Posterior Elements Research Articles

Magnetic resonance imaging (MRI) Raw Data Results and Its Diagnosis of Spinal Cord Injuries: Patient Case

In the present study, we discussed the best techniques for the clear scan of the spine. For this investigation, it was found that magnetic resonance imaging (MRI) is a better technique as compared to others. It gives proper images and results in the case of hard tissues like the spine compared to X-Ray and computed tomography (CT) scans. It is also better in sense of it has a small radiation risk as compared to X-Ray and CT have some radiation hazards to patient health. Thirteen patients were scanned by MRI technique and the result was evaluated. It is a non-invasive technique and is used for different pathological diseases. It was found that most doctors and surgeons preferred the MRI techniques in the case of the Spinal Cord. Many radiologists exercised X-rays, CT, and MRI methods for viewing clear images of the spine. It was concluded that MRI is the best technique than X-rays and CT scans. MRI is a modality choice for the evaluation of soft tissue changes in the case of Cord. In the case of the Spinal Cord MRI better evaluates changes in spinal cord compression due to its high-resolution property. The CT could not tell us about the soft tissue change in Cord however it more clearly tells us about the fracture of vertebral bodies and posterior elements.

Anterior Decompression via a Single Posterior Approach Using the Ultrasonic Bone Scalpel for the Treatment of the Thoracic Segmental Ossification of Posterior Longitudinal Ligament: A Report of Three Cases

Introduction Thoracic myelopathy due to ossification of the posterior longitudinal ligament (T-OPLL) is an indication for surgical treatment because the symptom is usually progressive. The surgery for T-OPLL is technically challenging for several reasons. Various operational procedures were developed for dealing with T-OPLL. The anterior decompression through a single posterior approach is a procedure to achieve the complete decompression via the direct resection of the ossified lesion, especially for the beak-type OPLL. Previous reports showed better postoperative outcomes using this method than using other procedures. However, the difficulty and risk of complications are also reported because of the blinded resection of the lesion positioning ventrally to the dura mater. Technical Note We describe a novel method using an anterior decompression through a single posterior approach using an ultrasonic bone scalpel. The following procedure is for a case of beak-type OPLL at the T5-6 level. The posterior elements at T2-9 were exposed after a median skin incision was created above a spinous process. First, pedicle screws were inserted bilaterally at T3-5 and T7-9. After the laminectomies and dekyphosis maneuver at T3-9, the spinal cord compression by OPLL was evaluated using intraoperative ultrasonography. After the slight medial facetectomy and pediclotomy at T5-6, the ultrasonic bone scalpel was inserted through the bilateral side of the spinal cord. The tip of the handpiece was angled to reach OPLL. The resection of OPLL was performed under intraoperative spinal cord monitoring. The intraoperative ultrasonography revealed the normal pulsation of the spinal cord and the space between the vertebral body and dura mater after completing the resection of OPLL. Posterolateral fusion was completed with local bone and harvested iliac crest. Conclusions The anterior decompression through a single posterior approach using an ultrasonic bone scalpel is a safe and effective treatment of thoracic OPLL.

The Effect of William Flexion Exercise on Low Back Pain in Traditional Weaving Workers in The Village of Sidemen Karangasem

Low back pain (LBP) is a subjective sensation characterized by a major symptom of pain in the lower spine region. One of the basic causes is the stress inflicted on the inter-vertebral disk due to poor posture, so that the lumbar spine of the lumbar lordosis has too much strain on the posterior element. These complaints usually occur in workers due to incorrect posture or work position that does not meet the ergonomic principles of one of the traditional weavingworker. Exercise has been widely developed to cope with LBP such as stretching and muscle strengthening. William's flexion exercise (WFE) is an exercise aimed at stretching the posterior muscles and strengthening the abdominal muscles so that the tendon and spongy muscles are expected to relax. The purpose of this study is to determine the effect of WFE on LBP on traditional weaving workers. This study is a pre-experimental study (One-Group Pretest-Posttest Design). The sample consists of 28 respondents selected by using Purposive Sampling technique. Data collected by using questionnaires for respondent characteristics and Numeric Rating Scale for measuring pain scale before and after intervention. The result of the research before intervention was 75% of respondents had moderate pain, while after intervention 85.7% of respondents had mild pain. Based on the Wilcoxon test results obtained p = 0.000 which means there is the influence of WFE on LBP on traditional weavingworker. Based on the above research, it is suggested to health workers teach WFE in order to reduce LBP on traditional weavingworkers.
 Index Terms— Low back pain,Traditional weaving worker, William’s flexion exercise

Front-Back Cervical Deformity Correction by Anterior Cervical Discectomy and Fusion With Posterior Instrumentation: 2-Dimensional Operative Video.

Front-back procedures for cervical deformity permit the correction of cervical kyphosis in the setting of unfused facets. Here, we highlight the operative treatment of a 65-yr-old female entailing a 4-level anterior cervical discectomy and fusion (ACDF) at C3-C4, C4-C5, C5-C6, and C6-C7 with hyperlordotic interbody implants, supplemented by a posterior C2-T2 instrumented fusion. The patient initially presented with symptoms of treatment-refractory neck pain while neurologically intact on examination. Her imaging demonstrated significant cervical kyphosis measuring 46° as the Cobb angle between C2 and C7 without neural compression. The patient consented to the procedure and publication of their image. After 2 d of traction, the operation proceeded with the patient initially in a supine position with dissection medial to the sternocleidomastoid muscle down to the vertebral bodies. Discectomies were performed at each level followed by installation of the interbody implants. After closure of this access wound, the patient was turned to a prone position for the posterior element of the operation. The posterior bony elements were exposed and a C2-T2 instrumented fusion performed. Postoperative imaging demonstrated improvement of her sagittal cervical curvature and the patient described improvement in her neck pain.

Multiple developmental craniovertebral junction anomalies associated with fusion of the third and fourth cervical vertebrae: A case report and review of the literature

Craniovertebral junction (CVJ) is formed by the occipital condyles of the skull, atlas (C1), and axis (C2). CVJ anomalies are a complex group of disorders with a variable course and complicated line of management. A cross-sectional imaging is indispensable for the evaluation of CVJ as it may unmask pathologies unsuspected by clinical evaluation and conventional radiography. We present a case report in which we describe multiple developmental CVJ anomalies in a 25-year-old male patient. These include fusion defects of anterior and posterior arches of C1, os odontoideum, atlantoaxial subluxation (with compression of the cervical cord at the cervicomedullary junction), and fusion of C3 and C4 vertebral bodies as well as posterior elements.

The role of Gdf5 in the development of the zebrafish fin endoskeleton.

The development of the vertebrate limb skeleton requires a complex interaction of multiple factors to facilitate the correct shaping and positioning of bones and joints. Growth and differentiation factor 5 (Gdf5) is involved in patterning appendicular skeletal elements including joints. Expression of gdf5 in zebrafish has been detected in fin mesenchyme condensations and segmentation zones as well as the jaw joint, however, little is known about the functional role of Gdf5 outside of Amniota. We generated CRISPR/Cas9 knockout of gdf5 in zebrafish and analyzed the resulting phenotype at different developmental stages. Homozygous gdf5 mutant zebrafish displayed changes in segmentation of the endoskeletal disc and, as a consequence, loss of posterior radials in the pectoral fins. Mutant fish also displayed disorganization and reduced length of endoskeletal elements in the median fins, while joints and mineralization seemed unaffected. Our study demonstrates the importance of Gdf5 in the development of the zebrafish pectoral and median fin endoskeleton and reveals that the severity of the effect increases from anterior to posterior elements. Our findings are consistent with phenotypes observed in the human and mouse appendicular skeleton in response to Gdf5 knockout, suggesting a broadly conserved role for Gdf5 in Osteichthyes.

Prone Single-Position Lateral Lumbar Interbody Fusion With Posterior Decompression and Pedicle Screw Fixation for the Treatment of Grade II Spondylolisthesis: 2-Dimensional Operative Video.

Lateral lumbar interbody fusion (LLIF) provides indirect decompression without disruption of the posterior elements. It involves a larger implant footprint than that of posterior approaches. LLIF is typically performed with the patient in the lateral decubitus position. When a posterior fixation is indicated, a second-stage procedure is performed with the patient in the prone position. Single-position surgery provides the potential advantage of decreased operative time because both procedures can be performed without patient repositioning. Single-position LLIF and posterior fixation in the prone position have not been well validated to date. Herein, techniques for LLIF, percutaneous pedicle screw fixation, and facetectomy in the prone position are shown. A 76-yr-old woman with osteoporosis presented with severe back and bilateral leg pain refractory to conservative management and imaging findings of grade 2 dynamic anterolisthesis at L4-L5 with severe stenosis. She underwent LLIF with percutaneous pedicle screw fixation and facetectomy. She was placed on a Jackson table in the prone position for the entire procedure, which was performed in a single stage. Percutaneous pedicle screws were placed, followed by a left-sided minimally invasive facetectomy. A left-sided retroperitoneal transpsoas approach was used to perform the LLIF in standard fashion. Finally, the rods were locked into place. Postoperatively, the patient was neurologically stable, and imaging confirmed good hardware placement. At the 6-wk follow-up, the patient was doing well. This case demonstrates the feasibility of performing LLIF and posterior fixation in a single stage in the prone position. The patient provided informed consent. Used with permission from Barrow Neurological Institute.

Alternatives to Traditional Pedicle Screws for Posterior Fixation of the Degenerative Lumbar Spine.

Traditional pedicle screws are currently the gold standard to achieve stable 3-column fixation of the degenerative lumbar spine. However, there are cases in which pedicle screw fixation may not be ideal. Due to their starting point lateral to the pars interarticularis, pedicle screws require a relatively wide dissection along with a medialized trajectory directed toward the centrally located neural elements and prevertebral vasculature. In addition, low bone mineral density remains a major risk factor for pedicle screw loosening, pullout, and pseudarthrosis. The purpose of this article is to review the indications, advantages, disadvantages, and complications associated with posterior fixation techniques of the degenerative lumbar spine beyond the traditional pedicle screws. Comprehensive literature searches of the PubMed, Scopus, and Web of Science databases were performed for 5 methods of posterior spinal fixation, including (1) cortical bone trajectory (CBT) screws, (2) transfacet screws, (3) translaminar screws, (4) spinous process plates, and (5) fusion mass screws and hooks. Articles that had been published between January 1, 1990, and January 1, 2020, were considered. Non-English-language articles and studies involving fixation of the cervical or thoracic spine were excluded from our review. After reviewing over 1,700 articles pertaining to CBT and non-pedicular fixation techniques, a total of 284 articles met our inclusion criteria. CBT and transfacet screws require less-extensive exposure and paraspinal muscle dissection compared with traditional pedicle screws and may therefore reduce blood loss, postoperative pain, and length of hospital stay. In addition, several methods of non-pedicular fixation such as translaminar and fusion mass screws have trajectories that are directed away from or posterior to the spinal canal, potentially decreasing the risk of neurologic injury. CBT, transfacet, and fusion mass screws can also be used as salvage techniques when traditional pedicle screw constructs fail. CBT and non-pedicular fixation may be preferred in certain lumbar degenerative cases, particularly among patients with osteoporosis. Limitations of non-pedicular techniques include their reliance on intact posterior elements and the lack of 3-column fixation of the spine. As a result, transfacet and translaminar screws are infrequently used as the primary method of fixation. CBT, transfacet, and translaminar screws are effective in augmenting interbody fixation and have been shown to significantly improve fusion rates and clinical outcomes compared with stand-alone anterior lumbar interbody fusion. Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Assessment of Chance fracture on Computed Tomography Scan in Tertiary Trauma Care Center of Nepal.

Introduction: Chance fracture is a horizontal fracture of the vertebra extending from the posterior element to the vertebral body due to flexion-distraction injury and is potentially unstable. The aim of this study was to evaluate the demography and Computed Tomography scan findings in Chance fracture of the spine. Method: A retrospective study was conducted at the National Trauma Center, National Academy of Medical Sciences over a period of one year (December 2019 to December 2020). Demographic data, mechanism of injury, and computed tomographic findings of Chance fracture were recorded. Result: Computed tomography scans of 41 patients with Chance fracture were identified. Fall injury (76%) was the most common cause of Chance fracture followed by road traffic accidents. This fracture was most commonly seen in thoracolumbar junction TLJ (D10-L2); with L1 being the most affected vertebra (36.5%). Among posterior elements, facet distraction (84%) was the most common finding followed by lamina fracture (83%), and pedicle fracture (68%). Regarding vertebral body fracture, involvement of both superior and inferior endplates were common than isolated involvement of either one of them. CT revealed that a burst component was a common finding (68%) in Chance fracture. Conclusion: Chance fracture was commonly caused by fall injury in our context which is higher in incidence than previously reported. More than half of patients with Chance fracture also had Burst-type components that could influence surgical management. Computed tomography scans is a useful imaging modality for the assessment of Chance fracture and burst component.

Expandable Cage Technology-Transforaminal, Anterior, and Lateral Lumbar Interbody Fusion.

This review of the literature will focus on the indications, surgical techniques, and outcomes for expandable transforaminal lumbar interbody fusion (TLIF), anterior lumbar interbody fusion (ALIF), and lateral lumbar interbody fusion (LLIF) operations. The expandable TLIF cage has become a workhorse for common degenerative pathology, whereas expandable ALIF cages carry the promise of greater lordotic correction while evading the diseased posterior elements. Expandable LLIF cages call upon minimally invasive techniques for a retroperitoneal, transpsoas approach to the disc space, obviating the need for an access surgeon and decreasing risk of injury to the critical neurovascular structures. Nuances between expandable and static cages for all 3 TLIF, ALIF, and LLIF operations are discussed in this review.

Current concepts of spondylosis and posterior spinal motion preservation for radiologists.

Spinal fusion is performed to eliminate motion at a degenerated or unstable segment. However, this is associated with loss of motion at the fused levels and increased stress on adjacent levels. Motion-preserving implants have been designed in effort to mitigate the limitations of fusion. This review will focus on posterior spinal motion-preserving technologies. In the cervical spine, laminoplasty is a posterior motion-preserving procedure used in the management of myelopathy/cord compression. In the lumbar spine, motion-sparing systems include interspinous process devices (also referred to as interspinous process spacers or distraction devices), posterior dynamic stabilization devices (also referred to as pedicle screw/rod fixation-based systems), and posterior element replacement systems (also referred to as total facet replacement devices). Knowledge of the intended physiologic purpose, hardware utilized, and complications is important in the assessment of imaging in those who have undergone posterior motion preservation procedures.

A Scoring System for Outpatient Orthopedist to Preliminarily Distinguish Spinal Metastasis from Spinal Tuberculosis: A Retrospective Analysis of 141 Patients.

Objective Spinal tuberculosis (TB) misdiagnosed of spinal metastasis was not rarely reported, especially in outpatients department. This study was aimed to establish an outpatient scoring system to preliminarily distinguish spinal metastasis from spinal TB. Methods We retrospectively reviewed consecutive 141 patients with a pathological diagnosis of spinal metastasis (82 cases) or spinal TB (59 cases) in our hospital from January 2017 to June 2018. The following clinical characteristics which can be obtained by outpatient orthopedist were recorded and analyzed: age, gender, malignant tumor history, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and imaging features including distribution characteristics of vertebral lesions, subligamentous spread, paravertebral or psoas abscess, involved vertebral element, intervertebral disc, and sequestra formation. The prevalence of clinical characteristics in spinal metastasis was evaluated, and the scoring system was established using logistic regression analysis. The performance of the scoring system was also prospectively validated. Results The outpatient scoring system was based on five clinical characteristics confirmed as significant predictors of spinal metastasis, namely, malignant tumor history, subligamentous spread, posterior element lesions, preserved discs, and no sequestra formation. Spinal metastasis showed a significant higher score than spinal TB (8.17 points vs. 1.97 points, t = 18.621, P < 0.001), and the optimal cut-off value for the scoring system was 5 points. The sensitivity and specificity of the scoring system for predicting spinal metastasis were 97.85% and 88.33%, respectively, in the validation set. Conclusion Spinal lesions with the score of 5 to 10 would be considered a diagnosis of spinal metastasis, while the score of 0 to 4 may be spinal TB. Because the scoring system is mainly based on the clinical characteristics that can be obtained by an outpatient orthopedist, it is suitable to be used as a diagnostic tool in the outpatient department.

Statistical learning of blunt cerebrovascular injury risk factors using the elastic net.

To compare logistic regression to elastic net for identifying and ranking clinical risk factors for blunt cerebrovascular injury (BCVI). Consecutive trauma patients undergoing screening CTA at a level 1 trauma center over a 2-year period. Each internal carotid artery (ICA) and vertebral artery (VA) was independently graded by 2 neuroradiologists using the Denver grading scale. Unadjusted odds ratios were calculated by univariate and adjusted odds ratios by multiple logistic regression with FDR correction. We applied logistic regression with the elastic net penalty and tenfold cross-validation. Total of 467 patients; 73 patients with BCVI. Maxillofacial fracture, basilar skull fracture, and GCS had significant unadjusted odds ratios (OR) for ICA injury and C-spine fracture, spinal ligamentous injury, and age for VA injury. Only transverse foramen fracture had significant adjusted OR for VA injury, with none for ICA injury, after FDR correction. Using elastic net, ICA injury variables included maxillofacial fracture, basilar skull fracture, GCS, and carotid canal fracture. For VA injury, these included cervical spine transverse foramen fracture, ligamentous injury, C1-C3 fractures, posterior element fracture, and vertebral body fracture. Elastic net statistical learning methods identified additional risk factors and outperformed multiple logistic regression for BCVI. Elastic net allows the study of a large number of variables, and is useful when covariates are correlated.

Control of mouse limb initiation and antero-posterior patterning by Meis transcription factors

Meis1 and Meis2 are homeodomain transcription factors that regulate organogenesis through cooperation with Hox proteins. Elimination of Meis genes after limb induction has shown their role in limb proximo-distal patterning; however, limb development in the complete absence of Meis function has not been studied. Here, we report that Meis1/2 inactivation in the lateral plate mesoderm of mouse embryos leads to limb agenesis. Meis and Tbx factors converge in this function, extensively co-binding with Tbx to genomic sites and co-regulating enhancers of Fgf10, a critical factor in limb initiation. Limbs with three deleted Meis alleles show proximal-specific skeletal hypoplasia and agenesis of posterior skeletal elements. This failure in posterior specification results from an early role of Meis factors in establishing the limb antero-posterior prepattern required for Shh activation. Our results demonstrate roles for Meis transcription factors in early limb development and identify their involvement in previously undescribed interaction networks that regulate organogenesis.

Identifying draught cattle in the past: Lessons from large-scale analysis of archaeological datasets

PurposeImprove understanding of the links between biological variables (sex, body size and anatomical position) and adaptive remodelling of autopodia, and the identification of traction use in the archaeological record. MethodsA modified version of the recording system for identifying draught cattle in the archaeological record (Bartosiewicz et al., 1997) was applied to a sample of 1509 bones from six sites from medieval England. Analysis focused on identifying correlations between pathological and sub-pathological changes in lower-limb bones in relation to anatomy, sex and body mass. ResultsA correlation between sex, body mass and lower limb bone changes was demonstrated. The need to consider anterior and posterior limb bone elements separately to maximise the potential for identifying cattle used for traction was identified. Changes in hindlimb elements were highlighted as the most useful indicator of draught use. ContributionThis study provides new, detailed evidence for a previously poorly understood correlation between the effects of anatomical position, sex and body size and the nature of skeletal changes traditionally associated with draught cattle. It pulls together findings and makes comprehensive suggestions for future studies. LimitationsThis is a purely methodological paper. Although general results are presented, there is insufficient space to include a full case study. This will be published separately within the results of the FeedSax project. Further researchFuture studies into the use of cattle for draught purposes in the past should take in to account the sex and size of the animals under consideration, and analyse anterior and posterior elements separately.

MRI-based early diagnosis: a diabetic Charcot spine case report

BackgroundSpinal neuroarthropathy (SNA), also known as Charcot spine, is an uncommon aggressive arthropathy, secondary to loss of proprioceptive and nociceptive feedback from the spine. A diagnosis of SNA is frequently delayed due to the scarcity of symptoms in its early stages, leading to significant neurological deterioration. Therefore, prompt suspicion of the disease is critical to providing better outcomes. This case assembles two rare characteristics of SNA: diabetic aetiology and a precocious time of diagnosis, and aims to highlight the magnetic resonance imaging (MRI) findings that allowed for the diagnosis.Case presentationA 44-year-old woman, with long-term type 1 diabetes, presented with a two-month history of progressive lumbar pain, difficulty in maintaining an upright position, and discrete trunk forward-leaning. Diabetes-related vasculopathy and nephropathy were already known, and laboratory test results did not show any new abnormalities. A lumbar MRI revealed extensive signal intensity changes of the L2 and L3 vertebral bodies associated with marginal areas of enhancement and the involvement of regions adjacent to interapophyseal articulations and spinous processes from L2–L3 to L5–S1, in association with degenerative changes of the thoracolumbar spine. These findings were identified by the radiologist as suggestive of SNA. To rule out neoplastic and infectious disease, a bone biopsy at the L2–L3 level was executed. The pathology report revealed intervertebral disc material and fragments of fibrous tissue, with a complete absence of inflammatory cells. It was decided to perform a six-month MRI follow-up, which showed stability of the findings, confirming the hypothesis of Charcot spine. The patient was under clinical and radiological follow-up and did not require surgical fixation at the moment of diagnosis. After 2.5 years from the initial diagnosis, a new MRI revealed progression of the lesions with oedema and enlarged paravertebral soft tissues; these findings are compatible with the patient’s latest complaints of lumbar pain recurrence.ConclusionTo the best of our knowledge, this is the first case report of an MRI-based early diagnosis of diabetic SNA, a rare disease with nonspecific symptoms in its initial stages and a wide spectrum of differential diagnoses. The MRI findings, distinctly the involvement of both anterior and posterior spinal elements, were the key to allowing for the proper diagnosis. A precocious diagnosis, although challenging, is fundamental to providing early intervention and to preventing further neurological impairment.

Can Additional Facet Joint Block Improve the Clinical Outcome of Kyphoplasty for Acute Osteoporotic Vertebral Compression Fractures?

Percutaneous kyphoplasty (PKP) has been reported to provide a favorable analgesic effect for pain caused by osteoporotic vertebral compression fractures (OVCFs). However, a systematic review demonstrated that pain relief was only reported for approximately 86% of kyphoplasty treatments. To explore whether an additional facet joint block (FJB) can minimize pain and improve the clinical outcome of PKP in patients with acute OVCFs. Prospective study. All data were from Honghui Hospital in Xi'an. According to the inclusion and exclusion criteria, 194 patients were eventually included in our study; they were randomly divided into 2 groups of 97 patients each and treated with either PKP + FJB or PKP alone. Follow-up consultations were scheduled 1 day, 3 days, 1 week, 1 month, 3 months, and 1 year postoperatively; the demographic characteristics, related surgical information, and complications observed within both groups were recorded. The clinical evaluation parameters included the intraoperative satisfaction score, the Visual Analog Scale (VAS) score, and the Oswestry Disability Index (ODI). A total of 171 patients (61 men and 110 women; age range: 62-85 years) completed the full postoperative follow-up schedule, with 83 patients in the PKP + FJB group and 88 in the PKP group. No significant differences were observed in the genders, ages, preoperative bone mineral density, surgical levels, or volume of cement injected between the 2 groups (P > 0.05, respectively). The average duration of the surgeries in the PKP + FJB group was slightly longer than that in the PKP group (35.5 ± 4.8 min vs. 31.8 ± 4.3 min; P = 0.038), and in terms of the clinical outcomes, the average intraoperative satisfaction score was significantly higher in the PKP + FJB group (8.6 ± 1.1 vs. 6.3 ± 1.3; P < 0.001). Compared with the preoperative data, significant improvements in the VAS scores of back pain and ODI were observed at each follow-up interval (P < 0.05, respectively). These scores were significantly higher in the PKP + FJB group than in the PKP group; however, this was only observed within the first month after the procedure. A single-center noncontrol study. The addition of an FJB (which in our study involved a unique combination of ropivacaine, prednisolone, and vitamin B12) improved the short-term clinical outcome of PKP for acute OVCFs. The local anti-inflammatory and analgesic effects on the facet joints resulted in higher intraoperative satisfaction and lower VAS and ODI scores for the first postoperative month when compared with the PKP group.

ZPA Regulatory Sequence (ZRS) Activity in the Limb is Eliminated by Loss of Hand2, Twist1, and Hoxd13 Binding Sites

During limb development a cluster of mesodermal cells in the distal posterior limb bud, the zone of polarizing activity (ZPA), regulates patterning along the anterior-posterior axis. The signaling molecule responsible for this patterning is Sonic hedgehog (Shh), which is controlled by a highly conserved limb-specific enhancer, the ZPA regulatory sequence (ZRS).ZRS microdeletion results in limbs that fail to express Shh and do not develop posterior limb elements, whereas many ZRS single nucleotide variants (SNVs) lead to anterior ectopic Shh expression causing preaxial polydactyly (PPD). However, the ZRS mechanism of action is not well characterized. The ZRS contains putative binding sites for Hand2, Twist1, and Hoxd13: transcription factors (TFs) known to regulate Shh. Both Hand2 and Twist1 are basic helix-loop-helix (bHLH) TFs and are thought to function as homo- or heterodimers, while Hoxd13 has been shown to interact with Hand2.The present study's objective is to determine the role of these TFs in ZRS function. We hypothesize that altering Hand2, Twist1, and Hoxd13 bindings sites, either alone or in concert, will disrupt ZRS activity. To evaluate enhancer activity, ZRS was cloned into an enhancer-GFP reporter construct. Hand2, Twist1, and Hoxd13 binding sites were altered using site-directed mutagenesis, and constructs were electroporated into the presumptive limb buds of chicken embryos (Hamburger-Hamilton stage 14). GFP expression was evaluated 48 hours post-electroporation. We determined that mutating the binding sites for all three TFs in concert resulted in loss of ZRS activity. However, constructs with either Twist1 or Hoxd13 binding sites intact remained active. These data suggest that Twist1 and Hoxd13 may have either redundant or temporally distinct roles in ZRS regulation of Shh. Future work will determine whether these TFs bind the ZRS at the specific sites we have identified.

“Wrap-Around Sign” in Non-Hodgkin Lymphoma of the Spine: A Common yet Overlooked Imaging Feature?

Anecdotal cases of the so-called "wrap-around" appearance in non-Hodgkin lymphoma (NHL) of the spine exist in the medical literature. In this paper, we looked at the prevalence of this imaging feature in our institutional cases. We screened our institutional database for biopsy-proven NHL. Our inclusion criteria were the histologically confirmed diagnosis of NHL involving any vertebra, available magnetic resonance imaging of the affected site, and a positive wrap-around sign. Exclusion criteria included lymphoma cases without the wrap-around sign and/or histology other than NHL. We subdivided the cases into 3 groups: 1) lymphoma wrapped around the vertebral body; 2) the posterior elements alone; or 3) both the vertebral body and posterior elements. Our search identified 147 cases of NHL in which a confirmatory biopsy at the primary tumor site was available. Of those, 23 cases fulfilled the inclusion criteria (16 men and 7 women with average age at diagnosis of 63.3 years), yielding prevalence of 15.6% in our series. Most commonly the lymphoma involved the vertebral body with or without some involvement of the posterior vertebral elements (n= 20, 86.9%), followed by posterior vertebral elements (n= 2, 8.7%). One remaining case (4.4%) had lymphoma involving the anterior vertebral body and posterior elements. Findings of our pilot study indicated that the wrap-around sign in cases of NHL could be helpful diagnostically. This sign may be frequently under-recognized, leading to potential for a diagnostic dilemma on imaging. Larger studies are necessary to obtain more precise information about the prevalence of the wrap-around sign.

CT-based structural analyses of vertebral fractures with polymeric augmentation: A study of cadaveric three-level spine segments

Pathologic vertebral fractures due to metastasis can occur under normal physiologic activities, leading to pain and neurologic deficit. Prophylactic vertebroplasty is a technique used to augment vertebral strength and reduce the risk of fracture. Currently, no technique is available to objectively assess vertebral fracture risk in metastatically-involved vertebral bodies. The aim of the current study was to develop an image-based computational technique to estimate fracture force outcomes during bending. To this end, mechanical testing was performed on intact, simulated defect, PMMA-augmented, and PPF-augmented 3-level spine segments from both sexes under a compression/flexion-type loading condition. The augmentation performance of poly(methyl methacrylate) (PMMA) and poly(propylene fumarate) (PPF) were also evaluated and compared. Cylindrical defects were created in 3-level spine segments with attached posterior elements and ligaments. Using CT images of each segment, a rigidity analysis technique was developed and used for predicting fracture forces during bending. On average, PPF strengthened the segments by about 630 N, resulting in fracture forces similar to those observed in the intact and PMMA-augmented groups. Female spines fractured at about 1150 N smaller force than did male spines. Rigidity analysis, along with age, explained 66% variability in experimental outcomes. This number increased to 74% when vertebral size and age were added to the rigidity analysis as explanatory variables. Both PPF and PMMA similarly increased fracture strength to the level of intact specimens. The results suggest that PPF can be a suitable candidate for augmentation purposes and rigidity analysis can be a promising predicting tool for vertebral fracture forces.