Aims. The aim of this study was to investigate the impact of the level of upper instrumented vertebra (UIV) in frail patients undergoing surgery for adult spine deformity (ASD). Methods. Patients with adult spinal deformity who had undergone T9-to-pelvis fusion were stratified using the ASD-Modified Frailty Index into not frail, frail, and severely frail categories. ASD was defined as at least one of: scoliosis ≥ 20°, sagittal vertical axis (SVA) ≥ 5 cm, or pelvic tilt ≥ 25°. Means comparisons tests were used to assess differences between both groups. Logistic regression analyses were used to analyze associations between frailty categories, UIV, and outcomes. Results. A total of 477 patients were included (mean age 60.3 years (SD 14.9), mean BMI 27.5 kg/m. 2. (SD 5.8), mean Charlson Comorbidity Index (CCI) 1.67 (SD 1.66)). Overall, 74% of patients were female (n = 353), and 49.6% of patients were not frail (237), 35.4% frail (n = 169), and 15% severely frail (n = 71). At baseline, differences in age, BMI, CCI, and deformity were significant (all p = 0.001). Overall, 15.5% of patients (n = 74) had experienced mechanical complications by two years (8.1% not frail (n = 36), 15.1% frail (n = 26), and 16.3% severely frail (n = 12); p = 0.013). Reoperations also differed between groups (20.2% (n = 48) vs 23.3% (n = 39) vs 32.6% (n = 23); p = 0.011). Controlling for osteoporosis, baseline deformity, and degree of correction (by sagittal age-adjusted score (SAAS) matching), frail and severely frail patients were more likely to experience mechanical complications if they had heart failure (odds ratio (OR) 6.6 (95% CI 1.6 to 26.7); p = 0.008), depression (OR 5.1 (95% CI 1.1 to 25.7); p = 0.048), or cancer (OR 1.5 (95% CI 1.1 to 1.4); p = 0.004). Frail and severely frail patients experienced higher rates of mechanical complication than ‘not frail’ patients at two years (19% (n = 45) vs 11.9% (n = 29); p = 0.003). When controlling for baseline deformity and degree of correction in severely frail and frail patients, severely frail patients were less likely to experience clinically relevant proximal junctional kyphosis or failure or mechanical complications by two years, if they had a more proximal UIV. Conclusion. Frail patients are at risk of a poor outcome after surgery for adult spinal deformity due to their comorbidities. Although a definitively prescriptive upper instrumented vertebra remains elusive, these patients appear to be at greater risk for a poor outcome if the upper instrumented vertebra is sited more distally. Cite this article: Bone Joint J 2024;106-B(11):1342–1347

The October 2024 Spine Roundup³⁶⁰ looks at: Analysis of risk factors for non-fusion of bone graft in anterior cervical discectomy and fusion: a clinical retrospective study; Does paraspinal muscle mass predict lumbar lordosis before and after decompression for degenerative spinal stenosis?; Return to work after surgery for lumbar disk herniation: a nationwide registry-based study; Can the six-minute walking test assess ambulatory function impairment in patients with cervical spondylotic myelopathy?; Complications after adult deformity surgery: losing more than sleep; Frailty limits how good we can get in adult spine deformity surgery.

Adult Spine Deformity (ASD) is a degenerative condition of the adult spine leading to altered spine curvatures and mechanical balance. Computational approaches, like Finite Element (FE) Models have been proposed to explore the etiology or the treatment of ASD, through biomechanical simulations. However, while the personalization of the models is a cornerstone, personalized FE models are cumbersome to generate. To cover this need, we share a virtual cohort of 16807 thoracolumbar spine FE models with different spine morphologies, presented in an online user-interface platform (SpineView). To generate these models, EOS images are used, and 3D surface spine models are reconstructed. Then, a Statistical Shape Model (SSM), is built, to further adapt a FE structured mesh template for both the bone and the soft tissues of the spine, through mesh morphing. Eventually, the SSM deformation fields allow the personalization of the mean structured FE model, leading to generate FE meshes of thoracolumbar spines with different morphologies. Models can be selectively viewed and downloaded through SpineView, according to personalized user requests of specific morphologies characterized by the geometrical parameters: Pelvic Incidence; Pelvic Tilt; Sacral Slope; Lumbar Lordosis; Global Tilt; Cobb Angle; and GAP score. Data quality is assessed using visual aids, correlation analyses, heatmaps, network graphs, Anova and t-tests, and kernel density plots to compare spinopelvic parameter distributions and identify similarities and differences. Mesh quality and ranges of motion have been assessed to evaluate the quality of the FE models. This functional repository is unique to generate virtual patient cohorts in ASD. Acknowledgements: European Commission (MSCA-TN-ETN-2020-Disc4All-955735, ERC-2021-CoG-O-Health-101044828)

Currently, between 17% of patients undergoing surgery for adult spinal deformity experience severe instrumentation related problems such as screw pullout or proximal junctional failure necessitating revision surgery. Cables may be used to reinforce pedicle screw fixation as an additive measure or may provide less rigid fixation at the construct end levels in order to prevent junctional level problems. The purpose of this study is to provide insight into the maximum expected load during flexion in UHMWPE cable in constructs intended for correction of adult spine deformity (degenerative scoliosis) in the PoSTuRe first-in-man clinical trial. Following the concept of toppinoff, a new construct is proposed with screw/cable fixation of rods at the lower levels and standalone UHMWPE cables at the upper level (T11). A parametric FE model of the instrumented thoracolumbar spine, which has been previously validated, was used to represent the construct. Pedicle screws are modeled by assigning a rigid tie constraint between the rod and the lamina of the corresponding spinal level. Cables are modeled using linear elastic line elements, fixing the rod to the lamina medially at the cranial laminar end and laterally at the caudal laminar end. A Youngs modulus was assigned such that the stiffness of the line element was the same as that of the cable. An 8 Nm flexion moment was applied to the cranial endplate. The maximum value of the force in the wire (80 N) is found at the T11 (upper) level. At the other levels, forces in the cable are very small because most of the force is carried by the screw (T12) or because the wires are force shielded by the contralateral and adjacent level pedicle screws (L2, L3). The model provides first estimates of the forces that can be expected in the UHMWPE cables in constructs for kyphosis correction during movement. It is expected that this approach can help in defining the number of wires for optimal treatment

The April 2023 Spine Roundup³⁶⁰ looks at: Percutaneous transforaminal endoscopic discectomy versus microendoscopic discectomy; Spine surgical site infections: a single debridement is not enough; Lenke type 5, anterior, or posterior: systematic review and meta-analysis; Epidural steroid injections and postoperative infection in lumbar decompression or fusion; Noninferiority of posterior cervical foraminotomy versus anterior cervical discectomy; Identifying delays to surgical treatment for metastatic disease; Cervical disc replacement and adjacent segment disease: the NECK trial; Predicting complication in adult spine deformity surgery.

Aims

This study aimed to evaluate sagittal spinopelvic alignment (SSPA) in the early stage of rapidly destructive coxopathy (RDC) compared with hip osteoarthritis (HOA), and to identify risk factors of SSPA for destruction of the femoral head within 12 months after the disease onset.