Present-day sedentary lifestyle and problems with overweight and aging are reflected in an increased number of spine and spine-related diseases. Surgical interventions are the preferred treatment for patients with acute disorders or traumatic spine injuries, and are inevitable when other approaches, e.g. painkillers, physiotherapy or bracing, are not effective. Vertebral fixation is a surgical procedure for treating conditions such as scoliosis, kyphosis, spondylolisthesis and other degenerative conditions that cause instability of the spine. As spinal instability may cause damage to the spinal cord and nerve roots, the aim of vertebral fixation is to reduce vertebral mobility and, as a result, avoid such damage. The vertebral fixation procedure is based on anchoring two (or more) vertebrae to each other by metal fixation devices such as rods, plates and/or screws. One of the most widely used fixation techniques is pedicle screw placement, which consists of inserting screws through vertebral pedicles from the posterior side so that they reach the interior of the vertebral body, and then attaching a stabilizing rod to the exterior part of the screws on each side of the vertebra. As there is a limited visibility of anatomical structures during surgery, it is important to gain a mental conceptualization and reconstruction of the three-dimensional (3D) anatomy of spinal structures that are hidden from direct view. For a safe pedicle screw placement, the spine surgeon has to perform proper surgery planning by taking into account pedicle morphology (shape and structure), and choosing the appropriate size (diameter and length) and insertion trajectory (entry point and inclination) of each pedicle screw, which has proved valuable for reducing the risk of screw misplacement. As a result, preoperative surgery planning has become essential for pedicle screw placement, during which the surgeon on the basis of 3D spine images accurately studies the anatomy of the treated patient. Preoperative imaging is therefore necessary for reliable surgery planning, and computed tomography (CT) proved to be the imaging modality of choice for assessing the bone structures forming the spine and vertebrae. Modern computer software allows the surgeon to manually plan the size and insertion trajectory of each pedicle screw by navigating through 3D images and manipulating with 3D models of the spine, vertebrae and screws in 3D space. However, human capability of surgery planning by proper interpretation of medical images is limited due to our nonsystematic search patterns and natural biological variability of human anatomy, while the presence of noise may conceal actual geometrical relationships between anatomical structures. As a result, surgery planning is a relatively time-consuming task, and its reliability and accuracy depend on the subjective interpretation of the surgeon. Our research objective is to achieve a quantitative, objective and reproducible evaluation of vertebral morphology from 3D spine images, especially of the morphology of pedicles and vertebral bodies for the purpose of preoperative planning of vertebral fixation by pedicle screw placement procedures. For this purpose, we will develop new computer-assisted techniques that will be based on automated processing and quantitative analysis of 3D spine images, and as such contribute to an improved planning of pedicle screw placement procedures as well as of other spine surgical procedures that require an accurate evaluation of vertebral morphology. The topic of this research project is therefore to develop and validate new techniques for automated computer-assisted quantitative analysis of 3D images for spine surgery planning.
