Age / Sex : 65 / F

Chief complaint: left ankle pain for 6 months

What is your diagnosis?

Two weeks later, you can see the final diagonosis with a brief discussion of this case (Please submit only one answer).


Courtesy : 최윤선, Yun Sun Choi, MD, 노원을지대학교병원, Nowon Eulji Medical Center, Eulji University

Rupture of the tibialis anterior tendon and extensor retinaculum

Discussion

Findings:

Sagittal fat suppression T2-weighted FSE MR images of the ankle show a bulbous tibialis anterior tendon with partial thickness tear. Axial fat suppression T2-weighted and PD-weighted FSE MR images show the anteriorly displaced tendon with peritendinous high signal. The extensor retinaculum is also torn.

Differential Diagnosis:

1. Soft tissue mass


2. Tendinosis

Discussion:

Tibialis anterior (TA) tendon is the strongest among the anterior tendons. It is covered by the extensor retinaculum. It receives its blood supply exclusively from the anterior tibial artery, which puts it at risk for ischemia. TA tendon passes through three retinacular tunnels formed by the superior and inferior extensor retinacula, and inserts on the medial cuneiform and the adjacent base of 1^st metatarsal bone.

Rupture of the TA tendon is uncommon. The common sites for TA tendon rupture are its insertion into the adjacent surface of the medial cuneiform, beneath the oblique superomedial limb of the inferior extensor retinaculum, and in a triangular space between with a lateral base formed by the superior extensor retinaculum and the oblique superomedial limb of the inferior extensor retinaculum. Weakness of dorsiflexion, localized tenderness, foot drop, and a palpable mass and/or defect are observed on clinical examination.

Ruptures of the TA tendon are generally divided into two categories: acute and acute-on-chronic. It is important to differentiate a partial and complete rupture. The MRI characteristics of TA tendon tear are discontinuity and/or an empty tendon sheath in a complete tear, attenuation in a partial tear, and thickening in a partially or completely torn retracted tendon. Tears can also be manifested by increased signal within and surrounding the tendon on T1WI and (FS) PDWI or T2WI. It may be difficult to distinguish a partial tear from tendinosis as both may be thickened and have increased intrasubstance signal. Bianchi et al. advocated ultrasonography as a relatively inexpensive alternative to MRI. The relationship of the TA tendon and extensor retinaculum is well depicted on MRI.   

References:

1. Resnick D, Kang HS, Pretterklieber ML. Internal derangements of joints, 2^nd Philadelphia: Saunders, 2007:2164-2166


2. Lee MH, Chung CB, Cho JH, Mohana-Borges AV, Pretterklieber ML, Trudell DJ, et al. Tibialis anterior tendon and extensor retinaculum: imaging in cadavers and patients with tendon tear. AJR Am J Roentgenol. 2006;187(2):W161-168


3. Gallo RA, Kolman BH, Daffner RH, Sciulli RL, Roberts CC, DeMeo PJ. MRI of tibialis anterior tendon rupture. Skeletal Radiol. 2004;33(2):102-106


4. Bianchi S, Zwass A, Abdelwahab IF, Zoccola C. Evaluation of tibialis anterior tendon rupture by ultrasonography. J Clin Ultrasound. 1994;22:564-566