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Peroneus longus tendon tear – Rob Mast, Extended Scope Physiotherapist

This case involved a patient in their 70s who sustained an acute lateral ankle injury when turning and pivoting on his right foot whilst at work. The pain was very severe and he therefore visited his local Accident and Emergency department. He subsequently had an x-ray taken of the ankle as it was feared that he had fractured his ankle or his lateral foot. This was reported as normal.

Unfortunately despite icing and resting his ankle,the pain did not settle and he was still unable to fully bear weight on his foot. Objective examination demonstrated active instability of the ankle with his ankle giving way into supination when bearing full weight on it. On ultrasound in clinic the lateral collateral ligaments, perhaps surprisingly, seemed to be intact with both ATFL and CFL not showing signs of acute tearing. However what was evident was effusion in the tendon sheaths of the peroneal tendons most markedly around peroneus longus (Figure 1).
Figure 1: Transverse view of effusion in the tendon sheath of peroneal tendons
Figure 1: Transverse view of effusion in the tendon sheath of peroneal tendons
Peroneus longus teat on ultrasound
Figure 2: Void where peroneus longus would normally been seen
Figure 3: Surface anatomy of peroneal tendons
Figure 3: Surface anatomy of peroneal tendons
The Peroneus Brevis could be followed down to its terminal insertion into the fifth metatarsal head. There was however a void over the more inferior aspect of the calcaneus where the Peroneus Longus tendon would normally be seen (Figure 2). In order to evaluate the normal anatomy in this region please see Figure 3.

I felt that the combination of clinical and US findings indicated a full thickness Peroneus Longus tendon tear. I referred him to an Orthopaedic ankle specialist pending an MRI scan that I had also requested.The MRI confirmed my suspicions of a FTT of peroneus longus (Figure 4), the full report being :'There is a full thickness tear of the peroneus longus tendon immediately distal to the cuboid tunnel within the plantar aspect of the foot. I cannot confidently identify an avulsed bony fragment. The peroneus brevis tendon is normal and intact. The anterior and medial tendons are normal and intact'.

The tear however was located more plantar than I had expected. In retrospect I think that the tendon appeared hypo-echogenic in Figure 2, simply due to the fact that it had lost its normal tension.

A useful reference point for a Peroneus Longus tendon rupture is this free access article by Smania et al (2007)

 

Figure 4: MRI demonstrating full thickness peroneal tendon tear.
Figure 4: MRI demonstrating full thickness peroneal tendon tear.

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More pathology demonstrated on ultrasound can be found in the video gallery and image gallery.

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