How To Diagnose Lateral Ankle Injuries

Author(s): 
By Remy Ardizzone, DPM, and Ronald L. Valmassy, DPM

Pearls For Diagnosing Peroneal Tendon Injuries

   Injury to the peroneal tendons can manifest in several ways, including peroneal tendon tears, tenosynovitis and subluxation. During an inversion injury, the peroneus brevis and peroneus longus tendons fire in an attempt to evert the foot forcibly, thereby stabilizing the ankle to prevent it from inverting.25 This can result in a subtle, longitudinal tear to one of the tendons. The peroneus brevis tendon is commonly injured given its close proximity to the posterolateral tip of the fibula.26    Additional contributing factors may attenuate the superior peroneal retinaculum. These factors include an anomalous tendon or low-lying peroneal muscle belly.27 This condition constrains the peroneal tendon within the fibular groove, leading to mechanical attrition of the peroneus brevis tendon against the sharp posterior ridge of the fibula.8,26,28,29    Many of these subtle injuries heal uneventfully. Occasionally, however, the patient will complain of persistent pain posterior to the lateral malleolus that is exacerbated by lateral cutting maneuvers such as the swift side-to-side motion one frequently sees in tennis or soccer, or abrupt changes in direction that occur when pivoting on one foot. Swelling may or may not be present but one may frequently reproduce pain via palpation of the tendons posterior to the lateral malleolus and through resisted ankle eversion.    Frequently, clinicians may see evidence of a tear on a MRI as indicated by a C-shaped appearance to the tendon on an axial projection with abundant scar tissue formation surrounding the tendon and increased fluid signal on T2 STIR sequences.28,30,31,32 Magnetic resonance imaging may also help distinguish between a discrete tendon tear and less serious conditions of tendonitis or tendonosis although chronic tendonosis may be a precursor to an actual tear.30 Comparing T1 and T2 images at the distal tip of the fibula will help clarify potential “false positive” findings due to the magic angle phenomenon.28,31 Bear in mind that a normal study does not preclude surgical intervention under appropriate clinical circumstances.    However, one cannot appreciate peroneal tenosynovitis on MRI. In order to diagnose this condition, which involves hypertrophic synovium within the peroneal tendon sheath within the tendons themselves, one should use a tenogram.33 When the tenogram is positive, the flow of radioopaque dye will be impeded by adhesion or stricture of the sheath or scar tissue about the tendon.34 Additionally, a tenogram may be potentially therapeutic as well as diagnostic. The mixture of local anesthetic and radioopaque dye into the closed space of the tendon sheath acts as a “balloon” to separate the adherent scar tissue from the surface of the tendon. Adding corticosteroid into the injection may potentially “shrink” any adhesive scar tissue and decrease inflammation. Given the risk of tendon rupture with corticosteroid injection to tendons, this procedure requires a skilled radiologist to ensure an injection into the space between the tendon sheath and the actual tendon itself.

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