The 3D anatomical complexity of the foot and ankle and the importance of weight-bearing in diagnosis have required the combination of conventional radiographs and medical CT.Conventional plain ...radiographs (XR) have demonstrated substantial limitations such as perspective, rotational and fan distortion, as well as poor reproducibility of radiographic installations. Conventional CT produces high levels of radiation exposure and does not offer weight-bearing capabilities.The literature investigating biometrics based on 2D XR has inherent limitations due to the technology itself and thereby can focus only on whether measurements are reproducible, when the real question is whether the radiographs are.Low dose weight-bearing cone beam CT (WBCT) combines 3D and weight-bearing as well as 'built in' reliability validated through industry-standardized processes during production and clinical use (quality assurance testing).Research is accumulating to validate measurements based on traditional 2D techniques, and new 3D biometrics are being described and tested.Time- and cost-efficient use in medical imaging will require the use of automatic measurements. Merging WBCT and clinical data will offer new perspectives in terms of research with the help of modern data analysis techniques. Cite this article:
2018;3 DOI: 10.1302/2058-5241.3.170066.
Background:
Syndesmotic injury in an athletic population is associated with a prolonged ankle disability after an ankle sprain and often requires a longer recovery than a lateral collateral ligament ...injury. Although several imaging tests are available, diagnosing syndesmotic instability remains challenging.
Purpose:
To determine the diagnostic accuracy of conventional ankle computed tomography (CT) scans with the joint in external rotation and dorsiflexion and compare it with that of conventional ankle CT scans in a neutral position.
Study Design:
Cohort study (Diagnosis); Level of evidence, 2.
Methods:
Between September 2018 and April 2021, this prospective study consecutively included adults visiting the foot and ankle outpatient clinic with a positive orthopaedic examination for acute syndesmotic injury. Participants underwent 3 CT scan tests. First, ankles were scanned in a neutral position. Second, ankles were scanned with 45° of external rotation, dorsiflexion, and extended knees. Third, ankles were scanned with 45° of external rotation, dorsiflexion, and flexed knees. Three measurements, comprising rotation (measurement
a
), lateral translation (measurement
c
), and anteroposterior translation (measurement
f
) of the fibula concerning the tibia, were used to diagnose syndesmotic instability in the 3 CT scans. Magnetic resonance imaging was used as a reference standard. The area under the curve (AUC) was used to compare the diagnostic accuracy, and Youden’s J index was calculated to determine the ideal cutoff point.
Results:
Images obtained in 68 participants (mean age, 36.5 years; range, 18-69 years) were analyzed, comprising 36 syndesmotic injuries and 32 lateral collateral ligament injuries. The best diagnostic accuracy occurred with the rotational measurement
a
, in which the second and third CT scans with stress maneuvers presented greater AUCs (0.97 and 0.99) than did the first CT scan in a neutral position (0.62). The ideal cutoff point for the stress maneuvers was 1.0 mm in the rotational measurement
a
and reached a sensitivity and specificity of 83% and 97% for the second CT scan with extended knees and 86% and 100% for the third CT scan with flexed knees, respectively. The ideal cutoff point for the first CT scan with a neutral position was 0.7 mm in the rotational measurement
a
, with a sensitivity of 25% and specificity of 97%.
Conclusion:
Conventional ankle CT with stress maneuvers has excellent performance for diagnosing subtle syndesmotic rotational instability, as it shows a greater AUC and enhanced sensitivity at the ideal cutoff point compared with ankle CT in the neutral position.
Background:
Varus hindfoot deformity may increase the risk of chronic lateral ankle instability (CLAI). Our aim was to analyze hindfoot alignment (HFA) in patients with CLAI using weight-bearing cone ...beam computed tomography (WBCT) to assess this risk.
Methods:
This retrospective, comparative analysis was carried out using an existing WBCT database (Talas, CurveBeam LLC), including data sets for 370 consecutive feet (189 patients) obtained between July 2016 and October 2018 at a single institution. The software provided semiautomated measurement of HFA, given as foot ankle offset (FAO). Univariate analysis was conducted to compare feet with and without CLAI against sex, age, body mass index, and FAO. Significant variables were included in a multivariable logistic model with random effects to take into account correlation between feet of the same patient.
Results:
Forty-three feet had CLAI (34 patients). FAO (P = .0009) was significant for CLAI by univariate analysis. Mean FAO was −2.2% ± 5.5% (varus) and + 2.6% ± 4.7% (valgus) with and without CLAI history, respectively. Multivariable logistic regression adjusted for sex and age demonstrated a 35% increased odds ratio (OR) of CLAI per 1% reduction in FAO value (varus) (adjusted OR=0.64, 95% confidence interval CI: 0.49-0.84; P = .001) and no significant effect of sex (adjusted OR=0.52; P = .617) or age (adjusted OR=0.94; P = .165) after adjustment for FAO.
Conclusion:
A positive relationship was found between varus HFA and the risk to have CLAI. Systematic recording of FAO measurements from WBCT images along with clinical data regarding CLAI history proved successful at quantifying the risk of CLAI.
Level of Evidence:
Level III, retrospective cohort study.
In the last decade, cone-beam computed tomography technology with improved designs allowing flexible gantry movements has allowed both supine and standing weight-bearing imaging of the lower ...extremity. There is an increasing amount of literature describing the use of weightbearing computed tomography in patients with foot and ankle disorders. To date, there is no review article summarizing this imaging modality in the foot and ankle. Therefore, we performed a systematic literature review of relevant clinical studies targeting the use of weightbearing computed tomography in diagnosis of patients with foot and ankle disorders. Furthermore, this review aims to offer insight to those with interest in considering possible future research opportunities with use of this technology.
Level of Evidence: Level V, expert opinion.
Spatial understanding of osteoarticular deformities of the foot and ankle is vital to correct diagnosis and therapeutic decision making. Poor reproducibility in conventional standing radiography in ...three orthogonal views has driven the development of weight-bearing computed tomography (WBCT) technology over the last decade. We analyzed the available literature on WBCT imaging in patients with foot and ankle disorders by performing a literature review of relevant clinical studies in multiple databases including PubMed, MedLine, and Scopus from January 1999 to October 2017. WBCT imaging allows correct evaluation of foot and ankle anatomy with the patient in a standing position, providing images with high spatial resolution, short image acquisition time, low dose of radiation, and costs which are similar to other available imaging technologies. This diagnostic tool can be used for decision making in the treatment of deformities of the ankle, hindfoot, midfoot, and forefoot. Level of Evidence III; Systematic review of level III studies.
A variety of biomechanical models have been used in studies of foot and ankle disorders. Assumptions about the element types, material properties, and loading and boundary conditions are inherent in ...every model. It was hypothesized that the choice of these modeling assumptions could have a significant impact on the findings of the model.
We investigated the assumptions made in a number of biomechanical models of the foot and ankle and evaluated their effects on the results of the studies. Specifically, we focused on: (1) element choice for simulation of ligaments and tendons, (2) material properties of ligaments, cortical and trabecular bones, and encapsulating soft tissue, (3) loading and boundary conditions of the tibia, fibula, tendons, and ground support.
Our principal findings are: (1) the use of isotropic solid elements to model ligaments and tendons is not appropriate because it allows them to transmit unrealistic bending and twisting moments and compressive forces; (2) ignoring the difference in elastic modulus between cortical and trabecular bones creates non-physiological stress distribution in the bones; (3) over-constraining tibial motion prevents anticipated deformity within the foot when simulating foot deformities, such as progressive collapsing foot deformity; (4) neglecting the Achilles tendon force affects almost all kinetic and kinematic parameters through the foot; (5) the axial force applied to the tibia and fibula is not equal to the ground reaction force due to the presence of tendon forces.
The predicted outcomes of a foot model are highly sensitive to the model assumptions.
•Assumptions about material properties and loading conditions are inherent in a model.•Choice of modeling assumptions has a significant impact on the results of a model.•Choice of boundary conditions is especially important in simulating foot deformities.
Objective
To evaluate the influence of weight-bearing (WB) load in standard axial ankle syndesmotic measurements using cone beam CT (CBCT) examination of asymptomatic uninjured ankles.
Materials and ...methods
In this IRB approved, prospective study, patients with previous unilateral ankle fractures were recruited. We simultaneously scanned the injured ankles and asymptomatic contralateral ankles of 27 patients in both WB and NWB modes. For this study, only asymptomatic contralateral ankles with normal plain radiographs were included. Twelve standardized syndesmosis measurements at two axial planes (10 mm above the tibial plafond and 5 mm below the talar dome) were obtained by two expert readers using a custom CBCT viewer with the capability for geometric measurements between user-identified anatomical landmarks. Inter-reader reliability between two readers was obtained using the intra-class correlation coefficient (ICC). We compared the WB and NWB measurements using paired
t
test.
Results
Significant agreement was observed between two readers for both WB and NWB measurements (
p
<0.05). ICC values for WB and NWB measurements had a range of 50–95 and 31–71 respectively. Mean values of the medial clear space on WB images (1.75, 95% confidence interval 95% CI: 1.6, 1.9) were significantly lower than on NWB images (2.05, 95% CI: 1.8, 2.2) measurements (
p
<0.001). There was no significant difference between the remaining WB and NWB measurements.
Conclusion
Measurements obtained from WB images are reliable. Except for the medial clear space, no significant difference in syndesmotic measurements were observed during the WB mode of CBCT acquisition, implying that the tibio-fibular relationship remains unchanged when the physiological axial weight-bearing load is applied.
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