Development of patient specific guides for posterior pedicle screw insertion for Scoliosis patients

Scoliosis correction surgery involves insertion of screws in the spine (called pedicle screws), and these screws then provide anchor points for metal rods to straighten the spine. Currently, the techniques to insert these screws are not completely accurate. During “freehand” technique surgeons estimate the direction of the spine and insert the screws according to anatomical landmarks. Even in international experts’ hands, 25-30% of the screws are not inserted in the correct position. Misplacement of screw has a high risk of bone weakening or injuries to the spinal cord, nerve roots or blood vessels. Getting screw placement wrong could essentially means patients not able to walk again. More accurate methods use computer navigation or image guidance techniques. However, these involve using more radiation (X-rays, CT scans) before or during the operation. Therefore, there is the need to solve this problem, to improve patient safety for screw insertion during scoliosis surgery.

This study aims to improve the accuracy of placing screws in the spine during surgery to correct scoliosis. Using the patients’ routine CT or MRI scans before the surgery, screw insertion guides can be manufactured for each spinal level so that the screws are inserted accurately. These guides will be produced using 3D printing, so that each guide is completely specific to the patient and to each level of the spine. This approach is safe and can reduce amount of radiation patient exposed before or during surgery. Devices will be lower in cost compared to currently used invasive devices, thus provide low cost but effective solution for our patients and NHS.

This research has a direct impact on safety and wellbeing of both patients and surgical team involved in scoliosis surgery.

1. Minimize radiological exposer during spinal surgery for scoliosis patients and surgical team.CT Scans are widely used to verify the correct insertion of the pedicle screws during spinal surgery for scoliosis patients. Exposure to CT radiation to patients is of concern to both patients and clinical team. Primary reason for using CT scan is to verify correct positioning of posterior pedicle screw insertion during surgery. Pedicle screw placement is mainly done by experience surgeons and require enhance knowledge of anatomy and surgical experience to reduce chances of screw misplacement. As this has a direct implication on patient’s safety.This research projects aims to address this challenge by providing customized pedicle screw placement guides, which are manufactured based on patients’ images (CT/BBMRI MRI scans) taken during their diagnosis. This is expected to match with patient’s anatomy and help in accurate placement of pedicle screws and reduce use of X-rays for further validation during surgery.

2. Minimizing the surgery time and improving the operability for the surgical unit.As the surgery is pre-planned and we already know where to place the screws and in what angle, it will not be necessary to take radiologic postsurgical images.This will directly impact decreasing the surgery time and the risks associated with it such as reduced amount of anaesthesia, less open surgery exposer, tiredness of the surgeon, risk of infection, etc.

3. Minimize the learning curve of the surgeons.The pedicle screw insertion guides would not require as much experience as the current free hand technique used by experienced surgeons. They will be able to go from training to the operation room in a very short period and without compromising patient safety. They will be able to use model generated through this project to practice screw placement process using customise templates. This will increase the availability of specialized surgeons and streamline the patient treatment care, especially in urgent cases.