Lateral hindfoot impingement.

A 3D representation of the normal appearance of the structures involved with lateral hindfoot impingement. On the left a lateral view of the ankle shows the normal space between the lateral talar process (asterisk) and the calcaneal angle of Gissane (arrowhead). The image on the right depicts the plane just anterior to the posterior subtalar joint demonstrating normal alignment and spacing between the lateral talus (asterisk), the lateral calcaneus (arrowhead), and the lateral malleolus (arrow).

3D representation in the coronal plane just anterior to the posterior subtalar joint demonstrates changes of lateral hindfoot impingement. On the left the lateral talus impacts the lateral calcaneus. With more severe hindfoot valgus and lateral calcaneal subluxation additional impingement may occur between the lateral malleolus and lateral calcaneus as depicted on the right.

A sagittal T1-weighted image of the ankle in a 54 year-old woman demonstrates normal talocalcaneal alignment, with a normal small interval between the apex of the lateral talar process and the calcaneus at apex of the angle of Gissane (blue lines). Dotted red lines demonstrate the landmarks for measuring the angle of Gissane. An unremarkable cervical ligament at the sinus tarsi, with adjacent normal fat signal is indicated (arrowhead).

The “critical” angle of Gissane was devised on lateral radiographs to evaluate calcaneal fractures, as commonly the talar lateral process is driven downward into the adjacent relatively weak part of the calcaneus5. The angle is measured using a line along the superior calcaneal cortex at the body and anterior calcaneal process, and another line along the posterior articular facet of the calcaneus (8a); normally it measures around 130 degrees. The apex of the angle of Gissane is at the location of chronic talar impact with lateral hindfoot impingement, and this is the center of the bony changes, therefore the angle of Gissane, or “calcaneal angle” can be used as a term to identify the calcaneal location of pathology. The actual angle measurement is not critical and indeed typically remains normal in hindfoot impingement cases.

The corresponding fat-suppressed T2-weighted image demonstrates the normal rounded to slightly pointed apex of the lateral talar process (arrow), and the unremarkable cervical ligament (arrowhead). Normal minimal fluid is present at the posterior subtalar joint, without capsular distension into the sinus tarsi.

A fat-suppressed proton density-weighted image, obtained coronal to the apex of the angle of Gissane in a 54 year-old woman showing normal talocalcaneal alignment, with a normal interval between the lateral malleolar tip and the lateral calcaneus (arrow), and normal position of the peroneal tendons (arrowheads).

A fat-suppressed T2-weighted image in a 52 year-old patient with lateral hindfoot impingement demonstrates characteristic bone marrow edema at the inferior apex of the lateral talar process (asterisk) as well as at the subjacent angle of Gissane (arrowhead).

A sagittal fat-suppressed T2-weighted image in 70 year-old woman with clinical symptoms of posterior tibial tendon insufficiency and lateral hindfoot pain, shows extra-articular distribution of bone marrow edema at lateral talar process (arrow), with a small flat facet at the distal apex, and with subcortical calcaneal bone marrow edema extending anteriorly (arrowhead).

A T1-weighted sagittal image in a 61 year-old male with lateral hindfoot pain, demonstrating mild sclerosis at the lateral talar process (arrowhead) and adjacent calcaneus. The corresponding T2-weighted images (not shown) demonstrated adjacent mild bone marrow edema and very subtle cystic changes in this region as well.

A T1-weighted sagittal image in a 65 year-old female with cortical remodeling with bone loss and "neofacet" formation at both the lateral talar process and the calcaneus, as well as subcortical sclerosis. Note the absence of signs of osteoarthritis at the adjacent posterior subtalar joint.

A T1-weighted sagittal image in a 52 year-old male with ankle pain and swelling shows features characteristic of sinus tarsi syndrome, with absence of fat signal at the sinus tarsi (arrow).

The corresponding sagittal STIR image shows edema throughout the sinus tarsi with subcortical bone marrow edema along the talus and calcaneus at margins of the sinus (arrows).

A fat-suppressed T2-weighted sagittal image in a 34 year-old man with a history of an ankle sprain 2 weeks prior, demonstrates an incidental finding of cystic changes at the calcaneal body (arrow), typical for an intraosseous ganglion cyst.

The sagittal T1-weighted image demonstrates extra-articular subcortical cystic changes and bone marrow edema at the lateral talar process and the adjacent calcaneus (arrowheads). Normal fat signal is seen at the sinus tarsi (long arrow).

The sagittal T2-weighted image with fat saturation shows extra-articular subcortical cystic changes and bone marrow edema at the lateral talar process and the adjacent calcaneus (arrowheads). Also demonstrated is unremarkable articular cartilage at the posterior subtalar joint (arrow).

A coronal fat-suppressed proton density-weighted image obtained just anterior to the posterior subtalar joint reveals the extra-articular subcortical bone marrow edema and cystic changes at both the talocalcaneal region (arrowheads), and the calcaneofibular region, with bony remodeling and flat neo-facets at the fibula distally and at the adjacent lateral calcaneus (red arrows). There is peroneal tendinosis (blue arrow), and edema at interposed lateral soft tissues.

A posterior coronal view demonstrates that severe heel valgus is present, with an abnormal, 40 degree angle between the medial calcaneal cortex and the long axis of the tibia, measured just posterior to the sustentaculum at the level of the posterior talus and tibia. As the MR was not obtained during weight-bearing, the measurement may underestimate the extent of functional malalignment.

The MRI hindfoot valgus angle measurement suggested in the literature has been adapted from methods using frontal weight-bearing radiographic studies and CT reconstruction exams. It is calculated as the angle between the long axis of the tibia, and the border of the calcaneal medial cortex (D)2. The measurement is performed on the most posterior coronal image that includes both the tibia and calcaneus, taking care not to use an image through the calcaneal sustentaculum tali as that would increase the angle. The medial, rather than the lateral, calcaneal wall is selected for MR measurements because it has less variability and fewer bony protuberances. Hindfoot valgus on MRI has been graded as mild (7-16°), moderate (17-26°), and severe (> 26°), with normal at 0-6 degrees.

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