1578. Freehand pedicle screw fixation; a safe recipe for dorsal, lumbar and sacral spine

Authors: Syed Sarmad Bukhari, MBBS; Muhammad Junaid; Mamoon Rashid, MBBS (Karachi, Pakistan)

Introduction: Free hand techniques have the unique advantage of being universally applicable especially in the developing world with a dearth of equipment. In our study we used the the following entry points: thoracic spine; 3 mm caudal to the junction of the transverse process and the lateral margin of the superior articulating process, and the sagittal trajectory was always orthogonal to the dorsal curvature of the spine at that level as described by Fennel et al, lumbar spine; the junction of the pars interarticularis, the midpoint of the transverse process and the inferior point of the superior articular facet, sacral; the infero-lateral margin of the basis of the superior articular process of the sacrum. Methods: This was a prospective non randomized study. All surgeries were performed by a single surgeon. Intraoperative localization was confirmed by using fixed bony landmarks and prior review of radiological studies. Screw placement was confirmed using either post op AP and lateral X rays or a single C-arm image when available. Results: Among total 751 free hand placed pedicle screws, 12 screws (1.59%) were identified to have cause minor breach out of which 9 had lateral breaches and 3 inferior breaches. Minor breaches didn’t require repositioning and were only identified by postoperative imaging. There were no medial breaches while 8 screws (1.06%) caused major breach/misdirected and were identified peroperatively due to giving way feel of screws which were rectified there and then.6 screws (0.79%) had partially misdirected trajectory towards the disc space and were left undisturbed due to good individual holding strength and of whole construct. No repositioning was done postoperatively. Conclusion: Free hand pedicle screw placement based on external landmarks showed remarkable safety and accuracy in our center. The authors conclude that experience and assiduous adherence to technique and preoperative planning is vital to success.