Th12 Vertebra Research Articles

Impact of transpedicular fixation on thoracolumbar junction burst fracture stability: a biomechanical perspective

Introduction. The treatment of burst fractures at the thoracolumbar junction remains a contentious issue in vertebrology. Despite a broad array of surgical interventions available, many surgeons favor isolated posterior stabilization, which can be performed using either minimally invasive or open approaches. However, the biomechanical properties of these methods have not been thoroughly investigated. Objective: This study aims to evaluate the biomechanical stability of the thoracolumbar junction following transpedicular stabilization of a burst fracture at the Th12 vertebra, under different system configurations influenced by lateral flexion. Materials and Methods: A mathematical finite element model of the human thoracolumbar spine, featuring a burst fracture at the Th12 vertebra, was developed. The model included a transpedicular stabilization system with eight screws, simulating “long” stabilization. We examined four variants of transpedicular fixation using both mono- and bicortical screws, with and without the inclusion of two cross-links. Results: The study found that the load borne by the damaged Th12 vertebral body varied depending on the fixation system employed. Specifically, stress levels were 24.0 MPa, 27.3 MPa, 18.4 MPa, and 25.8 MPa for models with short screws without cross-links, long screws without cross-links, short screws with cross-links, and long screws with cross-links, respectively. At the screw entry points in the vertebral arch, the highest stress values were recorded at the L2 vertebra, showing 11.8 MPa, 14.0 MPa, 9.4 MPa, and 13.4 MPa for each respective model. Among the metal construct elements, the connecting rods consistently exhibited the highest stress, with values of 226.7 MPa, 313.4 MPa, 212.4 MPa, and 293.98 MPa, respectively. Conclusion: The results underscore that utilizing cross-links in the stabilization of burst fractures at the thoracolumbar junction, which is only feasible through an open installation, somewhat mitigates stress within the stabilized spinal segment. Meanwhile, the modeling of lateral flexion revealed only minimal differences in stress values between open and minimally invasive installations.

Assessment of biomechanical stability of the thoracolumbar junction with a burst fracture of Th12 following surgical stabilization under rotational loading

The thoracolumbar junction is the most vulnerable to traumatic injuries, with over 65 % of injuries to the thoracolumbar spine occurring in this region. Objective: To examine the stress-strain state of the thoracolumbar spine model with a burst fracture of the Th12 vertebra under various transpedicular fixation options influenced by rotational loading. Materials and Methods: A mathematical finite-element model of the human thoracolumbar spine was developed, including a burst fracture of the Th12 vertebra and a transpedicular stabilization system containing eight screws implanted in the Th10, Th11, L1, and L2 vertebrae. Four variants of transpedicular fixation were modelled using short and long screws passing through the anterior surface of the vertebra, with and without two crosslinks. Results: The analysis showed sufficiently high loading values for both the bone structures of the models and the elements of the metal construct. The maximum stress level in the body of the damaged vertebra was 33.2, 26.7, 30.1, and 24.2 MPa, respectively, for models with monocortical screws without crosslinks, bicortical screws without crosslinks, monocortical screws with crosslinks, and bicortical screws with crosslinks. High values were also recorded for the vertebrae adjacent to the damaged one: 13.0, 8.4, 10.9, and 7.1 MPa for the L1 vertebra and 10.2, 8.9, 7.1, and 6.2 MPa for the Th11 vertebra in the respective models. The stress on the supporting rods was registered at 582.0, 512.5, 512.6, and 452.7 MPa respectively. Conclusion: The conducted analysis demonstrated that under rotational loading, the model with monocortical screws without crosslinks shows the highest peak loads at control points, whereas the model with bicortical screws and crosslinks shows the minimum. Meanwhile, models with short screws and crosslinks and long screws without crosslinks exhibit comparable results

Analysis of load distribution after transpedicular stabilization of burst fractures in the thoracolumbar junction

Background. In the structure of all traumatic spine injuries, the thoracolumbar junction is predominant, accounting for over 53 % of all vertebral fractures. One of the most clinically significant types of injuries in this area are burst fractures. The purpose was to study the stress-strain state of the thoracolumbar spine model with a burst fracture of the Th12 vertebra in various transpedicular fixation options under compression load. Materials and methods. The study developed and investigated a finite element model of the thoracolumbar spine with a burst fracture of the Th12 vertebra. The burst fracture was modeled by dividing the vertebral body of the Th12 into several planes, transforming it into separate fragments. The gaps between these fragments were filled with a material that simulated the interfragmentary regenerate. Variants of transpedicular stabilization using different types of screws, mono- or bicortical, and with or without cross-links, were examined. The model was analyzed under compression load. Results. The maximum level of stress among the bone structures directly involved in fixation was registered in the L2 vertebral body. It amounted to 19.9, 15.6, 19.4, and 15.1 MPa, respectively, for models with monocortical screws without cross-links, bicortical screws without cross-links, monocortical screws with cross-links, bicortical screws with cross-links. Simultaneously, the zone of screw entry into the arch of this vertebra shows values of 10.1, 15, 10.2, and 14.3 MPa for these models, respectively. Peak loads on the metal structure elements are observed on the rods, amounting to 212.5, 159.6, 203.7, 142.8 MPa, respectively, for the considered models. Conclusions. The results of the study showed that under the influence of compression load when modeling a burst fracture of the thoracolumbar junction, the use of long screws leads to a reduction in stress levels, both in the elements of the metal structure and in the bone elements of the model, while the use of cross-links has a negligible effect.

AI-based fully automatic image analysis: Optimal abdominal and thoracic segmentation volumes for estimating total muscle volume on computed tomography scans

ObjectivesEvaluation of sarcopenia from computed tomography (CT) is often based on measuring skeletal muscle area on a single transverse slice. Automatic segmentation of muscle volume has a lower variance and may be a better proxy for the total muscle volume than single-slice areas. The aim of the study was to determine which abdominal and thoracic anatomical volumes were best at predicting the total muscle volume. MethodsA cloud-based artificial intelligence tool (recomia.org) was used to segment all skeletal muscle of the torso of 994 patients who had performed whole-torso CT 2008–2020 for various clinical indications. Linear regression models for several anatomical volumes and single-slice areas were compared with regard to predicting the total torso muscle volume. ResultsThe muscle volume from the tip of the coccyx and 25 cm cranially was the best of the abdominal volumes and was significantly better than the L3 slice muscle area (R2 0.935 vs 0.830, P < 0.0001). For thoracic volumes, the muscle volume between the top of the sternum to the lower bound of the Th12 vertebra showed the best correlation with the total volume, significantly better than the Th12 slice muscle area (R2 0.892 vs 0.775, P < 0.0001). Adjusting for body height improved the correlation slightly for all measurements but did not significantly change the ordering. ConclusionsWe identified muscle volumes that can be reliably segmented by automated image analysis which is superior to single slice areas in predicting total muscle volume.

Mathematical modeling of variants of thoracolumbar junction transpedicular fixation after resection of Th12 vertebra under compressive load

Background. The area of the thoracolumbar junction is characterized by a significant load that dictates increased requirements to stabilization, which should not only provide a reliable and rigid fixation, but also ensure the maximum uniform distribution of the load on all elements of both the metal structure and the bone tissue to exclude the failure of fixation in the long run. Purpose of the study is to investigate the influence of the transpedicular screw length and the presence of crosslinks on the load distribution during surgical resection of one vertebra from the thoracolumbar junction under the influence of axial compressive load. Materials and methods. We analyzed mathematical finite-element model of the part of thoracolumbar spine (Th9-L5), where the Th12 vertebra was removed and replaced by an interbody implant with additional fixation by a transpedicular system. Four variants of transpedicular fixation were modeled using short and long screws, as well as with and without two crosslinks. The stress-strain state of the models was studied under the influence of a vertical compressive distributed load of 350 N. Results. When using short screws and in the absence of crosslinks, the maximum stresses in the Th10, Th11, L1, and L2 vertebrae are 7.2, 5.3, 4.2, and 14.3 MPa, respectively, when using long screws without crosslinks — 6.5, 4.6, 3.8 and 13.5 MPa. The model with short screws and crosslinks shows 7.1, 4.4, 3.9 and 14.0 MPa, while the application of long screws with crosslinks is 6.3, 4.5, 3.5 and 13.2 MPa, respectively. Conclusions. With a compressive load, the use of long screws allows to reduce the level of stress in the bone elements of the models, the use of crosslinks provides greater rigidity to the posterior support of the transpedicular structure, which leads to an increase in stress on the fixing screws but allows to reduce the level of stress in the bone tissue.

Study of the stress-strain state of the posterior lumbar fusion models in case of normal indicators of the sagittal balance of the spine and pelvis

Background. Patients suffering from hip-spine syndrome with significant changes in the hip joint complain of pain in the lumbar spine in 21.2–49.4 % of cases. After performing lumbar fusion, the mobility of the pelvis decreases, which leads to an increased risk of dislocations and the development of impingement after hip arthroplasty that is the cause for repeated surgical interventions. Goal: to study the stress distribution in the models of posterior lumbar fusion in case of normal values of the sagittal contour of the spine and lumbar lordosis. Materials and methods. A finite-element model has been developed reflecting the condition that occurs in the combined course of degenerative diseases of the lumbar spine and hip joint and is characterized by normal lordosis of 40º and forward body tilt due to flexion contracture in the hip joints. The following options were modeled: 1 — posterior fusion of the L4-L5 vertebrae using a transpedicular structure with 4 screws and an interbody support; 2 — posterior fusion of the L3-L4-L5 vertebrae using a transpedicular construction with 6 screws; 3 — posterior fusion of L1-L5 vertebrae using a transpedicular structure with 10 screws. When conducting the research, the values of stresses in the Th1-L5 vertebrae, on the screws and rods of the transpedicular structure were studied. Results. Posterior fusion with a transpedicular construction on two L4-L5 vertebrae leads to the occurrence of maximum stresses in vertebral bodies of the lumbar spine, especially L4-L5. The lowest stresses in the lumbar vertebral bodies can be obtained when the transpedicular structure is applied to all 5 vertebrae. The use of all options for posterior fusion, except for the 4-screw scheme, allows to reduce the stress in the vertebral arches of the lumbar spine below the level of the normal spine model, except for the L1 vertebra. This leads to an increase in the level of stress from the Th6 to Th12 vertebrae. The construction placed on all 5 vertebrae ensures the lowest level of stress in the arches of thoracic vertebrae. The construction placed on all the vertebrae of the lumbar spine provides a minimum level of stress in the bone tissue around the fixing screws. Reducing the length of fixation leads to a significant increase in stress in these zones. With all types of installation of the transpedicular construction, the values of the stresses on the screws in the L3-L5 vertebrae are comparable. When using the design for 5 vertebrae of the lumbar spine, the locking screws in the L1 and L2 vertebrae will experience significant loads, which, accordingly, will cause significant stress in them. The maximum level of stress in the rods occurs when two L4-L5 vertebrae are instrumented, the minimum is when the structure is placed on all five vertebrae of the lumbar spine. Conclusions. Given the stress distribution, the length of fixation plays an important role: the longer the length of fixation, the lower the stress level, both in the bone elements of the model and in the elements of metal structures.

Revision surgery effectiveness in late thoracolumbar junction traumatic injury

Traumatic injuries of the spine constitute a relatively small part of the consequences of the traumatic factor action on the human body but they significantly affect the social and economic component of the injured patients’ life. During the Russian-Ukrainian war, the number of patients with traumatic injuries to the spine and spinal cord increased significantly. The analysis of previous armed conflicts shows that most spinal injuries in both military and civilians are closed. Therefore, the treatment strategy correspond to those in peacetime. One of the least studied issues is the feasibility of surgical decompression of the spinal canal in the late period of spinal cord injury.An anamnestically complex case of traumatic injury of the thoracolumbar junction is presented. A patient with a combined injury underwent laminectomy of the Th12 vertebra and transpedicular fixation of the Th11, Th12, L1 and L2 vertebrae after fracture-dislocation of the Th12-L1, that was accompanied by gross neurological symptoms of ASIA A. Surgery was performed 11 days after the emergency hospitalization. 6 months after trauma it was revealed the screws malposition in the bodies of the Th12 and L1 vertebrae. After 10 months, a surgery was performed: removal of the left transpedicular screw from the body of the Th12 vertebra, laminectomy of the Th12, L1 and L2 vertebrae, an electronic neurostimulator was installed on the spinal cord, and 12 months after the injury, the transpedicular stabilization system was rearranged and the electrodes of neurostimulator were removed. Within 3 years and 7 months, after the appearance of acute pains in the area of the kidneys, an additional examination was performed. Fragmentation of the left rod of fusion system between the L1 and L2 vertebrae was revealed, as well as the presence of ossified fragments of the intervertebral disc at the Th12-L1 level, which caused absolute stenosis of the spinal canal. In Romodanov Neurosurgery Institute of National Academy of Medical Sciences of Ukraine, revision surgery was performed: adequate repositioning of the stabilization system and extensive decompression of the spinal canal with facetectomy and complete decompression of the dural sac. During the follow-up examination after 4 months, regression of the neurological deficit from ASIA A to ASIA B was recorded.In the article classic errors during surgery of traumatic injuries of the thoracolumbar junction and the expediency of performing decompressive-revision surgical interventions in the late period of spinal cord injury were analyzed. An anamnestically complex case of traumatic injury of the thoracolumbar junction is presented. A patient with a combined injury underwent laminectomy of the Th12 vertebra and transpedicular fixation of the Th11, Th12, L1 and L2 vertebrae after fracture-dislocation of the Th12-L1, that was accompanied by gross neurological symptoms of ASIA A. Surgery was performed 11 days after the emergency hospitalization. 6 months after trauma it was revealed an unsatisfactory location of the screws in the bodies of the Th12 and L1 vertebrae. After 10 months, a surgery was performed: removal of the left transpedicular screw from the body of the Th12 vertebra, laminectomy of the Th12, L1 and L2 vertebrae, an electronic neurostimulator was installed on the spinal cord, and 12 months after the injury, the transpedicular stabilization system was rearranged and the electrodes of neurostimulator were removed. Within 3 years and 7 months, after the appearance of acute pains in the area of the kidneys, an additional examination was performed. Fragmentation of the left rod of fusion system between the L1 and L2 vertebrae was revealed, as well as the presence of ossified fragments of the intervertebral disc at the Th12-L1 level, which caused absolute stenosis of the spinal canal. In the Romodanov Neurosurgery Institute of National Academy of Medical Sciences of Ukraine, revision surgery was performed: adequate repositioning of the stabilization system and extensive decompression of the spinal canal with facetectomy and complete decompression of the dural sac. During the follow-up examination after 4 months, regression of the neurological deficit from ASIA A to ASIA B was recorded. In the article we analyze classic errors during surgery of traumatic injuries of the thoracolumbar junction and the expediency of performing decompressive-revision surgical interventions in the late period of spinal cord injury.

The role of monoclonal antibodies in treatment of refractory multiple myeloma

Multiple myeloma (MM) is a B-cell malignant tumor; its morphological substrate – plasma cells – produces monoclonal immunoglobulin. Primarily, MM is diagnosed in elderly people and is characterized by a variety of clinical manifestations caused by plasma cells infiltration and organ damage. Despite successes in MM therapy, in the majority of cases recurrences of MM or refractory process are observed. In this case, the choice of antitumor drug is usually made depending on its tolerability, toxicity, and availability. Selection of correct treatment can be complicated by such frequent clinical manifestations of MM as osteolytic vertebral lesions leading to development of pathologic compression fractures which in some cases cause spinal cord compression and full immobility in the patients with MM.A clinical case of a 62-year-old female patient with refractory MM is presented. Pathologic compression fractures of the Th12 and L2 vertebral bodies with massive extraosseous component at the Th12 vertebra level posed a threat of spinal cord compression. At the 1st stage, percutaneous vertebroplasty was performed, then antitumor therapy with daratumumab without increased intercycle intervals which significantly increased patient’s quality of life.

Моделювання варіантів транспедикулярної фіксації грудного відділу хребта при резекції одного-трьох хребців

Актуальність. Патологічні переломи хребців є найбільшим ускладненням пухлинного процесу. Застосування додаткової внутрішньої фіксації металевими імплантатами значно покращує результати лікування й скорочує строки реабілітації хворих. Використання транспедикулярних пристроїв забезпечує стабільну фіксацію й стабільність сегментів хребта навіть при максимальному ступені його нестабільності. Мета: визначення оптимального варіанта протяжності заднього спондилодезу при паліативному та радикальному хірургічному лікуванні пухлин хребта. Матеріали та методи. Для вивчення можливостей стабілізації за допомогою транспедикулярної фіксації при резекції одного-трьох хребців провели експериментальні випробування на препаратах хребта свині. Використовували препарати сегментів грудного відділу хребта від Th3 до Th12 хребців. Вивчали 3 групи моделей: з одним резектованим хребцем Th6, з двома — Th5-Th6 і з трьома — Th5-Th7. Результати. Виявлено, що при резекції одного хребця в грудному відділі хребта транс-педикулярна фіксація за схемами 111х111, 101х101 та 011х110 має однакову ефективність. При резекції двох хребців найкращі стабілізуючі можливості мала конструкція за схемою 111хх111, схеми 101хх101 та 011хх110 показали доволі непогану фіксуючу здатність. При резекції трьох хребців грудного відділу хребта найбільш стабільну фіксацію показала схема 111ххх111. Схема фіксації 001ххх100 виявилась нестабільною при всіх видах резекції хребців. Висновки. Експериментальні дослідження транспедикулярної фіксації при радикальному хірургічному лікуванні пухлин хребта, який включає резекцію одного-трьох хребців, показали, що конструкція відповідає вимогам фіксації, коли кріплення відбувається не менше ніж за два верхніх та два нижніх хребці (можна через один), при резекції трьох хребців найбільш стабільною є конструкція з кріпленням за три верхні та три нижні хребці (без пропусків). Система кріплення за один хребець виявилася неспроможною майже при всіх видах резекції.

ИНДЕКС МЫШЕЧНОЙ МАССЫ НА УРОВНЕ ПОЗВОНКА Th12 КАК ПРОГНОСТИЧЕСКИЙ ФАКТОР ЛЕТАЛЬНОГО ИСХОДА У ПАЦИЕНТОВ С ПНЕВМОНИЕЙ, ВЫЗВАННОЙ SARS-COV2

Purpose: To develop a methodology for determining the muscle mass index (MMI) at the level of Th12 based on the computed tomography of the chest; to estimate the impact of MMI on the outcome of the COVID19 patients as a prognostic factor. &#x0D; Material and methods: The medical data and computed tomography of the chest of 247 patients with confirmed pneumonia caused by SARS-Cov2 were used. A technique has been developed for determining MMI based on the cross-sectional area of paraspinal muscles at the level of the Th12 vertebra and the length of the thoracic spine. A correlation analysis of MMI calculated based on the length of the thoracic spine MMI(L) and height MMI(H) was performed. A statistical analysis of the differences of the MMI(L) in the groups of male and female patients with fatal outcome and recovered, as well as younger and older than 65 years were performed. &#x0D; Results: A strong correlation was found between the MMI calculated on the basis of the length of the thoracic spine and height &#x0D; (r = 0.861, p &lt;0.001). The age threshold, which was associated with an increase in the likelihood of death, in men was 60 years (Se 77.3 %, Sp 60.5 %, PPV 51.5 %, NPV 83.1 %, Youden's index 0.378, area under ROC- curve 0.728), in women 65 years old (Se 72.2 %, Sp 68.6 %, PPV 49.1 %, NPV 85.5 %, Youden's index 0.408, the area under the ROC curve 0.734). The odds ratio of death when the age thresholds are exceeded was 5.2 for men (95 % CI: 2.3 – 12.0), for women – 5.7 (95 % CI: 2.4 – 13.4). MMI(L) 3.37cm2/m2 is a threshold value, below which the probability of death in male patients under 60 years increased 26.3 times (95 % CI: 4.8 – 143.0). In female patients, there was no statistically significant threshold value of MMI(L), which would be associated with a higher risk of death. &#x0D; Conclusion: MMI, calculated at the level Th12 on the basis of the length of the thoracic spine, can be reliably used as a tool to estimate sarcopenia associated muscle atrophy, if there is no anthropometric data. The MMI(D) less than 3.37 cm2/m2 is a strong predictor of death in men under 60 years of age. Further work is needed to study the effect of sarcopenia on the severity and outcome of COVID19 in female patients, taking into account comorbid conditions.

Exoskeleton Walk Training in Paralyzed Individuals Benefits From Transcutaneous Lumbar Cord Tonic Electrical Stimulation.

In recent years, advanced technologies featuring wearable powered exoskeletons and neuromodulation of lumbosacral spinal networks have been developed to facilitate stepping and promote motor recovery in humans with paralysis. Here we studied a combined effect of spinal cord electrical stimulation (SCES) and exoskeleton walk training (EWT) during an intensive 2-week rehabilitative protocol in spinal cord injury individuals (n = 19, American Spinal Injury Association Impairment Scale (AIS) A-11, B-5, C-3). The purpose of this study was to evaluate the compatibility of methods and to explore the main effects of combined SCES and EWT. All participants had a chronic state of paralysis (1–11 years after trauma). In addition, in the control group (n = 16, AIS A-7, B-5, C-4), we performed EWT without SCES. For EWT, we used a powered exoskeleton (ExoAtlet), while stability was assisted by crutches, with automatic arrest of stepping if excessive torques were detected. SCES was applied to the level of the mid-lumbar cord over the Th12 vertebra at 1 or 3 pulses/s (4 individuals with severe spasticity were also stimulated in an anti-spastic mode 67 pulses/s). The vertical component of the ground reaction force was recorded using the F-Scan system at the onset and after training with SCES. EWT with SCES significantly increased the foot loading forces, could decrease their asymmetry and 8 out of 19 subjects improved their Hauser Ambulation Index. The anti-spastic mode of stimulation also allowed individuals with severe spasticity to walk with the aid of the exoskeleton. Participants reported facilitation when walking with SCES, paresthesia in leg muscles and new non-differential sensation of passive motion in leg joints. Neurological examination showed an increase of tactile (7) and/or pain (7) sensation and an increase of the AIS motor scale in 9 individuals, including both incomplete and complete paralysis. Improvements in the neurological scores were, however, limited in the control group (EWT without SCES). The results suggest that SCES may facilitate training and walking in the exoskeleton by activating the locomotor networks and augmenting compensative sensitivity.

Evaluation of lumbar enlargement motor neuron excitability: Comparison between H-reflex and transcutaneous spinal cord stimulation

Multisegmental muscle responses (MMR) are reflexes in the leg muscles evoked by transcutaneous electrical spinal cord stimulation over the Th11–Th12 vertebrae. We have used MMR to evaluate the excitability of lumbosacral motor neurons in individuals having paraplegia of low limbs. Ten individuals were tested using H-reflexes and MMR bilaterally before (n0 = 20) and during 4-weeks course of rehabilitation (n=76). The H-reflex and MMR of m. gastrocnemius lateralis were obtained in: 15 and 13 cases out of 20, respectively. Both reflexes were recorded in 11 and were absent in 3 cases, matched up to 70% of recordings. In dynamic, the both methods were 100% reproducible and the responses’ amplitude varied in similar directions in 67% of records. The data confirm the validity and reproducibility of the MMR for evaluation of the motor neurons excitability in lumbosacral cord. The H-reflex magnitude shows moderate correlation with MMR in m. gastrocnemius lateralis (r = 0.59, p < 0.001), and weak correlation with MMR in mm. rectus femoris, biceps femoris, and tibialis anterior (r < 0.40, p < 0.001). These findings do not allow extrapolate the results from the H-reflex measurement on the state of lumbosacral cord on the whole. At the same time, measurements of the MMR allow estimate simultaneously the excitability of motor pools innervating several muscle groups. This gives the possibility to assess the functional state of the motor neurons in the lumbosacral cord for clinical and experimental studies, including the spinal cord damage.

Idiopathic Hypertrophic Spinal Pachymeningitis.

A 63-year-old man revealed a four-month history of muscle weakness of the lower limbs, hypoesthesia of the L5 and S1 area and ischuria. On MRI, the spinal cord was compressed by an encircled mass, which showed hypointensity on T1- and T2-weighted images with gadolinium enhancement at the Th11 to Th12 vertebra. Because of the rapid progression of myelopathy, posterior decompression was performed and idiopathic hypertrophic spinal pachymeningitis (HSP) was finally diagnosed. The patient's neurological signs markedly improved with postoperative corticosteroid treatment. Idiopathic HSP is a clinical emergency and early surgical intervention is essential to prevent irreversible damage to the nervous system.

Phase-Dependent Modulation of Percutaneously Elicited Multisegmental Muscle Responses After Spinal Cord Injury

Phase-dependent modulation of monosynaptic reflexes has been reported for several muscles of the lower limb of uninjured rats and humans. To assess whether this step-phase-dependent modulation can be mediated at the level of the human spinal cord, we compared the modulation of responses evoked simultaneously in multiple motor pools in clinically complete spinal cord injury (SCI) compared with noninjured (NI) individuals. We induced multisegmental responses of the soleus, medial gastrocnemius, tibialis anterior, medial hamstring, and vastus lateralis muscles in response to percutaneous spinal cord stimulation over the Th11-Th12 vertebrae during standing and stepping on a treadmill. Individuals with SCI stepped on a treadmill with partial body-weight support and manual assistance of leg movements. The NI group demonstrated phase-dependent modulation of evoked potentials in all recorded muscles with the modulation of the response amplitude corresponding with changes in EMG amplitude in the same muscle. The SCI group demonstrated more variation in the pattern of modulation across the step cycle and same individuals in the SCI group could display responses with a magnitude as great as that of modulation observed in the NI group. The relationship between modulation and EMG activity during the step cycle varied from noncorrelated to highly correlated patterns. These findings demonstrate that the human lumbosacral spinal cord can phase-dependently modulate motor neuron excitability in the absence of functional supraspinal influence, although with much less consistency than that in NI individuals.

Fibrocartilaginous mesenchymoma of the spine in a child: a case report

Originally described by Dahlin et al. in 1984, fibrocartilaginous mesenchymoma (FCM) constitutes a rare bone tumor of children and adolescents that mainly affects the long bones. A spinal location of this tumor is exceptional. Only two previous instances of vertebral FCM have been reported in the current literature, and both occurred in young adults. We report the case of a 9-year-old boy with backache caused by a neoplasm that involved the Th12 vertebra treated with tumor excision. Histopathological diagnosis was confirmatory of FCM. During a follow-up period of 2 years, there was no evidence of disease progression. Our patient, thus, represents the first case of FCM occurring in a child. Given the rarity of spinal FCM, there are no guidelines about its management. However, treatment of this neoplasm seems to be mainly surgical aiming at total removal of the lesion, if feasible, as FCM may recur locally.

Intraosseous schwannoma of thoracic 12 vertebra without spinal canal involvement

Schwannomas are common tumors of the nerve sheath cells. They present as well-circumscribed masses attached to the peripheral nerves, cranial nerves, or spinal nerve roots. Intraosseous localization of these tumors is rare. The presented case is a 55-year-old female patient, the very first case of intraosseous schwannoma of Th12 vertebra without spinal canal involvement. She was admitted with a progressive back pain and seldom pain and numbness in the right leg for 1 year. Preoperative findings on computed tomography and magnetic resonance images of the lesion resembled that of any primary tumor of the bone. The patient was operated on via posterior approach and the tumor was removed totally. Histopathological examinations revealed schwannoma. Our case emphasizes the heterogeneous presentation of the nerve sheath cell tumors in the differential diagnosis of the primary vertebral column tumors.

Cortical somatosensory potentials evoked by magnetic stimulation: effect of body height, age, and stimulus intensity

Cortical somatosensory evoked potentials elicited by non-invasive magnetic stimulation at Th10, Th12, and L5 vertebral levels and at mid-gluteus and ankle were studied in 45 normal controls varying in body height and age. Peak latencies of P2 evoked by ankle, mid-gluteus and L5 stimulation were correlated with body height. However, P2 latencies evoked by Th10 and Th12 stimulation were independent of body height. In contrast, all N2 latencies evoked by Th10, Th12, L5, mid-gluteus and ankle were correlated with body height. There were no correlations between latencies of P3 and N3 and body height. No peak latencies of cortical components were affected by age within the age group studied (15–67 years). In the intensity study, N2 showed double peaks when low to moderate stimulus intensities were applied to Th12 vertebra. Furthermore, in 2 patients with mild somatosensory dysfunction of lumbar roots or cord, N2 evoked by L5 stimulation revealed double peaks with prolonged interpeak latencies between the first peak of N2 and P3, which might be related to the temporal dispersion of the afferent fibers. These data suggest that the N2 component is induced by both fast and slow afferent fibers.