SLR - March 2019 - Zachary Bennett
Reference: Teramoto A, Shoji H, Kura H, Sakakibara Y, Kamiya T, Watanabe K, Yamashita T. Investigation of factors related to the occurrence of osteochondral lesions of the talus by 3D bone morphology of the ankle. Bone Joint J. 2018 Nov;100-B(11):1487–1490.
Scientific Literature Review
Reviewed By: Zachary Bennett, DPM
Residency Program: Hennepin Healthcare, Minneapolis, MN
Podiatric Relevance: The morphology of the ankle can be evaluated on plain radiographs using the tibial articular surface (TAS), the tibial bimalleolus (TBM) and tibial axis-medial malleolus (TMM) angles. Patients with an osteochondral lesion have been reported to have a large TMM angle and a morphology in which the medial malleolus opens distally. However, these reports are based on 2D evaluations. The normal talus is broader anteriorly than posteriorly, and, with the ankle in plantar flexion, the proportion of the mortise occupied by the talus is small with an increase in the joint space and decreased conformity. Thus, decreased conformity of the ankle in plantarflexion is related to the occurrence of osteochondral lesions. However, much remains unknown about talar dome lesion etiology. The aim of this study was to evaluate the morphology of the ankle in patients with osteochondral lesions using 3D CT and to investigate their etiology.
Methods: Nineteen ankles (13 men, six women) that had undergone surgery for medial osteochondral lesions (OLT group) and 19 controls without ankle pathology were evaluated. CT scans of the ankle were obtained in both groups, and bone surface 3D models were made using reconstruction software. The medial malleolar articular and tibial plafond surface and the medial and lateral surface area of the trochlea of the talus were defined. The TMM angle, the medial malleolar surface area and volume (MMA and MMV) and the anterior opening angle of the talus were measured.
Results: The mean TMM angle and anterior opening angle of the talus were significantly larger in the OLT group than in the control group. Also, the mean MMA and MMV were significantly smaller in the OLT group than in the control group. These results suggest that poor bony conformity of the ankle predisposes patients to talar dome injury.
Conclusions: The results point to an association between poor morphological conformity of the ankle and predisposition to osteochondral lesions of the talus. Berndt and Harty suggested that trauma to the ankle occurs with plantarflexion and anterior shift of the tibia in relation to the talus and inversion of the talus. It is likely that recurrent microtrauma is a more significant cause of an osteochondral lesion than a single severe injury. Surgical treatments for these injuries (i.e., drilling, microfracture, fragment fixation, autograft transplantation) often only address the lesion and not the cause. This study demonstrates that consideration should be given to improving the conformity of the ankle in addition to treating the lesion. A limitation of this study is that all patients with osteochondral lesions had surgical treatment, thus, the symptoms were severe enough to warrant surgery. Also, it was a relatively small sample size. Despite these limitations, it appears 3D bone morphology of the ankle joint is closely related to the occurrence of osteochondral lesions of the talus.