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Medial malleolar osteotomy has been widely performed for posteromedial osteochondral lesions of the talus (OLT) to expose the lesion. In osteochondral fragment fixation, bioabsorbable pins should be inserted as perpendicular as possible to obtain the rigid fixation. However, the exposure of the lesion may depend on the osteotomy angle, which affects the pin insertion angles. This study aimed to analyze the relationship between pin insertion and osteotomy angles in the medial malleolar osteotomy.Twenty-four ankles of 23 patients were included. The malleolar bisector angle which was calculated from radiographs and actual osteotomy angles were measured on radiographs, and the pin insertion and osteotomy angles were measured using MRI. The intersection angle was defined by the tangential line of the tibial plafond and medial malleolar articular facet, and the bisector of this angle was defined as the malleolar bisector angle. The relationship between pin insertion and osteotomy angles was analyzed.There was no significant difference between the actual osteotomy (55.7° ± 6.6°) and malleolar bisector angles (57.4° ± 4.3°) on the radiograph. There was a significant correlation between pin insertion and osteotomy angles (rs = 0.601). The pin insertion angle (54.3° ± 5.9°) in the lower actual osteotomy angle than the malleolar bisector angle was smaller than those in the higher actual osteotomy angle (63.4° ± 8.2°).This study showed the osteotomy angle affected pin insertion angle. The osteotomy angle should not be smaller than the malleolar bisector angle at medial malleolar osteotomy to insert pins as perpendicular as possible for fixation of posteromedial OLTs.

Background Lateral ankle ligament repair for chronic lateral ankle instability is common, and arthroscopic repair of the anterior talofibular ligament (ATFL) has been widely performed. However, it is desirable to repair of calcaneofibular ligament (CFL) combined with arthroscopic ATFL repair to obtain good long term clinical outcomes. Repairing CFL through small skin incision, there is the possibility to interfere with ATFL and CFL anchors because of close attachment of ATFL and CFL at fibula. The purpose of this study is to determine the safety anchor insertion angles for ATFL and CFL on CT images and to achieve ATFL and CFL repair with minimally invasive technique. Methods Fifty ankles in 50 patients were included in this study. On a sagittal CT image, the anchor drill hole angles for ATFL and CFL were measured to avoid interference with these anchors. Then, arthroscopic ATFL repair combined with CFL repair was performed on 15 patients according to the safety insertion angles obtained by CT. CFL repair was performed through 1.5 cm length of accessory anterolateral portal. Clinical outcome was evaluated using the Japanese Society for the Surgery of the Foot (JSSF) ankle hindfoot scale and the Karlsson score before surgery and at final follow-up. Results On the CT image, the mean angles between the ATFL drill hole and anterior border of the fibula was 59.4 ± 6.5°, and those between the longitudinal axis of the fibula and ATFL drill hole, and the CFL drill hole were 34.6 ± 5.0°, and 15.1 ± 5.7°, respectively. Postoperative CT after arthroscopic ATFL repair combined with CFL repair showed that no interference with 2 anchors, and JSSF scale and the Karlsson score were significantly improved from preoperative to final follow-up. Conclusions This study showed how safety ATFL and CFL anchor insertion angles comprise a minimally invasive anatomical repair technique.