Ultrasound of the ankle nowadays is very useful method to diagnose wide range of pathology , and help the patient to cut down on waiting time for the MRI exam.
It is recognised that ultrasound cannot adequately assess the deltoid ligament, the ankle mortice and some inter-tarsal ligaments.
Use of a high resolution, (8-15MHZ)small footprint probe , is essential when assessing the superficial structures of the ankle. Careful scanning technique to avoid anisotropy (and possible misdiagnosis) Beam steering or compounding can help to overcome anisotropy in linear structures such as tendons. Good colour / power / Doppler capabilities when assessing vessels or vascularity of a structure. Be prepared to change frequency output of probe (or probes) to adequately assess both superficial and deeper structures.
SCANNING TECHNIQUE
LATERAL ANKLE ; Peroneus longus and brevis tendons.Calcaneo-fibular ligament.Anterior Talofibular ligament
Peroneus longus and brevis tendons. Transverse at the medial malleolus.
Patient sits on the side of a raised bed with foot resting on the Sonographers knee for support. Alternatively, the patient may sit or lie supine on bed with their foot flat.
talo -fib ligm tear
Talofib ligm tear.
talofib ligm tear.
talofib partial tear, and effusion.
Peroneus longus and brevis tendons; Begin in transverse, posterior to the lateral malleolus. The two tendons are easily seen with the peroneus brevis closest to the bone. Follow them proximally to the muscle and distally with particular attention to the insertion of the peroneus brevis tendon onto the base of the 5th metatarsal.
Scan plane for the Peroneus Brevis insertion to the base of the 5th metatarsal.
Calcaneo fibular ligament scan plane.
Calcaneo-fibular ligament: With the probe diagonally under the malleolus, angled from the fibula to the heel, you will see the peroneus tendons in transverse and the calcaneo-fibular ligament underlying them.
ANTERIOR ANKLE
Anterior talofibular ligament-ATFL.Place the heel of the probe on the anterior aspect of the distal fibula and rotate the toe of the probe towards the 2nd toe. The ligament should be readily visible as a 2cm long, 3mm thick tight fibrillar structure.
Tibio- fibular ligament -TFL.
Anterior Talofibular ligament (ATFL).
From the ATAF, further rotate the toe of the probe until just above the horizontal. The TFL has a similar appearance to the ATAF.
Extensor tendons; In transverse across the anterior ankle crease, you will see, from lateral to medial, the extensor digitorum, extensor hallucis and tibialis anterior tendons. By independently mobilising each of the toes and watching the tendons glide, you can identify which is which and exclude tendon rupture The overlying extensor retinaculum should also be observed.
Normal Tibio fibular ligament. sometimes slightly higher scan plan.
Extensor digitorum tendon. There is a common tendon until the level of the extensor retinaculum at the anterior ankle crease. After this, the tendon divides to the 4 lateral toes. (The big toe has it’s own tendon – the extensor hallucis).
ANTERIOR ANKLE; EXTENSOR TENDONS .ETA, EHL, EDL.
Longitudinal extensor hallucis longus tendon.
MEDIAL ANKLE . FTP, FHL, FDL.
Tibialis posterior, Flexor hallucis longus, and flexor digitorum longus.Assess the tendons along their length in longitudinal and transverse. Pay particular attention to the insertion of the Tibialis Posterior tendon with caution not to mistake the often present accessory ossicle, for an avulsed fragment. Begin diagonally under the medial malleolus with the toe of the probe on the malleolus. You will see the tibialis posterior and flexor digitorum tendons in transverse. Slide the probe postero-inferiorly and you will see the flexor hallucis longus tendon deeper against the calcaneum.
Longitudinal Tibialis Anterior tendon.
Tibialis posterior, flexor Digitorum and flexor Hallucis longus tendons (known as “Tom, Dick & Harry”). If including the neurovascular bundle – Tom Dick And Very Nervous Harry.
| Deltoid Ligament scan plane: Use plenty of gel and have the probe tip overlie the malleolar tip.Remember that you are scanning Deltoid ( 3) segments Anterior, middle and posterior segment of the Deltoid ligament. |
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Deltoid ligament.anterior, middle and posterior segments.
Posterior tibial nerve; The neurovascular bundle is easily seen posterior to the medial malleolus
Scan plane for the Achilles tendon. do sag and trv scan, look for insertion spur,retro calc bursa, hyperemia and thickness, tears ,fluid,and soft tissue edema.
POSTERIOR ANKLE
Patient positioned prone with the feet off the end of the bed.
Achilles tendon; Perform a survey scan ,in transverse, from the calcaneum up to the musculo-tendinous junction (of both medial and lateral gastrocnemii). Rotate into longitudinal and examine for thickening and integrity. At the same time assess the retrocalcaneal fat pad and bursa- Kager’s. The calf muscles and Plantaris tendon should also be assessed as clinically indicated.
An ankle series should include the following minimum images;
- Peroneus tendons – long, trans + peroneus brevis insertion
- Calcaneo-fibular ligament
- Anterior talofibular ligament
- Tibio-Fibular ligament
- Extensor digitorum tendon
- Extensor hallucis longus tendon
- Tibialis anterior tendon
- Tibialis posterior tendon
- Flexor digitorum tendon
- Flexor hallucis longus
- Achilles tendon and retrocalcaneal bursa
- Document the normal anatomy. Any pathology found in 2 planes(ligament tears or thickening, synovial bulging/cysts, joint effusion, gross bony changes), including measurements and any vascularity.
Thank you for reading.
Steve Ramsey, PhD, Public health. MSc -Medical Ultrasound. Calgary, Alberta- Canada.