Ultrasound of the Gruberi Bursa with cadaveric and MRI correlation

OBJECTIVE. The purpose of this study was to describe the appearance and ultrasound characteristics of the Gruberi bursa using a cadaveric model and retrospective ultrasound imaging review. MATERIALS AND METHODS. For the cadaveric study, ultrasound of the dorsolateral ankle of a foot-ankle specimen was performed and was followed by injection of latex between the extensor digitorum longus (EDL) tendons and the talus and dissection. For the ultrasound imaging review, the radiology database was searched for ultrasound studies performed from September 15, 2000, through April 1, 2015, to identify subjects with a dorsolateral foot or ankle fluid collection detected on ultrasound. Images were retrospectively reviewed to characterize the location and size of the fluid collection, assess for the number of locules, and evaluate the compressibility of the fluid collection. It was determined whether the ultrasound findings were significantly different from chance: CI and p values were obtained from performing a test for one proportion. RESULTS. Dissection of a cadaveric specimen revealed latex within a well-defined region between the EDL tendons and the dorsolateral talus; this location is consistent with a Gruberi bursa. For the image review, the imaging examinations of 162 subjects (age range, 16-88 years; 31 male subjects and 131 female subjects) were reviewed. On the ultrasound images, a fluid collection with its epicenter between the dorsolateral talus and EDL was found in 93% of ankles. Of the fluid collections identified on ultrasound, 98% were unilocular and 94% were anechoic. Of these fluid collections, 133 were assessed for compressibility, and 89% were compressible. The positive findings for a Gruberi bursa that were different from chance (p < 0.0001) were a fluid collection being located between the EDL tendons and the dorsolateral talus and being unilocular, anechoic, and compressible. CONCLUSION. The Gruberi bursa characteristically is located between the EDL and the talus; on ultrasound, the Gruberi bursa is most commonly unilocular, anechoic, and compressible.