CT more accurately diagnoses a complete rupture of the Achilles tendon than does color Doppler ultrasound, according to a study from China published in Biomed Research International. Although ultrasound is usually performed in conjunction with a physical examination because of its availability, low cost, and ease of use, ultrasound may make a complete rupture appear to be a partial rupture, leading to an incorrect diagnosis, the study concludes.
Physicians from the Department of Orthopedics of the General Hospital of Shenyang Military Area Command of Chinese PLA in Shenyang, Liaoning conducted a 26-month long study to compare ultrasound and CT. The study group included 36 patients diagnosed with complete Achilles tendon rupture who had both imaging examinations.
The CT images were post-processed using 3D volume reconstruction (VR) to create a 3D image of the tendon and bone after hiding the skin and fat based on the Hounsfield unit values. Multiplanar reconstruction (MPR) was used to adjust the angle of the access to obtain axial, sagittal, and coronal images of the achilles tendon. Lead author Hai-Peng Xue, MD, and colleagues reported that by observing the continuity and tension of the Achilles tendon in 3DVR and MPR, they could make a CT diagnosis.
Thirty-three cases were diagnosed with a physical examination alone using the Thompson’s sign test. Doppler ultrasound identified 32 cases as a complete Achilles tendon rupture and four cases as a partial rupture. CT identified all cases as a complete rupture. The length of the distal stump measured in a CT image had a 96% correlation with the actual measurement taken during surgery.
An acute Achilles tendon rupture is the most common tendon injury of the lower leg. Doppler ultrasound will in all likelihood continue to be the initial imaging examination. However, in cases where ultrasound identifies a partial rupture, the authors suggest that a CT scan may be advisable.
They reported that 3DVR images showed bending and thickening of the tendon and that MPR images were even more obvious because the tension disappears and the distal part of tendon retreats slightly for the acute Achilles’ tendon rupture. They also said that accuracy of diagnosis can be improved if the uninjured leg is also scanned in the same procedure.
Other advantages include the ability of CT images to show the precise positioning of the broken end of the Achilles tendon, which is important for surgeons performing minimally invasive surgery to know. CT also enables physicians to determine the rupture location. The authors noted that in their study, there was high correlation between CT measurements and the measurements in the surgeries on the distal stump length. They also stated that the relationship of the Achilles tendon and the surrounding bone tissues can be shown on CT when the broken end involves the avulsed fragment.
CT outperforms Doppler US to diagnose complete rupture of acute Achilles tendon. Appl Radiol.