DOI: 10.5061/dryad.r7sqv9skk
title: Evaluation of the horizontal approach to the medial malleolar facet in sagittal talar fractures through dorsiflexion and plantarflexion positions

description: Background  Talar fractures often require osteotomy during
 surgery to achieve reduction and screw fixation of the fractured fragments
 due to limited visualization and operating space of the talar articular
 surface. The objective of this study was to evaluate the horizontal
 approach to the medial malleolus facet by maximizing exposure through
 dorsiflexion and plantarflexion positions. Methods  In
 dorsiflexion, plantarflexion, and functional foot positions, we
 respectively obtained the anterior and posterior edge lines of the
 projection of the medial malleolus on the medial malleolar facet.
 The talar model from Mimics was imported into Geomagic software for image
 refinement. Then Solidworks software was used to segment the medial
 surface of the talus and extend the edge lines from the three positions to
 project them onto the "semicircular" base for 2D projection. The
 exposed area in different positions, the percentage of total area it
 represents, and the anatomic location of the insertion point at the groove
 between the anteroposternal protrusions of the medial malleolus were
 calculated. Results  The mean total area of the
 "semicircular" region on the medial
 malleolus surface of the talus
 was 542.10 ± 80.05 mm2. In the
 functional position, the exposed mean area of the medial malleolar
 facet around the medial malleolus both anteriorly and
 posteriorly was 141.22 ± 24.34 mm2, 167.58
 ± 22.36mm2, respectively. In dorsiflexion, the mean area
 of the posterior aspect of the medial malleolar facet was 366.28
 ± 48.12 mm2. In plantarflexion, the mean of the
 anterior aspect of the medial malleolar facet was 222.70
 ± 35.32 mm2. The mean overlap area of unexposed
 area in both dorsiflexion and plantarflexion was 23.32
 ± 5.94 mm2. The mean percentage of the
 increased exposure area in dorsiflexion and plantarflexion were
 36.71 ± 3.25 % and 15.13 ± 2.83 %. The mean
 distance from the insertion point to the top of the talar
 dome was 10.69 ± 1.24 mm, to the medial malleolus facet
 border of the talar trochlea was 5.61 ± 0.96 mm, and to
 the tuberosity of the posterior tibiotalar portion of the deltoid ligament
 complex was 4.53 ± 0.64 mm. Conclusions  Within
 the 3D model, we measured the exposed area of the medial malleolus facet
 in different positions and the anatomic location of the insertion point at
 the medial malleolus groove. When the foot is in plantarflexion or
 dorsiflexion, a sufficiently large area and operating space can be exposed
 during surgery. The data regarding the exposed visualization area and
 virtual screws need to be combined with clinical experience for safer
 reduction and fixation of fracture fragments. Further validation of its
 intraoperative feasibility will require additional clinical research.
description: DICOM-formatted CT-scan images of each patient were imported into
 Mimics software (21.0 ; Materialise, Leuven, Belgium). We removed the soft
 tissue and affected bones by the function of image segmentation, region
 growth and multiple slice editing of Mimics software, respectively. A
 total of 273 virtual foot and ankle models were created. In dorsiflexion,
 plantarflexion, and functional foot positions, we respectively obtained
 the anterior and posterior edge lines of the projection of the medial
 malleolus on the medial malleolar facet (Fig. 1). At the same time, we
 found that the medial malleolar facet had a shape resembling a
 “semicircle”, and regardless of whether the foot was in the functional
 position, dorsiflexed, or plantarflexed, the movement of the medial
 malleolus occurred within this "semicircular" region (Fig.
 2A). Tracing the outline of the foot in the three positions on the talus,
 it is not difficult to observe that plantarflexion and dorsiflexion expand
 the exposure area on the anterior and posterior aspects of the talus (Fig.
 2B). The talar model from Mimics was imported into Geomagic software
 (2019, 3D Systems, North Carolina, USA) for image refinement. Then
 Solidworks software (2021, Dassault Systemes, USA) was used to segment the
 medial surface of the talus and extend the edge lines from the three
 positions to project them onto the "semicircular" base for 2D
 projection. The following areas were measured: Total area (TA) of the
 "semicircular" region on the medial malleolar facet; In the
 functional position, the exposed area of the medial malleolar facet around
 the medial malleolus both anteriorly (FAA) and posteriorly (FAP); In
 dorsiflexion, the exposed area of the posterior aspect of the medial
 malleolar facet (DA); In plantarflexion, the exposed area of the anterior
 aspect of the medial malleolar facet (PA); Unexposed overlap area in both
 dorsiflexion and plantarflexion (UA). The percentage of the increased
 exposure area in dorsiflexion and plantarflexion positions were
 calculated.
description: # Evaluation of the horizontal approach to the medial malleolar facet in
 sagittal talar fractures through dorsiflexion and plantarflexion positions
 In the positions of foot
 dorsiflexion, plantarflexion, and functional, we respectively obtained the
 anterior and posterior edge lines of the projection of the medial
 malleolus on the medial malleolar facet. The talar model from Mimics was
 imported into Geomagic software for image refinement. Then Solidworks
 software was used to segment the medial surface of the talus and extend
 the edge lines from the three positions to project them onto the
 "semicircular" base for 2D projection. The exposed area in
 different positions, the percentage of total area it represents, and the
 anatomic location of the insertion point at the groove between the
 anteroposternal protrusions of the medial malleolus were calculated. The
 mean total area of the "semicircular" region on the medial
 malleolus surface of the talus was 542.10 ± 80.05 mm2. In the functional
 position, the exposed mean area of the medial malleolar facet around the
 medial malleolus both anteriorly and posteriorly was 141.22 ± 24.34 mm2,
 167.58 ± 22.36mm2, respectively. In dorsiflexion, the mean area of the
 posterior aspect of the medial malleolar facet was 366.28 ± 48.12 mm2. In
 plantarflexion, the mean of the anterior aspect of the medial malleolar
 facet was 222.70 ± 35.32 mm2. The mean overlap area of unexposed area in
 both dorsiflexion and plantarflexion was 23.32 ± 5.94 mm2. The mean
 percentage of the increased exposure area in dorsiflexion (36.71 ± 3.25 %)
 and plantarflexion were 36.71 ± 3.25 % and 15.13 ± 2.83 %. The mean
 distance from the insertion point to the top of the talar dome was 10.69 ±
 1.24 mm, to the medial malleolus facet border of the talar trochlea was
 5.61 ± 0.96 mm, and to the tuberosity of the posterior tibiotalar portion
 of the deltoid ligament complex was 4.53 ± 0.64 mm. ## Description of data
 and file structure DICOM-formatted CT-scan images of each patient were
 imported into Mimics software (21.0; Materialise, Leuven, Belgium). We
 removed the soft tissue and affected bones by the function of image
 segmentation, region growth and multiple slice editing of Mimics software,
 respectively. A total of 273 virtual foot-and-ankle models were created.
 In the positions of foot dorsiflexion, plantarflexion, and functional, we
 respectively obtained the anterior and posterior edge lines of the
 projection of the medial malleolus on the medial malleolar facet (Fig. 1).
 At the same time, we found that the medial malleolar facet had a shape
 resembling a “semicircle”, and regardless of whether the foot was in the
 functional position, dorsiflexed, or plantarflexed, the movement of the
 medial malleolus occurred within this "semicircular" region
 (Fig. 2A). Tracing the outline of the foot in the three positions on the
 talus, it is not difficult to observe that plantarflexion and dorsiflexion
 expand the exposure area on the anterior and posterior aspects of the
 talus (Fig. 2B). The talar model from Mimics was imported into Geomagic
 software (2019, 3D Systems, North Carolina, USA) for image refinement.
 Then Solidworks software(2021, Dassault Systemes, USA) was used to segment
 the medial surface of the talus and extend the edge lines from the three
 positions to project them onto the "semicircular" base for 2D
 projection. This data can be used to describe the medial malleolar area of
 the talus. **Abbreviations** TA(mm2): Total area of the
 "semicircular" region on the medial malleolar facet. FAA(mm2):
 In functional position, the exposed area of the anterior aspect of the
 Medial malleolus. FAP(mm2): In functional position, the exposed area of
 the posterior aspect of the Medial malleolus. DA(mm2): In dorsiflexion,
 the exposed area of the posterior aspect of the medial malleolar facet.
 PA(mm2): In plantarflexion, the exposed area of the anterior aspect of the
 medial malleolar facet. UA(mm2): Unexposed area in both dorsiflexion and
 plantarflexion. L1(mm):The distance of the insertion point to the top of
 the talar dome. L2(mm):The distance of the medial malleolus facet border
 of the talar trochlea. L3(mm):The distance from the insertion point to the
 tuberosity of the posterior tibiotalar portion of the deltoid ligament
 complex. ## Code/Software Mimics software (21.0; Materialise, Leuven,
 Belgium); Geomagic software (2019, 3D Systems, North Carolina, USA);
 Solidworks software (2021, Dassault Systemes, USA)