Evaluation of efficacy and accuracy of free hand pedicle screw insertion technique in thoracic spine
Authors: Kunal Navale, Pramod P. Neema, Vishal Gupta, Murtuza Rassiwala.
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Introduction: Advanced internal fixation techniques, including pedicle screws, have been developed and used extensively in spine surgery, not only for traumatic injuries but also for degenerative conditions. Free hand pedicle screw fixation technique have the advantage of universal application, fixation strength, and stabilization of all three mechanical columns of the spine. Free hand pedicle screw placement based on external anatomy alone can be performed with acceptable safety and accuracy and avoids excessive radiation exposure.
Materials and Method: This was a prospective study done in Department of Orthopaedics at our institute. 30 consecutive patients who underwent posterior thoracic instrumentation from May 2015- May 2016 were analysed. The mean age was 39 years. The etiologic diagnoses were - spinal trauma-22, spinal tuberculosis-05, spinal deformity-02, and spinal tumour-01. Titanium pedicle screws used in all these vertebrae were polyaxial in nature and of 4.5mm or 5.5mm diameter with length ranging from 25mm to 50mm. 168 screws were inserted in 84 thoracic vertebra (T1-T12) by free hand technique as described by Kim et al. Informed consent was taken. Clearance from ethical committee of the institute was taken. The patients were followed-up with X-ray, CT Scan at immediate postoperative and reviewed at 1 month and 3 months postoperative with radiograph.
Results: 168 screws were inserted in 84 thoracic vertebra (T1-T12) with number of screws inserted at each level as follows T1 =0, T2=4, T3=6, T4=8, T5=14, T6=14, T7=16, T8=16, T9=18, T10=18, T11=24, T12=30. All the screw were evaluated post operatively. Of 168 screws 144 screws (85.70%) were intraosseous and accurately placed. 24 screws (14.28%) in patients were malpositioned. Of 24 perforations 3 screws (1.78%) had critical medial breach of more than 2 mm perforation, however no neurological worsening was noted post operatively in any case. Rest 21screws (12.50%) perforations were non-critical. In 3 patients (deformity 1, trauma 1 and infection 1) sudden give away was felt during gear shift probing, and a breach confirmed on palpation/probing and the screw was re directed. None of the patients had any incident of CSF leak or excessive bleeding during screw insertion.
Conclusion: The free hand technique of thoracic pedicle screw placement performed in a stepwise, consistent, and compulsive manner is an accurate, reliable, efficient and safe method of insertion to treat a various spinal conditions, with almost same rate or less number of complications as performed with fluoroscopy guided pedicle screw insertion. Our results with less than 2 percent of critical breach, document that we have been able to create a safe method of thoracic pedicle screw placement without use of other intra operative imaging modalities. One must have a thorough knowledge of spine and vertebral anatomy, follow and use deligent and repetitive confirmatory steps to compulsively assure interosseous screw placement.