surface integrated EMG (iEMG). We compared chronological changes in dynamic spinal alignment parameters and iEMG values 1) immediately after gait initiation (first trial), 2) half of the distance walked (half trial), and 3) immediately before cessation (last trial).

RESULTS

This study included 26 patients (22 women, four men) with ASD. Spinal sagittal vertical axis distance during gait (SpSVA) increased over time (first vs. half vs. last, 172.4 ± 74.8 mm vs. 179.9 ± 76.8 mm vs. 201.6 ± 83.1 mm; P < 0.001). Cervical paravertebral muscle (PVM) and gluteus maximus activity significantly increased (P < 0.01), but thoracic and lumbar PVM activity did not change. Dynamic spinal alignment showed significant correlation with all muscle activity (cervical PVM, r = 0.41-0.54; thoracic PVM, r = 0.49-0.66; gluteus maximus, r = 0.54-0.69; quadriceps, r = 0.46-0.55) except lumbar PVM activity.

CONCLUSION

Spinal balance exacerbation occurred continuously in patients with ASD over maximum walking distance and not at specific points. To maintain horizontal gaze, cervical PVM and gluteus maximus were activated to compensate for a dynamic spinal alignment change. All muscle activities, except lumbar PVM, increased to compensate for the spinal malalignment over time.

The Function Assessment Scale for Spinal Deformity: Validity and Reliability of a New Clinical Scale

STUDY DESIGN

Cross-sectional study.

OBJECTIVE

The aim of this study was to develop and validate the Function Assessment scale for Spinal Deformity (FASD).

SUMMARY OF BACKGROUND DATA

Spinal malalignment impacts daily functioning. Standard evaluation of adult spinal deformity (ASD) is based on static radiography and patient-reported scores, which fail to assess functional impairments. A clinical scale, quantifying function and balance of patients with ASD, could increase our insights on the impact of ASD on functioning.

METHODS

To develop the FASD, 70 ASD patients and 20 controls were measured to identify the most discriminating items of the Balance Evaluation Systems Test and Trunk Control Measurement Scale. Discussions between experts on the clinical relevance of selected items led to further item reduction. The FASD's discriminative ability was established between 43 patients and 19 controls, as well as between three deformity subgroups. For its responsiveness to treatment, 10 patients were reevaluated 6 months postoperatively. Concurrent validity was assessed through correlation analysis with radiographic parameters (pelvic tilt; sagittal vertical axis [SVA]; pelvic incidence minus lumbar lordosis [PI-LL]; coronal vertical axis) and patient-reported scores [Oswestry Disability Index]; Scoliosis Research Society outcome questionnaire; Falls Efficacy Scale-International). Test-retest and interrater reliability were tested on two groups of ten patients using intraclass correlation coefficients (ICC).

RESULTS

Patients with ASD, mainly with sagittal malalignment, scored worse compared to controls on FASD (P < 0.001) and its subscales. No significant improvement was observed 6 months postoperatively (P = 0.758). FASD correlated significantly to all patient-reported scores and to SVA and PI-LL. Reliability between sessions (ICC = 0.97) and raters (ICC = 0.93) was excellent. Subscales also showed good to excellent reliability, except FASD 1 on "spinal mobility and balance" between sessions (ICC = 0.71).

CONCLUSION

FASD proved to be a valid and reliable clinical scale for evaluation of functional impairments in ASD. Objective information on function and balance might ultimately guide physiotherapeutic treatment toward improved functioning.Level of Evidence: 2.

The standing T1-L1 pelvic angle: a useful radiographic predictor of proximal junctional kyphosis in adult spinal deformity

OBJECTIVE

Proximal junctional kyphosis (PJK), which can worsen a patient's quality of life, is a common complication following the surgical treatment of adult spinal deformity (ASD). Although various radiographic parameters have been proposed to predict the occurrence of PJK, the optimal method has not been established. The present study aimed to investigate the usefulness of the T1-L1 pelvic angle in the standing position (standing TLPA) for predicting the occurrence of PJK.

METHODS

The authors retrospectively extracted data for patients with ASD who underwent minimum 5-level fusion to the pelvis with upper instrumented vertebra between T8 and L1. In the present study, PJK was defined as ≥ 10° progression of the proximal junctional angle or reoperation due to progressive kyphosis during 1 year of follow-up. The following parameters were analyzed on whole-spine standing radiographs: the T1-pelvic angle, conventional thoracic kyphosis (TK; T4-12), whole-thoracic TK (T1-12), and the standing TLPA (defined as the angle formed by lines extending from the center of T1 and L1 to the femoral head axis). A logistic regression analysis and a receiver operating characteristic curve analysis were performed.

RESULTS

A total of 50 patients with ASD were enrolled (84% female; mean age 74.4 years). PJK occurred in 19 (38%) patients. Preoperatively, the PJK group showed significantly greater T1-pelvic angle (49.2° vs 34.4°), conventional TK (26.6° vs 17.6°), and standing-TLPA (30.0° vs 14.9°) values in comparison to the non-PJK group. There was no significant difference in the whole-thoracic TK between the two groups. A multivariate analysis showed that the standing TLPA and whole-thoracic TK were independent predictors of PJK. The standing TLPA had better accuracy than whole-thoracic TK (AUC 0.86 vs 0.64, p = 0.03). The optimal cutoff value of the standing TLPA was 23.0° (sensitivity 0.79, specificity 0.74). Using this cutoff value, the standing TLPA was the best predictor of PJK (OR 8.4, 95% CI 1.8-39, p = 0.007).

CONCLUSIONS

The preoperative standing TLPA was more closely associated with the occurrence of PJK than other radiographic parameters. These results suggest that this easily measured parameter is useful for the prediction of PJK.

Volume of spinopelvic muscles: comparison between adult spinal deformity patients and asymptomatic subjects

PURPOSE

Spinal muscles are a major component of posture in spinal pathologies and changes to the spine with aging. Specifically, spinopelvic muscles may compensate for underlying anomalies such as pelvic retroversion, knee flexion, and cervical or thoracic spinal balance abnormalities. To increase understanding between muscular characteristics and compensatory mechanisms, this study aimed to compare the volume of spinopelvic muscles in adults with a spinal deformity (ASD) to a control group of well-aligned adult subjects.

METHODS

Twenty-eight lumbar ASD patients [Cobb angle > 20°, > 40 years old (yo)] were prospectively included and compared to 35 normal subjects divided into 2 different groups: one group of young (Y) subjects (n = 23, < 20 yo) and one group of old (O) subjects (n = 12, > 40 yo). All subjects had a fat/water separation MRI (from C7 to the knees). Volumetric 3D reconstructions of 30 spinopelvic muscles were performed and muscles volumes were compared.

RESULTS

Mean age was 60 ± 16 yo, without significant differences between the ASD and O groups (57 ± 11 yo). Age and BMI were smaller in the young group. Mean Cobb angle of the ASD group was 45 ± 11°. Comparing the ASD and O groups, total muscular volume was similar; however, erector spinae (0.24 ± 0.06 vs 0.68 ± 0.08 dm³, p = 0.001), iliopsoas (0.49 ± 0.09 vs 0.60 ± 0.09 dm³, p = 0.001) and obliquus (0.42 ± 0.08 vs 0.50 ± 0.08 dm³, p = 0.02) were significantly smaller in the ASD group. Comparing the Y and the ASD groups, total muscular volume was higher in the Y group than the ASD group (+ 3.3 dm³, p = 0.003) and erector spinae (0.24 ± 0.06 vs 0.74 ± 0.08, p = 0.0001), gluteus medius (0.51 ± 0.07 vs 0.62 ± 0.13, p = 0.01) and vastus lateralis (1.33 ± 0.21 vs 2.08 ± 0.29, p = 0.001) were significantly bigger in the Y group.

CONCLUSION

This is the first study to compare volume of spinopelvic muscles between ASD patients and a control group without spinal deformity. Our results demonstrate that muscular degeneration has a double origin: aging and deformity. Erector spinae, iliopsoas, and obliquus are the muscles most affected by degeneration.

Prevalence and Related Factors of Low Back Pain in the General Elderly Population: A Japanese Cross-Sectional Study Randomly Sampled from a Basic Resident Registry

Low back pain (LBP) is one of the main etiologies of disability in daily life. In the face of LBP increases in super-aged societies, there are serious concerns of escalating medical costs and deteriorations in the social economy. It is therefore important to identify the factors associated with LBP for prompt preventative and therapeutic measures. This study investigated the prevalence of LBP and the impact of subject-specific factors on LBP development in Japanese community-dwelling older adults. We established eight groups based on age (50's, 60's, 70's, and 80's) and gender after random sampling from a resident registry. A total of 411 participants (201 male and 210 female) were enrolled for a whole-spine lateral radiographic examination and dual-energy X-ray absorptiometry. All subjects were evaluated for the presence and degree of LBP. We analyzed the impact of clinical factors on LBP using multivariate analysis. Fifty-three (12.9%) participants (23 (11.4%) male and 30 (14.3%) female) were found to have LBP. The prevalence of LBP tended to increase with age, and similar results were found between genders. In univariate analysis, the subject-related factors of the sagittal vertebral axis, pelvic incidence minus lumbar lordosis (PI-LL) mismatch, and aging had significant associations with LBP. PI-LL mismatch was a significant independent factor in multivariate analysis. In conclusion, this study identified LBP prevalence and subject-specific factors on a general population basis. Multivariate analysis revealed PI-LL mismatch as an independent factor associated with LBP in the healthy community-dwelling elderly.

Relationships Between Spinal Alignment and Muscle Mass in Osteoporosis Patients Over 75 Years of Age Who Were Independent and Maintained Their Activities of Daily Living

Introduction

Elderly patients with osteoporosis often complain of back pain associated with pathological vertebral fractures caused by abnormal spinal alignment. Few reports evaluate the relationships among muscle mass, bone mineral density (BMD), sagittal spinal alignment, and low back pain. We hypothesized that decreasing muscle mass in elderly patients with osteoporosis could cause spinal alignment abnormalities. The aim of the current study were to compare the characteristics between spinal sagittal normal alignment and malalignment and to evaluate the relationships between sagittal spinal alignment and muscle mass in elderly patients with osteoporosis.

Methods

Fifty patients aged 75 years or more (mean age = 80.5 years) with osteoporosis were included in this study. We evaluated the sagittal vertical axis (SVA), pelvic tilt (PT), pelvic incidence minus lumbar lordosis (PI-LL), the number of vertebral fractures (N of VFs), BMD by dual-energy X-ray absorptiometry, and trunk and skeletal muscle mass using bioelectrical impedance. Low back pain was evaluated using the Oswestry Disability Index (ODI). Corrected trunk muscle mass (trunk muscle mass index, TMI) and corrected limb muscle mass (skeletal mass index, SMI) also were measured. Patients were divided into two groups for comparison: a ‘normal’ group and a sagittal spinal ‘malalignment’ group. Multiple regression analysis was carried out to evaluate the relationship between spinal sagittal parameters and muscle mass.

Results

Comparisons between normal and malalignment groups for SVA, N of VFs, BMI, and SMI showed significantly higher in the malalignment group versus the normal group (p < 0.05). N of VFs, BMI, and TMI, for PT, and BMI, TMI, SMI, and ODI scores for PI-LL showed significantly higher in the malalignment group versus the normal group (p < 0.05). There were significantly more vertebral fractures in the malalignment group than in the normal group (p < 0.05). However, there were no significant differences of pure muscle mass between the two groups. When adjusted by BMD and the number of vertebral fractures, SMI and TMI were positively correlated to PI-LL and SVA (p < 0.05).

Conclusion

Elderly patients with osteoporosis and a sagittal spinal malalignment had more vertebral fractures and a higher risk of low back pain than patients with normal spinal alignment. Patients with a sagittal spinal malalignment who were independent and maintained their activities of daily living (ADL) showed high BMI and maintained muscle mass, independent of BMD and the N of VFs, contrary to our hypothesis. 

Toward understanding the underlying mechanisms of pelvic tilt reserve in adult spinal deformity: the role of the 3D hip orientation

PURPOSE

To explore 3D hip orientation in standing position in subjects with adult spinal deformity (ASD) presenting with different levels of compensatory mechanisms.

METHODS

Subjects with ASD (n = 159) and controls (n = 68) underwent full-body biplanar X-rays with the calculation of 3D spinopelvic, postural and hip parameters. ASD subjects were grouped as ASD with knee flexion (ASD-KF) if they compensated by flexing their knees (knee flexion ≥ 5°), and ASD with knee extension (ASD-KE) otherwise (knee flexion < 5°). Spinopelvic, postural and hip parameters were compared between the three groups. Univariate and multivariate analyses were then computed between spinopelvic and hip parameters.

RESULTS

ASD-KF had higher SVA (67 ± 66 mm vs. 2 ± 33 mm and 11 ± 21 mm), PT (27 ± 14° vs. 18 ± 9° and 11 ± 7°) and PI-LL mismatch (20 ± 26° vs - 1 ± 18° and - 13 ± 10°) when compared to ASD-KE and controls (all p < 0.05). ASD-KF also had a more tilted (34 ± 11° vs. 28 ± 9° and 26 ± 7°), anteverted (24 ± 6° vs. 20 ± 5° and 18 ± 4°) and abducted (59 ± 6° vs. 57 ± 4° and 56 ± 4°) acetabulum, with a higher posterior coverage (100 ± 6° vs. 97 ± 7° for ASD-KE) when compared to ASD-KE and controls (all p < 0.05). The main determinants of acetabular tilt, acetabular abduction and anterior acetabular coverage were PT, SVA and LL (adjusted R² [0.12; 0.5]).

CONCLUSIONS

ASD subjects compensating with knee flexion have altered hip orientation, characterized by increased posterior coverage (acetabular anteversion, tilt and posterior coverage) and decreased anterior coverage which can together lead to posterior femoro-acetabular impingement, thus limiting pelvic retroversion. This underlying mechanism could be potentially involved in the hip-spine syndrome.

The relationship of global sagittal malalignment to fatty infiltration in the aging spine

PURPOSE

To investigate associations between muscle size, fat infiltration (FI), and global sagittal alignment in patients with adult spinal deformity (ASD).

METHODS

Retrospective cohort study was conducted on a single-institution database of ASD patients with preoperative radiographs and CTs. Following multiplanar reconstructions of CTs, images in the plane of each vertebra were generated. The posterior vertebral musculature (PVM) was contoured on axial images at three vertebral levels (T2, T10, L3). FI was calculated by comparing Hounsfield units within muscles to the normative values of fat. Correlation analyses were conducted between demographics, alignment, and muscle characteristics.

RESULTS

107 patients underwent preoperative spine CT (58yo, 79%F, BMI 27 kg/m²). Muscle data were available for 49 pts at T2, 39 pts at T10, and 81 pts at L3. Mean FI was T2 = 33% ± 18, T10 = 28% ± 19, L3_Erector = 39% ± 19, and L3_Psoas = 19% ± 9. FI correlated across levels (T2 vs. T10 r = 0.698; T10 vs L3_Erector r = 0.506; L3_Erector vs Psoas r = 0.419) and with demographics; older pts had greater fat percentages (r = 0.31-0.45) and BMIs (r = 0.24-0.51). Increased FI at T2, T10, and L3 was associated with increased pelvic retroversion (PT: r = 0.25-0.43), global deformity (TPA: r = 0.27-0.45), and anterior malalignment (SVA: r = 0.23-0.41). The degree of FI in the PVM increased with the severity of SRS-Schwab PT and SVA modifiers.

CONCLUSION

In ASD patients, global sagittal malalignment is related to FI of the PVM throughout the lumbar and thoracic spine, as identified through CT. Future research should investigate how FI relates to ASD pathogenesis.

Assessment of isokinetic trunk muscle strength and its association with health-related quality of life in patients with degenerative spinal deformity

Background

A considerable portion of the elderly population are increasingly afflicted by degenerative spinal deformity (DSD), which seriously affects patient health-related quality of life (HRQoL). HRQoL index is used across many studies to show correlations between radio-graphical alignment, disability, and pain in patients with DSD. However, imaged structural deformity represents only one aspect for consideration, namely, the disability effect of DSD. We assessed the isokinetic strength of trunk muscle in patients with degenerative spinal deformity (DSD), and investigated its relationship with HRQoL.

Methods

In total, 38 patients with DSD (DSD group) and 32 healthy individuals (control group) were recruited. Both groups were homogeneous for age, weight, height and body mass index (BMI). Assessments were performed using the isokinetic dynamometer IsoMed-2000; trunk extensor, flexor strength and flexion/extension (F/E) ratios were explored concentrically at speeds of 30°, 60° and 120° per second. The grip strength of both hands was measured using a hand-held dynamometer. Visual analogue scale (VAS) scores, the Oswestry Disability Index (ODI), a Roland-Morris disability questionnaire (RDQ), and a 36-item Short Form Health Survey (SF-36) evaluated patient HRQoL. Correlations between trunk strength and HRQoL were analyzed.

Results

When compared with the control group, the DSD group showed lower trunk extensor strength at three velocity movements, and higher F/E ratios at 60° and 120°/s (p < 0.05). Both groups exhibited similar trunk flexor strength and grip strength (p > 0.05). In DSD group, trunk extensor strength at 60°/s was negatively associated with ODI and RDQ (p < 0.05). A negative relationship between trunk flexor strength at 120°/s and ODI was also recorded (p < 0.05). In addition, trunk extensor strength at 60°/s and trunk flexor strength at 120°/s were positively correlated with physical functioning and role-physical scores according to the SF-36 (p < 0.05).

Conclusions

We identified isolated trunk extensor myopathy in DSD, which causes an imbalance in trunk muscle strength. Isokinetic trunk extensor strength at 60°/s and trunk flexor strength at 120°/s can predict disability, and decrease physical HRQoL in DSD patients.

The prevalence of adult de novo scoliosis: A systematic review and meta-analysis

INTRODUCTION

Primary degenerative scoliosis represents a new scoliosis developing in patients with no prior history of spinal curvature. Researchers sought to determine the prevalence of this type of scoliosis.

METHODS

MEDLINE, Embase, CINAHL, Web of Science and PubMed were searched from inception to 28th March, 2018. Studies that assessed adults from the general population for scoliosis using imaging techniques were included. Studies were included only if the study authors had excluded participants with previously diagnosed scoliosis and/or spinal disorders. Mixed-effects logistic-regression was used to establish an overall prevalence estimate with 95% confidence intervals (primary outcome) and to examine the effect of age and sex (secondary outcomes).

RESULTS

Four cross-sectional studies and one cohort study, involving 4069 participants (66.6% Female), aged between 41 and 94 years, were eligible for inclusion. Reported prevalence figures ranged from 13 to 68%. The pooled prevalence estimate from the mixed-effects logistic regression analysis was 37.6% (95% CI 18.7-61.8). Females were more likely to suffer from scoliosis compared with males (p < 0.001), with prevalence figures of 41.2% (95% CI 20.7-65.8) versus 27.5% (95% CI 12.2-51.1), respectively. Individuals aged < 60 years had a prevalence of 13% (95% CI 5.2-30.2), whereas the prevalence estimates were substantially higher in the > 60 age group [36% (95% CI 17.4-60.6)].

CONCLUSION

Primary degenerative scoliosis is a highly prevalent condition, especially in females. Further research targeting this type of scoliosis is required to obtain more precise global prevalence estimates and to understand the influence of age and sex.

State of the art advances in minimally invasive surgery for adult spinal deformity

Adult spinal deformity (ASD) can be associated with substantial suffering due to pain and disability. Surgical intervention for achieving neural decompression and restoring physiological spinal alignment has shown to result in significant improvement in pain and disability through patient-reported outcomes. Traditional open approaches involving posterior osteotomy techniques and instrumentation are effective based on clinical outcomes but associated with high complication rates, even in the hands of the most experienced surgeons. Minimally invasive techniques may offer benefit while decreasing associated morbidity. Minimally invasive surgery (MIS) for ASD has evolved over the past 20 years, driven by improved understanding of open procedures along with novel technique development and technologic advancements. Early efforts were hindered due to suboptimal outcomes resulting from high pseudarthrosis, inadequate correction, and fixation failure rates. To address this, multi-center collaborative groups have been established to study large numbers of ASD patients which have been vital to understanding optimal patient selection and individualized management strategies. Different MIS decision-making algorithms have been described to better define appropriate candidates and interbody selection approaches in ASD. The purpose of this state of the review is to describe the evolution of MIS surgery for adult deformity with emphasis on landmark papers, and to discuss specific MIS technology for ASD, including percutaneous pedicle screw instrumentation, hyperlordotic grafts, three-dimensional navigation, and robotics.