A comparison of the accuracy and safety of vertebral body pin placement using a fluoroscopically guided versus an open surgical approach: an in vitro study.

ABSTRACT

OBJECTIVE: To compare the safety and accuracy of Steinmann pin placement in vertebral bodies T10 through L7 using either an open or closed fluoroscopic method. STUDY DESIGN: In vitro radiographic and anatomic study. ANIMALS Ten medium-sized canine cadavers. METHODS: Cadavers were randomly assigned to 2 groups open and closed. Steinmann pins were placed in vertebral bodies through a standard dorsal incision in the open group and percutaneously with the aid of fluoroscopy in the closed group. Pins were placed bilaterally in vertebral bodies T10 through L7 at approximately 30 degrees from horizontal and driven to a uniform depth. Necropsies were performed to examine potential pulmonary, vascular, or neurological trauma as a result of pin placement. Spines were cross-sectioned through intervertebral disc spaces, and radiographs were performed to evaluate accuracy of pin placement. Descriptive statistics were determined for pin angle, percentage of bone purchase, and penetration length. Means of interest between groups were compared using a Student t test. Complication incidence was compared using Chi;(2) analysis. Significance was P <.05. RESULTS: Mean pin insertion angle was significantly different than 30 degrees for the open group in thoracic and lumbar vertebrae and for the closed group in thoracic vertebrae. Mean pin insertion angle for all vertebrae was significantly greater than 30 degrees for the open group. Mean pin penetration distance in each vertebra was significantly different between groups with the closed group having less penetration and lower variance. Both groups were significantly different from the ideal penetration distance. The mean percentage of bone purchase was greater in the closed group for all vertebrae except T10 and T11. The complication incidence was significantly greater in the open group for thoracic vertebrae. CONCLUSION AND CLINICAL RELEVANCE The results of this study suggest that a closed technique for placement of Steinmann pins in lumbar vertebrae for use in external skeletal fixation is a reasonable and safer alternative to the traditional open technique. Use of either technique in thoracic vertebrae should be avoided.