PMC7140132_01
Preoperative photograph showing swelling of the posteromedial side of the left ankle (white arrow).
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fig1
Physical examination revealed swelling and tenderness on the medial side of the left ankle (Figure 1).
Lateral radiograph showing the os trigonum (arrow).
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fig2
An os trigonum was visible on a weight-bearing lateral radiograph of the left ankle (Figure 2) and on a computed tomography (CT) scan (Figures 3(a) and 3(b)).
Computed tomography images showing the os trigonum connected to the posterior aspect of the talus. (a) Plain image, sagittal view (arrow). (b) Three-dimensional image, posterior view (arrow).
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fig3
An os trigonum was visible on a weight-bearing lateral radiograph of the left ankle (Figure 2) and on a computed tomography (CT) scan (Figures 3(a) and 3(b)).
T1-weighted, T2-weighted, and T2-spectral attenuated inversion recovery magnetic resonance images showing a massive effusion around the flexor hallucis longus (arrow) at a level proximal to the ankle joint posteriorly in the (a) sagittal, (b) coronal, and (c) axial planes and between the talar tubercles and the master knot of Henry in the (d) sagittal, (e) coronal, and (f) axial planes.
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fig4
MRI revealed massive effusion around the FHL tendon at a level proximal to the ankle joint posteriorly (Figures 4(a)-4(c)) and between the talar tubercles and the master knot of Henry (Figures 4(d)-4(f)).
Arthroscopic views of the posterior aspect of the left ankle. (a) The posterior aspect of the os trigonum (arrow) can be visualized. (b) The fibrous portion of the tunnel compressed the flexor hallucis longus (FHL) tendon (arrow) after removal of the os trigonum. (c) Stenosis was not seen (arrow) after the release of the FHL tendon. Suction was performed along the FHL tendon (d) toward a level proximal to the ankle joint posteriorly and (e) anterior to the talar tubercles and the master knot of Henry.
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fig5
The posterior aspect of the talus and os trigonum was then visualized (Figure 5(a)). The FHL was thick, and a fibroosseous tunnel was seen adherent to the tendon (Figure 5(b)). Next, the tendon was released (Figure 5(c)). Suction was performed along the FHL tendon toward a level proximal to the ankle joint posteriorly (Figure 5(d)) and anterior to the talar tubercles and the master knot of Henry (Figure 5(e)).
Fat saturation T2-weighted magnetic resonance images showing no effusion along the flexor hallucis longus (FHL) tendon at a level proximal to the ankle joint posteriorly in the (a) sagittal and (b) axial planes. T2-weighted and fat saturation T2-weighted images showing no accumulation of effusion along the FHL between the talar tubercles and the master knot of Henry in the (c) sagittal and (d) axial planes.
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fig6
At the 1-year follow-up visit, the patient remained asymptomatic and MRI showed no recurrence of the fluid around the FHL (Figures 6(a)-6(d)).