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Introduction/Purpose: Peritalar subluxation is a key feature of both flatfoot and cavovarus deformities. Our preliminary studies have found that on WBCT there is 20% subluxation of the middle facet of the subtalar joint in normal controls, and >35% in patients with flexible flatfoot deformities; In the spherical talonavicular joint there is physiological uncovering of the talar head regardless of whether the joint is bearing weight or not, since the articular area of the talar head is 1.2 times of the navicular. We hypothesize that there may be a tendency to overestimate the pathological peritalar subluxation on both XR and WBCT. This study aimed to investigate the congruency of each peritalar joint using a weightbearing 3D CT scan remodeling technique. Methods: Five below-knee-amputated fresh frozen cadaveric feet were used (no history of surgery, trauma, arthritis, and deformities). Each specimen was CT scanned using both non-weightbearing and weightbearing protocols. Segmentation on Materialise Mimics software was used to remodel each peritalar bone three dimensionally. Congruency of the restored talonavicular joint and subtalar middle facet was evaluated in the GeoMagic. The total articular surface area for each bone was reconstructed, calculated and recorded. The articulation of each joint with or without weightbearing was restored for analyzing joint uncoverage. Paired t-test (P value ≤0.05) was used to compare the coverage % differences. Results: In the anterior and middle facets of the subtalar joint, There was 16.40% uncoverage of the calcaneus under non- weightbearing, and 30.68% of uncoverage under weightbearing; 17.94% uncoverage of the talus under non-weightbearing, and 24.89% of uncoverage under weightbearing. In the posterior facet of the subtalar joint, the total articular surface on the talus side (683.96±112.07 mm 2 ) was 1.13 times larger than the calcaneus side (606.78±107.23 mm 2 ). In the talonavicular joint, the total articular surface on the talus side (714.18±124.97 mm 2 ) was 1.28 times larger than the navicular side (556.76±97.65 mm 2 ). Conclusion: Our preliminary study in this group of normal cadaver feet has found that in both the talonavicular and middle facet of the subtalar joints, there is physiological uncovering or subluxation regardless of whether the joint is bearing weight or not. Further investigation with a larger sample size is in process.

Category: Hindfoot; Midfoot/Forefoot Introduction/Purpose: When AP, lateral, and hindfoot views weight bearing XR's were taken, patients were frequently asked to stand on the foot being examined with the other foot lifted off the floor. However, we have found that alignments of the hind and midfoot during unilateral standing are different from those when bearing weight on both feet. This study compared the kinematics and plantar pressures between unilateral and bilateral standing positions in a group of asymptomatic volunteers. Methods: Ten participants (20 feet) without symptoms, previous trauma and surgical history in both lower limbs were included. Each participant first stood comfortably on both feet, then lifted the non-examined foot off the floor. Each person switched between the above two positions three times. Kinematic data was collected using an eight-camera Optitrack 3D motion capture system to reflect changes in alignments of the ankle, subtalar, and midtarsal joints. Plantar pressure distribution was assessed using a pressure platform. Paired t-tests were used to compare the metrics between the two standing positions, with statistical significance level set at P < 0.05. Results: From bilateral to unilateral weightbearing, 14 out of 21 kinematic angular parameters showed medium to high level of statistical significance (p=0.001-0.046) reflecting differences in the relative positions of the ankle, subtalar, and midtarsal joints in the two weightbearing positions resulting from pronation of the hindfoot and midfoot; the average plantar pressure change underneath the hallux (0.1616N), toes 2-5 (0.0907N), metatarsals 2-4 (0.2481N, 0.3204N, 0.2649N), midfoot (0.1794N), medial and lateral heel (0.259N, 0.246N) all showed statistically significant increase. There was a significantly higher plantar pressure increase on the medial than the lateral side of the feet. This corresponded to both the kinematic changes, and our findings in another study investigating the alignment change between the positions radiographically. Conclusion: The hindfoot and midfoot are more pronated in unilateral weightbearing than in bilateral weightbearing which may mask the severity of the deformity in a flexible cavovarus foot but increase that in a flexible flatfoot. Modification of the traditionally used unilateral weightbearing position in obtaining clinical radiographs should be considered. Bilateral WBCT scans may be a better alternative, taking advantage of allowing both feet to bearing weight naturally without concerning about one foot blocking the other during the radiographic imaging.

Category: Hindfoot; Other Introduction/ Purpose: Lateral column lengthening calcaneus osteotomy is a common procedure used to treat flatfoot deformity. However, the incidence of subtalar joint impingement and sinus tarsi pain presents a concern related to this treatment. The hypothesis of this study was with opening of the osteotomy, the anterior fragment of the calcaneus anterior process moves anteriorly, while the posterior fragment simultaneously moves posteriorly which can compromise the outcome as well as cause subtalar joint impingement. The goal of this study was to observe movements of the anterior and posterior fragments with an osteotomy of different sizes. Methods: Eight fresh frozen cadaveric feet were used. A vertical calcaneus osteotomy was designed 1.5cm posterior to the calcaneocuboid joint. Optical markers were attached on each side of the osteotomy to measure movements of the anterior and posterior segments during the lengthening procedure. Three more markers were placed for reference purposes with one on the lateral process of the talus, one on the table, and one on the base of the 3rd metatarsal (Figure 1). Following the osteotomy 4mm, 6mm, 8mm, 10mm and 12mm of lengthening was obtained for each specimen using a lamina spreader. The exact lengthening achieved was measured with a micro-caliper. Movements of the anterior and posterior fragments were recorded using a Sentech model STC-MBCM401U3V camera and calculated with MaxTRAQ motion analysis software. Mixed linear regression analyses were performed using R Studio. Results: With the open osteotomy, the anterior fragment moved anteriorly, while the posterior fragment moved posteriorly (Table 1, 2). The anterior movement was larger than the posterior one. There was no difference in the amount of anterior movements during each attempted 2mm lengthening, however, the amount of the posterior movement peaked at 6mm-8 mm and went down at 8mm-10mm and 10mm-12mm, which was caused by subtalar joint impingement and limited the posterior excursion. Starting at 6mm lengthening there was a linear regression relationship between the anterior & posterior movement and the lengthening (anterior movement = -4.80 + 1.06 × Lengthening of the Lateral Column, posterior Movement = -1.26 + 0.22 × Lengthening of the Lateral Column) (Figure 2,3). 1mm lengthening induced 1.06mm anterior (p < 0.05), and 0.22mm posterior shift (p < 0.05). Conclusion: Lateral lengthening causes the calcaneus to move both anteriorly and posteriorly which not only compromises the power of the procedure, but also can cause subtalar impingement. The findings of this study provide our colleagues with more insight into the correlation between the size of the lengthening, results, and potential complications.

Category: Midfoot/Forefoot; Other Introduction/Purpose: The first tarsometatarsal (TMT) joint plays a crucial role in maintaining the stability of the midfoot and medial column. Disorders of this joint are associated with hallux valgus, hallux rigidus, flatfoot, Lisfranc injury and arthritis, and many others. It has been proven that there is a high variability in the morphology of the joint which may be related to joint stability thereby leading to certain deformities. Understanding the morphology of the articular surfaces comprising the joint is necessary. While prior studies have used XR and CT to analyze the joint[1], we present our work using 3D surface mapping to evaluate the cartilaginous articulation of the1st TMT joint. Methods: 22 fresh-frozen cadaveric feet without trauma nor surgery or significant deformities were dissected to expose the medial cuneiform (MeC) and 1st metatarsal (MT) bones, and the articular surfaces of the 1st TMT joint. Surface mapping of the articular surfaces and the two bones was completed using an Artec Space Spider 3D scanner and Mmics. Further digital analysis was completed using GeoMagic Studio 10. Results: Means and Standard Deviations (SDs) of the articular surface and the bone length were summarized in Table 1. The average articular area of the 1st TMT joint was 337.26 (±63.43) mm 2 on MeC, and 337.94 (±66.16) mm 2 on the 1st MT, with the length of the bones measured 25.50 (±2.56) mm for MeC and 63.93 (±4.22) mm for the 1st MT. There were statistically significant linear correlation between the articular-area and the length of the bone on both sides. 1 mm bone length increase was correlated with 11.48 mm 2 articular-area increase on MeC; and 10.33 mm 2 articular-area increase on 1st MT. (Figure 1,2) There were three types of morphologies of the 1st TMT joint (Type 1, with 2 facets linked to each other; Type 2, with 2 facets separated; Type 3, 1 large dorsal facet and two separate smaller facets inferiorly). The facet pattern is more obvious on the 1st MT than the MeC side. (Figure 3) Conclusion: Previous studies of the 1st TMT morphology were done using either direct manual measurements with descriptive reporting which does not reflect the exact contour of the joint, or XR/WBCT which cannot demonstrate the cartilaginous articulation. This study used a novel technique of surface mapping which overcame the above issues. The remodeled cartilaginous articular surfaces provide foundations for further comparison study, as well as integration of 3D surface mapping with weight- bearing CT analysis, which is currently under investigation by our research group. This will provide important information for diagnosis, surgical planning, and follow-up treatment for relevant disorders.

Category: Hindfoot; Midfoot/Forefoot Introduction/Purpose: In clinical practice and research, there are several scenarios when a hindfoot alignment view weightbearing XR is not obtained whether as a result of a lack of resources, technology, in retrospective studies when a hindfoot view was not obtained, as well as in many practices where a hindfoot view XR is not considered a routine examination for foot and ankle disorders. A lateral weightbearing radiograph however is almost routinely obtained, and the goal of this study was to correlate the hindfoot alignment angle with measurements on lateral weightbearing images. Methods: Four volunteers (8 feet) with flexible feet and ankles and no symptoms, nor significant trauma & surgical history in their lower limbs were recruited for this study. A portable fluoroscopy machine (Smart C, Turner Imaging, Salt Lake City, USA) was used for imaging. The participant was asked to stand on different custom wooden wedges with the angle changed every 5 degrees from 30 degrees of varus to 30 degrees of valgus and a weightbearing lateral image was taken for each position. The hindfoot alignment was measured using a skin marker which had been drawn prior to initiation of the imaging, and the angular changes of the hindfoot was measured with the placement of each wedge placed. All standardized measurements of the midfoot and hindfoot were obtained on the lateral images. Results: With the hindfoot positional changes between 30o of varus to 30o of valgus, there was a gradual measurable change in the subtalar joint, with corresponding changes in the midfoot and hindfoot. There was a significant linear correlation between the hindfoot alignment angle and all radiographic parameters on lateral images. When the hindfoot alignment angle increased by 1 degree in the valgus direction, there was 0.49o decrease in the pitch angle, 0.58o of decrease in the middle vs posterior facet angle, 0.06o of decrease in the proximal cuneiform/cuboid height, 0.40o of decrease in the proximal cuneiform/5th Metatarsal height, 0.40o of increase in the fifth metatarsal/cuboid height, 0.009o of increase in the sinus tarsi/lateral process height, and 0.015o increase in Cuboid/Anterior Process Height. (Figure 1) Conclusion: The lateral weightbearing XR can be used to predict the status of the hindfoot alignment, and this study has proven that this can be none not only qualitatively but also quantitatively. This novel research can provide our colleagues with linear regression equations to correlate the lateral imaging metrics with the hindfoot alignment angle. Further study with a larger sample size and participants with different types of hindfoot deformities is needed to help develop an algorithm that would help both clinical practice and research.

Category: Other Introduction/Purpose: It is often difficult for early career investigators to identify the ideal journal readership for foot and ankle research without knowledge of each journal’s culture and article preferences. Bibliometric analyses have shown the popularity of certain topics can vary widely between similar journals. However, in the foot and ankle literature, there is very little information available regarding the publication preferences of common journals. The goal of this project was to provide a practical table with publishing trends to help investigators identify one or more journals most suitable for a given manuscript. Methods: We examined 43 journals, including both general orthopedic journals and foot and ankle-specific publications. We utilized the National Library of Medicine’s MEDLINE database for general article information, and Web of Science’s (WOS) Journal Citation Report for citation counts. Journals were only included for analysis if they published a minimum of 50 foot and ankle (FA) articles in the past five years, and were indexed in both MEDLINE and WOS. Variables such as publishing nationality, number of authors, and article type were collected using MEDLINE article metadata. Keyword lists were generated by our author team for each topic, and keywords were then searched to calculate the percentage of articles categorized under that topic. To measure the impact factor of a journal, we calculated a 5-year “impact factor” following modified WOS guidelines (total citations in 2020 for articles published 2015-2019 / total publications from 2015-2019). Results: 29 journals met our inclusion criteria for analysis (67%), of which 6 specialized in foot and ankle (Table 1). The popularity of certain article topics varies widely between journals. For example, while the Journal of Foot and Ankle Research publishes more than twice as many sports articles than any other FA publication (25%), it publishes five times less arthroscopy publications (2%). Similarly, we also find notable differences in the type of article published by journals – while only 1% of the total articles published by FAI are case reports, the Journal of Foot and Ankle Surgery published 30% case reports the past five years. We also found the distribution of American first authors can vary widely – ranging from 95% to 0% in different journals. Conclusion: This data set is aimed to provide a practical tool for early investigators to select ideal journals that would be appropriate for their work. Metrics like nationality may help authors intentionally reach out to a more diverse international audience, or an American readership, when appropriate. Likewise, targeting manuscripts that are a topic of interest to journals can save time in the publication process that is spent in initial review. While this data set relies exclusively on publicly available metadata from MEDLINE and WOS, we believe it offers an encouraging start to better understand the foot and ankle publishing landscape.

Category: Hindfoot; Midfoot/Forefoot Introduction/Purpose: Choosing between a double arthrodesis or a triple arthrodesis in treating severe flatfoot deformities is often a matter of surgeon preference with proponents of each, and this study compared the radiographic outcomes of the two procedures. Methods: A retrospective chart review was performed for patients who underwent either a double or triple arthrodesis during a period of one year. Twenty-one double and 9 triple arthrodesis with at least one year of follow up were included in this study. Radiographic measurements on pre and postoperative anteroposterior and lateral weightbearing images were collected to reflect the correction of the hind and midfoot deformities, in particular, the relative height of the medial and lateral columns. Results: Both procedures significantly improved the talus-1st metatarsal angle (AP), talar declination angle, and the Meary’s angle. The double arthrodesis more significantly improved the talo-navicular coverage angle, while the triple arthrodesis significantly was far more effective in correcting the talar declination angle, the calcaneal pitch angle, and the cuneiform/cuboid height ratio. (Tables 1,2) Conclusion: Both double and triple arthrodesis have the ability to correct severe flatfoot deformities with improved radiographic outcomes. The triple arthrodesis has more power to improve the arch height as noted on the significant differences between the two groups in the calcaneal pitch angle and the medial cuneiform/cuboid height ratio.

Category: Hindfoot; Midfoot/Forefoot Introduction/Purpose: When weight bearing radiographs are taken, the patient is frequently asked to stand on the foot being examined with the other foot lifted off the floor. We have found however that alignments of the hind and midfoot change when bearing weight switches from bilateral to unilateral standing. This study investigated the possible differences in hindfoot alignments between unilateral and bilateral weight bearing using radiographical evaluation. Methods: Eight flexible feet without symptoms symptoms, nor significant trauma & surgical history in their lower limbs were recruited for this study. A portable fluoroscopy machine (Smart C, Turner Imaging, Salt Lake City, USA) was used to take weightbearing lateral views. The patient first stood on both feet with the non-examined foot standing outside of the collimator but bearing weight evenly (Figure 1), and then lifted the non-examined foot off the floor when the lateral XR image was taken for the examined foot. Hindfoot alignment in both positions was reflected by measuring the angle between the long axes of the proximal and distal portions of the Achilles tendon on the skin using the subtalar joint line as the intersection. On lateral XRs, various parameters were measured to reflect the subtalar joint alignment, the position of the calcaneus with inversion and eversion of the hindfoot, and the lateral and medial arch heights. Results: From bearing weight on two feet (bilaterally) to one foot (unilaterally), the Hindfoot Alignment Angle (Achilles) increased (6.23 to 11.21 degrees), the Calcaneal Pitch Angle decreased (22.06 to 19.22 degrees), the Middle vs Posterior Facets Angle decreased (166.46 to 160.74 degrees), and the 5th metatarsal/cuboid height decreased (0.73 to 0.67) all significant changes (p < 0.05). All of these represented a pronation movement in the mid and hindfoot, ie, valgus tilt/eversion of the calcaneus, decreased sinus tarsi opening, and reduced lateral arch height. In this small cohort, these differences were more obvious in the feet that were either slightly flat or cavus shaped (Figure 1, Table 1, and 2) than in feet with a more neutral alignment. Conclusion: The hindfoot and midfoot are more pronated in unilateral weightbearing than in bilateral weightbearing which may mask the severity of the deformity in a flexible cavovarus foot, but increase that in a flexible flatfoot. Modification of the traditionally used unilateral weightbearing position in obtaining clinical radiographs should be considered. Bilateral WBCT scans may be a better alternative, taking advantage of allowing both feet to stand in the most natural position without one foot blocking the other during the radiographic imaging.

Category: Hindfoot; Midfoot/Forefoot Introduction/Purpose: The deformities associated with Müller Weis Disease (MWD) have not been well understood which inevitably impacts clinical and surgical decision making. Despite most previous studies characterizing MWD as a paradoxical flatfoot deformity, ie, a flat arch and a varus heel, some studies have treated MWD as a flatfoot deformity by performing a medializing calcaneus osteotomy, and others as an arthritic disorder treated with hind foot arthrodesis but without correcting the deformity. This study used an automatic 3D segmentation program to create an average 3D foot model for both normal controls and a large group of MWD feet, to demonstrate the deformity pattern, and to provide surgeons with a foundation for detailed alignment evaluation and surgical planning. Methods: Weight bearing Scans of 55 health feet without deformities, trauma and surgical histories, and 69 MWD feet were included in this study. The Bonelogic program (Disior, Paragon 28,) was used to automatically segment the bones and 3D information of each foot in the same group was pooled to create an average foot model for both the controls and the MWD feet. Videos were created using all feet in both groups to demonstrate the deformity patterns ranging from normal feet transitioning to MWD feet. Since current axial and angular metrics for alignment evaluation using traditional 2D imaging cannot be extrapolated to 3D this study was kept as a descriptive paper, and no traditional metrics were analyzed and reported. Results: Compared to the average normal foot, the MWD foot model demonstrated the following features: narrowing on the lateral pole and dorsal side of the navicular, lateral rotation and slight dorsal lifting of the talar head and medial rotation of the navicular, a varus heel with more opening in the sinus tarsi, proximal shift of the calcaneal tuberosity, a flat medial arch with subsidence at the talonavicular joint, decreased adduction of the forefoot, medial translation of the cuboid at the calcaneocuboid articulation, and a shortened 1st metatarsal. All of the above changes were consistently demonstrated in video one (a comparison between the two foot models), and video two (a comparison of the peritalar joint alignment between the two groups). Conclusion: The foot models were built up with pixels, with each pixel carrying its own 3D information in space allowing exploration of real 3D alignment evaluation tools. The MWD foot model clearly demonstrated and validated the deformity patterns originally described by Maceira, and subsequently by other authors using both radiographs and WBCT scans. This model facilitates evaluation of alignment from the hindfoot to the forefoot, as well as advanced 3D analysis to assess the morphology of the bones and joints and can be the foundation for surgical planning and predication of outcomes.

Category: Hindfoot; Sports Introduction/Purpose: New surgical techniques for Achilles tendon insertional pathology are evolving rapidly. Whether via open surgery, minimally invasive, or endoscopic approaches, more information about the Achilles' insertional footprint is needed to help surgeons with decision making. This study investigated the footprints of the Achilles insertion in sagittal orientation to delineate the anatomical landmarks, safe zones for bone resection3-down surgeries in treating insertional Achilles tendinopathies. Methods: Twenty fresh frozen cadavers were selected excluding insertional Achilles tendon pathology on lateral view x-rays. The calcanei were dissected maintaining the Achilles tendon insertion intact. Dimensions of the posterior tuberosity were recorded and marked to plan for three sagittal cuts (medial, middle, and lateral) (Fig 1 A). Using an oscillating saw (Fig 1 B.), the posterior tuberosity was cut into four pieces (Fig 1 C,E). A trapezoid shape (Fig 1 D) was reconstructed demonstrating relative location of the footprints of the Achilles insertion compared to the boundaries of the tuberosity on each piece (A, most superior point in the posterior tuberosity; B, most superior point in the Achilles insertion; C, most inferior point in the Achilles insertion; D, most inferior point in the posterior tuberosity). Data regarding footprints of the Achilles tendon insertion in the sagittal orientation was analyzed and compared within each trapezoid region and among different regions. Results: AB (calcaneal tuberosity tip to the upper limit of the Achilles insertion) was shortest at the medial cut (9.35mm) and longest at the lateral cut (12.15mm). However, the tendon thickness at the insertion (the distance from the proximal to the distal limits) represented by BC was shortest at the lateral cut (13.19mm) and longest at the middle cut (14.04mm). AD, the distance from the highest to the lowest point of the calcaneal tuberosity, was the longest at the middle cut (41.20mm). AB:BC ratio was highest at the lateral cut and lowest at the medial cut, indicating the safe amount of bone to be resected at the Achilles insertion. Tendon thickness relative to the whole calcaneal tuberosity (BC:CD) was highest at the medial wall (Table1). Conclusion: The sagittal orientation and variability of the Achilles tendon insertion is an under-studied topic in the literature. It needs to be addressed given recent trends towards minimally invasive procedures in treating insertional Achilles pathology. This study precisely delineated the footprint in each region of the insertion by creating a trapezoid pattern to compare the coordinates across these areas. This could lead to future three-dimensional reconstruction of the Achilles insertional footprint and patient- specific instrumentation software directed towards optimizing the management of Insertional Achilles pathology.

Category: Hindfoot; Midfoot/Forefoot Introduction/Purpose: It is believed that Müller Weiss Disease (MWD) starts with narrowing of the lateral and dorsal side of the navicular, followed by lateral rotation and slight dorsal lifting of the talar head and medial rotation of the navicular, a varus heel, and ultimately additional changes in the hindfoot and midfoot. This study used the technique of distance mapping to measure the space of the “peri-navicular” joints on an averaged 3D foot model for both normal controls and a group of MWD feet, to prove the key pathologic changes of MWD. Methods: Weight bearing Scans of 55 health feet without deformities, trauma and surgical history, and 69 feet with MWD were included in this study. The Bonelogic program (Disior, Paragon28) was used to automatically segment the bones and 3D information of each foot in the same group was pooled to create an average foot model for both the controls and the MWD feet. On the two foot models, distance mapping was applied and compared to compare the space of the perinavicular joints (the talonavicular joint, the three navicular cuneiform joints, and the calcaneocuboid joint). The morphology of the navicular bone and the talonavicular articulation in the two groups were also studied. Results: In the MWD foot model, there was significant narrowing of the lateral pole and the dorsal side of the navicular compared with the average normal foot model. The bone articular surfaces of the two foot models matched well, meaning that the deformity changes occurred predominantly to the shape of the navicular but not the contour of the joint surface. The joint space measured using distance mapping was significantly greater in the talonavicular joint, middle and lateral naviculocuneiform joints, and the calcaneocuboid joint in the MWD feet than in normal controls. There was no difference in the joint space of the medial naviculocuneiform joint between the two foot models. Conclusion: It is the change in the shape of navicular bone but not articular surface contour which causes the development of the cascade of deformities in MWD. The sequalae includes increased joint space on both sides of navicular tail, and in the calcaneocuboid joint, lateral subluxation of the talus head, relative medial subluxation of the navicular, a varus heel with more opening in the sinus tarsi, proximal shift of the calcaneal tuberosity, a flat medial arch with subsidence at the talonavicular joint, decreased adduction of the forefoot, medial translation of the cuboid at the calcaneocuboid articulation, and a shortened 1st metatarsal.

Category: Hindfoot; Midfoot/Forefoot Introduction/Purpose: Weight bearing CT has been widely used recently to provide detailed 3D information of the foot and ankle. Orthopedic surgeons have been exposed to this new technology, but do not have the equivalent tools to use to explore it. A lot of metrics were directly borrowed from plain radiographic imaging, while some new parameters were developed using traditional axes and angular concepts but on only one specific WBCT view out of hundreds of scans. Some metrics used similar measurement concepts, but on 3D reconstructed bones, while a few new parameters were introduced based on semi 3D and 3D thinking. Small sample sizes, obscure inclusion/exclusion criteria, and skewed validation methods are noted, and a thorough review of WBCT-based measurements used in foot and ankle is warranted. Methods: A literature search was conducted in two databases: PubMed (MEDLINE) and EMBASE (Elsevier). The main search terms and logics were: ((foot) OR (ankle) OR (hindfoot) OR (midfoot) OR (forefoot)) AND ((WBCT) OR (Weightbearing CT) OR (Cone beam CT scan) OR (PedCAT)). A longer string of key words was utilized to further narrow down the results to WBCT imaging associated with foot and ankle pathologies. The terms were expanded using the MeSH and Emtree expansion features of PubMed and EMBASE, respectively. All articles were reviewed by two independent senior foot and ankle surgeons based on pre-designed exclusion criteria. Off-topic articles were removed, and remaining articles were categorized based on measurement techniques. All articles were managed using Zotero. (Figure 1) Results: A total of 216 articles were selected for retrieval and further organized by measurement techniques. Seven groups were set by the type of the methodology used. Among them, 123 studies utilized traditional 2D measurement parameters (eg, hindfoot moment arm, Meary’s angle, talonavicular uncoverage, hallux valgus angle, etc.), 8 introduced new parameters but based on 2D axial/angular concepts (eg, middle facet subluxation percentage and angle), 22 used semi-automated 3D measurement techniques (3D segmentation + 2D axial and angular methods), 19 using semi-3D measurement techniques (Foot and Ankle Offset), 29 measured real 3D parameters (volume evaluation in the syndesmosis and Lisfranc joints, distance mapping), 3 morphological studies used 3D segmentation and sphere fitting. The advantages and disadvantages of each type of measurement were carefully examined and explored. Conclusion: 3D imaging measurements with WBCT appear to be highly variegated. Axial and angular measurements do not apply well to irregular bones and there is a low reproducibility in 3D scenarios. Although inter- and intraobserver reproducibility scores have been reported in multiple studies, they were only part of the validation system that should be done. A high correlation between parameters such as 2D and 3D hindfoot angles has been reported, but debate remains as to whether one method of measurement is more accurate than the other. Furthermore, variations in analytical methods warrant a more uniformly defined coordinate or anatomical system.

Category: Hindfoot; Ankle Introduction/Purpose: Recent studies have highlighted the important role of peritalar joint congruence in maintaining the alignment of the hindfoot. Peritalar subluxation is associated with a variety of pathological deformities including flatfoot, cavovarus foot, clubfoot, as well as foot and ankle stress fractures. To date, studies of peritalar joint congruence have all been performed using either XR, WBCT based direct measurements, or 3D segmentation and analysis. However, none of these techniques can demonstrate the cartilage location nor disruption, nor the exact location of the articulation on the bone surface. Data bias caused by the limitations of these study methodologies is therefore inevitable. This study used 3D surface mapping to assess morphometrics of the cartilage surfaces of the peritalar joints. Methods: 11 fresh-frozen cadaveric feet without trauma nor surgery or significant deformities were dissected to expose the calcaneus, cuboid, talus, and navicular bones, and the articular surfaces. Surface mapping of the articular surfaces and the two bones was completed using an Artec Space Spider 3D scanner and Mmics. Further digital analysis was completed using GeoMagic Studio 10. T-test was used for statistical comparisons, with p< 0.05 as statistically significantly different. Results: Detailed information of the articular surfaces is summarized in Table 1. The average articular area on both sides of the joint matched each other well in the posterior facet of the subtalar joint (4% difference), and calcaneocuboid joint (3% difference) without significant statistical difference, but not in the anterior & middle facets of the subtalar joint, nor the talonavicular joint. In the anterior & middle facets of the subtalar joint, the cartilage articular area on the talar side was 124% of that on the calcaneus (p < 0.05), and in the talonavicular joint the cartilage articular area on the navicular was 138% of that on the talus (p < 0.05). Conclusion: The cartilage articular surfaces in certain peritalar joints do not match its opposing surface in size. In the talonavicular joint, it is easy to understand since area of the socket must be much smaller than that of the ball in order for the joint to glide and rotate. There must be functional reasons for this phenomenon to happen in the anterior and middle facets of the subtalar joint, which need further investigation. This study shows that the extent of subluxation of the peritalar joints may be physiological and should not necessarily be considered as pathological.

Category: Hindfoot Introduction/Purpose: Lateral column lengthening calcaneus osteotomy has been used widely in treating Stage IIB flexible flatfoot deformity in order to shift the anterior segment of the calcaneus forwards, which improves the coverage of the talonavicular joint by forefoot adduction. The premise of this investigation is that in addition to shifting the forefoot anteriorly around the axis of the talar head, there is also a posterior translation of the tuberosity of the calcaneus which is detrimental in that the angle of Gissane then impinges upon the posterior facet of the subtalar joint causing pain. Our hypothesis is that in addition to anterior translation of the calcaneus, posterior shift of the calcaneal tuberosity occurs with lengthening osteotomy of the calcaneus. Methods: An acute cadaveric flatfoot model was created on 5 fresh frozen cadaver feet with no previous foot and ankle deformity. In order to simulate the surgical scenario, the study was performed with no external load on the limb. A vertical osteotomy was performed 1 cm posterior of the calcaneocuboid joint. Commercially available precut wedges of 6 mm, 8 mm, 10 mm, and 12 mm were used for lateral column lengthening. After the insertion of the bone grafts, positional changes in sagittal plane of both the anterior and posterior calcaneus segments were monitored on lateral views under both fluoroscopy and a 3D digital high-resolution motion capture system. Results were calculated in percentage change from the base line horizontal distance between the talar and both anterior and posterior calcaneus markers before insertion of the wedges. Results: According to fluoroscopic measurements, the anterior translation of the anterior calcaneus segment was 7.27%+/-0.06 for 6 mm wedge, 16.11%+/-0.06 for 8 mm wedge, 20.81%+/- 0.08 for 10 mm wedge and 18.16%+/-0.07 for 12 mm wedge. The posterior translation of the posterior calcaneus segment was 9.85%+/-0.09 for 6 mm wedge, 13.15%+/-0.09 for 8 mm wedge, 12.04+/-0.09 for 10 mm wedge, and 14.06%+/-0.10 for 12 mm wedge. Statistical analysis showed that: 6 mm wedges did not cause significant changes in the translation of both anterior and posterior calcaneus segments with respect to the talus. 8 mm, 10 mm and 12 mm wedges caused significant translations both anteriorly and posteriorly. There was no statistically significant difference in the amount of either anterior or posterior translation caused by 8 mm, 10 mm or 12 mm wedges. These results were corroborated by 3D measurements. Conclusion: Of interest is that a 6 mm graft did not cause any significant anterior or posterior shift of the calcaneus. Lateral column lengthening with the 8,10, and 12 mm grafts however caused forward shifting of the anterior calcaneus, but also statistically significant posterior translation of the tuberosity, causing impingement of the posterior facet which was visible in each cadaver tested. There was no statistical difference between the sizes of the wedge above 6 mm and the translations they caused either anteriorly or posteriorly. Surgeons should be aware of the potential for painful impingement with the lateral column lengthening osteotomy.

Category: Hindfoot Introduction/Purpose: Subtalar arthrodesis is an invaluable tool in managing arthritis, deformity, and muscular imbalance of the hindfoot. However, failed arthrodesis is complicated by bone necrosis, sclerosis with loss of bone, less than ideal biologic settings, and the literature reports a high rate of non-union. The aim of this study was to review all subtalar arthrodeses performed within a single institution, and specifically describe the management of non-union. Methods: 492 consecutive subtalar arthrodesis cases were retrospectively analyzed between October 2001 and July 2013. From the primary arthrodesis group 91 (18%) were treated for subtalar coalition (100% arthrodesis), and were excluded to better depict the arthrodesis rate; the remaining 401 patients were treated primarily for post-traumatic arthritis. Pertinent demographics, comorbidities, and clinical notes were all retrieved through the electronic medical record and radiographs were reviewed through a PACS system. Results: 49 patients with a mean age of 49 years (range 23 - 80) presented with subtalar non-union (overall rate 10%, adjusted rate 18%). 41 (84%) underwent revision at a mean of 16.2 months (range 2.8 - 57.1) from the index arthrodesis. The rate of revision arthrodesis was 78%, 21/30 (70%) in situ arthrodeses, 7/7 bone block arthrodesis (p=.028), and 4/4 triple arthrodesis (p=.028). Arthrodesis was present at a mean of 3.4 months (range 1.6 - 7.6). 4/9 (44%) of the recurrent nonunions elected to abstain from surgery. Of the 5 remaining patients, 2/5 had a successful third attempt at arthrodesis, 1/5 had an additional nonunion followed by a successful fourth attempt at arthrodesis, 1/5 had a successful tibiotalocalcaneal arthrodesis, and 1/5 required a below-knee amputation. Conclusion: Risk factors identified for non-union were post-traumatic arthritis, ipsilateral ankle arthrodesis, and individual patient factors (smoking, diabetes, and infection). Different methods of screw fixation were not found to be significantly different between the fused and nonunion groups. Despite directed management to obtain rigid fixation and adequate compression, the rates of subtalar arthrodesis from primary (82%), revision (78%) and secondary revision (60%) cases were very poor with the exception of the group which underwent a bone block arthrodesis (100%, p=.028).

Category: Ankle Introduction/Purpose: In order to design an implant for the ankle joint that mimics normal joint motion, the condylar geometry of the talus must be anatomically accurate. Previous attempts to describe the curvature of the talus have typically involved fitting single-radius arcs to the medial and lateral facets. The purpose of this investigation was to determine if the curvature of the medial and lateral sides of the talus can be more accurately described by dividing the condyles into anterior and posterior regions, thus creating bi-radial curves for both the medial and lateral sides of the talus. Methods: After IRB approval, 18 subjects (9 male, 9 female; mean age 34.5 years) underwent weight-bearing CT scans at mid- stance of simulated gait. All subjects were deemed to have a healthy right ankle by the surgeon investigator. CT images were used to generate 3D models of each talus. A coordinate system was defined and the articular surface of the talus was separated into four sections: medial-anterior (MA), medial-posterior (MP), lateral-anterior (LA) and lateral-posterior (LP). The curvature of each section was defined by selecting points on the articular surface at 10° intervals. The extent of each radius was 30° of arc and the magnitude of each radius was selected to minimize the gaps between the radii and the spline curve to define a best-fit bi-radial approximation to the spline curve using geometry that could be easily used to define the articular surface of the talus. Ratios of the aforementioned radii were calculated. Results: The average MA, MP, LA and LP radii were 18.3 mm, 26.6 mm, 21.5 mm and 25.1 mm, respectively. The medial (A/P), lateral (A/P), anterior (M/L) and posterior (M/L) radii ratios were 0.70, 0.87, 0.88 and 1.07, respectively. The anterior and posterior ratios were compared using a paired t-test and found to be statistically different (P=.019). Further, the data were compared against a hypothesized value of 1 using a one-tailed one-sample t-test. The anterior ratio was significantly lower than 1 (P=.014) while the posterior ratio was significantly greater (P=.037). On the lateral side, 83.3% of the subjects exhibited a larger posterior radius than anterior radius. Only one subject (5.6%) had a larger anterior radius than posterior radius on the medial side. Conclusion: This study shows that the radius increases in the sagittal plane from the anterior portion to the posterior portion of both the medial and lateral sides of the talus. Furthermore, the MA radius is smaller than the LA radius. Conversely, the MP radius is larger than the LP radius. These results substantiate the validity of an implant design that incorporates a condylar radius ratio that is smaller for the anterior dorsiflexion surface and greater for the posterior plantar flexion surface. Implants with more accurate anatomical geometry may allow for more normal kinematics and potentially prolong the life of the implant.

Category: Trauma Introduction/Purpose: The first tarsometatarsal (TMT) joint is very crucial for midfoot stability. To address its importance, retrospective analyses of treatment for the first TMT joint dislocation with Lisfranc injury was performed in a multi-center manner. Comparison of open reduction internal fixation (ORIF) and primary arthrodesis was conducted for the injury. Methods: This multi-center study was involved ten clinical institutions in different area of China. .From January 2003 to June 2015, 126 Lisfranc injuries with first TMT joint dislocation underwent surgical intervention. Of this group, forty one (32.5%) feet were first TMT joint dislocation only. Eighty five feet were first TMT joint dislocation and fractures. They were 76 males (60.3%) and 50 females (39.7%) with a mean age of 45.5 (range, 20-87) years. The duration from injury to surgery is 11.7 (range, 4-26) days. Two groups were divided by surgery methods as open reduction internal fixation (ORIF) group and primary arthrodesis group. Ninety two patients were performed by ORIF, while primary arthrodesis group including 34 cases. Outcome measures included clinical examination, radiographs, AOFAS ankle-hindfoot scores, visual analogue scale (VAS) and SF-36 scores. Complications and revision rate were analyzed as well. Results: 126 patients were followed up for 29.5 months. At 1.5 years postoperatively, the AOFAS score was 79 and 85 in ORIF group and arthrodesis group.The VAS score was 3.1 separately in two groups.The mean Physical Functioning sores of SF-36 was 80.3 points and 83.5• points. The Bodily Pain score of SF-36 was 76.1 points and 84.6• points.Redislocation of first tarsometarsal joint were observed in 16 cases among ORIF group.36 patients in ORIF group had pain in midfoot, eight of them had persistent pain with the development of deformity or osteoarthrosis.No redislocation and no hardware failure was identified in arthrodesis group Conclusion: Primary stable arthrodesis of the first ray gives a better short and medium term outcome than open reduction and internal fixation for Lisfranc injury with the first ray dislocation. Possible complication and revision could be avoided by primary arthrodesis for dislocated first ray injuries.

Category: Ankle Arthritis Introduction/Purpose: The last decade has seen a considerable increase in the use of in total ankle arthroplasty (TAA) to treat patients with end-stage arthritis of the knee. However, the longevity of the implants is still far from that of total knee and hip arthroplasties Methods: To introduce a systematic approach to the painful TAA based on the literature and on the senior author’s experience Results: See algorithm attached Conclusion: This new diagnostic and treatment algorithm may be useful to guide less experienced surgeons navigate through the possible causes and treatments of a painful TAA

Category: Hindfoot, Diagnostic Imaging Introduction/Purpose: Multiple techniques have been described in determining the hindfoot alignment radiographically. While these studies have traditionally showed good reliability, the 2-dimensional nature of radiographs fails to consider the contribution of the remainder of the foot on the overall alignment. A new technique has been recently published in which the hindfoot alignment is calculated using the Ground Reaction Force Calcaneal Offset off radiographs. This technique accounts for the individual forefoot contributions on overall alignment, however is still limited by the 2-dimensional nature of plain radiographs. The purpose of this study is to compare two accepted radiographic measurements, the hindfoot moment arm (HMA) and the hindfoot alignment angle (HAA), with a novel technique determining the ground reaction force calcaneal offset (GRF-CT) using 3- dimensional weight bearing CT Scans. Methods: Retrospective chart review was performed over a two-year period from 2014-2016 to identify patients with weight bearing hindfoot alignment radiographs and PedCat (Curvebeam, Warrington, USA) 3-D weight bearing CT scans. The HMA, HAA, and GRF-CT were measured by three different investigators. Each of these measurements were calculated two times on separate occasions by each investigator to determine the intra- and inter-observer reliability with each of these techniques Results: One-hundred and four patients underwent weight bearing hindfoot alignment radiographs and 3-dimensional weight bearing CT scans. There were 33 patients with varus deformities and 71 patients with valgus deformities. There was excellent intra- and inter-observer reliability with all three measurement techniques, however the GRF-CT showed the best intra- and inter-observer reliability with the lowest standard deviation Conclusion: The GRF-CT technique is more reliable than traditional radiograph techniques for measuring the hindfoot alignment. While the intra- and inter-observer reliability is good for all three techniques, the GRF-CT technique resulted in the best intra- and inter-observer reliability with the lowest standard deviation. This technique provides the most accurate hindfoot alignment as it takes into account the effect of forefoot on overall alignment, preventing inaccuracies of projection and foot orientation in contrast to traditional radiographic techniques, which may be valuable in surgical decision making.