The influence of the land-to-sea macroevolutionary transition on vertebral column disparification in Pinnipedia.

The repeated returns of vertebrates to the marine ecosystems since the Triassic serve as an evolutionary model to understand macroevolutionary change. Here we investigate the effects of the land-to-sea transition on disparity and constraint of the vertebral column in aquatic carnivorans (Carnivora; Pinnipedia) to assess how their functional diversity and evolutionary innovations influenced major radiations of crown pinnipeds. We use three-dimensional geometric morphometrics and multivariate analysis for high-dimensional data under a phylogenetic framework to quantify vertebral size and shape in living and extinct pinnipeds. Our analysis demonstrates an important shift in vertebral column evolution by 10-12 million years ago, from an unconstrained to a constrained evolutionary scenario, a point of time that coincides with the major radiation of crown pinnipeds. Moreover, we also demonstrate that the axial skeleton of phocids and otariids followed a different path of morphological evolution that was probably driven by their specialized locomotor strategies. Despite this, we found a significant effect of habitat preference (coastal versus pelagic) on vertebral morphology of crown taxa regardless of the family they belong. In summary, our analysis provides insights into how the land-to-sea transition influenced the complex evolutionary history of pinniped vertebral morphology.

Epichordal vertebral column formation in Xenopus laevis.

Although Xenopus Laevis is the most widely used model amphibian, skeletal development of its vertebral column has not been well illustrated so far. The mode of vertebral column development in anurans has been classified into two modes: perichordal and epichordal. Xenopus vertebral column formation is believed to follow the epichordal mode, but this aspect has been underemphasized, and illustrative examples are currently unavailable to the scientific community. This study documents the entire process of vertebral column formation in X. laevis, from the initial neural arch formation to the completion of metamorphosis. These images reveal that the neural arch arises from the dorsal lamina and lateral pedicle primordia, with no strict adherence to an anteroposterior sequence. Unlike other species, Xenopus centrum primordia exclusively form at the expanded ventral margins of neural arches, rather than from the cartilaginous layer surrounding the notochord. These paired centrum primordia then fuse at the ventral midline, dorsal to the notochord, and subsequently the notochord degenerates. This mode of centrum formation differs from the traditional epichordal mode, indicating that Xenopus might have lost the ability to form a cartilaginous layer around the notochord. Instead, the neural arch's ventral margin appears to have evolved to incorporate centrum precursor cells at its base, thereby forming a centrum-like structure compensating for the absence of a true centrum. It is widely accepted that postsacral vertebrae lack centra, only possessing neural arches, and eventually fuse with the hypochord to form the urostyle. However, we have shown that the paired ventral ends of the postsacral vertebrae also fuse at the midline to form a centrum-like structure. This process might extend to the trunk region during centrum formation. In addition to these findings, we offer evolutionary insights into the reasons why Xenopus retains centrum primordia at the base of neural arches.

International survey of equine orthopaedic specialists reveals diverse treatment strategies for horses with overriding spinous processes.

BACKGROUND: Overriding spinous processes, also known as 'kissing spines', are one of the most common causes of back pain in horses. The aim of this study was to investigate which options for diagnosis and treatment are preferred by equine orthopaedic specialists and assess which techniques are used for local injection. METHODS: An online survey was distributed among members of the European/American College of Veterinary Surgeons, the European/American College of Veterinary Sports Medicine and Rehabilitation, the International Society of Equine Locomotor Pathology and nationally recognised advanced equine orthopaedic practitioners. RESULTS: The survey was completed by 353 respondents. The injection techniques most commonly used involve placing two needles abaxial to the interspinous space (42%) under ultrasonographic guidance (32%) or one needle in the midline (35%) between two spinous processes. The most popular combination for overriding dorsal spinous process therapy was local injection (26.7%) combined with controlled exercise (25.5%). Manual therapy was considered by 42% of European and 25% of American specialists (p = 0.01). Surgical intervention as a first-line treatment was recommended mainly by specialists working in the United States, the UK or Ireland (p = 0.001). Overall, most equine orthopaedic veterinarians (71%; n = 201) preferred conservative management and recommended surgery only for horses that did not respond to conservative therapy. LIMITATIONS: Respondents' personal bias may have skewed the findings. CONCLUSIONS: Despite a growing body of evidence, the therapeutic approach to 'kissing spines' in horses is influenced by professional specialisation and regional preferences. Variations in injection techniques and differing criteria for surgical intervention warrant further investigation.

Functional diversity of snake locomotor behaviors: A review of the biological literature for bioinspiration.

Organismal solutions to natural challenges can spark creative engineering applications. However, most engineers are not experts in organismal biology, creating a potential barrier to maximally effective bioinspired design. In this review, we aim to reduce that barrier with respect to a group of organisms that hold particular promise for a variety of applications: snakes. Representing >10% of tetrapod vertebrates, snakes inhabit nearly every imaginable terrestrial environment, moving with ease under many conditions that would thwart other animals. To do so, they employ over a dozen different types of locomotion (perhaps well over). Lacking limbs, they have evolved axial musculoskeletal features that enable their vast functional diversity, which can vary across species. Different species also have various skin features that provide numerous functional benefits, including frictional anisotropy or isotropy (as their locomotor habits demand), waterproofing, dirt shedding, antimicrobial properties, structural colors, and wear resistance. Snakes clearly have much to offer to the fields of robotics and materials science. We aim for this review to increase knowledge of snake functional diversity by facilitating access to the relevant literature.

Gait analysis, trunk movements, and electromyographic patterns after minimally invasive spine surgery for lumbar instability: An observational prospective study.

Objective: The aim of the present study was to investigate trunk kinematics and spine muscle activation during walking after minimally invasive surgery in patients with L4-L5 degenerative spondylolisthesis suffering from lumbar instability (LI). Methods: Eleven patients suffering from LI and 13 healthy controls (HC) were enrolled. Trunk kinematics and spine muscle activation patterns during walking were collected. Maximal trunk ranges of motion were also recorded from standing position. Assessments were performed pre-operatively (T0), 1 month (T1) and 3 months (T2) after MIS. Results: We found significant improvement in spine muscle activation during walking at T2 compared to T0, mainly involving right/left symmetry at the operated level (L4-L5) and up-down synchronization from L3 to S1. Significant improvements in trunk rotation nearing to the HC group during walking were also found at T2 after surgery, though no changes were observed in the maximal range of motion of the trunk during standing. Furthermore, trunk rotation improvement correlated with a lower grade of residual disability. Conclusions: Our findings indicate that trunk rotation improves after surgery, and impaired aspects of spine muscle activation can be improved with surgery. These biomechanical parameters could represent novel tools for monitoring the effect of surgery in LI and preventing impaired spine mobility and muscle activation.

The complex treatment paradigms for concomitant tethered cord and scoliosis: illustrative case.

BACKGROUND: Scoliosis associated with tethered cord syndrome is one of the most challenging spinal deformities to manage. Multiple surgical approaches have been developed, including traditional staged and concomitant procedures, spine-shortening osteotomies, and individual vertebral column resections. OBSERVATIONS: A 10-year-old female presented with congenital kyphoscoliosis with worsening curve progression, tethered spinal cord, and a history of enuresis. The scoliosis had progressed to a 26° coronal curve and 55° thoracolumbar kyphosis. Preoperative magnetic resonance imaging of the spine revealed a tethered cord between the levels of L3-4 and a large kyphotic deformity at L1. The patient underwent laminectomy, during which intraoperative motor signals were lost. A planned hemivertebrectomy at L1 was performed prior to an L4 laminectomy, untethering of the filum terminale, and posterior spinal fusion from T11 to L2. After surgery, the patient experienced transient lower-extremity weakness, with her neurological function improving from baseline over the next 2 months. Ultimately, the goal of this surgery was to halt the progressive decline in motor function, which was successfully achieved. LESSONS: Much remains to be learned about the treatment of this complicated disease, especially in the setting of concomitant scoliosis. This case serves to exemplify the complex treatment paradigms that exist when attempting to manage this clinical syndrome and that more remains to be learned.

Comparative ontogeny of functional aspects of human cervical vertebrae.

OBJECTIVES: Differences between adult humans and great apes in cervical vertebral morphology are well documented, but the ontogeny of this variation is still largely unexplored. This study examines patterns of growth in functionally relevant features of C1, C2, C4, and C6 in extant humans and apes to understand the development of their disparate morphologies. MATERIALS AND METHODS: Linear and angular measurements were taken from 530 cervical vertebrae representing 146 individual humans, chimpanzees, gorillas, and orangutans. Specimens were divided into three age-categories based on dental eruption: juvenile, adolescent, and adult. Inter- and intraspecific comparisons were evaluated using resampling methods. RESULTS: Of the eighteen variables examined here, seven distinguish humans from apes at the adult stage. Human-ape differences in features related to atlantoaxial joint function tend to be established by the juvenile stage, whereas differences in features related to the nuchal musculature and movement of the subaxial elements do not fully emerge until adolescence or later. The orientation of the odontoid process-often cited as a feature that distinguishes humans from apes-is similar in adult humans and adult chimpanzees, but the developmental patterns are distinct, with human adultlike morphology being achieved much earlier. DISCUSSION: The biomechanical consequences of the variation observed here is poorly understood. Whether the differences in growth patterns represent functional links to cranial development or postural changes, or both, requires additional investigation. Determining when humanlike ontogenetic patterns evolved in hominins may provide insight into the functional basis driving the morphological divergence between extant humans and apes.

Who gets staged surgery in severe pediatric and adolescent spine deformity?

BACKGROUND: There is significant debate regarding the indications of staged surgery for severe adolescent spinal deformity, and the factors associated with the decision to perform staged compared to same-day surgery have not been previously investigated. Thus, the purpose of this study was to determine which factors were most strongly associated with this decision. METHODS: A prospective multicenter registry of adolescent patients with severe spinal deformity was reviewed. Two cohorts were identified: those who underwent a planned staged surgical procedure for deformity correction and those who underwent a same-day procedure. Patients who underwent an unplanned staged procedure secondary to complications during the initial procedure were excluded. Comparisons were made between these cohorts with respect to preoperative patient and radiographic variables to determine which factors were associated with the decision to perform a staged procedure. Surgical data was also compared to evaluate for differences in the intraoperative management of staged versus same-day patients. RESULTS: Two hundred and twenty-nine patients with severe spinal deformities were identified. Forty patients (17%) underwent a planned staged procedure and 189 patients (80%) underwent a same-day procedure. On univariate analysis of preoperative variables, patients who underwent staged surgery had a significantly younger age at surgery, greater major curve magnitude, greater major curve AVT to CSVL, lesser thoracic spine height, greater radiographic trunk shift, and a greater proportion of patients undergoing revision surgery (as opposed to primary correction) compared to those who underwent a planned single-stage procedure. Multivariate logistic regression of pre-operative variables showed that age < 16 years, maximum cobb angle ≥ 120 degrees, major curve AVT to CSVL of ≥ 3.5 cm, and revision surgery were independently associated with the decision to perform a staged procedure. Intraoperatively, patients in the staged cohort more frequently underwent combined anterior and posterior procedures, grade 4 or higher Schwab osteotomies, and had a greater number of levels fused. CONCLUSION: There is substantial variability with respect to the decision to perform surgery for severe adolescent spine deformities in a staged versus same-day fashion. This large analysis of prospectively collected data is the first to describe the factors most strongly associated with the decision to perform a staged procedure and may help guide the surgical decision-making for these patients.

Building a vertebra: Development of the amniote sclerotome.

In embryonic development, the vertebral column arises from the sclerotomal compartment of the somites. The sclerotome is a mesenchymal cell mass which can be subdivided into several subpopulations specified by different regulatory mechanisms and giving rise to different parts of the vertebrae like vertebral body, vertebral arch, ribs, and vertebral joints. This review gives a short overview on the molecular and cellular basis of the formation of sclerotomal subdomains and the morphogenesis of their vertebral derivatives.

Post-mortem ultrasonographic and computed tomographic features of the anatomical variations and acquired pathological bony changes of the lumbosacroiliac region in a mixed population of horses.

BACKGROUND: Transrectal ultrasonography is the best technique for evaluating the ventral aspect of the lumbosacral and sacroiliac regions yet this diagnostic technique does not always lead to a final diagnosis of back pain in horses. OBJECTIVES: To describe anatomical variations and acquired pathological bony changes (APBCs) in the lumbosacral and sacroiliac regions detected by ultrasonography (US) and computed tomography (CT) examinations on specimens. We hypothesised that age, body mass, previous use and anatomical variations may be correlated with the presence and/or severity of APBCs. STUDY DESIGN: Descriptive cadaver study. METHODS: Lumbosacroiliac specimens were obtained from 51 horses that died or were euthanised for reasons other than the study and underwent US and CT examinations post-mortem. RESULTS: Forty-two specimens were analysed. The most prevalent lumbosacral disc morphology was type 2 (21/42), and protrusions were found in 15/42 specimens. Abnormal echogenicity of the L5-L6 and lumbosacral discs was detected in 11/42 and 30/42 specimens, respectively. Abnormalities in the size of the L5-L6 disc were found in 10/42 specimens and correlated with promontorium localisation (Cramér's V coefficient [V] = 0.42) and lumbosacral disc morphology (type 1: V = 0.41; type 5: V = 0.69). The most prevalent orientation of the L6 spinous process (SP) was convergent (24/42). The promontoria were mostly located between L6 and S1 (36/42). Lumbosacral spondylosis was detected in 24/42 specimens and spondylolisthesis in one. Age was associated with the severity of APBCs in the sacroiliac joints, lumbosacral intertransverse joints, articular process joints, spondylosis and L6 or S1 bone plate irregularities. Lumbosacral spondylosis or L6 extremitas caudalis irregularity was associated with lumbosacral angulation, variability in the size of the L5-L6 disc and localisation of the promontorium, L6 SP orientation and L6 extremitas caudalis irregularity with abnormal echogenicity of the LS disc. MAIN LIMITATIONS: Lack of information on clinical signs. CONCLUSIONS: High variability and prevalence of the anatomical variations and APBCs in the lumbosacroiliac region were observed, and correlations between some anatomical variations and APBCs and between APBCs and age were reported.

Machine Learning Models for Prediction of Sex Based on Lumbar Vertebral Morphometry.

BACKGROUND: Identifying skeletal remains has been and will remain a challenge for forensic experts and forensic anthropologists, especially in disasters with multiple victims or skeletal remains in an advanced stage of decomposition. This study examined the performance of two machine learning (ML) algorithms in predicting the person's sex based only on the morphometry of L1-L5 lumbar vertebrae collected recently from Romanian individuals. The purpose of the present study was to assess whether by using the machine learning (ML) techniques one can obtain a reliable prediction of sex in forensic identification based only on the parameters obtained from the metric analysis of the lumbar spine. METHOD: This paper built and tuned predictive models with two of the most popular techniques for classification, RF (random forest) and XGB (xgboost). Both series of models used cross-validation and a grid search to find the best combination of hyper-parameters. The best models were selected based on the ROC_AUC (area under curve) metric. RESULTS: The L1-L5 lumbar vertebrae exhibit sexual dimorphism and can be used as predictors in sex prediction. Out of the eight significant predictors for sex, six were found to be particularly important for the RF model, while only three were determined to be important by the XGB model. CONCLUSIONS: Even if the data set was small (149 observations), both RF and XGB techniques reliably predicted a person's sex based only on the L1-L5 measurements. This can prove valuable, especially when only skeletal remains are available. With minor adjustments, the presented ML setup can be transformed into an interactive web service, freely accessible to forensic anthropologists, in which, after entering the L1-L5 measurements of a body/cadaver, they can predict the person's sex.

Antagonistic regulation of homeologous uncx.L and uncx.S genes orchestrates myotome and sclerotome differentiation in the evolutionarily divergent vertebral column of Xenopus laevis.

In anurans, the vertebral column diverges widely from that of other tetrapods; yet the molecular mechanisms underlying its morphogenesis remain largely unexplored. In this study, we investigate the role of the homeologous uncx.L and uncx.S genes in the vertebral column morphogenesis of the allotetraploid frog Xenopus laevis. We initiated our study by cloning the uncx orthologous genes in the anuran Xenopus and determining their spatial expression patterns using in situ hybridization. Additionally, we employed gain-of-function and loss-of-function approaches through dexamethasone-inducible uncx constructs and antisense morpholino oligonucleotides, respectively. Comparative analysis of the messenger RNA sequences of homeologous uncx genes revealed that the uncx.L variant lacks the eh1-like repressor domain. Our spatial expression analysis indicated that in the presomitic mesoderm and somites, the transcripts of uncx.L and uncx.S are located in overlapping domains. Alterations in the function of uncx genes significantly impact the development and differentiation of the sclerotome and myotome, resulting in axial skeleton malformations. Our findings suggest a scenario where the homeologous genes uncx.L and uncx.S exhibit antagonistic functions during somitogenesis. Specifically, uncx.S appears to be crucial for sclerotome development and differentiation, while uncx.L primarily influences myotome development. Postallotetraploidization, the uncx.L gene in X. laevis evolved to lose its eh1-like repressor domain, transforming into a "native dominant negative" variant that potentially competes with uncx.S for the same target genes. Finally, the histological analysis revealed that uncx.S expression is necessary for the correct formation of pedicles and neural arch of the vertebrae, and uncx.L is required for trunk muscle development.

The influence of lumbosacral transitional vertebrae on lumbar lordosis and the angle of pelvic incidence.

Pelvic incidence and lumbar lordosis have only normative values for spines comprising five lumbar and five sacral vertebrae. However, it is unclear how pelvic incidence and lumbar lordosis are affected by the common segmentation anomalies at the lumbo-sacral border leading to lumbosacral transitional vertebrae, including lumbarisations and sacralisations. In lumbosacral transitional vertebrae it is not trivial to identify the correct vertebral endplates to measure pelvic incidence and lumbar lordosis because ontogenetically the first sacral vertebra represents the first non-mobile sacral segment in lumbarisations, but the second segment in sacralisations. We therefore assessed pelvic incidence and lumbar lordosis with respect to both of these vertebral endplates. The type of segmentation anomaly was differentiated using spinal counts, spatial relationship with the iliac crest and morphological features. We found significant differences in pelvic incidence and lumbar lordosis between lumbarisations, sacralisations and the control group. The pelvic incidence in the sacralised group was mostly below the range of the lubarisation group and the control group when measured the traditional way at the first non-mobile segment (30.2°). However, the ranges of the sacralisation and lubarisation groups were completely encompassed by the control group when measured at the ontogenetically true first sacral vertebra. The mean pelvic incidence of the sacraliation group thus increased from 30.2° to 58.6°, and the mean pelvic incidence of the total sample increased from 45.6° to 51.2°, making it statistically indistinguishable from the control sample, whose pelvic incidence was 50.2°. Our results demonstrate that it is crucial to differentiate sacralisations from lumbarisation in order to assess the reference vertebra for pelvic incidence measurement. Due to their significant impact on spino-pelvic parameters, lumbosacral transitional vertebrae should be evaluated separately when examining pelvic incidence and lumbar lordosis.

The contribution of preoperative balanced halo-pelvic traction to severe rigid spinal deformity correction.

PURPOSE: The aim of this study was to assess the clinical efficacy of balanced halo-pelvic traction (HPT) and evaluate its contribution to the correction surgery in treating adult severe rigid spinal deformity. METHODS: One hundred and eight adult patients with severe rigid spinal deformity who underwent preoperative HPT and correction surgery were reviewed. The main coronal curve, segmental kyphotic angle, coronal balance (CB), sagittal balance (SVA), and the length of spine were measured before HPT, after HPT, post-operatively, and at final follow-up. The HPT contribution rates to deformity correction were calculated. RESULTS: The pre-HPT main coronal curve was 103.4 ± 10.6°, improved to 61.0 ± 13.4° after traction and further improved to 44.2 ± 10.2° after surgical correction, and maintained at 50.3 ± 9.9° at final follow-up. CB started at 4.2 ± 4.8 cm, improved to 2.1 ± 2.5 cm after HPT, 0.8 ± 1.2 cm after operation, and 0.7 ± 0.9 cm at final follow-up. The pre-HPT sagittal segmental kyphotic angle was 67.3 ± 17.7°, was then improved to 42.2 ± 27.5° after traction and further improved to 34.9 ± 10.2° after surgery, and maintained at 35.4 ± 10.4° at final follow-up. The length of spine improved from 35.9 ± 5.9 to 42.6 ± 6.0 cm via HPT, reached up to 45.0 ± 6.0 cm after operation, and maintained at 44.3 ± 5.2 cm at final follow-up. CONCLUSION: HPT is effective for the treatment of severe rigid spinal deformity. Balanced HPT can dramatically improve coronal and sagittal deformity as well as spinal length before corrective surgery.

Posterior-based Osteotomies for Deformity Correction.

Posterior-based osteotomies are crucial to the restoration of lordosis in adult spinal deformity. Posterior-column osteotomies are suited for patients with an unfused anterior column and non-focal sagittal deformity requiring modest correction in lordosis. When performed on multiple levels, posterior-column osteotomy may provide significant harmonious correction in patients who require more extensive correction. Pedicle subtraction osteotomy and vertebral column resection are appropriate for patients with a fused anterior column and more severe deformity, particularly focal and/or multiplanar deformity. The power of pedicle subtraction osteotomy and vertebral column resection to provide greater correction and to address multiplanar deformity comes at the cost of higher complication rates than posterior-column osteotomy.

Intervertebral Canals and Intracanal Ligaments as New Terms in Terminologia anatomica.

This study addresses the cervical part of the vertebral column. Clinical pictures of dystrophic diseases of the cervical part of the vertebral column do not always correspond only to the morphological changes-they may be represented by connective tissue formation and nerve and vessel compression. To find out the possible reason, this morphometric study of the cervical part of the vertebral column in 40 cadavers was performed. CT scans were performed on 17 cadaveric material specimens. A total of 12 histological samples of connective tissue structures located in intervertebral canals (IC) were studied. One such formation, an intracanal ligament (IL) located in the IC, was found. Today, there is no term "intervertebral canal", nor is there a detailed description of the intervertebral canal in the cervical part of the vertebral column. Cervical intervertebral canals make up five pairs in segments C2-C7. On cadavers, the IC lateral and medial apertures were 0.9-1.5 cm and 0.5-0.9 cm, correspondingly. According to our histological study, the connective tissue structures in the IC are ligaments-IL. According to the presence of these ligaments, ICs were classified into three types. Complete regional anatomy characterization of the IC of the cervical part of the vertebral column with a description of its constituent anatomical elements was provided. The findings demonstrate the need to include the terms "intervertebral canal" and "intervertebral ligament" in the Terminologia anatomica.

Postoperative dysesthesia after PVCR without anterior support applied in Yang's type A severe spinal kyphoscoliosis.

Backgrounds: The incidence and characteristics of postoperative dysesthesia (POD) have not been reported for posterior vertebral column resection (PVCR) in the treatment of severe spinal kyphoscoliosis. Objective: The objective of the study is to investigate the incidence and characteristics of POD in PVCR without anterior support applied in Yang's type A severe spinal kyphoscoliosis. Material and methods: From August 2010 to December 2019, 167 patients diagnosed with Yang's type A severe spinal kyphoscoliosis who underwent PVCR without anterior support applied were retrospectively reviewed. All the patients were monitored using five modes of intraoperative multimodal neurophysiological monitoring. Neuromonitoring data, radiographic parameters, and neurological complications were reviewed and analyzed. The incidence and characteristics of POD were further summarized. POD was defined as dysesthetic pain or burning dysesthesia which could be caused by spinal cord kinking or dorsal root ganglion (DRG) injury but with no motor deficits. Results: PVCR without anterior support was successfully conducted in all 167 patients. Intraoperative monitoring events occurred in five patients. One out of these five patients showed postoperative spinal cord injury (Frankel level C) but completely recovered within 9 months postoperation (Frankel level E). The number of levels and osteotomy space for vertebra resection were 1.28 and 3.6 cm, respectively. POD was confirmed in three patients (3/167, 1.8%), characterized as kyphosis with the apex vertebrae in T12 with the kyphotic Cobb angles of 100°, 115°, and 122°, respectively. The osteotomy space of vertebra resection in these three patients were 3.9, 3.8, and 4.2 cm, respectively. After the treatment by drug administration, they reported pain relief for 12-36 days. The pain gradually moved to the distal end of a proper DRG innervated region near the end. Conclusions: In this study, the incidence rate of POD in Yang's type A severe spinal kyphoscoliosis patients who underwent PVCR without anterior support applied was 1.8% (3/167). Evoked potential monitoring could not detect the occurrence of POD. POD in Yang's type A severe spinal kyphoscoliosis after PVCR could be ascribed to spinal cord kinking and DRG injury.

The lower Osteotomy Level is Associated With Decreased Revision Surgery Due to Mechanical Complications After Three-Column Osteotomy in Patients With Adult Spinal Deformity: A Multi-Institutional Retrospective Study.

STUDY DESIGN: A multi-institutional retrospective study. OBJECTIVES: To investigate risk factors of mechanical failure in three-column osteotomy (3COs) in patients with adult spinal deformity (ASD), focusing on the osteotomy level. METHODS: We retrospectively reviewed 111 patients with ASD who underwent 3COs with at least 2 years of follow-up. Radiographic parameters, clinical data on early and late postoperative complications were collected. Surgical outcomes were compared between the low-level osteotomy group and the high-level osteotomy group: osteotomy level of L3 or lower group (LO group, n = 60) and osteotomy of L2 or higher group (HO group, n = 51). RESULTS: Of the 111 patients, 25 needed revision surgery for mechanical complication (mechanical failure). A lower t-score (odds ratio [OR] .39 P = .002) and being in the HO group (OR 4.54, P = .03) were independently associated with mechanical failure. In the analysis divided by the osteotomy level (LO and HO), no difference in early complications or neurological complications was found between the two groups. The rates of overall mechanical complications, rod failure, and mechanical failure were significantly higher in the HO group than in the LO group. After propensity score matching, mechanical complications and failures were still significantly more observed in the HO group than in the LO group (P = .01 and .029, respectively). CONCLUSIONS: A lower t-score and osteotomy of L2 or higher were associated with increased risks of mechanical failure. Lower osteotomy was associated with better correction of sagittal balance and a lower rate of mechanical complications.

Type 3 bone-disc-bone osteotomy (grade 4+ osteotomy) combined with presurgical halo-pelvic traction: a safe and effective solution to correct severe angular-like kyphoscoliosis.

Background: Treatment of severe angular-like kyphoscoliosis is a technically demanding surgical challenge and requires high-risk spinal osteotomy, such as vertebral column resection. Preoperative halo-pelvic traction is commonly used to decrease the curve magnitude. However, few studies have utilized the potent method of bone-disc-bone osteotomy, which could theoretically provide correction up to 60°. This study aimed to evaluate the safety and effectiveness of type 3 bone-disc-bone osteotomy combined with presurgical halo-pelvic traction to correct severe angular-like kyphoscoliosis. Methods: This was a retrospective cohort study. Patients with severe angular-like kyphoscoliosis who underwent presurgical halo-pelvic traction and type 3 bone-disc-bone osteotomy from January 2017 to December 2019 were consecutively reviewed. Patient demographics and clinical data were recorded. The coronal and sagittal Cobb angles were measured preoperation, post-traction, post-operation, and at the final follow-up. Complications were also recorded. Patients' health-related quality of life was evaluated by the Scoliosis Research Society 22 (SRS-22) questionnaire. Paired Student's t test and one-way analysis of variance were used for comparisons among different groups. Results: Thirty patients (18 females and 12 males) with an average age of 20.2 years (range, 13-33 years) were included. The mean preoperative coronal and sagittal Cobb angles were 123.1°±16.4° (range, 90°-155°) and 120.3°±19.9° (range, 90°-156°), respectively. After 2.9±0.7 months (range, 2-4 months) of halo-pelvic traction, the coronal and sagittal Cobb angles decreased significantly to 81.9°±13.2° and 76.0°±12.6°, respectively. Postoperatively, the scoliotic and kyphotic angles further decreased to 42.4°±12.2° and 33.9°±8.8°, respectively. After a mean follow-up of 2.93±1.05 years, the correction rates were maintained at 64.3%±10.6% and 70.5%±6.3%, respectively. Nine patients experienced positive evoked potential events during surgery. Common complications after surgery included transient lower extremity weakness, pneumonia, and pleural effusion. The self-image scores were significantly improved from 2.66±0.27 to 3.36±0.23 compared to preoperation. Conclusions: This study proposes a novel strategy to correct severe angular-like spinal deformities. The combination of presurgical halo-pelvic traction and type 3 bone-disc-bone osteotomy (grade 4+ osteotomy) achieves substantial correction and satisfactory aesthetic outcomes without serious complications.

Direct BMP signaling to chordoblasts is required for the initiation of segmented notochord sheath mineralization in zebrafish vertebral column development.

The vertebral column, with the centra as its iteratively arranged building blocks, represents the anatomical key feature of the vertebrate phylum. In contrast to amniotes, where vertebrae are formed from chondrocytes and osteoblasts deriving from the segmentally organized neural crest or paraxial sclerotome, teleost vertebral column development is initiated by chordoblasts of the primarily unsegmented axial notochord, while sclerotomal cells only contribute to later steps of vertebrae formation. Yet, for both mammalian and teleostean model systems, unrestricted signaling by Bone Morphogenetic Proteins (BMPs) or retinoic acid (RA) has been reported to cause fusions of vertebral elements, while the interplay of the two signaling processes and their exact cellular targets remain largely unknown. Here, we address this interplay in zebrafish, identifying BMPs as potent and indispensable factors that, as formerly shown for RA, directly signal to notochord epithelial cells/chordoblasts to promote entpd5a expression and thereby metameric notochord sheath mineralization. In contrast to RA, however, which promotes sheath mineralization at the expense of further collagen secretion and sheath formation, BMP defines an earlier transitory stage of chordoblasts, characterized by sustained matrix production/col2a1 expression and concomitant matrix mineralization/entpd5a expression. BMP-RA epistasis analyses further indicate that RA can only affect chordoblasts and their further progression to merely mineralizing cells after they have received BMP signals to enter the transitory col2a1/entpd5a double-positive stage. This way, both signals ensure consecutively for proper mineralization of the notochord sheath within segmented sections along its anteroposterior axis. Our work sheds further light onto the molecular mechanisms that orchestrate early steps of vertebral column segmentation in teleosts. Similarities and differences to BMP's working mechanisms during mammalian vertebral column formation and the pathomechanisms underlying human bone diseases such as Fibrodysplasia Ossificans Progressiva (FOP) caused by constitutively active BMP signaling are discussed.