Abstract
Purpose
Functional ultrasound Elastography (FUSE) of Tendo Achilles is an ultrasound technique utilising controlled, measurable movement of the foot to non-invasively evaluate TA elastic and load-deformation properties. The study purpose is to assess Achilles tendons, paratenon and bursa mechanical properties in healthy volunteers and establish an outcome tool for TA treatment.
Methods
Forty asymptomatic Achilles tendons of 20 healthy volunteers were recruited (10 men and 10 women, age range 18-55). One patient with Acute Achilles rupture scanned to evaluate the tendon gap. Each volunteer answered the Foot and Ankle Outcome Score (FAOS) and Victorian Institute Sport Assessment score (VISA-A) questionnaires. The Achilles Tendons were divided into three thirds (total 120 Proximal, middle and distal thirds). Three longitudinal images of each third were obtained using portable US scan device (Z.one, Zonare Medical System Inc., USA, 8.5 MHz). Images processing was achieved using a MatLAb software (developed by the research team) in parallel Oxford university computers. Each 1/3rd Achilles tendon under went the following scans:
Free hand US scan
Free hand Compression decompression Elastography scan
Dorsal Flexion elastography
Planter flexion elastography
Zonare real-time Elastography
Elastography scan with the Oxford isometric dynamic foot and Ankle mover (OIDFA)
B mode and elasticity images were derived from the raw ultrasound radio frequency data. The anatomical structures mechanical properties were evaluated by a quantitative score of different colours representing stiff tissue (blue) to more soft tissue (green, yellow, red).
Results
The Achilles tendons showed mainly a hard structured pattern (82.5%) (99/120 tendon thirds) on sonoelastography; however, mild softening was found in 17.5% (21/120) of the tendons. Therefore, suggesting subclinical changes. The minimal lateral movement of the tendon produced by applying the FOAIDM resulted in well defined elasticity images with tendon in blue colour (stiff) and surrounding soft tissues. The average strain along the tendon was 2% (range 0-6%). The overall correlation (κ) between real-time sonoelastography and ultrasound findings was < 0.3. However, the correlation (κ) between FUSE UEI and US findings was 1.0. Patients with Achilles tendon rupture lateral strain and axial elastography images using FUSE methods revealed a larger gap with spreading of the haematoma along the paratenon.
Conclusion
Our findings show that FUSE seems to be a sensitive method for assessment of TA mechanical properties. The B mode and elasticity images must be viewed simultaneously. FUSE method can easily identify the regeneration of ruptured TA. Elasticity and stiffness measurement may offer an invaluable tool to guide TA rupture and tendenopathy treatment and rehabilitation protocols.
