Three-dimensional morphological analysis and clinical application of ankle joint in Chinese population based on CT reconstruction

The feasibility of diagnosing sprained ankle via 3D MRI reconstructing three-dimensional model of anterior talofibular ligament

Introduction

The anterior talofibular ligament (ATFL) is the most vulnerable ligament in ankle sprains. Most patients recover after this injury with conservative treatment, while 20%-40% progress to chronic ankle instability that requires surgical stabilization. Conventional MRI does not provide a comprehensive image of the ATFL. We aimed to evaluate the feasibility of using 3D MRI to facilitate the understanding of ATFL injuries and the operative planning.

Methods

A total of 21 healthy asymptomatic volunteers with 30 normally functioning ankles and 13 patients with 18 sprained ankles were studied. MRI scans were divided into two groups: Group 1 (normal ankle) and Group 2 (injured ankle). The data of all 48 cases were exported to Mimics and reconstructed into 3D models. The image quality of all 3D models was evaluated using a 5-point subjective scoring system. The length, width, and thickness of the ATFL were measured in the 3D model in Mimics and compared to the 3D MPR image data.

Results

The image quality score was 4.57 ± 0.32. There was no statistically significant difference between the 3D model and the 3D MPR image of ATFL measurements in both groups (P > 0.05).

Discussion

We concluded that 3D MRI can be used to reconstruct a 3D model of the ATFL for accurate measurements of the ATFL anatomical structure, which holds potential to improve preoperative planning and intraoperative navigation for young sports medicine doctor, facilitate diagnosis of ATFL injuries and make the decision about the operative method.

Morphological and morphometric analysis of tarsal bones according to sex

PURPOSE

Our aim in the study is to measure the area and volume of the tarsal bones and examine the typing of the talus and calcaneus joint surfaces according to sex.

METHODS

In our study, the area and volume measurements of 630 tarsal bones and the morphology of the talus/calcaneus were analyzed by transferring thin-section Computed Tomography (CT) images to the 3D Slicer program.

RESULTS

The volume and area sizes of the foot bones are calcaneus, talus, cuboid, navicular, medial cuneiform, lateral cuneiform, and intermediate cuneiform, respectively. All area and volume values of males were statistically higher than females (p < 0.05). The right side calcaneus area, intermediate cuneiform area, and lateral cuneiform area values were statistically higher than the left side (p < 0.045, p < 0.044, p < 0.030, respectively). There was no statistical relationship between age and area/volume values (p > 0.05). Three different types were seen in the calcaneus and seven in the talus. The most common type in the calcaneus was B1 (40%), and the least common type was A (27.8%). Regardless of the subgroups, the most common type in the talus was type B (37.8%), while the least common type was E2 (1.1%).

CONCLUSION

Although morphometric measurements of tarsal bones differed according to sex, they did not differ according to age. The frequency of occurrence of the types of articular surfaces of the talus and calcaneus varies according to populations. We think that the morphometry and morphology of tarsal bones will contribute to invasive procedures regarding tarsal bones and surrounding structures, and that three-dimensional bone modeling can be used to create educational materials.

Anthropomorphic Characterization of Ankle Joint

Even though total ankle replacement has emerged as an alternative treatment to arthrodesis, the long-term clinical results are unsatisfactory. Proper design of the ankle device is required to achieve successful arthroplasty results. Therefore, a quantitative knowledge of the ankle joint is necessary. In this pilot study, imaging data of 22 subjects (with both females and males and across three age groups) was used to measure the morphological parameters of the ankle joint. A total of 40 measurements were collected by creating sections in the sagittal and coronal planes for the tibia and talus. Statistical analyses were performed to compare genders, age groups, and image acquisition techniques used to generate 3D models. About 13 measurements derived for parameters (TiAL, SRTi, TaAL, SRTa, TiW, TaW, and TTL) that are very critical for the implant design showed significant differences (p-value < 0.05) between males and females. Young adults showed a significant difference (p-value < 0.05) compared to adults for 15 measurements related to critical tibial and talus parameters (TiAL, TiW, TML, TaAL, SRTa, TaW, and TTL), but no significant differences were observed between young adults and older adults, and between adults and older adults for most of the parameters. A positive correlation (r > 0.70) was observed between tibial and talar width values and between the sagittal radius values. When compared with morphological parameters obtained in this study, the sizes of current total ankle replacement devices can only fit a very limited group of people in this study. This pilot study contributes to the comprehensive understanding of the effects of gender and age group on ankle joint morphology and the relationship between tibial and talus parameters that can be used to plan and design ankle devices.

A Novel Method for Preoperative Positioning of Total Ankle Replacement Using 3D Digital Model

OBJECTIVE

To establish a digital model of the ankle joint through 3D imaging technology and explore the preoperative placement of ankle replacement prostheses.

METHODS

Computed tomography images of intact ankle joints from 54 cases in the outpatient and inpatient departments of our hospital were collected; according to the INBONE® total ankle system surgery process, the surgery model and surgical osteotomy were finished using MIMICS based on computer simulation method. The shortest distance was measured between the center point and the anterior, posterior, medial, and lateral, respectively, to ensure the precise position of the ankle replacement prosthesis by digital simulation surgery. The relationship between the two variables was analyzed by bivariate correlation analysis.

RESULTS

The dataset of this study included 48 cases of the sub-data set (26 males and 22 females) and included 27 cases of left ankle and 21 cases of right ankle. The average medial malleolar angle was 18.67°± 2.87°, the average amount of bone resection was 12.13 ± 1.86 cm³ , the mid-anterior distance was 1.72 ± 0.19 cm, the mid-posterior distance was 2.00 ± 0.19 cm, the ratio of mid-anterior to mid-posterior was 0.87, the mid-medial distance was 1.26 ± 0.17 cm, the mid-lateral distance was 1.19 ± 0.16 cm, and the ratio of mid-medial to mid-lateral was 1.06. After osteotomy, the anteroposterior diameter was 3.73 ± 0.32 cm, the transverse diameter was 2.46 ± 0.27 cm, and the ratio of anteroposterior diameter to transverse diameter was 1.53. In the bottom view, the shape after osteotomy is rectangular. The mid-anterior distance was strongly negatively correlated with age, the mid-anterior distance and the amount of bone resection, the mid-medial distance and the amount of bone resection, the mid-lateral distance and the amount of bone resection, the mid-lateral distance and the anteroposterior diameter, the anteroposterior diameter and the transverse diameter were all strongly positively correlated.

CONCLUSION

The projection point of the lower tibia centerline on the tibial horizontal osteotomy surface is located at a position slightly anterior to the midpoint of the transverse diameter after ankle arthroplasty. The rational positioning of the total ankle replacement is located at both a position slightly anterior to the midpoint of the transverse diameter and midpoint of the anteroposterior diameter, which can be used as a reference method before total ankle arthroplasty surgery.

Shape Approximation and Size Difference of the Upper Part of the Talus: Implication for Implant Design of the Talar Component for Total Ankle Replacement

The implant design of the talar component for total ankle replacement (TAR) should match the surface morphology of the talus so that the replaced ankle can restore the natural motion of the tibiotalar joint and may reduce postoperative complications. The purpose of this study was to introduce a new 3D fitting method (the two-sphere fitting method of the talar trochlea with three fitting resection planes) to approximate the shape of the upper part of the talus for the Chinese population. 90 models of the tali from CT images of healthy volunteers were used in this study. Geometrical fitting and morphological measurements were performed for the surface morphology of the upper part of the talus. The accuracy of the two-sphere fitting method of the talar trochlea was assessed by a comparison of previously reported data. Parameters of the fitting geometries with different sizes were recorded and compared. Results showed that compared with previously reported one-sphere, cylinder, and bitruncated cone fitting methods, the two-sphere fitting method presented the smallest maximum distance difference, indicating that talar trochlea can be approximated well as two spheres. The radius of the medial fitting sphere $R_M$ was $20.69\pm 2.19$  mm which was significantly smaller than the radius of the lateral fitting sphere $R_L$ of $21.32\pm 1.88$  mm. After grouping all data by the average radius of fitting spheres, the result showed that different sizes of the upper part of the talus presented significantly different parameters except the orientation of the lateral cutting plane, indicating that the orientation of the lateral cutting plane may keep consistent for all upper part of the talus and have no relationship with the size. The linear regression analyses demonstrated a weak correlation ( $R^2<0.5$ ) between the majority of parameters and the average radius of the fitting spheres. Therefore, different sizes of the upper part of the talus presented unique morphological features, and the design of different sizes of talar components for TAR should consider the size-specific characteristics of the talus. The parameters measured in this study provided a further understanding of the talus and can guide the design of different sizes of the talar components of the TAR implant.