Laminar Avulsion in a Cervical Vertebra

Transcription

1 Laminar Avulsion in a Cervical Vertebra CHRISTIAN V. CIMMINO AND DAVID W. SCOTT, III An unusual avulsion fracture involving the lamina of a cervical vertebra, most likely due to tear of a ligamentum flavum, is described. Its radiographic features may be quite subtle. Simulation of this fracture on dried skeleton allowed a better understanding of its appearance on the standard projections. its mechanism of occurrence, and its delayed recognition on the patient s anteroposterior view. Only awareness of the existence of this type of fracture and special efforts directed toward its detection will determine its true frequency. A fracture of the cervical spine is described which we have not recognized before and have not found noted in recent orthopedic or radiologic literature. It s radiographic features may be quite subtle. When knowledge of its existence is more widely disseminated, it may be found that this fracture is not as unusual as now believed. Schmorl 111 mentions isolated injuries to the ligamenta flava (yellow ligaments) as an association of subluxations. He believes these injuries are constantly present in most forms of vertebral body and arch fractures. The ligamenta flava connect the Iaminae of adjacent vertebrae, extending from the articular capsules to the point where the Iaminae fuse to form the spinous process. The ligaments are made up chiefly of yellow elastic tissue (hence, the name). They allow separation of the Iaminae during flexion, but permit the gradual approach to the endpoint of normal flexion. With a violent stress of flexion, the endpoint is reached and exceeded, and the ligament is torn with or without avulsion of a piece of its bony attachment. Case Report A 1 5-year-old girl injured in an automobile accident was seen in the emergency room with neck pain. Physical examination was normal except for pain on motion of the neck. Radiographs were interpreted as normal. She was treated with a collar and analgesics. Because of continued neck pain, repeat studies were made 9 days later, and again were called normal. Symptomatic treatment continued for several months until the pain eventually disappeared. The avulsion fracture was finally recognized on the studies made 1 year later, prior to her discharge from medical follow-up. Review of the previous films showed indisputable evidence of the fracture. Laminography would probably have been of great aid in defining this fracture. Discussion The rationality of our diagnosis of avulsion of the lamina due to tear of a yellow ligament was supported by our studies on a dried skeleton. We cut out a piece of bone from the caudal surface of the right lamina of the third cervical vertebra and ressecured it to the lamina after separating it several millimeters therefrom with radiolucent plastic (fig. 1 ) to better see the fracture after radiography. We then made radiographs in anteroposterior. lateral, and two oblique projections, comparing these with the patient s studies (figs. 2-5). It is evident that the patient s fracture was practically identical to the simulated fracture in the dried bone. Remarkably, only after we did the in vitro studies did we recognize the patient s fracture on the anteroposterior study. The laminae are usually radiographically silent on the frontal studies because their bone mass is so slight in relation to the superimposed vertebral bodies. Close observation of the area between the pedicle and the bulbous or bifid tip of the spinous process will often allow recognition of the normal Iaminae. The oblique views confirm their delicate nature, where they appear as biconcave lenslike structures. There are primarily three differential diagnoses. One is avulsion from the spinous process associated with overflexion of the interspinous ligament (the familiar clayshoveler s fracture of the seventh cervical vertebra). This fracture is more dorsal, involving the spinous process rather than the lamina. The basic mechanism of the two fractures, overflexion, must be similar. In the case of the spinous process avulsion, the interspinous ligament is involved; in the case of the laminar fracture, the ligamentum caudal aspect of third cervical vertebra showing simulated fracture of right lamina Fragment is separated by radiolucent plastic Received October , accepted after revision April Radiologic Associates of Fredericksburg, Ltd Fall Hill Avenue, Fredericksburg, Virginia Address reprint requests to D W Scott. III Am J Roentgenol 129:57-60, July

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4 60 CIMMINO AND SCOTT flavum is involved. Second, prominent osteophytoses Identification of the two intact structures will exclude a about a degenerated apophyseal joint, if large enough, laminar fracture. may mimic a laminar fracture. Careful inspection will permit the diagnosis of osteoarthritis. Finally, overlapping REFERENCE of the right and left laminae can produce a Mach effect. 1. Schmorl G: The Human Spine in Health and Disease. New York, Grune & Stratton, 1971

5 This article has been cited by: 1. Anouar Bourghli, Clement Ribes, Ibrahim Obeid, Louis Boissiere, Jean-Marc Vital Complete fracture of the lamina of the sixth cervical vertebra with hemiplegia: a case report. European Spine Journal 25:S1, [CrossRef] 2. Seamus Looby, Adam Flanders Spine Trauma. Radiologic Clinics of North America 49:1, [CrossRef] 3. Pradeep Makan Neurologic Compromise After an Isolated Laminar Fracture of the Cervical Spine. Spine 24:11, [CrossRef]