Study design. Literature review of the best available evidence on the accuracy of computer assisted pedicle screw insertion. Background. Pedicle screw misplacement rates with the conventional insertion technique and adequate postoperative CT examination have ranged from 5 to 29 % in the cervical spine, from 3 to 58 % in the thoracic spine, and from 6 to 41% in the lumbosacral region. Despite these relatively high perforation rates, the incidence of reported screw-related complications has remained low. Interestingly, the highest rates of neurovascular injuries have been reported from the lumbosacral spine in up to 17% of the patients. Gertzbein and Robbins introduced a 4-mm “safe zone” in the thoracolumbar spine for medial encroachment, consisting of 2-mm of epidural and 2-mm of subarachnoid space. Later, several authors have found the safety margins to be significantly smaller, suggesting that the “safe zone” thresholds of Gertzbein and Robbins do not apply to the thoracic spine, and seem to be too high even for the lumbar spine. The midthoracic and midcervical spine, as well as the thoracolumbar junction set the highest demands for accuracy in pedicle screw insertion, with no room for either translational or rotational error at e.g. T5 level. Computer assisted pedicle screw insertion (navigation) was introduced in the early 90's to increase the accuracy and safety of pedicle screw insertion. Material. PubMed literature search revealed two randomized controlled trials (RCT) comparing the in vivo accuracy of conventional and computer assisted pedicle screw insertion techniques. Three meta-analyses have assessed the published reports on the accuracy of pedicle screw insertion with or without computer assistance, one additional meta-analysis concentrated on the functional outcome of computer assisted pedicle screw insertion. Results. The RCTs by Laine et al and Rajasekaran et al achieved significantly higher screw placement accuracy with computer assistance than with the conventional techniquebased on anatomical landmarks. In a degenerative patient population, Laine et al reported a misplacement rate of 4.6% with computer assistance compared to 13.4% with the conventional technique. In addition to this quantitative difference, a qualitative difference in the misplaced screws was noticed: in the conventional group, 28 out of 37 misplaced screws were either inferior or medial, whereas in the computer assisted group, 1 out of 10 misplaced screws was situated in these ”danger zones”. In deformity surgery, Rajasekaran et al reported a 2% pedicle screw misplacement rate with a computer assisted technique compared to 23% with the conventional technique. Interestingly, in their study, the average screw insertion time in the computer assisted group was significantly shorter than with the conventional technique. The three meta-analyses, assessing up to 37 337 pedicle screws, reported significantly higher accuracy in the placement of pedicle screws with computerassistance compared with the conventional methods. The superiority of the computer assisted technique was even more obvious with abnormal surgical anatomy. CT-based and 3D-fluoroscopy-based navigation methods provided better accuracy compared to 2Dfluoroscopy-based navigation. No statistically significant benefit with computer assistance in the incidence of neuro-vascular complications, or in functional outcome was demonstrated. Conclusion. High pedicle screw misplacement rates have been reported with the conventional technique based on anatomical landmarks and intraoperative fluoroscopy. The concept of ”safe zone” is hypothetical, and underestimates the true risks of misplaced pedicle screws. Computer assistance significantly improves the accuracy and safety of pedicle screw insertion. It will, however, be difficult to correlate this increased accuracy to improved patient outcomes

Computer assisted surgery is becoming more prevalent in spinal surgery with most published literature suggesting an improvement in accuracy and reduction in radiation exposure. This has been particularly highlighted in scoliosis surgery with regard to the placement of pedicle screws. Anecdotally this has been challenged with concerns with regard to the steep learning curve using this equipment and the high cost of purchasing said systems. The more traditional technique utilises the surgeon's knowledge of anatomic landmarks and tactile palpation added with fluoroscopy to place pedicle screws. We retrospectively looked at 161 scoliosis corrections performed using this technique over three years by 3 main surgeons at the same centre (Frenchay). With an average of 10 levels per procedure and over 2000 pedicle screws inserted. We reviewed the radiation time exposure and dose of radiation given during each case. Our results compared favourably to published data using computer and robot assisted surgery with an average exposure time of 80 seconds and a mean dose of 144 mGy using a standard C-arm guided fluoroscopy. Our study suggests that armed with good surgical knowledge and technique it is possible to obtained low levels of radiation exposure of benefit to both patient and the operating team

To determine the current practice of scoliosis surgery in the UK. A 10 point questionnaire was constructed to identify the philosophy of surgeons on various aspects of scoliosis surgery such as choice of implant, bone graft, autologous blood transfusion (ABT), cord monitoring and computer assisted surgery. Results are compared with the current best evidence. Consultants and Fellows attending the 2009 British Scoliosis Society meeting. 50 questionnaires were completed: 45 Consultants and 5 Fellows. All pedicle screw construct favored by 25/50, hybrid 24/50 (one undecided). Posterior construct of less than 10 levels, 20/50 would not cross-link, 11/50 used one and 19/20 used two or more. More than ten levels 17/50 considered cross-links unnecessary, 4/50 used one and 29/50 used two or more. 88% preferred titanium alloy implants, while a mixture of stainless steel and cobalt chrome was used by others. For bone graft, substitutes (24), iliac crest (14), allograft (12) and demineralised bone matrix (9) in addition to local bone. 10/50 would use recombinant bone morphogenetic protein (3 for revision cases only). 39/50 routinely used intra-operative cell salvage or ABT drains and 4/50 never used autologous blood. All used cord monitoring, Sensory (19/50), Motor (2/50) and combined (29/50). None used computer-aided surgery. 26 operated alone 12 operated in pairs and 12 varied depending on type of case. This survey has brought to light interesting variations in scoliosis surgery in UK. It may reflect the conflicting evidence in the literature