Forced plantar flexion on an extended foot. Anterior ankle pain and weakness • Xray of the Week
What is the diagnosis?
Figure 1. What is the important finding on this MRI of the ankle.
A: T1 weighted axial image with tibialis anterior rupture (yellow arrow).
B: T1 weighted sagittal image with tibialis anterior tendon discontinuity, retraction and soft tissue edema (yellow arrow).
C: T2 weighted axial image with tibialis anterior rupture (yellow arrow).
D: T2 weighted sagittal image with tibialis anterior tendon discontinuity, retraction, and soft tissue edema (yellow arrow).
Anterior ankle tendinopathy can involve the tibialis anterior, extensor digitorum longus, or extensor hallucis longus. Anatomically, the anterior tibialis muscle tendon inserts at the plantar and medial aspect of the first metatarsal and cuneiform bones (4). The tibialis anterior muscle is the main dorsiflexor for the foot. Since the tendon is under the retinaculum, mechanical demand is less compared to the other tendons, leading to less irritation and tearing (4). Rupture of the tibialis anterior tendon can occur due a sudden force typically in the opposite direction of tendon function: forced plantar flexion of an extended foot. Rupture can also occur with degenerative processes typically affecting the distal avascular portion of the tendon (1). These degeneration etiologies can include impingement, inflammatory arthritis, diabetes mellitus, or chronic microtrauma leading to tendinosis (4). Upon tendon rupture, patients may present with anterior ankle pain and weakness. In addition, there may be a painless mass on the anteromedial aspect of the ankle due to the ruptured tendon and adjacent inflammation. Patients can have delayed presentation due to the compensation of the extensor hallucis longus and extensor digitorum muscles (1,3). This injury typically presents more in an older population due to the decreased tendon elasticity (2). In this case, the patient presented due to forced plantar flexion on an extended foot leading to a retracted full thickness tear.
Imaging can prove helpful in making the diagnosis of tendon rupture, especially when the clinical and physical findings are vague. When evaluating an MR image of the ankle, normal tendons have low signal intensity on all sequences (4). With complete anterior tibial tendon rupture, discontinuity and retraction of the proximal tendon segment is apparent (4). Figures 2B and 2D demonstrate discontinuity, with rupture of the tendon and adjacent soft tissue swelling. In the setting of a tendon rupture, the tibialis anterior tendon is visualized on the medial side of the ankle with surrounding edema denoted by the yellow arrow on Figures 2A and 2C.
Common sequelae of tendon rupture include foot drop, flatfoot, and compromised gait (3). Initial treatment includes conservative methods such as casting or orthotics. Surgery with direct repair or reconstruction may be indicated in athletes or after failure of conservative management (3).
Waizy H, Bouillon B, Stukenborg-Colsman C, et al. Ruptur der Musculus-tibialis-anterior-Sehne : Ätiologie, klinische Symptome und Therapie [Rupture of the tendon of the tibialis anterior muscle : Etiology, clinical symptoms and treatment]. Unfallchirurg. 2017;120(12):1015-1019. doi:10.1007/s00113-017-0417-z
Kausch T, Rütt J. Subcutaneous rupture of the tibialis anterior tendon: review of the literature and a case report. Arch Orthop Trauma Surg. 1998;117(4-5):290-293. doi:10.1007/s004020050250
Christman-Skieller C, Merz MK, Tansey JP. A systematic review of tibialis anterior tendon rupture treatments and outcomes. Am J Orthop (Belle Mead NJ). 2015;44(4):E94-E99. https://pubmed.ncbi.nlm.nih.gov/25844597/
Khoury NJ, el-Khoury GY, Saltzman CL, Brandser EA. Rupture of the anterior tibial tendon: diagnosis by MR imaging. AJR Am J Roentgenol. 1996;167(2):351-354. doi:10.2214/ajr.167.2.8686602
Amer Ahmed is a fourth-year medical student at Midwestern University Chicago College of Osteopathic Medicine. There, he has served as the President for the Medical Business Association and Secretary for the Radiology Interest Group. Before medical school, Amer earned a degree in Economics at Loyola University Chicago and spent some time as an Investment Specialist at Merrill Edge before deciding to pursue his interest in medicine. Radiology intrigued Amer following a back injury requiring him to get an MRI. That is when he was able to appreciate the eye for detail Radiologists possess. Amer is passionate about finance, medicine, and technology.
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Phillip Tirman, MD is the Medical Director of Musculoskeletal Imaging at the Renaissance Imaging Center in Westlake Village, California. A nationally recognized expert in the applications of MRI for evaluating MSK and spine disorders, Dr. Tirman is the co-author of three textbooks, including MRI of the Shoulder and Diagnostic Imaging: Orthopedics. He is also the author or co-author of over sixty original scientific articles published in the radiology and orthopedic literature.
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Kevin M. Rice, MD is the president of Global Radiology CME
Dr. Rice is a radiologist with Renaissance Imaging Medical Associates and is currently the Vice Chief of Staff at Valley Presbyterian Hospital in Los Angeles, California. Dr. Rice has made several media appearances as part of his ongoing commitment to public education. Dr. Rice's passion for state of the art radiology and teaching includes acting as a guest lecturer at UCLA. In 2015, Dr. Rice and Natalie Rice founded Global Radiology CME to provide innovative radiology education at exciting international destinations, with the world's foremost authorities in their field. In 2016, Dr. Rice was nominated and became a semifinalist for a "Minnie" Award for the Most Effective Radiology Educator.
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