Congenital Absence of the Odontoid Process

Abstract

Congenital absence of the odontoid process has been reported in the literature only seven times since 1933. One of these reports was of 2 cases, so that a total of 8 cases have been recorded (1–3, 5–8). A ninth case is described in this paper. The odontoid process is ossified from three centers—two lateral centers, which soon merge, appearing in the fifth month, and one apical center, appearing from the second to fifth year. In the third or fourth year the odontoid process and the body of the axis co-ossify, the line of union being indicated frequently by a small disk of cartilage entirely surrounded by bone, which may persist to old age. The apical ossification center of the odontoid unites with the odontoid process proper at the twelfth year (4). Failure of development of the three centers is undoubtedly what occurs to produce congenital absence of the odontoid process. Case Report B. H., a 56-year-old male, complained of pain in the left trapezius muscle following head injury six weeks before hospital admission. He had been in good health up to that time, when he hit the top of his head on the rung of a ladder which he was climbing. He did not lose consciousness, but there was immediate onset of posterior cervical pain, which persisted. The past history revealed no unusual symptoms, pain, or previous injury to neck. On physical examination, the neck was supple, and no masses were palpable in the cervical region. There was good range of motion of the head and neck. Some tenderness was noted over the posterior cervical musculature on the left. The remainder of the physical examination was negative. Roentgenograms (Fig. 1) revealed absence of the odontoid process, with characteristic flattening of the upper margin of C-2. The patient received six diathermy treatments during his stay in the hospital and was much improved on discharge.