Quantitative 3-dimensional CT analyses of fractures of the middle phalanx base

Quantitative 3-dimensional computed tomography (3DCT) analyses can provide a more detailed understanding of fracture morphology. For fracture-dislocation of the proximal interphalangeal joint, the extent of fragmentation of the volar lip of the middle phalanx-a factor that might influence treatment-is not always apparent from radiographs. We hypothesized that there is no correlation between number of fracture fragments and the percentage of articular surface area involved in intra-articular fractures of the base of the middle phalanx using quantitative 3DCT analyses.

We used 13 computed tomography scans with a slice thickness of 1.25 mm or less to create 3-dimensional models of 15 intra-articular fractures of the base of the middle phalanx in 13 patients. We resized 3-dimensional models of a non-fractured middle phalanx of the same hand to fit the fractured middle phalanx in order to approximate the size and shape of the fractured middle phalanx in its pre-injury state. We created a heatmap to demonstrate the location of the fractured articular surface.

With the number of scans available, we did not find a significant correlation between the percentage of articular surface area involved and the number of fracture fragments. The median percentage of articular surface area involved was 46 % (range, 21-90 %). The heatmap demonstrated that the radio-volar side of the articular surface seems to be more involved than the ulnar-volar side in intra-articular fractures of the base of the middle phalanx.

Quantitative 3DCT analysis of fracture fragments provides useful information that could facilitate surgery and analysis of complex fractures of the base of the middle phalanx.

IV, Basic Science Study, Anatomic Study, Imaging.