The oblique cranial tilt view for spondylolysis.

Spondylolysis is a common cause of backache and the detection of subtle cases is therefore important. Oblique views considerably increase the detection rate (Appleby and Stabler 1969), but a number of cases require additional views. The 30#{176} oblique cranial tilt view is more reliable than the standard oblique views in detecting spondylolysis as it visualises the pars interarticularis tangentially. To obtain this view the patient lies supine and is rotated 40#{176} to each side. The beam is centred at the level of the anterior superior iliac spine in the mid-clavicular line, with the tube angled 30#{176} cranially. Standard radiographic exposures and technique are employed. We reviewed 45 cases of spondylolysis at L4-5 and L5-Sl ; 15% were not visualised by the standard radiographic technique but were diagnosed with certainty on the oblique cranial tilt view. All the cases detected by the standard oblique views were also visualised on an oblique cranial tilt view. Discussion. On the standard lateral, anteroposterior and oblique views of the spine spondylolytic defects can be overlooked. Ravichandran (1980) showed that the isolated lateral deviation and rotation of a spinous process as seen in the anteroposterior radiograph seems to be associated with pathology in the pars interarticularis. Libson and Bloom (1983) used an angulated anteroposterior view to detect the defects in the pars interarticularis more clearly. We feel, however, that the 30#{176} oblique cranial tilt view is simple and reliable. It should replace standard oblique views because it permits more accurate detection of defects in