Comparative study of the incidence and severity of degenerative change in the transition zones after instrumented versus noninstrumented fusions of the lumbar spine.

The purpose of this study was to determine whether the addition of pedicle screws and rods to a fusion of two or more vertebrae of the lowest three motion segments of the lumbar spine increases the incidence or severity of transition zone change (TZC) above or below the fused area. A study group of 52 patients who had a fusion with fixation and a control group of 31 who had a nearly identical operation but without fixation were obtained. Radiographs and computed tomography scans of the area of study were taken preoperatively and were repeated approximately 7 years after the operation. Results showed that the addition of pedicle screw fixation does not increase the incidence or severity of TZC in the first 7 years after surgery.

Radiographic identification of loose bodies in the traumatized hip joint.

Acrylic spacers and cubes of cortical bone of known dimensions were placed in predetermined locations in cadaver hip joints, which were then studied with plain radiography and linear, hypocycloidal, and computed tomography (CT). Joint space widening was not measurable on plain radiographs of the pelvis when 2-mm spacers were placed anywhere within the hip joint. When 4-mm spacers were used, widening measured 2 mm in the axis of measurement corresponding to the location of the spacer. Linear tomography did not permit identification of the 2-mm cubes; however, hypocycloidal tomography and CT consistently showed them anywhere within the hip joint. Radiation dose and clinical recommendations are discussed.