OBJECTIVETo study the relevant position of the pedicle of C1 to the lateral mass of C(2-4), set up an identification technique for the entry point decision of C1 pedicle screw by using the lateral mass of C(2-4) as anatomic landmarks.

METHODSTwenty cadaver specimens were used to measure the distance from the sagittal midline of spine to the medial border, the midpoint and the lateral border of C1 pedicle or the lateral mass of C2, C3 or C4. The anatomic relation between the measurements data of C1 pedicle and that of the lateral masses of the cervical vertebrae were analyzed, and the technique of C1 pedicle screw fixation was established.

RESULTSThe average medial border of the lateral mass of C2, C3 and C4 was 0.37 mm, 0.27 mm and 0.24 mm lateral to that of C1 pedicle, the average midpoint of the lateral mass of C2, C3 and C4 was 1.18 mm, 1.41 mm and 1.74 mm lateral to that of C1 pedicle, and the average lateral border of the lateral mass of C2, C3 and C4 was 1.96 mm, 2.54 mm and 3.24 mm lateral to that of C1 pedicle, respectively.

CONCLUSIONThere is a steady anatomic location relation between C1 pedicle and the lateral mass of C2, C3 or C4. As well as the lateral mass of C2, the lateral mass of C3 or that of C4 could be convenient anatomic landmarks to determine the location of C1 pedicle and the position of C1 pedicle screw entry point.