Epidemiology of spinal fractures and associated spinal cord injuries in Iceland.

STUDY DESIGN: A retrospective epidemiological study. SETTING: Landspítali University Hospital, Iceland. OBJECTIVES: Assessment of epidemiological data and risk factors for traumatic spinal fractures (SFs) and associated spinal cord injury (SCI). METHODS: A retrospective review of hospital admissions due to traumatic SFs during a 5-year period, with analysis of epidemiological parameters and occurrence of concomitant SCI. Patients with asymptomatic SFs and non-traumatic SCI were excluded. RESULTS: A total of 487 patients were diagnosed with a SF or 310 PMI (per million inhabitants), 42 of them (9%, 27 PMI) with an associated SCI. The mean age was 56 years, males were 57%. Falls were the leading cause of both SFs (49%) and SCIs (43%). Low falls (<1 m) caused SFs more often in elderly women (67%, mean age 77 years) and more than 96% were without SCI. Road traffic accidents (RTA) caused 31% of SFs and 26% of SCIs. Seat belts were not used in 20% of car accidents, but information was missing in 27%. Sports/leisure-related accidents caused SFs in 12% of cases, whereof horseback riding accidents were the most common (36%). CONCLUSIONS: SFs led to SCI in 9% of patients. Several risk factors were common for SFs and SCIs but two major differences were seen: SFs without SCI were most common in older women due to low falls, while the risk of a concomitant SCI increased in young patients, in males, in falls from high levels and when driving without using seat belts. Preventive efforts should therefore be directed towards these risk factors.

[Epidemiology of Spinal Cord Injury in Iceland from 1975 to 2014].

INTRODUCTION: Traumatic spinal cord injury (TSCI) is serious and often has long-term consequences. Since no cure has been found the emphasis has been on preventive measures. The incidence of TSCI varies between countries and the epidemiology has been changing. The aim of this study was to gather epidemiological data on patients with TSCI in Iceland and search for risk factors. MATERIAL AND METHODS: Hospital records of everyone diagnosed with TSCI in 1975-2014 admitted to Landspitali University Hospital were reviewed and information gathered on incidence, age, gender and causes of injury. The American Spinal Injury Association Impairment Scale (AIS) was used to assess the extent of TSCI. RESULTS: A total of 233 patients were diagnosed with TSCI during the study period or 26 per million annually on average. Males were 73% and the mean age was 39 years. Traffic accidents were the most common cause of TSCI. The majority were car rollovers in rural areas. Around 50% did not use a seatbelt. The second most common cause of TSCI were falls. The most common sport/leisure accidents were those related to horseback-riding and winter sports. A third of patients had a complete SCI. At discharge 9% had gained full recovery. CONCLUSIONS: Safe roads and good traffic culture are essential factors in the prevention of serious traffic accidents. Strict safety regulations in the work place and an investigation of causes of falls amongst the elderly could decrease SCIs due to falls. Further preventive measures and protective equipment could possibly be of use in sport- or leisure-related activities. Key words: Traumatic spinal cord injury, incidence, age, gender, causes, extent. Correspondence: Pall E. Ingvarsson, palling@landspitali.is.

Finite Element Modelling of the Femur Bone of a Subject Suffering from Motor Neuron Lesion Subjected to Electrical Stimulation.

Bone loss and a decrease in bone mineral density is frequently seen in patients with motor neuron lesion due to lack of mechanical stimulation. This causes weakening of the bones and a greater risk of fracture. By using functional electrical stimulation it is possible to activate muscles in the body to produce the necessary muscle force to stimulate muscle growth and potentially decrease the rate of bone loss. A longitudinal study was carried out on a single patient undergoing electrical stimulation over a 6 year period. The patient underwent a CT scan each year and a full three dimensional finite element model for each year was created using Mimics (Materialise) and Abaqus (Simulia) to calculate the risk of fracture under physiologically relevant loading conditions. Using empirical formulas connecting the bone mineral density to the stiffness and ultimate tensile stress of the bone, each element was assigned a unique material property, based on its density. The risk of fracture was estimated by calculating the ratio between the predicted stress and the ultimate tensile stress, should it exceed unity, failure was assumed. The results showed that the number of elements that were predicted to be at risk of failure varied between years.

Quantitative color three-dimensional computer tomography imaging of human long-term denervated muscle.

OBJECTIVES: A new non-invasive method was developed to analyse macroscopic and microscopic structural changes of human skeletal muscle based on processing techniques of medical images, here exemplified by monitoring progression and recovery of long-term denervation by home based functional electrical stimulation. METHODS: Spiral computer tomography images and special computational tools were used to isolate the quadriceps muscles and to make three-dimensional reconstructions of denervated muscles. Shape, volume and density changes were quantitatively measured on each part of the quadriceps muscle. Changes in tissue composition within the muscle were visualized associating Hounsfield unit values of normal or atrophic muscle, fat and connective tissue to different colors. The minimal volumetric element (voxel) is approximately ten times smaller than the volume analysed by needle muscle biopsy. The results of this microstructural analysis are presented as the percentage of different tissues (muscle, loose and fibrous connective tissue, and fat) in the total volume of the rectus muscle and displaying the first cortical layer of voxels that describe the muscle epimysium directly on the muscle three-dimensional reconstruction. RESULTS: In normal and paraplegic patients, this new monitoring approach provides information on macroscopic shape, volume, and the increased adipose and fibrous tissue content within the denervated muscle. In particular, the change displayed at epimysium level is structurally important and possibly functionally relevant. Here we show that muscle restoration induced by homebased functional electrical stimulation is documented by the increase in normal muscle tissue from 45 to 60% of the whole volume, while connective tissue and fat are reduced of 30 and 50% with respect to the pre-treatment values. These changes are in agreement with the muscle biopsy findings, and self-evident when epimysium thickness is depicted. CONCLUSION: Color three-dimensional imaging of human skeletal muscle is an improved computational approach of non-invasive medical imaging able to detect not only macroscopic changes of human muscle volume and shape, but also their tissue composition at microscopic level.

Restoration of muscle volume and shape induced by electrical stimulation of denervated degenerated muscles: qualitative and quantitative measurement of changes in rectus femoris using computer tomography and image segmentation.

This study demonstrates in a novel way how volume and shape are restored to denervated degenerated muscles due to a special pattern of electrical stimulation. To this purpose, Spiral Computer Tomography (CT) and special image processing tools were used to develop a method to isolate the rectus femoris from other muscle bellies in the thigh and monitor growth and morphology changes very accurately. During 4 years of electrical stimulation, three-dimensional (3D) reconstructions of the rectus femoris muscles from patients with long-term flaccid paraplegia were made at different points in time. The growth of the muscle and its changes through the time period are seen in the 3D representation and are measured quantitatively. Furthermore, changes in shape are compared with respect to healthy muscles in order to estimate the degree of restoration. The results clearly show a slow but continuing muscle growth induced by electrical stimulation; the increase of volume is accompanied by the return of a quasi-normal muscle shape. This technique allows a unique way of monitoring which provides qualitative and quantitative information on the denervated degenerated muscle behavior otherwise hidden.

Monitoring muscle growth and tissue changes induced by electrical stimulation of denervated degenerated muscles with CT and stereolithographic 3D modeling.

In the frame of the EU-funded RISE project, patients with lower motor neuron lesion and denervated and degenerated muscles are treated with electrical stimulation, with the aim of restoring muscle mass and force. Spiral computer tomography from the hip joint down to the knee joint is used to gather three-dimensional data on the upper leg tissue. These data are analyzed in order to monitor tissue changes induced by the electrical stimulation treatment. Especially the data representing muscle tissue and bone tissue were isolated for measurement purposes. Computer models and models made with rapid prototyping methods were used to display and demonstrate changes in muscle shape and size, as well as position relative to bone. Results showed that time and spatial dependencies of muscle growth can be monitored and studied quantitatively and qualitatively with the aid of a three-dimensional data set displayed on the computer screen or in the form of plastic models. These first results indicate muscle growth and an increase in bone density.