Combined 33rd SICOT & 17th PAOA Orthopaedic World Conference F 9 O 2 9 N 1 D E É E BR À TO PA OC R I S LE 10 28‐30 November 2012 Dubai, United Arab Emirates ABSTRACT BOOK E-POSTERS Abstract no.: 30715 ACCURACY OF INTRAOPERATIVE CT-BASED NAVIGATION FOR PLACEMENT OF PERCUTANEOUS PEDICLE SCREWS Jason ECK1, Jeffrey LANGE1, John STREET2, Anthony LAPINSKY1, Patrick CONNOLY1, Christian DIPAOLA1 1University of Massachusetts, Worcester (UNITED STATES), 2University of British Columbia, Vancouver (CANADA) Introduction: Previous studies on fluoroscopically guided percutaneous pedicle screws have demonstrated a cortical breach rate of approximately 25%. The purpose of this study was to evaluate the accuracy of intraoperative CT-based navigation for placement of percutaneous pedicle screws in a cadaveric model. Methods: Two specimens were utilized. CTs were obtained using an O-Arm and coupled to the Stealth navigation system. Navigation was used for placement of percutaneous pedicle screws bilaterally from T5-S1 and from T6-S1 respectively. Post insertion CTs were obtained. Pedicle breach was assessed and classified accordingly (I: none, II: <2 mm, III: 2-4 mm, or IV: >4 mm). Results: Thirty thoracic screws were placed with 3 (10%) medial and 17 (56.7%) lateral breaches (all grade III). Of twenty lumbar there were 0 medial and 2 (10%) lateral breaches (one grade III, one grade IV). Four sacral screws were placed without breaches. The real-time computer-aided navigation tool was limited in identifying a breach. Manipulation of the surgeon’s hand or driver could change the orientation of the navigation tool without changing the screw trajectory. Discussion: CT-based navigation for placement of percutaneous pedicle screws appears safe for the lumbar spine. Thoracic breaches laterally appeared commonly but were not clinically significant. The 10% rate of medial thoracic breach was concerning. We cannot recommend use of CT-guided navigation for placement of thoracic percutaneous pedicle screws. Further study is warranted to define the roles and limits of this technology as factors including body habitus and pedicle morphology may limit use in percutaneous spinal surgery. Abstract no.: 30735 HOW EFFECTIVE IS CT BASED NAVIGATION IN PEDICLE SCREW FIXATION:OUR EXPERIENCE IN A TERTIARY CARE CENTRE IN INDIA. Saurabh KAPOOR1, Rajbahadur SHARMA2, Sudhir KUMAR2, Rohit JINDAL2 1c-610 saraswati vihar pitampura, new delhi (INDIA), 2government medical college and hospital, chandigarh (INDIA) introduction:Conventional technique of pedicle srew fixation has limited accuracy potentially endangering vital structres.CT based navigation is a technique to improve the accuracy of pedicle screw fixation which needs to be tested for its feasibility and effectiveness in a third world country.methods and materials:30 consecutive patients of fractures of dorsolumbar spine were subjected to an optoelectronic navigation system consisting of a computer work station,infrared camera system and instruments equipped with gleons.the preoperative CT scan was fed into the computer work station and the process of paired point matching was done on patients exposed spine.time taken for matching process as well as insertion of each pedicle screw was recorded and placement assesed with a postoperative CT scan which was graded using Laine's grading system.results:only one srew out of a total of 118 screws was misplaced with a laine's grade 5 placement,showing a misplacement rate of 0.847% only.average time for matching was 7.8 minutes.time taken insertion of a single screw was 4.19 minutes and total time taken for all screws was 34.23 minutes.no neurovascular complications were seen in any of the patients.conclusion:CT based navigation significantly improved the accuracy of pedicle screw placement.the rate of screw misplacement in our study was lesser than those reported with conventional technique(14.3-42%) and is comparable to reported rates with other computer assisted techniques,however, this technique involves a steep learning curve and additional costs of procuring a pre-operative CT scan. Abstract no.: 30739 LOW-GRADE CENTRAL OSTEOSARCOMA OF THE METATARSAL BONE: A CLINICOPATHOLOGIC, IMMUNOHISTOCHEMICAL, CYTOGENETIC, AND MOLECULAR CYTOGENETIC ANALYSIS Jun NISHIO1, Hiroshi IWASAKI2, Satoshi TAKAGI3, Mikiko AOKI2, Kazuki NABESHIMA2, Masatoshi NAITO1 1Department of Orthopaedic Surgery, Faculty of Medicine, Fukuoka University, Fukuoka (JAPAN), 2Department of Pathology, Faculty of Medicine, Fukuoka University, Fukuoka (JAPAN), 3Department of Plastic and Reconstructive Surgery, Faculty of Medicine, Fukuoka University, Fukuoka (JAPAN) Low-grade central osteosarcoma (LGCOS) is a very rare low-grade malignant neoplasm that is often confused with a variety of benign fibro-osseous lesions. It rarely involves the small bones of the foot. We present an unusual case of LGCOS arising in the third metatarsal bone of a 16-year-old man. The radiographic appearance was suggestive of a benign lesion. An open biopsy was performed and the initial pathologic diagnosis was fibrous dysplasia. The patient underwent curettage of the lesion and packing of the bony defect with a synthetic bone substitute. Histologically, the tumor consisted of spindle cells admixed with irregular bony trabeculae and osteoid. The spindle cells were fairly uniform with mild atypia, and cellularity varied from low to high. Immunohistochemically, the tumor cells were focally positive for CDK4 and p53, but negative for MDM2. The MIB-1labeling index was 36.7% in the highest spot. Cytogenetic analysis exhibited the following clonal karyotypic aberrations: 48,XY,del(6)(p11),add(8)(q24),add(12)(p11.2),+mar1,+mar2. Spectral karyotyping demonstrated that marker chromosomes were mainly composed of chromosome 6. Metaphase-based comparative genomic hybridization analysis showed a high-level amplification of 6p12-p21 and gains of 8q21-q24, 10p15, 12q13-q15, and 16q23-q24. The histological diagnosis of the curetted specimen was revised to LGCOS, and the patient was finally treated with an additional wide excision, followed by reconstruction with a free vascularized osteocutaneous scapular flap. Our case highlights the diagnostic difficulty of this tumor on limited tissue samples and the importance of immunohistochemical analysis in ambiguous cases. Abstract no.: 30748 TECHNIQUE TIP: USE OF ACL JIG FOR HIND FOOT FUSION BY TIBIO- TALO CALCANIAL NAIL Syed HAQUE1, J SARKAR2 1Luton and Dunsatable Hospital NHS Foundation Trust, Luton (UNITED KINGDOM), 2Luton and Dunstable Hospital NHS Foundation Trust, Luton (UNITED KINGDOM) Introduction: The use of intramedullary nail fixation for tibio-talo-calcaneal fusion is gaining popularity. There is chance of failure of procedure following faulty operative technique specially alignment. Objective: We describe a useful application of tibial tunnel jig used for ACL reconstruction in inserting the calcanio-talotibial guide wire which is extremely important for correct alignment of the ankle. Method: We describe a useful application of tibial tunnel jig in inserting the calcanio-talo-tibial guide wire with a precision of few millimetres through the calcanium into talus and finally into tibia. The guide arm of the tibial jig is oriented desirably by adjusting the guide arm with respect to the drill sleeve. There are markings on the guide arm to indicate the optimum orientation of the guide arm with respect to the drill sleeve. Now the guide arm is placed on the desirable exit point of the guide wire on talus and the drill sleeve is put on the entry point of calcanium . The guide wire is drilled through the drill sleeve. The guide wire comes out at the desirable place on the talus and then the tibial tunnel jig is removed and the wire is further drilled into the tibial medullary canal. Result and conclusion: There is precision of few millimetres in the exit point of guide wire on talus.This we think helps in better positioning of nail and hence better alignment and better operative outcome. Abstract no.: 30751 SWELLING AROUND BIO ABSORBABLE INTERFERENCE SCREW FOLLOWING ACL RECONSTRUCTION- A CASE SERIES Syed HAQUE1, M UMAR2, S SUNDARARAJAN3 1Luton and Dunstable Hospital Hospital NHS Foundation Trust, Luton (UNITED KINGDOM), 2Luton and Dunstable Hospital NHS Foundation Trust, Luton (UNITED KINGDOM), 3Luton and Dunstable Hospital NHS Foundation trust, Luton (UNITED KINGDOM) Introduction: Bio absorbable interference screws have been effective for graft fixation in anterior cruciate ligament (ACL) reconstruction. Complications associated with these bio absorbable screws are few. Objective:We report a case series of 6 patients who underwent arthroscopic ACL reconstruction with symptoms associated with knee instability. In these six patients, Bio absorbable interference screw (PLLA) fixation at the tibial end was done.Methods: 18months to 2 yrs following ACL reconstruction these patients were referred back to us with a painless lump at the proximal end of tibia overlying the tunnel opening of the tibia. There was no history of infection or recent injury. They did not complain/report any pain in the knee and there was no instability of the knee. On examination, below the tibial incision there was a non-tender firm lump about 2cmx2 cm in dimension fixed to the proximal tibia. Skin over the lump was mobile and not warm to touch.Results:Patients were taken to theatre for exploration / excision and biopsy of lump. Exploration revealed chalky white remnants of the bio absorbable screw with no evidence of infection.