Lateral Spread of the Atlas Without Fracture

Abstract

Simultaneous congenital defects in both the anterior and posterior arches of the atlas have been reported in 17 cases (1–3, 6–8, 10, 12–15, 19, 20, 22, 23). The majority of these were anatomic specimens described in the nineteenth century. Two additional cases, with the further finding of lateral offset of the atlas in relation to the axis, were recently observed. As our patients presented after injuries, differentiation from fractures of the ring of the atlas was essential. Case Reports Case I: A 45-year-old laborer was carrying a 100-lb. sack when he stepped into a deep crevice, landing with full weight upon his buttocks. He immediately felt pain in the neck, but was able to drive himself to a nearby hospital. There was no past history of any injury or difficulty referable to the neck. Physical examination revealed considerable restriction of voluntary motion, with severe pain deep in the neck elicited by the slightest movement of the cervical spine or mandible. There was no neurologic or other abnormality. Radiographic examination performed with the patient supine demonstrated lateral offset of each lateral mass of C-1 in relation to C-2 (Fig. 1,A), associated with congenital defects in both the anterior (Fig. 1,B) and posterior (Fig. 1,C) arches of the atlas. A retropharyngeal hematoma was also visible (Fig. 1,D). The patient was placed in head traction and experienced nearly complete subsidence of pain by the third day. Radiographic examination at that time showed no change except for resorption of the hematoma. He was transferred to a four-poster type neck brace and discharged from the hospital on the fourth day. Further recovery was uneventful. Case II: A 13-year-old boy was first seen after he was struck in the eye by a ball. A defect in the anterior arch of C-1 was incidentally noted in the Waters' view of a facial bone study. There was no history of previous or concurrent neck injury or of symptoms referable to the cervical spine. Seven months later the boy was again admitted to the hospital. On the morning of admission he “felt something pop” in his neck while putting on a sweater. Pain in the left side of the neck aggravated by any motion developed immediately. Physical examination showed that the neck was held tilted to the right with limitation of rotation to the left. The remainder of the examination was normal. Radiographic examination of the cervical spine disclosed lateral offset of the right lateral mass of C-1 without medial offset on the opposite side (Fig. 2,A). The midline defect in the anterior arch of the atlas was unchanged (Fig. 2,B), and in addition there was a massive defect in the posterior arch (Fig. 2,C). The patient was treated with traction and muscle relaxants and improved sufficiently to be discharged with a Thomas collar after three days.