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Purpose: This study was designed to investigate (1) the contour of the distal tibial cutting surface, and (2) the bone mineral density (BMD) of the distal tibial cutting surface used during total ankle arthroplasty (TAA). Methods: Eight-four distal tibial models were created using foot and ankle computerized tomographic (CT) images taken from normal people. The distal tibial cutting surface for TAA was determined to be 10 mm proximal to the tibial plafond. The bony contour and BMD values were determined from the CT image at that level. A bounding box was made on the contour and the width and length of the contour was measured. Regional BMD was evaluated by Hounsfield units (HU) value measurement, with 7 regions of interest (ROI) on 8 different directions for all the 84 CT images. Two different observers made independent measurements and mean HU values for all the 56 ROIs were calculated. Results: Great variations were found among the contours of the cutting surface especially in term of the shape of the anterior and posterior tibial tubercle, and the fibular notch. These variations could be grouped into six categories. For the BMD of the cutting surface, the medial border of the cutting surface did not included cortical bone. The HU value of seven ROIs, which included cortical bone, were significantly greater than all the other ROIs. Few statistical differences were found by multiple comparisons among HU value of all the 49 ROIs without cortex. Conclusions: Great variability existed in the shape and the BMD of the distal tibial cutting surface.

Purpose: The study described a novel surgical treatment of Haraguchi type 1 posterior malleolar fracture in tri-malleolar fracture and patient outcomes at intermediate period follow-up. Methods: All patients from January 2015 to December 2017 with tri-malleolar fracture of which posterior malleolar fractures were Haraguchi type 1, were surgically treated in this prospective study. Lateral and medial malleolar fractures were managed by open reduction and internal fixation through dual incision approaches. 36 cases of Haraguchi type 1 posterior malleolar fractures were randomly performed by percutaneous posteroanterior screw fixation with the aid of medial exposure (group 1). And 40 cases were performed by percutaneous anteroposterior screw fixation (group 2). Clinical outcomes, radiographic outcomes and patient-reported outcomes were recorded. Results: Seventy-six patients with mean follow-up of 30 months were included. There were no significant differences in the mean operation time (81.0 ± 11.3 vs. 77.2 ± 12.4), ankle function at different periods of follow-up, range of motions and visual analog scale (VAS) at 24 months between the two groups ( p > 0.05). However, the rate of severe post-traumatic arthritis (Grade 2 and 3) and the rate of step-off rather than gap in radiological evaluation were lower in group 1 than that in group 2 ( p < 0.05). Conclusion: Using our surgical technique, more patients had good outcome with a lower rate of severe post-traumatic arthritis, compared with the group of percutaneous anteroposterior screw fixation. Percutaneous posteroanterior screw fixation can be a convenient and reliable alternative in treating Haraguchi type 1 posterior malleolar fracture.