3D Weightbearing CT Research Articles

Different Positions of Weightbearing CT Images Can Influence the Hindfoot Alignment Evaluation Using 2-Dimensional Methodology.

Three-dimensional weightbearing CT (WBCT) has been widely used to assess foot and ankle alignment. However, most current measurement methods are based on 2-dimensional concepts-distance, long axis, angulation, etc-and are sensitive to changes in orientation of the WBCT images. This study demonstrated how changes in positioning of the image can significantly influence the evaluation of hindfoot alignment. WBCT scans of 10 feet without deformities were used. In the horizontal view, the long axis of the foot image was aligned to a neutral position and then rotated 5, 10, 15, and 20 degrees both internally and externally to simulate malposition. The Calcaneal Moment Arm (CMA) was measured by 2 investigators independently in the above positions. An intraclass correlation coefficient (ICC) model was used to assess the intra- and interobserver reliabilities. The correlation between the CMA and the rotation angle of the foot images was analyzed using linear regression. The CMA measurements demonstrated that internal rotation of the image changed the neutral hindfoot into valgus, whereas external rotation led to varus. A 1-degree internal or external rotation of the image correlated with 0.48 (±0.03) mm increase or decrease in the modified WBCT-CMA value (P < .0001, R2 = 0.6406). This study demonstrated that although 3D WBCT provides the ability to observe the foot from different perspectives, current alignment evaluation tools are limited to 2 dimensions. Therefore, positioning the WBCT images in a consistent orientation is important to generate correct data.

Clubfoot Correction with Ponseti Technique: Three-Dimensional Alignment Analysis and Residual Adult Deformity Effects on Patient-Reported Outcomes

Introduction/Purpose: Few studies have assessed the long-term outcomes of the Ponseti technique and none have utilized 3- dimensional weightbearing analysis. The goal of this study was to understand how potential residual 3D deformities and abnormalities influence patient reported outcomes (PROs). This was accomplished by assessing anatomical foot and ankle alignment in adult clubfoot patients treated with the Ponseti method using 3D weightbearing CT (WBCT) imaging and then correlating residual foot and ankle malalignment with PROs. Methods: There were 37 consecutive patients (57 feet) included and 14 volunteers healthy controls (28 feet) included in this study. Every participant was evaluated using a WBCT (HiRise©) in a bipedal standing position. From these scans Cavus, Adductus, and Varus components were evaluated using multiple 3D measurements calculated using the semi-automatic segmentation software Bonelogic®. Specific Cavus related measurements included sagittal talus-first metatarsal angle and the calcaneal inclination angle. Varus related measurements included talocalcaneal angle in both the sagittal and axial planes as well as the hindfoot moment arm and the hindfoot alignment angle. Adductus deformity was evaluated using talonavicular coverage angle. These measurements were then correlated with patient reported outcome surveys, which included Visual Acuity Scale for pain, PROMIS general health, PROMIS physical function, PROMIS pain interference, pain catastrophic scale, and European foot and ankle society score. Results: There was no significant overall residual 3D-deformity observed in clubfoot patients when compared to controls, with similar FAO measurements observed between the groups, clubfoot=2.63% (95%CI=1.41%-3.85%) and control=3.2% (CI=1.6%- 4.8%,P=0.58). The sagittal talus-first-metatarsal in the clubfoot-patients had a mean-value of -0.12° compared to the controls, −5.2°. Clubfoot patients also had a decreased calcaneal-inclination-angle relative to the controls, 13.01° and 21.5° respectively. Talocalcaneal-angle for clubfoot patients in both the sagittal-plane,44.28°, and axial-plane, 17.74°, were reduced compared to the controls, 57.51° and 25.78°. Talonavicular-coverage-angle in the clubfoot-group (18.63°) was less than the controls (29.19°). Talus- first-metatarsal-angle in the sagittal-plane was significantly correlated with VAS-scores (RSquare=0.19,P=0.0118) and the EFAS- Score (RSquare=0.27,P=0.0025). Talocalcaneal-angle in the sagittal plane was also significantly correlated with the PROMIS-Pain- Interference-score (P=0.038) and PROMIS-Physical-Function-score (RSquare=0.32,P=0.0007). Conclusion: The Ponseti technique is an effective nonsurgical treatment for the overall three-dimensional foot and ankle alignment of Clubfoot. While mild, but statistically significant residual Varus and Adductus deformities were observed in adult clubfoot patients, the overall 3D alignment (FAO) was found to be similar between clubfoot patients and controls. These findings highlight the efficacy of the Ponseti technique and potentially explain the overall good PROs. The results of this study could potentially provide insight into treatment targets that may be applied to help optimize patient outcomes when treating children with Clubfoot in the future. The Ponseti technique is an effective nonsurgical treatment for Clubfoot's overall three-dimensional foot and ankle alignment. While mild, but statistically significant residual Varus and Adductus deformities were observed in adult clubfoot patients, the overall 3D alignment (FAO) was found to be similar between clubfoot patients and controls. These findings highlight the efficacy of the Ponseti technique and potentially explain the overall good PROs. The results of this study could potentially provide insight into treatment targets that may be applied to help optimize patient outcomes when treating children with Clubfoot in the future.

Evaluation of Automated Coverage and Distance Mapping Selections to Improve Reliability and Clinical Utility of 3D Weightbearing CT Assessments

Category: Other; Hindfoot Introduction/Purpose: Progressive collapsing foot deformity (PCFD) is a complex three-dimensional (3D) deformity where adjacent structures may adopt subtle differences in positioning that result in increased contact or subluxation. Recent studies have highlighted the need for and utility of 3D analyses in PCFD using weightbearing CT (WBCT) and bone segmentation. Beyond the limitations of triplanar imaging, 3D distance and coverage mapping analyses have further highlighted key regional differences like sinus tarsi narrowing ahead of impingement and early middle facet uncoverage ahead of collapse. However, these analyses rely upon manual identification of subregions hindering the utility of 3D mapping clinically. The objective of this study was to compare an automated selection process with manual selections in the context of subtalar regional distance and coverage maps in PCFD. Methods: In this IRB-approved retrospective study, WBCT data of 20 consecutive patients with flexible PCFD and 10 controls were analyzed. Subregions of the peritalar surface (middle and posterior facets of the calcaneus and talus; sinus tarsi area) were manually selected by two experts on manually generated bone surfaces of all 30 feet. An automated algorithm for selecting coverage area was applied to identify the same regions on the semi-automatically generated bones (Figure). A 3D distance mapping (DM) technique was used to create coverage maps (CMs) across the entire peritalar surface where areas with distances less than 4mm were defined as covered. DM and CM percentages were compared using intra-class correlations and t-tests between PCFD and control groups. The Sørensen–Dice index, or Dice coefficient, was used for comparisons of selections on the semi-automated surfaces to evaluate reproducibility of expert selections. Results: The automated process produced identical selections resulting in perfect intra-method ICCs of 1.00 for all regions and Dice coefficients of 1.00. The average Dice coefficient for all manual selections was 0.903 (range: 0.865-0.935) indicating that observers were able to reliably select the same regions with 90% overlap. When assessing reliability of manual selections, intra- observer ICCs ranged from 0.41-0.92 while inter-observer ICCs ranged from 0.47-0.99 were found. Despite strong significant correlations, average coverage was significantly lower in the sinus tarsi region of the automated selections vs the manual selections (34.3±16.8% vs 23.1±12.7%, p&lt; 0.005). However, mean distances in each region were not significantly different in the middle facet or the sinus tarsi regions (p=0.323, p=0.095, respectively). Conclusion: Understanding of the complex 3D deformities that constitute PCFD requires sensitive and reproducible measures. Fully automated 3D assessments of coverage and bone relations can help improve understanding these deformities aiding in diagnosis, staging, and objective evaluation of treatment effects. Prior work with this method has specifically identified the middle facet and sinus tarsi regions as being of particular importance. Compared to manual selections, these regions were well identified by the automated process. This represents a major step toward viable use of fully automated 3D coverage and distance mapping when evaluating PCFD patients.

Medializing Calcaneal Osteotomy for progressive collapsing foot deformity alters the three-dimensional subtalar joint alignment

BackgroundA medializing calcaneal osteotomy (MCO) is considered as one of the key inframalleolar osteotomies to correct progressive collapsing foot deformity (PCFD). While many studies were able to determine the post-operative hind- and midfoot alignment, alternations of the subtalar joint alignment remained obscured by superposition on plain radiography. Therefore, we aimed to assess the hind-, midfoot- and subtalar joint alignment pre- compared to post-operatively using 3D weightbearing CT (WBCT) imaging. MethodsSeventeen patients with a mean age of 42 ± 17 years were retrospectively analyzed. Inclusion criteria consisted of PCFD deformity corrected by a medializing calcaneal osteotomy (MCO) as main procedure and imaged by WBCT before and after surgery. Exclusion criteria were patients who had concomitant calcaneal lengthening osteotomies, mid-/hindfoot fusions, hindfoot coalitions, and supramalleolar procedures. Image data were used to generate 3D models and compute the hindfoot (HA), midfoot (MA) - and subtalar joint (STJ) alignment in the coronal, sagittal and axial plane, as well as distance maps. ResultsPre-operative measurements of the HA and MA improved significantly relative to their post-operative equivalents p < 0.05). The post-operative STJ alignment showed significant inversion (2.8° ± 1.7), abduction (1.5° ± 1.8), and dorsiflexion (2.3° ± 1.7) of the talus relative to the calcaneus (p < 0.05) compared to the pre-operative alignment. The displacement between the talus and calcaneus relative to the sinus tarsi increased significantly (0.6 mm±0.5; p < 0.05). ConclusionThis study detected significant changes in the sagittal, coronal, and axial plane alignment of the subtalar joint, which corresponded to a decompression of the sinus tarsi. These findings contribute to our clinical practice by demonstrating the magnitude of alteration in the subtalar joint alignment that can be expected after PCFD correction with MCO as main procedure.

Syndesmotic Malreduction Assessment using Three-Dimensional Distance Mapping: A Cadaveric WBCT Study

Category: Sports; Ankle; Ankle Arthritis; Arthroscopy; Trauma Introduction/Purpose: Diagnosing syndesmotic injuries is challenging. Avoiding intra-operative syndesmotic malreduction is even more challenging. Malreduction can be devastating to the long-term health of the ankle joint and has been shown to be more frequent and unforgiving with rigid screw fixation when compared to flexible implants. Syndesmotic position assessment postoperatively is usually performed using bilateral CT. Evaluation is frequently subjective or based on conventional distance, angular, area, and volumetric measurements. Diagnostic accuracy of these measurements is still questionable. The goal of this study was to utilize a 3D Weightbearing CT distance mapping algorithm to objectively assess syndesmotic position in a cadaveric model simulating different patterns of syndesmotic malreduction. We also aimed to evaluate the relative changes in syndesmotic position when fixation was converted from rigid to flexible. Methods: In this cadaveric experimentation, four below-knee specimens were utilized. Specimens were mounted in an external frame simulated weightbearing condition (350N of axial load). Specimens underwent sequential WBCT imaging in four different conditions: native normal ankle, syndesmotic instability, malreduced, and released conditions. In the instability condition, syndesmotic ligaments were surgically released using a conventional limited lateral approach. The malreduced position consisted of controlled 5mm anterior displacement, 5mm posterior displacement, 15o of internal rotation, and over-compressed (160N) states. Fixation was performed with a single implant 20mm proximal to the ankle joint. Implant utilized allowed initial rigid screw- type fixation, followed by implant flexibilization similar to a suture-type fixation (released position). Tibia, fibula, and talus WBCT images were segmented, and syndesmotic incisura and gutter distances were assessed using a 3D distance map algorithm. The syndesmotic position was compared between normal, unstable, malreduced, and released positions. Color-coded representations of the observed differences were presented (Figure). Results: When comparing normal to unstable condition, we observed significant widening of the syndesmotic posterior aspect (average, 13.9%; p=0.004). Overall, all four malreduced positions lead to significantly decreased tibiofibular distances when compared to the unstable state, consistent with syndesmotic over-compression (average, 19.8%; p=0.01), particularly in the posterior aspect of the joint (average, 26.9%; p=0.04). This over-compression was also more pronounced in the anterior displacement (31.5%) and internal rotation malreductions (23.1%). In the released flexible position we found a non-significant trend towards widening of the tibiofibular distances (average, 12%; p=0.08) when compared to the malreduced conditions, indicating partial restoration the syndesmotic relationship. The syndesmotic distances in the released position were also not significantly different from the normal condition. When compared to normal, the lateral gutter demonstrated significant widening in the unstable condition (average 16.7%; p=0.02), narrowing in the malreduced state (average 6.6%; p=0.04), and widening in the released position (average 3.7%; p=0.002). Conclusion: In this study we used 3D WBCT distance mapping to assess syndesmotic position in a cadaveric model simulating syndesmotic instability and multiple syndesmotic malreduction conditions (anterior and posterior displacement, internal rotation and over-compression). We observed significant widening when the syndesmotic ligaments were sectioned, followed by significant tibiofibular narrowing in the malreduced and fixed rigid states. When the implant fixation was released, we observed a trend towards restoration of normal syndesmotic alignment, with relative widening that was however not significantly different from the malreduced rigidly fixed state. Increased sample size cadaveric assessment and clinical studies are necessary to validate our results.

Evaluation of Automated Coverage and Distance Mapping Selections to Improve Reliability and Clinical Utility of 3D Weightbearing CT Assessments

Category: Hindfoot; Basic Sciences/Biologics; Other Introduction/Purpose: Progressive collapsing foot deformity (PCFD) is a complex three-dimensional (3D) deformity where adjacent structures may adopt subtle differences in positioning that result in increased contact or subluxation. Recent studies have highlighted the need for and utility of 3D analyses in PCFD using weightbearing CT (WBCT) and bone segmentation. Beyond the limitations of triplanar imaging, 3D distance and coverage mapping analyses have further highlighted key regional differences like sinus tarsi narrowing ahead of impingement and early middle facet uncoverage ahead of collapse. However, these analyses rely upon manual identification of subregions hindering the utility of 3D mapping clinically. The objective of this study was to compare an automated selection process with manual selections in the context of subtalar regional distance and coverage maps in PCFD. Methods: In this IRB-approved retrospective study, WBCT data of 20 consecutive patients with flexible PCFD and 10 controls were analyzed. Subregions of the peritalar surface (middle and posterior facets of the calcaneus and talus; sinus tarsi area) were manually selected by two experts on manually generated bone surfaces of all 30 feet. An automated algorithm for selecting coverage area was applied to identify the same regions on the semi-automatically generated bones (Figure). A 3D distance mapping (DM) technique was used to create coverage maps (CMs) across the entire peritalar surface where areas with distances less than 4mm were defined as covered. DM and CM percentages were compared using intra-class correlations and t-tests between PCFD and control groups. The Sørensen–Dice index, or Dice coefficient, was used for comparisons of selections on the semi-automated surfaces to evaluate reproducibility of expert selections. Results: The automated process produced identical selections resulting in perfect intra-method ICCs of 1.00 for all regions and Dice coefficients of 1.00. The average Dice coefficient for all manual selections was 0.903 (range: 0.865-0.935) indicating that observers were able to reliably select the same regions with 90% overlap. When assessing reliability of manual selections, intra- observer ICCs ranged from 0.41-0.92 while inter-observer ICCs ranged from 0.47-0.99 were found. Despite strong significant correlations, average coverage was significantly lower in the sinus tarsi region of the automated selections vs the manual selections (34.3+-16.8% vs 23.1+-12.7%, p&lt;0.005). However, mean distances in each region were not significantly different in the middle facet or the sinus tarsi regions (p=0.323, p=0.095, respectively). Conclusion: Understanding of the complex 3D deformities that constitute PCFD requires sensitive and reproducible measures. Fully automated 3D assessments of coverage and bone relations may have the potential to improve understanding of these deformities aiding in diagnosis, staging, and objective evaluation of treatment effects. Prior work with 3D coverage and distance maps specifically identified the middle facet and sinus tarsi regions as being of particular importance. Compared to manual selections, these regions were well identified by the automated process. This represents a step toward the goal of viable use of fully automated 3D coverage and distance mapping when evaluating PCFD patients.

Automated Volume Measurement of the Syndesmosis Using 3D Weightbearing CT

Category:Ankle; Trauma; OtherIntroduction/Purpose:Recent studies have shown that weight-bearing computed tomography (WBCT) that allows 3D volume measurement of the distal syndesmosis while under physiologic load brings about a higher accuracy in detection of syndesmotic instability, especially if subtle. Since the volume measurement method is complex, time-consuming, and has a noticeable interobserver bias, most clinicians might not still be interested in utilizing it in practice. Automatization of this measurement using computer-assisted methods will not only reduce the interobserver bias but also will be faster and more applicable in practice. This study aimed to develop an automated 3D syndesmosis volume measurement tool using image processing methods and compare the speed and the interobserver bias with human interpreters.Methods:We included 30 patients with subtle syndesmotic instability who had undergone WBCT and were diagnosed intraoperatively. Thirty individuals with otherwise healthy ankles who had WBCT images were allocated to the control group. The volume measurement up to 5cm proximal to the tibial plafond was considered as the most sensitive and specific method to assess syndesmotic stability based on the literature. An algorithm was developed using MATLAB software that could recognize and calculate the syndesmotic volume using WBCT images. The volume measurement method was used by two orthopaedic surgeons for the same population. The time spent by each surgeon and the algorithm was measured. Finally, the values were compared using the t-test; the interobserver correlation coefficient (ICC) was also calculated. P<0.05 was considered statistically significant.Results:The percentage of changes in 3D volume showed a significant difference at 5cm (25.4%; p<0.001), proximal to the tibial plafond. Based on our clinical study, the volume measurement up to 5cm showed a sensitivity of 95.8%, 95%CI:87.8-100, and specificity of 83.3%, 95% CI:68.4-98.2 for detection of syndesmotic instability. The ICC between the clinicians was 75% while using the automated measurement algorithm showed an ICC of 97%. The mean time spent by the clinicians was 268.4+-56.4 and by the algorithm was 2.9+-0.3 seconds (p<0.001, Figure 1).Conclusion:Given the fact that 3D volume measurement of the syndesmosis using WBCT is still a complex technique for most clinicians while it is one of the most accurate diagnostic methods based on recent literature, developing a faster and more accurate method for 3D volume measurement of the syndesmosis leads to a more reliable and easier to use the technique to be used in practice.

Weight-bearing radiographs and cone-beam computed tomography examinations in adult acquired flatfoot deformity

BackgroundOptimal characterization of Adult acquired flatfoot deformity (AAFD) on two-dimensional radiograph can be challenging. Weightbearing Cone Beam CT (CBCT) may improve characterization of the three-dimensional (3D) structural details of such dynamic deformity. We compared and validated AAFD measurements between weightbearing radiograph and weightbearing CBCT images. Methods20 patients (20 feet, right/left: 15/5, male/female: 12/8, mean age: 52.2) with clinical diagnosis of flexible AAFD were prospectively recruited and underwent weightbearing dorsoplantar (DP) and lateral radiograph as well as weightbearing CBCT. Two foot and ankle surgeons performed AAFD measurements at parasagittal and axial planes (lateral and DP radiographs, respectively). Intra- and Inter-observer reliabilities were calculated by Intraclass correlation (ICC) and Cohen’s kappa. Mean values of weightbearing radiograph and weightbearing CBCT measurements were also compared. ResultsExcept for medial-cuneiform-first-metatarsal-angle, adequate intra-observer reliability (range:0.61−0.96) was observed for weightbearing radiographic measurements. Moderate to very good interobserver reliability between weightbearing radiograph and weightbearing CBCT measurements were observed for the following measurements: Naviculocuneiform-angle (ICC:0.47), Medial-cuneiform-first-metatarsal-gapping (ICC:0.58), cuboid-to-floor-distance (ICC:0.68), calcaneal-inclination-angle(ICC:0.7), axial Talonavicular-coverage-angle(ICC:0.56), axial Talus-first-metatarsal-angle(ICC:0.62). Comparing weightbearing radiograph and weightbearing CBCT images, statistically significant differences in the mean values of parasagittal talus-first-metatarsal-angle, medial-cuneiform-first-metatarsal-angle, medial-cuneiform-to-floor-distance and navicular-to-floor-distance was observed (P < 0.05). ConclusionModerate to very good correlation was observed between certain weightbearing radiograph and weightbearing CBCT measurements, however, significant difference was observed between a number of AAFD measurements, which suggest that 2D radiographic evaluation could potentially underestimate the severity of AAFD, when compared to 3D weightbearing CT assessment.

Displacement of Sequential Syndesmotic Ankle Injuries Assessed by a 3D Weightbearing CT

Category:AnkleIntroduction/Purpose:Syndesmotic ankle injuries are challenging to diagnose, since current 2D imaging techniques try to quantify a 3D displacement. Therefore, our aim was two-fold: to determine displacement of sequential syndesmotic ankle injuries under various amounts of load using a 3D weightbearing CT (WBCT) and to assess the relation with current 2D imaging.Methods:Seven paired male cadaver specimens were included (tibia plateau to toe-tip) and mounted into a custom-built frame. WBCT scans were obtained after different patterns of load (0 kg or 85 kg) were combined with torque (0 Nm or 10 Nm external rotation). These conditions were repeated after each ligament condition: intact ligaments, sequential sectioning of the anterior inferior tibiofibular ligament (AITFL), deltoid ligament (DL), and interosseous membrane (IOM). CT images were segmented to obtain 3D models. These allowed quantification of displacement based on the position of computed anatomical landmarks in reference to the intact position of the fibula. A correlation analysis was performed between the 2D and 3D measurements.Results:The effect of torque caused significant displacements in all directions (P<0.05), except for shortening of the fibula (P>0.05). Weight caused a significant lateral (mean=-1.4 mm, SD=1.5) and posterior translation (mean=-0.6 mm, SD=1.8). The highest displacement consisted of external rotation (mean=-9.4°, SD=6.5) and posterior translation (mean=6.1 mm, SD=2.3) after IOL sectioning combined with torque (Fig. 1). Pearson correlation coefficients were moderate (range 0.31-0.51, P<0.05).Conclusion:Torque demonstrated superiority over weight in detecting syndesmotic ankle instability after 3D analysis. The clinical relevance of these findings can improve diagnosis by incorporating rotatory platforms during imaging and treatment strategies by providing appropriate stabilization against rotation.

The hind- and midfoot alignment computed after a medializing calcaneal osteotomy using a 3D weightbearing CT.

A medializing calcaneal osteotomy (MCO) is a surgical procedure frequently performed to correct an adult acquired flatfoot (AAFD) deformity. However, most studies are limited to a 2D analysis of 3D deformity. Therefore, the aim is to perform a 3D assessment of the hind- and midfoot alignment using a weightbearing CT (WBCT) preoperatively as well as postoperatively. Eighteen patients with a mean age of 49.4years (range 18-67) were prospectively included in a pre-post-study design. A MCO was performed and a WBCT was obtained pre- and postoperative. Images were converted into 3D models to compute linear and angular measurements, respectively, in millimeters (mm) and degrees (°), based on previously reported landmarks of the hind- and midfoot alignment. A regression analysis was performed between the displacement of a MCO and the obtained postoperative correction. The mean 3D hindfoot angle improved significantly preoperative compared to postoperative (p < 0.001). This appeared according to a linear relation with the amount of medial translation in a MCO (R2 = 0.84, p < 0.001). The axes of the tibia showed significant coronal as well as axial changes (p < 0.05). Analysis of the midfoot showed significant changes in the navicular height and rotation as well as the Méary angle (p < 0.05). Additionally, a linear trend between the midfoot measurements and amount of medial translation in a MCO was observed, but not significant (p > 0.05). This study demonstrates an effective 3D correction of an AAFD by a MCO according to a linear relationship. The concomitant formula can be used to perform a preoperative planning. The novelty is the comparative 3D weightbearing CT assessment of both the computed hind- and midfoot alignment after a medializing calcaneus osteotomy. This could improve accuracy of the currently performed preoperative planning in clinical practice.

Effect of Lateral Column Lengthening Calcaneal Osteotomy on Radiographic Measurements of Foot Alignment

Category: Hindfoot Introduction/Purpose: Lateral column lengthening (LCL) with calcaneal osteotomy has been increasingly used for reconstruction in flexible flat foot reconstruction. The aims of this study were to 1) evaluate the effects of variably sized LCL blocks on the restoration of alignment in an acute flat foot cadaveric model; 2) create a computer algorithm to more objectively measure foot alignment; and 3) develop an acute flat foot model that does not require cyclic loading for creating a type IIB flat foot. Determining if overcorrection with lateral column lengthening can occur would provide guidance surgeons to avoid lateral column overload. A computer guided measurement program could make studies more comparable. An acute flat foot model would clarify the ligament deficiencies necessary to create a type IIB flat foot. Methods: A type IIB flat foot model was used in which the medial and medial-plantar fibers of the calcaneonavicular (CN), the interosseous talo-calcaneal (ITCL) and the cervical (CL) ligaments were transected. Metallic markers were placed in the PF origin. 3D weightbearing CT scans were obtained with the specimens in a custom jig that permitted loading with 100 lbs. (445 N). The jig allowed full pronation under load. Scans were obtained: intact, flat, and with 6, 8 and 10 mm LCL blocks. Simulated AP and lateral radiographs were created using a custom MATLAB program. A custom ImageJ plugin was created which guided measurement of Meary’s angle, naviculo-cuneiform overlap, AP talo-first metatarsal angle, and a novel plantar fascia (PF) distance and PF angle. The program automatically calculated midpoints and perpendicular lines from guided user input. Four observers performed all measurements in blinded and randomized fashion on two occasions greater than 12 weeks apart. Results: The ligament sectioning model reliably produced a type IIB flat foot as noted by talo-navicular sag, increased talar head uncovering (forefoot abduction) and divergence of the talus and calcaneus as seen on the AP weightbearing view (Figure 1). Cyclic loading was not required in any specimens and the remaining medial column ligaments were not sectioned. Intraobserver and interobserver comparisons indicated naviculo-cuneiform overlap and plantar fascia distance had excellent interobserver agreement and Meary’s and plantar fascia angle had good interobserver agreement (Figure 1). Lateral column lengthening trended toward overcorrection at 10 mm suggesting a possible threshold for over-correction. Conclusion: The trend toward overcorrection with 10 mm LCL may indicate a threshold for lateral column overload. Computer guided measurement may improve consistency when comparing studies. The PF measurements are not possible in vivo. The use of a heel centering ring might be a surrogate for the implanted metallic beads. The CL sectioning was essential for creating type IIB flat foot without cyclic loading. The CL has been noted to be a main subtalar stabilizer, but has not entered into mainstream discussions regarding flat foot. Changes that occurred with cyclic loading performed in other flat foot studies have not been defined.

True 3D Weight Bearing CT Imaging for Foot and Ankle

: Foot and ankle surgery is a sub-specialty of orthopedics and podiatry that deals with the treatment, diagnosis and prevention of disorders of the foot and ankle. For the first time, physicians can get three-dimensional, weight bearing images of the foot and ankle with the pedCAT system. The pedCAT uses cone beam volumetric tomography to reconstruct the foots bony anatomy in its true physiological position within minutes. The pedCAT is a compact device that requires minimal radiation shielding, which means it could fit in a primary care podiatrist's office as easily as it could in a large imaging center. The pedCAT is manufactured by CurveBeam. CurveBeam was founded in 2009 with the primary mission of adapting cone beam volumetric tomography technology to imaging all body extremities. Over the past decade, CBVT has revolutionized oral and maxillofacial care. Three-dimensional scans of the skull have become an essential tool in diagnosis and treatment planning, especially for orthodontics and dental implants. The pedCAT is expected to transform the fundamentals of diagnostic imaging for the foot and ankle specialty by providing an ideal starting point to evaluate and treat a patients foot condition. The pedCAT is easy to use for both the doctor and the patient. The patient steps onto a platform and the gantry closes behind him. The physician pushes a single button, and the pedCAT scans one foot in less than 20 s or both feet in less than 40 s in weight bearing or non-weight bearing positioning. The manufacturer estimates the radiation dose delivered to the patient to be slightly higher than a similar plain X-ray. CubeVue, the accompanying software, stitches together the slices to create an exact digitized replica of the foot and ankle in less than three minutes. Using CubeVue, the physician can get an unobstructed view of the foot from any angle, rotate and navigate the 3D data, and make exact measurements. The physician can scroll through the slices, which can be as thin as 3 mm, in any direction. The pedCAT? , first in-office TRUE 3D weight bearing CT for the foot and ankle, helps optimize treatment planning for our patients. Via this low dose radiation option, the pedCAT? assesses clinical conditions including, but not limited to, fractures, dislocations, arthritic joints, deformity and for quicker diagnosis, evaluation and treatment planning. The patient experience benefits include: in-office and on-site compact imaging; TRUE weight bearing and non-weight bearing 3D imaging for one or both feet; capture unprecedented diagnostic information not seen in regular x- rays; easy to use visualization software that adds a new dimension to diagnosis and evaluation; fast acquisition of 3D data allows you to start your treatment planning in minutes; If needed, we can confidently plan surgeries with precision and speed.