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Remote Fellowship – Foot & Ankle Fundamentals – 11/2/2020

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Diagnosis

Posterior Tibial Tendinopathy

Case Discussion

The posterior tibial tendon inverts and plantar flexes the foot and acts as a supporting structure for the medial arch of the foot (preventing pes planus).

Chronic tearing of the posterior tibial tendon is commonly associated with flat foot/pes planus deformity. Chronic tearing or rupture of the posterior tibial tendon with resultant medial longitudinal arch failure (pes planus) results in increased stress on the medial arch stabilizers, including the spring ligament complex, sinus tarsi ligaments, and plantar fascia.

Chronic tearing of the posterior tibial tendon occurs most frequently at the juxtamalleolar region, near the retromalleolar groove. Morphological abnormalities of the retrotibial groove (including a buffered prominent retrotibial groove) can contribute to posterior tibial tendinopathy and tearing. In addition, the tendon is relatively hypovascular in this region.

Acute tearing or rupture of the posterior tibial tendon occurs in a younger athletic demographic and most commonly occurs at the navicular insertion.

Conditions predisposed to posterior tibial tendinopathy include accessory navicular bone (particularly type 2 os navicularis), pes planus, inflammatory arthropathy such as rheumatoid arthritis, and others.

Posterior tibial tendinopathy manifests as a series of degenerative changes to the posterior tibial (PT) tendon. These changes range from tenosynovitis to complete tendon tears.

On MRI, the posterior tibialis tendon appears as a continuous black structure, without any internal signal intensity. It is typically twice as large in diameter as the flexor digitorum longus (FDL) tendon.

Chronic posterior tibial tendon ruptures may be divided into 3 types:

– Type I: partial tendon tears with tendon hypertrophy and intrasubstance degeneration/longitudinal splits (most common).

– Type II: partial tendon tear with an atrophic tendon

– Type III: complete tear

MRI findings of posterior tibial tendon pathology include thickening or thinning of the tendon associated with increased peritendinous signal intensity indicating tenosynovitis; tendon thickening associated with increased heterogenous intrasubstance signal and longitudinal tears; and in complete tendon ruptures, a tendinous gap and discontinuity of the tendon course.

Note: Abnormalities of the spring ligaments have a strong association with chronic posterior tibial tendinopathy. It is important to evaluate the spring ligaments prior to surgical intervention in patients with posterior tibial tendinopathy/tearing. Other important, often coexisting pathology, includes sinus tarsi syndrome and chronic plantar fasciitis.

Key Images

Hypertrophic tendinopathy and tear of the posterior tibial tendon in a 64-year-old man with 6 months of medial right ankle pain.

A. Axial PD FS image of the right ankle shows hypertrophy of the posterior tibial tendon and longitudinal intrasubstance tearing (red arrow) and surrounding tenosynovitis at the posterior aspect of the medial malleolus. There is also a retrotibial bifid groove anomaly (green arrow), where the posterior tibial tendon sits, and reactive osteoedema (yellow arrow).
B. Coronal T2 FS image shows a hypertrophic posterior tibial tendon and supra-, juxta-, and inframalleolar (red arrow) tearing.

References:

  1. Schweitzer ME, Karasick D. MR imaging of disorders of the posterior tibialis tendon. American Journal of Roentgenology 2000; 175:627-635
  2. Khoury NJ, El-Khoury GY, Saltzmann CL, Brandser EA. MR imaging of posterior tibial tendon dysfunction. American Journal of Roentgenology 1996; 167:675-682