Use of the finite element method to study the mechanism of spinal cord injury without radiological abnormality in the cervical spine

Finite element modeling of the human cervical spinal cord and its applications: A systematic review

Background Context

Finite element modeling (FEM) is an established tool to analyze the biomechanics of complex systems. Advances in computational techniques have led to the increasing use of spinal cord FEMs to study cervical spinal cord pathology. There is considerable variability in the creation of cervical spinal cord FEMs and to date there has been no systematic review of the technique. The aim of this study was to review the uses, techniques, limitations, and applications of FEMs of the human cervical spinal cord.

Methods

A literature search was performed through PubMed and Scopus using the words finite element analysis, spinal cord, and biomechanics. Studies were selected based on the following inclusion criteria: (1) use of human spinal cord modeling at the cervical level; (2) model the cervical spinal cord with or without the osteoligamentous spine; and (3) the study should describe an application of the spinal cord FEM.

Results

Our search resulted in 369 total publications, 49 underwent reviews of the abstract and full text, and 23 were included in the study. Spinal cord FEMs are used to study spinal cord injury and trauma, pathologic processes, and spine surgery. Considerable variation exists in the derivation of spinal cord geometries, mathematical models, and material properties. Less than 50% of the FEMs incorporate the dura mater, cerebrospinal fluid, nerve roots, and denticulate ligaments. Von Mises stress, and strain of the spinal cord are the most common outputs studied. FEM offers the opportunity for dynamic simulation, but this has been used in only four studies.

Conclusions

Spinal cord FEM provides unique insight into the stress and strain of the cervical spinal cord in various pathological conditions and allows for the simulation of surgical procedures. Standardization of modeling parameters, anatomical structures and inclusion of patient-specific data are necessary to improve the clinical translation.

Cervical Single-Level Pincer Stenosis Causing Myelopathy: A Technical Note and Medium-term Results of a One-Session Microsurgical 360-Degree Treatment

BACKGROUND AND STUDY AIMS

 Single-level circumferential or pincer stenosis (PS) affects few patients with degenerative cervical myelopathy (DCM). The surgical technique and medium-term results of a one-session microsurgical 360-degree (m360°) procedure are presented.

PATIENTS

 Between 2013 and 2018, the data of 23 patients were prospectively collected out of 371 patients with DCM. The m360° procedure comprised a microsurgical anterior cervical decompression and fusion (ACDF), with additional plate fixation, followed by flipping the patient and performing a microsurgical posterior bilateral decompression via a unilateral approach in crossover technique.

RESULTS

 The mean age of the patients was 72 years (range: 50-84); 17 patients were males. The mean follow-up time was 12 months (range: 6-31). The patients filled in the patient-derived modified Japanese Orthopaedic Association (P-mJOA) questionnaire on average 53 months after surgery. One patient received a two-level ACDF. Lesions were mostly (92%) located at the C3/C4 (8/24), C4/C5 (7/24), and C5/C6 (7/24) levels. Functional X-rays showed segmental instability in 10 of 23 patients (44%). All preoperative T2-weighted magnetic resonance imaging (MRI) showed an intramedullary hyperintensity. The median preoperative mJOA score was 13 (range 3), and it improved to 16 (range 3) postoperatively. The mean improvement rate in the mJOA score was 73%. When available, postoperative MRI confirmed good circumferential decompression with persistent intramedullary hyperintensity. There were two complications: a long-lasting radicular paresthesia at C6 and a transient C5 palsy. No revision surgery was required.

CONCLUSION

 The one-session m360° procedure was found to be a safe surgical procedure for the treatment of PS, and the medium-term clinical outcome was satisfactory.

The Correlation Between Facet Tropism and Intervertebral Disc Herniation in the Subaxial Cervical Spine

STUDY DESIGN

A retrospective case-control study.

OBJECTIVE

Investigating the correlation between the facet tropism (FT) and subaxial cervical disc herniation (CDH).

SUMMARY OF BACKGROUND DATA

Although debatable, it was widely reported that FT was associated with lumbar disc herniation. However, the exact correlation between FT and subaxial CDH is still unclear.

METHODS

Two-hundred patients with any disc herniation at C3/4, C4/5, C5/6, or C6/7 and 50 normal participants without CDH (normal control group) were included in this study. For patients, the cervical levels with CDH and the levels without herniation were classified into the "herniation group" and "patient control group," respectively. Bilateral facet joint angles at C3/4, C4/5, C5/6, and C6/7 on sagittal, axial, and coronal planes were measured on computed tomography (CT). The disc degeneration at each level was assessed on magnetic resonance imaging (MRI).

RESULTS

Both the mean difference between left and right facet angles and tropism incidence in herniation group were significantly greater than those in two control groups whenever at C3/4, C4/5, C5/6, or C6/7 level and whenever on sagittal, axial, or coronal plane. The mean differences of angles and tropism incidences in most patient control groups were not significantly greater than those of corresponding normal control groups. The incidence of greater facet angle at the left or right side was not significantly different among the left, central, and right herniation groups. The mean disc degeneration grades in both herniation and patient control groups were significantly higher than those in normal control groups while no difference between herniation and patient control groups.

CONCLUSION

The FT on the sagittal, axial, and coronal planes are all associated with CDH in the subaxial cervical spine. The greater facet angle at the left or right side does not affect the side of herniation. The severity of cervical disc degeneration is not associated with FT.Level of Evidence: 3.

Correlating Tissue Mechanics and Spinal Cord Injury: Patient-Specific Finite Element Models of Unilateral Cervical Contusion Spinal Cord Injury in Non-Human Primates

Non-human primate (NHP) models are the closest approximation of human spinal cord injury (SCI) available for pre-clinical trials. The NHP models, however, include broader morphological variability that can confound experimental outcomes. We developed subject-specific finite element (FE) models to quantify the relationship between impact mechanics and SCI, including the correlations between FE outcomes and tissue damage. Subject-specific models of cervical unilateral contusion SCI were generated from pre-injury MRIs of six NHPs. Stress and strain outcomes were compared with lesion histology using logit analysis. A parallel generic model was constructed to compare the outcomes of subject-specific and generic models. The FE outcomes were correlated more strongly with gray matter damage (0.29 < R² < 0.76) than white matter (0.18 < R² < 0.58). Maximum/minimum principal strain, Von-Mises and Tresca stresses showed the strongest correlations (0.31 < R² < 0.76) with tissue damage in the gray matter while minimum principal strain, Von-Mises stress, and Tresca stress best predicted white matter damage (0.23 < R² < 0.58). Tissue damage thresholds varied for each subject. The generic FE model captured the impact biomechanics in two of the four models; however, the correlations between FE outcomes and tissue damage were weaker than the subject-specific models (gray matter [0.25 < R² < 0.69] and white matter [R² < 0.06] except for one subject [0.26 < R² < 0.48]). The FE mechanical outputs correlated with tissue damage in spinal cord white and gray matters, and the subject-specific models accurately mimicked the biomechanics of NHP cervical contusion impacts.

Postoperative changes in spinal cord signal intensity in patients with spinal cord injury without major bone injury: comparison between preoperative and postoperative magnetic resonance images

OBJECTIVE

Although increased signal intensity (ISI) on MRI is observed in patients with cervical spinal cord injury (SCI) without major bone injury, alterations in ISI have not been evaluated. The association between postoperative ISI and surgical outcomes remains unclear. This study elucidated whether or not the postoperative classification and alterations in MRI-based ISI of the spinal cord reflected the postoperative symptom severity and surgical outcomes in patients with SCI without major bone injury.

METHODS

One hundred consecutive patients with SCI without major bone injury (79 male and 21 female) with a mean age of 55 years (range 20-87 years) were included. All patients were treated with laminoplasty and underwent MRI pre- and postoperatively (mean 12.5 ± 0.8 months). ISI was classified into three groups on the basis of sagittal T2-weighted MRI: grade 0, none; grade 1, light (obscure); and grade 2, intense (bright). The neurological statuses were evaluated according to the Japanese Orthopaedic Association (JOA) scoring system and the American Spinal Injury Association Impairment Scale (AIS).

RESULTS

Preoperatively, 8 patients had grade 0 ISI, 49 had grade 1, and 43 had grade 2; and postoperatively, 20 patients had grade 0, 24 had grade 1, and 56 had grade 2. The postoperative JOA scores and recovery rate (RR) decreased significantly with increasing postoperative ISI grade. The postoperative ISI grade tended to increase with the postoperative AIS grade. Postoperative grade 2 ISI was observed in severely paralyzed patients. The postoperative ISI grade improved in 23 patients (23%), worsened in 25 (25%), and remained unchanged in 52 (52%). Patients with an improved ISI grade had a better RR than those with a worsened ISI grade.

CONCLUSIONS

Postoperative ISI reflected postoperative symptom severity and surgical outcomes. Alterations in ISI were seen postoperatively in 48 patients (48%) and were associated with surgical outcomes.

The influence of timing of surgery in the outcome of spinal cord injury without radiographic abnormality (SCIWORA)

Background

Spinal cord injury without radiographic abnormality (SCIWORA) is a rare traumatic myelopathy. Although surgery is one of the most important treatments, the surgery for SCIWORA is controversial, especially the time of surgery is a topic of controversy. Here, we investigate the effects of difference in duration from injury to surgery on the outcome of SCIWORA.

Methods

This retrospective study was performed in all patients with spinal cord injury admitted to the Third Affiliated Hospital of Hebei Medical University from January 2013 to April 2017. Fifty-seven patients who met the study requirements were divided into 3 groups according to the duration from injury to surgery. Group A (surgery within 3 days of injury) had 18 patients, group B (surgery within 3–7 days) had 18 patients, and group C (surgery later than 7 days) had 21 patients. All the groups were compared with Mann–Whitney U test; the functional improvement of spinal cord was compared and analyzed using the ASIA sports score and ASIA Impairment Scale (AIS).

Results

There was a significant improvement in the long-term AIS (final follow-up) in all the 3 groups compared to before surgery. The final follow-up recovery rate of group C was worse than group A and group B. The curative effect of operation within 7 days was significantly better than the surgery done 7 days later. The recovery rate of group C was worse than group A and B. The ASIA sports score showed that recovery was quicker in the early stage and slow in the later stage.

Conclusions

The optimal schedule of surgical treatment was 3–7 days after injury, which can significantly improve the short-term and long-term follow-up effects. Longer the time to surgery from the time of injury, the worse was the prognosis.

Multicenter study of 37 pediatric patients with SCIWORA or other spinal cord injury without associated bone lesion

BACKGROUND

Pure traumatic spinal cord injury (without associated bone lesion) are encountered in pediatric accidentology, the most typical being spinal cord injury without radiological abnormality (SCIWORA). The present study reports a multicenter series of under-18-year-olds admitted for traumatic medullary lesion. The objectives were: (1) to describe the causes of pure spinal cord injuries in children in France and their clinical presentation; (2) to identify any prognostic factors; and (3) to describe their medical management in France.

PATIENTS AND METHOD

A multicenter retrospective study was conducted in 3 pediatric spine pathology reference centers. Files of 37 patients with confirmed spinal cord injury between January 1988 and June 2017 were analyzed: SCIWORA (n=30), myelopathy associated with severe cranial trauma (n=2), and obstetric trauma (n=5). Accident causes, associated lesions, initial Frankel grade, level of clinical spinal cord injury, initial MRI findings, type of treatment and neurology results at last follow-up were collated. The main endpoint was neurologic recovery, defined by improvement of at least 1 Frankel grade.

RESULTS

Causes comprised 17 road accidents, 11 sports accidents, 5 obstetric lesions and 4 falls. Mean follow-up was 502 days. The rate of at least partial neurologic recovery was 20/30 in SCIWORA, 0/5 in obstetric trauma, and 0/4 in case of associated intracranial lesion. In SCIWORA, factors associated with recovery comprised age, accident type, and absence of initial MRI lesion.

DISCUSSION

We report a large series of pediatric spinal cord injury without associated bone lesion. This is a potentially serious pathology, in which prognosis is mainly related to age and trauma mechanism.

LEVEL OF EVIDENCE

IV, case series.

Engineering approaches to understanding mechanisms of spinal column injury leading to spinal cord injury

BACKGROUND

The mechanical interactions occurring between the spinal column and spinal cord during an injury event are complex and variable, and likely have implications for the clinical presentation and prognosis of the individual.

METHODS

The engineering approaches that have been developed to better understand spinal column and cord interactions during an injury event are discussed. These include injury models utilising human and animal cadaveric specimens, in vivo anaesthetised animals, finite element models, inanimate physical systems and combinations thereof.

FINDINGS

The paper describes the development of these modelling approaches, discusses the advantages and disadvantages of the various models, and the major outcomes that have had implications for spinal cord injury research and clinical practice.

INTERPRETATION

The contribution of these four engineering approaches to understanding the interaction between the biomechanics and biology of spinal cord injury is substantial; they have improved our understanding of the factors contributing to the spinal column disruption, the degree of spinal cord deformation or motion, and the resultant neurological deficit and imaging features. Models of the injury event are challenging to produce, but technological advances are likely to improve these models and, consequently, our understanding of the mechanical context in which the biological injury occurs.

MR T2 image classification in adult patients of cervical spinal cord injury without radiographic abnormality: A predictor of surgical outcome

OBJECTIVES

Although patients with cervical spinal cord injury without radiographic abnormality (SCIWORA) present increased signal intensity (ISI) on magnetic resonance imaging (MRI), its degree has not been examined. This study evaluated the clinical effectiveness of MRI-based ISI in adult patients of SCIWORA. Its predictive value for symptom severity was also evaluated.

PATIENTS AND METHODS

One-hundred consecutive SCIWORA patients who had undergone expansive laminoplasty were enrolled. Among them, 79 were male and 21 were female. The mean age was 55 years (range 20-87). All patients underwent MRI in the acute phase, and ISI was classified into three groups based on sagittal T2-weighted MRI: Grade 0, none; Grade 1, light (obscure); and Grade 2, intense (bright). The pre- and postoperative neurological status was evaluated using the Japanese Orthopaedic Association scoring system for cervical myelopathy (JOA score) and the ASIA impairment scale (AIS).

RESULTS

Preoperative MRI showed Grade 0 in 8 patients, Grade 1 in 49 patients, and Grade 2 in 43 patients. There were no differences in age and gender among three groups. The pre- and postoperative JOA scores decreased significantly with an increasing ISI grade. The recovery rate of JOA score decreased with the ISI grade. The ISI grade tended to increase with the pre- and postoperative AIS grades. ISI Grade 2 on MRI was observed in severely paralyzed cases.

CONCLUSIONS

MRI-based ISI classification is correlated with preoperative symptom severity in adult patients with SCIWORA and can be a predictor of surgical outcome.

Compressive mechanical characterization of non-human primate spinal cord white matter

The goal of developing computational models of spinal cord injury (SCI) is to better understand the human injury condition. However, finite element models of human SCI have used rodent spinal cord tissue properties due to a lack of experimental data. Central nervous system tissues in non human primates (NHP) closely resemble that of humans and therefore, it is expected that material constitutive models obtained from NHPs will increase the fidelity and the accuracy of human SCI models. Human SCI most often results from compressive loading and spinal cord white matter properties affect FE predicted patterns of injury; therefore, the objectives of this study were to characterize the unconfined compressive response of NHP spinal cord white matter and present an experimentally derived, finite element tractable constitutive model for the tissue. Cervical spinal cords were harvested from nine male adult NHPs (Macaca mulatta). White matter biopsy samples (3 mm in diameter) were taken from both lateral columns of the spinal cord and were divided into four strain rate groups for unconfined dynamic compression and stress relaxation (post-mortem <1-hour). The NHP spinal cord white matter compressive response was sensitive to strain rate and showed substantial stress relaxation confirming the viscoelastic behavior of the material. An Ogden 1st order model best captured the non-linear behavior of NHP white matter in a quasi-linear viscoelastic material model with 4-term Prony series. This study is the first to characterize NHP spinal cord white matter at high (>10/sec) strain rates typical of traumatic injury. The finite element derived material constitutive model of this study will increase the fidelity of SCI computational models and provide important insights for transferring pre-clinical findings to clinical treatments.

STATEMENT OF SIGNIFICANCE

Spinal cord injury (SCI) finite element (FE) models provide an important tool to bridge the gap between animal studies and human injury, assess injury prevention technologies (e.g. helmets, seatbelts), and provide insight into the mechanisms of injury. Although, FE model outcomes depend on the assumed material constitutive model, there is limited experimental data for fresh spinal cords and all was obtained from rodent, porcine or bovine tissues. Central nervous system tissues in non human primates (NHP) more closely resemble humans. This study characterizes fresh NHP spinal cord material properties at high strains rates and large deformations typical of SCI for the first time. A constitutive model was defined that can be readily implemented in finite strain FE analysis of SCI.

Biomechanical analysis of brachial plexus injury: Availability of three-dimensional finite element model of the brachial plexus

Adult brachial plexus injuries frequently lead to significant and permanent physical disabilities. Investigating the mechanism of the injury using biomechanical approaches may lead to further knowledge with regard to preventing brachial plexus injuries. However, there are no reports of biomechanical studies of brachial plexus injuries till date. Therefore, the present study used a complex three-dimensional finite element model (3D-FEM) of the brachial plexus to analyze the mechanism of brachial plexus injury and to assess the validity of the model. A complex 3D-FEM of the spinal column, dura mater, spinal nerve root, brachial plexus, rib bone and cartilage, clavicle, scapula, and humerus were conducted. Stress was applied to the model based on the mechanisms of clinically reported brachial plexus injuries: Retroflexion of the cervical, lateroflexion of the cervical, rotation of the cervical, and abduction of the upper limb. The present study analyzed the distribution and strength of strain applied to the brachial plexus during each motion. When the cervical was retroflexed or lateroflexed, the strain was focused on the C5 nerve root and the upper trunk of the brachial plexus. When the upper limb was abducted, strain was focused on the C7 and C8 nerve roots and the lower trunk of the brachial plexus. The results of brachial plexus injury mechanism corresponded with clinical findings that demonstrated the validity of this model. The results of the present study hypothesized that the model has a future potential for analyzing pathological conditions of brachial plexus injuries and other injuries or diseases, including that of spine and spinal nerve root.

The Transverse Isotropy of Spinal Cord White Matter Under Dynamic Load

The rostral-caudally aligned fiber-reinforced structure of spinal cord white matter (WM) gives rise to transverse isotropy in the material. Stress and strain patterns generated in the spinal cord parenchyma following spinal cord injury (SCI) are multidirectional and dependent on the mechanism of the injury. Our objective was to develop a WM constitutive model that captures the material transverse isotropy under dynamic loading. The WM mechanical behavior was extracted from the published tensile and compressive experiments. Combinations of isotropic and fiber-reinforcing models were examined in a conditional quasi-linear viscoelastic (QLV) formulation to capture the WM mechanical behavior. The effect of WM transverse isotropy on SCI model outcomes was evaluated by simulating a nonhuman primate (NHP) contusion injury experiment. A second-order reduced polynomial hyperelastic energy potential conditionally combined with a quadratic reinforcing function in a four-term Prony series QLV model best captured the WM mechanical behavior (0.89 < R2 < 0.99). WM isotropic and transversely isotropic material models combined with discrete modeling of the pia mater resulted in peak impact forces that matched the experimental outcomes. The transversely isotropic WM with discrete pia mater resulted in maximum principal strain (MPS) distributions which effectively captured the combination of ipsilateral peripheral WM sparing, ipsilateral injury and contralateral sparing, and the rostral/caudal spread of damage observed in in vivo injuries. The results suggest that the WM transverse isotropy could have an important role in correlating tissue damage with mechanical measures and explaining the directional sensitivity of the spinal cord to injury.

Significance of SCIWORA in adults

<sec><title>OBJECTIVE:</title><p> Recognizing the importance of SCIWORA in adult age; analyze the usefulness of complementary studies; evaluating therapeutic options; learn about the evolution of the treated patients.</p></sec><sec><title>METHODS:</title><p> A prospective evaluation with a minimum follow-up of 5 years, eight elderly patients with cervical arthrosis and diagnosis of SCIWORA. The Japanese Orthopaedic Association (JOA) scale and ASIA were used on admission and at 6, 12, 24, 36, 48 and 60 months.</p></sec><sec><title>RESULTS:</title><p> The central cord syndrome (CCS) was the neurological condition at admission. One patient recovered after corticosteroid therapy, but later, his disability worsened, and he was operated at 18 months, another patient recovered and a third died. The other patients underwent laminoplasty in the first 72 hours; patients with partial severity condition had a minimum improvement of five points in JAO scale and those with severe conditions died.</p></sec><sec><title>CONCLUSIONS:</title><p> The low-energy trauma can decompensate the relationship between container and content in the spine with asymptomatic arthrosis, and can be devastating to the patient. The diagnosis of intramedullary lesion is made by magnetic resonance imaging. Patients with incomplete deficit undergoing laminoplasty reached at least one level in ASIA score. The potential postoperative complications can be serious.</p></sec>

Significance of T2 Hyperintensity on Magnetic Resonance Imaging After Cervical Cord Injury and Return to Play in Professional Athletes

BACKGROUND:

Cervical cord magnetic resonance imaging (MRI) T2 hyperintensity is used as evidence of cord trauma in the evaluation and management of athletes in contact sports. The long-term pathophysiologic and prognostic value of this finding is poorly understood, especially in return to play (RTP).

OBJECTIVE:

To examine the significance of T2 hyperintensity in the cervical spinal cord of professional athletes.

METHODS:

Retrospective review of MRI T2 hyperintensity findings between 2007 and 2014 in 5 professional athletes. Pertinent examination and demographics, including mechanism of injury, surgical intervention, radiographs, MRI studies, long-term outcomes, and RTP recommendations were collected.

RESULTS:

Four National Football League players and 1 professional wrestler had prior traumatic neurapraxia that at the time of initial consultation had resolved. MRIs showed congenitally small cervical canal (1) and multilevel spondylosis/stenosis/disc herniation (4) along with focal cord T2 hyperintensity (5). The signal abnormalities were at C3/C4 (3), C4 mid-vertebral body (1), and C5/C6 (1). Four athletes had single-level anterior cervical discectomy and fusion, and 1 was nonoperative. Serial MRI imaging at 3 months after surgery showed hyperintensity partially resolved (4) and unchanged (1), and at 9-months 3 of the 5 completely resolved. Based on the author's RTP criteria, 4 of 5 were released to return to their sport. Clearance for RTP preceded complete resolution of MRI T2 hyperintensity in 3 of 4 athletes. The 2 athletes that have returned to profession sport have not had any additional episodes of neurapraxia or any cervical spine-related complications.

CONCLUSION:

MRI T2 hyperintensity in contact sport athletes who are symptom-free with normal examination and no evidence of spinal instability may not be a contraindication to RTP. Additional observations are needed to confirm this observation.

Nonlinear viscoelastic characterization of the porcine spinal cord

Although quasi-static and quasi-linear viscoelastic properties of the spinal cord have been reported previously, there are no published studies that have investigated the fully (strain-dependent) nonlinear viscoelastic properties of the spinal cord. In this study, stress relaxation experiments and dynamic cycling were performed on six fresh porcine lumbar cord specimens to examine their viscoelastic mechanical properties. The stress relaxation data were fitted to a modified superposition formulation and a novel finite ramp time correction technique was applied. The parameters obtained from this fitting methodology were used to predict the average dynamic cyclic viscoelastic behavior of the porcine cord. The data indicate that the porcine spinal cord exhibited fully nonlinear viscoelastic behavior. The average weighted root mean squared error for a Heaviside ramp fit was 2.8 kPa, which was significantly greater (p<0.001) than that of the nonlinear (comprehensive viscoelastic characterization method) fit (0.365 kPa). Further, the nonlinear mechanical parameters obtained were able to accurately predict the dynamic behavior, thus exemplifying the reliability of the obtained nonlinear parameters. These parameters will be important for future studies investigating various damage mechanisms of the spinal cord and studies developing high-resolution finite elements models of the spine.

Quantification of pediatric and adult cervical vertebra-anatomical characteristics by age and gender for automotive application

OBJECTIVE

The cervical anatomy has been shown to affect injury patterns in vehicle crashes. Characterizing the spine anatomy and changes associated with growth and gender is important when assessing occupant protection. In this study, selected cervical characteristics were quantified.

METHODS

Computed tomography (CT) scans of 750 patients were selected from the University of Michigan trauma database; 314 were children and 436 were adults. Four variables were obtained: the maximum spinal canal radius, vertebral body depth, facet angles, and retroversion angles.

RESULTS

The cervical spine measurements varied with age and gender. The body depth increased nonlinearly with age. The average vertebral body depth at C4 was 9.2 ± 0.38 mm in the 0-3 age group, 15.7 ± 0.29 mm in the 18-29 age group, and 17.2 ± 0.46 mm in the 60+ age group. Pediatric and adult males had larger vertebral body depth than females overall, irrespective of vertebral level (P <.001). Compared to females, the vertebral body depth was 8-9 percent greater in male children and 13-16 percent greater in adult males. The average radius varied with gender, with male children generally having a larger radius than females irrespective of vertebral level (P <.001). Overall, spinal canal radius was smallest in the 0-3 and 60+ age groups and largest in the 18-29 age group. The C4 radius was 5.91 ± 0.17, 6.28 ± 0.14, and 6.73 ± 0.17 mm respectively. The radius was larger in the 4-7 age group than in the 0-3 age group, irrespective of vertebral level (P <.0001). There were nonsignificant radius changes between the 4-7 and 8-11 age groups and the 8-11 and age 12-17 groups, suggesting that the size of the spinal cord reaches near maturation by the age of 7. Facet angles decreased with age in children and increased with age in adults. The average facet angles were largest in the 0-3 age group (P <.1, C2-C6). Adult facet angles were greater in the 60+ age group than in the 18-29 age group (P <.0001, C2-C6). Males had larger facet angles than females overall (P <.01 at C2, C5-C7). The retroversion angles were largest at C6 and C7. They increased with age in children and decreased in the adult population; they were larger (5-22%) in the 18-29 age group than in the 60+ age group (P <.0001, C2-C6).

CONCLUSIONS

The results obtained in this study help explain variations in cervical anatomical changes associated with age and gender. The information is useful when assessing differences in injury patterns between different segments of the population. Anatomical measurements of the cervical spine should be considered for the development of models used to assess injury mechanisms for various occupant age groups.

Predictores en el cuadro SCIWORA del adulto

OBJETIVOS: Analizar cinemática, reconocer cuadro clínico de presentación, describir imágenes, considerar posibilidades terapéuticas y evaluar evolución. MÉTODO: Se analizan 13 pacientes del sexo masculino que presentaron SCIWORA (en inglés Spinal cord injury without radiographic abnormality) entre el 2005 al 2012. Se evalúan cuadro clínico, tratamiento, complicaciones y evolución. RESULTADOS: 10 pacientes mayores de 45 años presentaban signos de espondiloartrosis con mínimos síntomas. De los tres menores de esta edad solo uno presentaba estenosis de canal constitucional asintomática. Todos sufrieron trauma de baja energía. En la resonancia magnética prevaleció el hematoma intramedular y clínicamente todos los pacientes presentaban un síndrome medular central, con cuadro severo (ASIA A-B) en los mayores de 45 años. Siete pacientes fueron tratados inicialmente en forma conservadora; un paciente empeoró y tuvo que ser sometido a intervención quirúrgica 18 meses después y otro falleció en las primeras horas, el resto de los pacientes tuvieron buena evolución. Seis pacientes requirieron cirugía (laminoplastía) en los primeros 10 días; tres fallecieron y el resto mejoro por lo menos un nivel ASIA. CONCLUSIONES: La menor edad, los cuadros leves y el edema intramedular son factores de buen pronóstico y se ven favorecidos con el tratamiento conservador. La mayor edad, la espondiloartrosis y los cuadros severos o progresivos, son factores de mal pronóstico y puede ser necesario su tratamiento quirúrgico.

Cervical spinal cord contusion in professional athletes: a case series with implications for return to play

STUDY DESIGN

Retrospective case series.

OBJECTIVE

This report provides long-term follow-up on athletes who have sustained a cervical spinal cord contusion. Their magnetic resonance (MR) image is correlated with clinical signs and symptoms. Mechanism of injury and a hypothesis of etiology are reported.

SUMMARY OF BACKGROUND DATA

Current return-to-play criteria for athletes who sustain a cervical cord contusion are based on expert opinion only. Decision making for this clinical situation in athletes carries significant clinical, legal, and economic ramifications. The natural history, clinical correlation, and effect of surgery for athletic cervical cord contusions have not been established. The mechanism of injury for this entity has historically emphasized axial loading.

METHODS

The case histories, physical examination, and MR images were reviewed for 4 professional athletes. All athletes had documented cervical cord contusions. None of the athletes had an acute disc herniation, fracture, instability, or focal cord compression. All athletes were contacted by telephone to assess symptoms at a minimum follow-up of 2 years after injury.

RESULTS

All 4 athletes had congenital stenosis, defined as lack of CSF signal around the cord on an MR image. All underwent anterior fusions at the level of their contusion. In follow-up, 2 athletes developed new contusions: one more than 5 years later, adjacent to a fusion; and 1, 2 years later, not adjacent to his previous fusion. No athlete developed permanent neurological sequelae. The presence of a contusion did not correlate with athletes' signs and symptoms. The mechanism of injury was hyperextension.

CONCLUSION

It is hypothesized that the horizontal facet orientation of the C3-C4 level, congenital stenosis, and relative hypermobility in extension are the contributing factors in the cause of this clinical entity. An anterior fusion at the C3-C4 level seems to be the most reliable method of preventing or delaying the return of symptoms. Return-to-play guidelines should emphasize the athletes' history of symptoms in context with their MR image because there is poor correlation between the finding of a contusion and the clinical presentation. Recurrence of symptoms is common and the long-term consequences of repeated episodes remain unknown.

Soft-tissue damage and segmental instability in adult patients with cervical spinal cord injury without major bone injury

STUDY DESIGN

A retrospective imaging and clinical study.

OBJECTIVE

To evaluate the extraneural soft-tissue damage and its clinical relevance in patients with traumatic cervical spinal cord injury (SCI) without major bone injury.

SUMMARY OF BACKGROUND DATA

To date, various kinds of cervical discoligamentous injuries have been demonstrated on magnetic resonance images in patients with SCI without bony injury. However, it has not been clear whether these magnetic resonance imaging abnormalities are actually related to spinal segmental instability and the patients' neurological status.

METHODS

Eighty-eight adult patients with acute traumatic cervical SCI without major bone injury were examined by flexion-extension lateral radiographs and magnetic resonance images within 2 days after trauma. We excluded patients with flexion recoil injury; therefore, most of the patients included were considered to have sustained a hyperextension injury. Instability of the injured cervical segment was defined when there was more than 3.5-mm posterior translation and/or more than a 11° difference in the intervertebral angle between the site of interest and adjacent segments. The neurological status was evaluated according to the American Spinal Injury Association motor score.

RESULTS

On magnetic resonance images, the damage to the anterior longitudinal ligament and intervertebral disc were apparent in 44 and 37 patients, respectively. Various degrees of prevertebral fluid collection (prevertebral hyperintensity) were demonstrated in 76 patients. These magnetic resonance imaging abnormalities were significantly associated with initial cervical segmental instability as judged by flexion-extension radiographs. Interestingly, the American Spinal Injury Association motor score had a significant association with either magnetic resonance imaging abnormalities or segmental instability but not with the cervical canal diameter.

CONCLUSION

A considerable proportion of the patients with traumatic cervical SCI without major bone injury were shown to have various types of soft-tissue damage associated with cervical segmental instability at the early stages of the injury. The severity of paralysis greatly depended on these discoligamentous injuries.

Epidemiological characteristics of adult SCIWORA in Tianjin, China: a preliminary study

INTRODUCTION

The epidemiology of spinal cord injury without radiographic abnormality (SCIWORA) is less frequently reported in adults as compared with children. The annual incidence of SCIWORA was approximately 5.74% per million in Tianjin from 2004 to 2008. Importantly, the epidemiological characteristics of adult SCIWORA may be different from that in children. The aim of this study was to evaluate the radiological-clinical data of patients with adult SCIWORA, and to relatively analyze the epidemiological features.

MATERIALS AND METHODS

Inpatients with cervical SCIWORA who were 16 and above in Tianjin were admitted in municipal hospitals in Tianjin from 2004 to 2008; all the patients received MRI scanning in sagittal and axial views. Epidemiological characteristics, such as injury origin, injury level or severity, neurological scale and MRI feature were acquired.

RESULTS

In total, 203 patients were enrolled. The average age among the adult groups was 55.9 years (men 55.8 years, women 53.6 years). SCIWORA occurred more commonly in adults in the 46-60 age group, and falls were the leading cause of injury (52.2%), followed by vehicular injury (28.6%). The most predominantly affected level was C4/5 (48.7%), followed by C5/6 (30.5%) and C3/4 (12.8%), respectively. The occurrence of central cord syndrome (50.2%) with posterior longitudinal ligament tear (43.8%) was relatively higher than other injury patterns.

CONCLUSION

It is clear that adult cervical SCIWORA is different from that in the pediatric group. Our study highlights the epidemiological properties of adult SCIWORA in Tianjin, China. Differing from other reports, particularly epidemiology study, we represent the first report regarding adult SCIWORA from China. As the geriatric population increases, it is very important to set up an individualized evaluation system based on a nationally scaled epidemiological database. The results from our study will be useful in assisting in the creation of such a database.

Can magnetic resonance imaging reflect the prognosis in patients of cervical spinal cord injury without radiographic abnormality?

STUDY DESIGN

This is a prospective imaging study of adult patients with cervical spinal cord injury without radiographic abnormality (SCIWORA).

OBJECTIVE

The purpose of this study was to investigate the occurrence rate of intramedullary high-signal intensity (increased signal intensity [ISI]) and prevertebral hyperintensity (PVH) in patients with SCIWORA, and examine their relationship to symptom severity and surgical outcome.

SUMMARY OF BACKGROUND DATA

SCIWORA is accompanied by the presence of neurologic symptoms in the absence of positive radiographic findings before the emergence of magnetic resonance imaging (MRI). There are few reports regarding the image features on MRI in these patients.

METHODS

One-hundred consecutive patients with SCIWORA who had undergone expansive laminoplasty were enrolled. There were 79 men and 21 women; the mean age was 55 years (range, 16-87 years). All patients underwent functional x-ray and MRI in the acute phase. On MR T2-weighted imaging sagittal view, occurrence of ISI and PVH was evaluated. Range of ISI and PVH was measured relative to C3 vertebral height. Japanese Orthopaedic Association (JOA) scoring system for cervical myelopathy (JOA score), it's recovery rate, and ASIA impairment scale were used to evaluate neurological status.

RESULTS

ISI was observed in 92 patients and PVH in 90 patients on MRI preoperatively. The range of ISI and PVH tended to increase with scores on the preoperative ASIA scale. ISI and PVH were seen in all patients with ASIA A and B. There was a significant negative correlation between the range of ISI and preoperative JOA score. A significant negative correlation between the range of ISI and recovery rate of JOA score was also seen.

CONCLUSION

ISI and PVH occurred in more than 90% of patients with SCIWORA. The range of ISI significantly reflected symptom severity and prognosis for neurologic outcome.