Evaluation of the geometric accuracy of computed tomography and microcomputed tomography of the articular surface of the distal portion of the radius of cats.

Objective: To evaluate accuracy of articular surfaces determined by use of 2 perpendicular CT orientations, micro-CT, and laser scanning.
Sample: 23 cat cadavers.
Procedures: Images of antebrachia were obtained by use of CT (voxel size, 0.6 mm) in longitudinal orientation (CT _LO images) and transverse orientation (CT _TO images) and by use of micro-CT (voxel size, 0.024 mm) in a longitudinal orientation. Images were reconstructed. Craniocaudal and mediolateral length, radius of curvature, and deviation of the articular surface of the distal portion of the radius of 3-D renderings for CT _LO , CT _TO , and micro-CT images were compared with results of 3-D renderings acquired with a laser scanner (resolution, 0.025 mm).
Results: Measurement of CT _LO and CT _TO images overestimated craniocaudal and mediolateral length of the articular surface by 4% to 10%. Measurement of micro-CT images underestimated craniocaudal and mediolateral length by 1%. Measurement of CT _LO and CT _TO images underestimated mediolateral radius of curvature by 15% and overestimated craniocaudal radius of curvature by > 100%; use of micro-CT images underestimated them by 3% and 5%, respectively. Mean ± SD surface deviation was 0.26 ± 0.09 mm for CT _LO images, 0.30 ± 0.28 mm for CT _TO images, and 0.04 ± 0.02 mm for micro-CT images.
Conclusions and Clinical Relevance: Articular surface models derived from CT images had dimensional errors that approximately matched the voxel size. Thus, CT cannot be used to plan conforming arthroplasties in small joints and could lack precision when used to plan the correction of a limb deformity or repair of a fracture.