Learning curve of thoracic pedicle screw fixation by freehand technique

Abstract

Background: The freehand method of inserting thoracic pedicle screw has become one of the most popular techniques; however, data on its learning curve are scanty. The purpose of this study was to delineate the learning curve and to evaluate the safety of freehand technique of thoracic pedicle screw placement in nondeformed spine. Materials and Methods: A total of 92 consecutive patients who underwent thoracic posterior stabilization with pedicle screws using freehand technique between 2012 and 2017 in various pathologies of nondeformed spine from T1 to T10 at a single institution by a single surgeon were analyzed. Patients were divided into four quartiles (Q1, Q2, Q3, Q4, with 23 patients each) with each consecutive group serving as control for its prior. Demographics (age, sex, pathology involved) and complications were evaluated. Postoperative computed tomography (CT) scan was taken for evaluation of screws perforation including level, direction, grade, and severity of perforation. Results: Of total of 735 screws inserted in 92 patients, 72 screws were perforated with a perforation rate of 9.79%. Of the total perforations, more than half (63.88%) were of Grade 2 and maximum perforations were seen in the lateral direction (58.3%). Total three critical perforations were noted but none of them were symptomatic. The highest rate of perforation was evident at T4 vertebra (18.29%), whereas it was lowest at T9 (3.79%). The perforation rate showed a statistically significant (P < 0.05) decline in Q2 as compared to Q1 achieving asymptote in Q1 after approximately 80–100 screws. Conclusion: A steep learning curve is associated with the freehand technique of thoracic pedicle screws and asymptote can be achieved after approximately 80–100 screws. Novice surgeons can reduce the learning curve by doing practice on saw bone models and cadaveric dissection learning to avoid perforations and other complications with understanding the complex anatomy and variations encountered in the typical thoracic spine.