VALIDATION OF 3 FORM THALAMIC FRACTURES - CLASSIFICATION USING 3-DIMENSIONAL COMPUTED-TOMOGRAPHY

Purpose of the study This technique has been used to validate our prev ious classification (using three forms :vertical, horizontal, and mixe d) which resulted from a two dimensional tomodensitometric study. Mate rial The study was based on a series of 74 fractures, all of them stud ied with 3D CT and 71 of which were operated. Method The previous clas sification relied on correlation between lateral radiographs and posit ion on coronal CT plane of the Palmer's fracture line. This we called the Fundamental Line (FL); so the vertical form had medial fundamental line, with thalamic verticalization; and so that the horizontal form with thalamic horizontalization had a lateral FL; the mixed form had a medio thalamic FL with double contoured image. Results In vertical fr actures (16 cases, i.e. 20 per cent), the FL was seen denting the thal amus inwards, continuing forward and damaging the forward facet in abo ut two thirds of cases. The thalamic fragment tilted on its axes frequ ently, with a great rotation movement; in about half cases, it extende d backwards (propagated variation). This lateral fragment, called ''co rtico thalamic'' (CT) explained the vertical thalamic x-ray image. In the horizontal fractures (15 cases, i.e. 20 per cent), the FL dents th e thalamus outwards, the medial fragment, pushed downwards, explaining the horizontal image. In the mixed cases (40 cases i.e. 55 per cent) the FL was medio thalamic; the two fragments, downed medially and tilt ed laterally, are of equivalent importance, hence the double contoured image. In half cases, an accessory line separates the sustentaculum t all, creating the two lined mixed form (14 cases i.e. 35 per cent of t he mixed). In those cases, the medial thalamic fragment is unsoldered, when in 50 per cent of cases (i.e. 7 out of 14), the pre-thalamic lin e, following the sinus tarsi, separates it from the forward part and c ompletely isolates it. Therefore, the initial classification in three forms was in fact confirmed. Moreover, the fundemental line appears in all three forms, being the boundary between the lateral thalamic frag ment (always tilted) and the medial fragment (always pushed downside). The anterior of cuboidian joint facets are frequently damaged by the forward prolongation of the Fundamental Line according to studied case s. Discussion This three form classification emphasizes the role of th e Fundamental Line, which in effect acts as a boundary between the two typical displacements of this fracture: downward or rotation movement of the thalamic fragments (since it is there that the main displaceme nts occur). A comparison with the Eastwood and Sanders classifications has been carried out. Conclusion This three dimensional CT approach v alidates, visualizes and completes the three form classification. This will help us to understand fracture displacements in different forms, and therefore, the particular fracture reduction and osteosynthesis b est suited for each case.