C1 Anatomy and Dimensions Relative to Lateral Mass Screw Placement

• DOI: 10.1097/01.brs.0000259833.02179.c0
• Publication Date: 2007-04-06T08:04:49Z
• Authors: David M. Christensen; Robert K. Eastlack; James J. Lynch; Michael J. Yaszemski; Bradford L. Currier
• Keywords: Adult; Aged, 80 and over; Male; Adolescent; Bone Screws; In Vitro Techniques; Middle Aged; 03 medical and health sciences; Spinal Fusion; 0302 clinical medicine; Humans; Female; Cervical Atlas; Tomography, X-Ray Computed; Axis, Cervical Vertebra; Aged

An anatomic surface osteometric analysis of cadaveric cervical spines.To assess the feasibility of placing a 3.5-mm cortical screw in the lateral mass of C1 in a large number of specimens for the purpose of gaining internal fixation for various conditions.Previous studies have addressed surface dimensions of the atlas vertebra and computerized tomography-measured dimensions of the lateral masses of the atlas. These studies used a limited number of specimens with potentially homogeneous origins.A total of 120 atlas (C1) vertebrae for a total of 240 lateral masses were examined and external measurements obtained to assess the feasibility of placing a 3.5-mm cortical screw in the lateral mass.The minimum lateral mass dimensions found from 240 C1 lateral masses were 13.15 mm anterior-posterior, 4.22 mm medial-lateral, and 4.73 mm cephalocaudal. The height of the posterior arch at the groove for the vertebral artery (pedicle analog) was less than 4 mm in 46 of 240 (19.2%) arches.It is feasible to safely and reproducibly place a 3.5-mm cortical screw in the lateral mass of C1 when the appropriate starting point and trajectory of the screw are chosen.