Indexed on: 04 Feb '10Published on: 04 Feb '10Published in: Computer Aided Surgery
A computer aided method for closed tibial shaft fracture reduction based on measurements of 12 projection parameters (6 angulations and 6 translations) from an anteroposterior radiograph, a lateral radiograph, and a transverse projection photograph is examined. The development, validation and reliability of the computer aided method are presented. A custom-made unilateral external fixation device consisting of 7 calibrated one-degree-of-freedom joints was employed to execute the reduction. Five tibial fracture phantoms with initial deformities that covered a wide range of misalignments were tested. The mean (standard deviation) resultant rotational and translational errors after the reduction were 3.32° (0.96°) and 1.65 (0.86) mm, respectively, which indicates good reduction accuracy. Three independent raters made the measurements of the projection parameters to test inter-rater reliability. The intra-class correlation coefficients were found to range between 0.935 and 1, indicating good reliability. Since ideal patient positioning for AP, lateral and transverse image acquisition is not easily attainable, the effect of patient positioning errors on the measurement of projection parameters was explored using a tibial phantom. The preliminary results revealed that 10° deviations in positioning do not greatly affect the measurement of AP and lateral angulation parameters (<1.7°). However, a 10° positioning error about the long bone axis may result in a change of as much as 10.7° in the measurements of transverse projection angulation parameters. In addition, a 10° positioning error about an arbitrary anatomical axis may result in translational projection parameter changes of up to 6.8 mm. For these reasons, a previously validated method that allows for accurate positioning of the tibia about its long axis and a two-step reduction strategy to achieve the best possible deformity reduction are proposed. Procedures to facilitate reliable measurement of tibial torsion are also discussed. It appears that the projection-based reduction method exposes the patient to less radiation and allows for simple, quick and accurate reductions, making it an attractive choice for acute clinical applications.