Study design. Retrospective study. Objectives. To optimise the radiation doses and image quality for the cone-beam O-arm surgical imaging system in spinal surgery. Summary of Background. Neurovascular compromise has been reported following screw misplacement during thoracic pedicle screw insertion. The use of O-arm with or without navigation system during spinal surgery has been shown to lower the rate of screw misplacement. The main drawback of such imaging surgical systems is the high radiation exposure. Methods. Chest phantom and cadaveric pig spine were examined on the O-arm with different scan settings: two were recommended by the O-arm manufacturer (120 kV/320 mAs, and 120 kV/128 mAs), and three low-dose settings (80 kV/80 mAs, 80 kV/40 mAs, and 60 kV/40 mAs). The radiation doses were estimated by Monte Carlo calculations. Objective evaluation of image quality included interobserver agreement in the measurement of pedicular width in chest phantom and assessment of screw placement in cadaveric pig spine. Results. The effective dose/cm for 120 kV/320 mAs-scan was 13, 26, and 69 times higher than those delivered with 80 kV/80 mAs, 80 kV/40 mAs, and 60 kV/40 mAs-scans, respectively. Images with 60 kV/40 mAs were unreliable. Images with 80 kV/80 mAs were considered reliable with good interobserver agreement when measuring the pedicular width (random error 0.38 mm and intraclass correlation coefficient 0.979) and almost perfect agreement when evaluating the screw placement (κ-value 0.86). Conclusions. The radiation doses of the O-arm system can be reduced 5–13 times without negative impact on image quality with regard to information required for spinal surgery

In foot and ankle surgery incorrect placement of implants, or inaccuracy in fracture reduction may remain undiscovered with the use of conventional C-arm fluoroscopy. These imperfections are often only recognized on postoperative computer tomography scans. The apparition of three dimensional (3D) mobile Imaging system has allowed to provide an intraoperative control of fracture reduction and implant placement. Three dimensional computer assisted surgery (CAS) has proven to improve accuracy in spine and pelvic surgery. We hypothesized that 3D-based CAS could improve accuracy in foot and ankle surgery. The purpose of our study was to evaluate the feasibility and utility of a multi-dimensional surgical imaging platform with intra-operative three dimensional imaging and/or CAS in a broad array of foot and ankle traumatic and orthopaedic surgery. Cohort study of patients where the 3D mobile imaging system was used for intraoperative 3D imaging or 3D-based CAS in foot and ankle surgery. The imaging system used was the O-arm Surgical Imaging System and the navigation system was the Medtronic's StealthStation. Surgical procedures were performed according to standard protocols. In case of fractures, image acquisition was performed after reduction of the fracture. In cases of 3D-based CAS, image acquisition was performed at the surgical step before implants placement. At the end of the operations, an intraoperative 3D scan was made. We used the O-arm Surgical Imaging system in 11 patients: intraoperative 3D scans were performed in 3 cases of percutaneus fixation of distal tibio-fibular syndesmotic disruptions; in 2 of the cases, revision of reduction and/or implant placement were needed after the intraoperative 3D scan. Three dimensional CAS was used in 10 cases: 2 open reduction and internal fixation (ORIF) of the calcaneum, 1 subtalar fusion, 2 ankle arthrodesis, 1 retrograde drilling of an osteochondral lesion of the talus, 1 Charcot diabetic reconstruction foot and 1 intramedullary screw fixation of a fifth metatarsal fracture. The guidance was used essentially for screw placement, except in the retrograde drilling of an osteochondral lesion where the guidance was used to navigate the drill tool. Intraoperative 3D imaging showed a good accuracy in implant placement with no need to revision of implants. We report a preliminary case series with use of the O-arm Surgical Imaging System in the field of foot and ankle surgery. This system has been used either as intraoperative 3D imaging control or for 3D-based CAS. In our series, the 3D computer assisted navigation has been very useful in the placement of implants and has shown that guidance of implants is feasible in foot and ankle surgery. Intraoperative 3D imaging could confirm the accuracy of the system as no revisions were needed. Using the O-arm as intraoperative 3D imaging was also beneficial because it allowed todemonstrate intraoperative malreduction or malposition of implants (which were repositioned immediately). Intraoperative 3D imaging system showed very promising preliminary results in foot and ankle surgery. There is no doubt that intraoperative use of 3D imaging will become a standard of care. The exact indications need however to be defined with further studies

Many operations have been recommended to treat Pars Interarticularis fractures that have separated and are persistently symptomatic, but little other than conservative treatment has been recommended for symptomatic incomplete fractures. 10 consecutive patients aged 15–28 [mean 21.7 years] were treated operatively between 2010–2014. All but one were either professional athletes [3 cricketers, 2 athletics, 1 soccer] or academy cricketers [3 patients]. 8 patients had unilateral fractures, and two had bilateral fractures at the same level. The duration of pre-operative pain and disability with exercise ranged from 4–24 months [mean 15.4 months]. The operation consists of a percutaneous compression screw inserted through a 1.5cm midline skin incision under fluoroscopic guidance: 6 cases were also checked with the O-arm intra-operatively. Post-operation the patients were mobilised with a simple corset and discharged the following day with a customised rehabilitation program. All 12 fractures in 10 patients healed as demonstrated on post-operative CT scans at between 3–6 months. One patient had the screw revised at 24 hours for an asymptomatic breach, and one patient developed a halo around the fracture site without screw loosening, and had a successful revision operation to remove the screw and graft the pars from the screw channel. All patients achieved a full return to asymptomatic activity, within a timescale of 4–12 months post-surgery, depending on the sport. Athletes that have persistent symptoms from incomplete pars interarticularis fractures should consider percutaneous fixation rather than undergoing prolonged or repeated periods of rest

Pedicle screws as the principal anchors of instrumentation in correction of scoliosis as described by Suk 15 years ago have now gained a wide acceptance among deformity surgeons. Pedicles in the concavity of the major as well as compensatory curves are often dysplastic making screw placement occasionally problematic. In cases of dural ectasia with dystrophic pedicles, the transpedicular screw anchorage is sometimes impossible. In 2009 Gardner et al. presented a case of NF-1 with a troublesome cervico-thoracic kyphosis where they created distal anchors by means of laminar screw fixation. In the presentation of this case, the idea is further developed. Case. A 14 year old girl without any obvious syndromic feature underwent surgery for a 70 degree thoracic scoliosis. A preoperatively MRI showed a dural ectasia. A preoperative low dose–CT revealed dystrophic pedicles from Th4 to L4, making transpedicular screw placement problematical. The operation was performed with the aid of an O-arm. At all levels from Th2 – L2 laminar screw fixation was used. Postoperatively, low-dose CT showed excellent screw positioning with the exceptiuon of one proximal screw which compromised a foramem but, without any symptoms. The postoperative course was quite uneventful and the patient was discharged at day 5days postoperatively. The correction rate was 70%. Conclusion. In cases of scoliosis with severe dystrophic pedicles, the use of laminar screws is a good alternative to problematic transpedicular screw placement