(ii) Thoracolumbar spinal fractures: review of anatomy, biomechanics, classification and treatment Grzegorz Rudol Nigel W Gummerson Abstract The management of thoracolumbar spine fractures remains a controver- sial issue. There is disagreement both as to how to describe these injuries and how to manage them. No ideal classification system, accepted by the world of spinal surgery, exists and such systems are under on-going development. While the ma- jority of these injuries can be managed conservatively, new surgical tech- niques have been developed alongside the evolution of diagnostic tools classification systems. This article aims to revise important concepts that may help surgeons in training to understand spinal injuries and the modern approach to the management of thoracolumbar trauma. We describe relevant thoracolumbar spine anatomy and biomechanics followed by a discussion of historical and modern classification systems, and the treatment methods available to surgeons. Keywords classification; spinal fracture management; thoracolumbar fracture Introduction Spinal fractures are less frequent than limb fractures, but generate significant interest in trauma surgery. Spinal trauma results in the poorest functional outcomes and the lowest rates of return to work after injury of all major organ system trauma. 1 Around 1000 patients in the UK sustain a spinal cord injury each year. In 2012 there were approximately 13,000 thor- acolumbar fractures in England and Wales. It is estimated that there were over 100,000 osteoporotic vertebral fractures; one quarter of these came to medical attention. The treatment of unstable spinal fractures has evolved dramatically over the past three decades, building on the ad- vances we have seen since the start of the 20th century. The availability of safe and effective surgical stabilization provides an attractive alternative for many patients who would otherwise be managed by a prolonged period of bed rest. However, it is important to remember that bone heals naturally and many fractures may be treated non-surgically. The goal of treatment is the same in all cases; identify and treat associated injuries, preserve neurological function, restore mobility, restore spinal stability and relieve pain. Thoracolumbar spine anatomy and biomechanics The spine’s mobility is facilitated by its segmentation. The spine comprises 29 vertebrae (cervical, thoracic, lumbar and sacral) and at birth it is C-shaped in the sagittal plane (kyphotic). It is straight in the coronal plane and should remain so. The cervical lordosis and lumbar lordosis develop as the child develops head control and starts to walk. The sagittal profile continues to develop during growth. The degree of thoracic spine kyphosis varies and is reported to be normal within the 10e40  range (Cobb’s measurement be- tween the upper endplate of the T5 vertebra and the inferior endplate of T12). Lumbar lordosis measured between the supe- rior endplate of T12 and the superior endplate of S1 is described as normal within the range of 40e60  . 2 In the standing position the vertebral column is subject to gravitational forces creating forward bending moments, as the center of gravity lies ventral to the S1 vertebra. This creates significant compressive forces across the vertebral bodies with the posterior ligamentous complex and paraspinal musculature loaded in tension. Fractures through the vertebral body will shift the axis of rotation posteriorly at the affected segment level, increasing its distance from the center of rotation. This increases the bending moment acting on the spine and shortens the lever arm of the posterior muscles and ligaments adding to potential instability. The rib cage and the sternum reinforce the overall resistance of the thoracic segment with the sternum being often described as the 4th column in spinal stability concept. The thoracolumbar junction, being the transitional zone between this relatively stiff thoracic and the mobile lumbar spine, is particularly susceptible to injuries. Vertebrae The thoracolumbar vertebra may be divided into three compo- nents: vertebral body, pedicles and posterior elements (Figure 1). Vertebral size increases from cranial to caudal in all three planes. The body is adapted to resist compressive loads. It consists of cancellous bone with an outer shell of cortical bone. Finite- element analysis suggests that it is the microarchitecture of the trabecula that give the vertebra its mechanical properties and the cortical shell is less important. As a simplification, one could consider the internal trabecula as being organized in vertical load-bearing struts connected by horizontal cross-beams adding to the overall resistance to deformity and failure, either in single or cyclic loading (Figure 2). Such a structure provides better resistance to dynamic loads compared to that of a solid block, which would resist static loads better. The posterior elements of the vertebra are the laminae, the articular, transverse and spinous processes. The articular pro- cesses of two consecutive vertebrae interlock at the facet joints. In the thoracic spine their articulating surfaces are relatively Grzegorz Rudol MSc FRCS (Tr & Orth) Specialist Registrar in Trauma and Orthopaedics, Spine Unit, Leeds General Infirmary, Leeds, United Kingdom. Conflicts of interest: none. Nigel W Gummerson MA FRCS (Tr & Orth) Consultant Spinal Surgeon, Spine Unit, Leeds General Infirmary, Leeds, United Kingdom. Conflicts of in- terest: none. MINI-SYMPOSIUM: SPINAL TRAUMA ORTHOPAEDICS AND TRAUMA 28:2 70 Ó 2014 Elsevier Ltd. All rights reserved.