Occipital fixation: effect of inner occipital protuberance alignment on screw position

Previous authors have demonstrated that the optimum position for screw placement in the occiput is in the inner occipital crest. The position of this structure is usually taken as being in the midline; however, this has not been previously validated. Computerized tomography (CT) of the occipital region was performed prospectively according to a standard protocol. The study included 100 patients (53 female and 47 male, 18-75 years of age). CT images were analyzed to determine the position of the inner occipital crest in relation to the midline. The inner occipital crest is located off the midline (> or = 2 degrees ) in 48% of patients. Preoperative CT evaluation may be helpful prior to occipitocervical fixation on the basis of this study.