Part II - Dorsal wrist pain and swelling post trauma 2

Abstract

DiagnosisTraumatic lipohaematoma of the extensor tendon sheaths(compartments 2–4) post distal radial fracture.DiscussionIn the same way that identification of a lipohaemarthrosisalerts the reading radiologist to the presence of an intra-articular fracture, the visualisation of a lipohaematoma ofthe tendon sheath after trauma may herald the presence offracture extending into an osseous groove for a tendon. Italso indicates injury to the tendon sheath, and raises thepossibility of associated tendon injury, which may warrantfurther assessment of the affected tendon with magneticresonance imaging.A 29-year-old man presented post cyclist vs car accident.CTshowed a comminuted distal radial fracture. As shown inFig. 3 of the case presentation, a fracture line cleavedcompletely through the base of Lister’s tubercle (largerarrow) with disruption of the floor of the fourth compart-ment by an acute angled sharp fracture fragment (smallerarrow). Fracture lines extended into the grooves for extensorpollicis longus (3rd extensor compartment) and extensordigitorum (4th extensor compartment). A separate fracturepassed into the grooves for extensor carpi radialis longusand brevis (2nd extensor compartment). The edges of thefracture fragments were sharply angulated and disrupted theosseous grooves for the 3rd and 4th compartment tendons.The medullary cavity of the distal radius appeared open tothe tendon sheaths of both the 3rd and 4th extensor compart-ments. An oblique sagittal fracture line was also seenextending from the volar surface of the radius through thearticular surface. A small lipohaemarthrosis of the radio-carpal joint was present. Further distally, within the tendonsheaths of the second, third and fourth extensor compart-ments prominent fat–fluid levels within the tendon sheathswere seen, accounting for the gross soft tissue swelling seenon the radiograph. The lipohaematoma was most volumi-nous within the distal third and fourth compartment sheaths,and comparatively small in the second compartmentsheaths. The average Hounsfield Unit density of the upper(and, by volume, larger) layer within the tendon sheaths wasapproximately −90, consistent with the presence of fat.Magnetic resonance imaging obtained 4 days after theinjury showed fat-fluid layers within the non-dependentaspect of the sheaths of the second, third and fourth com-partments. A layer of high T1 signal within the non-dependent aspect of the sheaths (part 1 figure 2 - arrow),which completely saturated on T2 fat suppression and cor-responded to the position of the −90 HU density materialseen on the CT, was present, confirming the presence of fat.The distal radial fracture is also evident on this image. Therewas focal irregular high T2 signal seen along the deep radialside surface of tendons of the extensor digitorum and exten-sor pollicis longus adjacent to the sharp fracture edges,consistent with tendon abrasion, but no frank split or rupturewas seen. The dependent portion of the lipohaematomashowed signal characteristics consistent with a mixture offluid and blood. Figure 4 of this article shows a fracture lineevident in the distal radius, which appears to have disruptedthe tendon sheath and is opening into the floor of the fourth