Combination of PedCAT with Pedography Shows Relationship of Morphology (Bone) Based Foot Center (FC) and Force/Pressure Based Center of Gravity (COG)

Category: Basic Sciences/Biologics Introduction/Purpose: PedCAT (Curvebeam, Warrington, USA) is a technology for 3D-imaging with full weight bearing which has been proven to exactly visualize the 3D-bone position. Center of gravity (COG) and Foot Center (FC) are discussed to be important parameters for corrections/fusion around the hindfoot and for total ankle replacement. For this study a customized pedography sensor (Pliance, Novel, Munich, Germany) was inserted into the pedCAT. The aim of this study was to analyze difference of morphology (Bone/PedCAT) based FC and Force/Pressure (Pedography) based COG. Motion of COG during PedCAT/Pedography scan should also be registered and analyzed. Methods: In a prospective consecutive study starting November 28, 2016, 36 patients / 72 feet were included. Inclusion criteria were 18 years of age or older, and indication for PedCAT scan based on the local standard. A pedCAT scan with simultaneous pedography with full weight bearing in standing position was performed. The morphology based definition of the FC was performed with the pedCAT data following the TALAS algorithm. This algorithm takes different bony landmarks (Posterior calcaneal process, center of talar dome/tibial plafond, metatarsal heads) into consideration and calculates the FC. The force/pressure based COG was defined with the pedography data using a software based algorithm. The distance between FC and COG and the direction of a potential shift (distal-proximal; medial lateral) was measured and analyzed. COG motion during data acquisition was recorded and analyzed. Results: Mean age of patients was 54.5 (range, 27-80) years, 27 (75%) were female. COG motion was 1.4 mm on average (range, 0-4.8 mm). The distance between FC and COG was 22.6 mm on average (range, 5-52). FC was distally to COG in all feet (mean, 27.4 mm; range, 3-50), and laterally in 49 feet (68%; shift 0 mm in remaining feet; mean for all feet, 3.3 mm; range, 0-12). No difference between right and left side occurred (t-test, each p>.05). Conclusion: COG is not relevantly moving during combined PedCAT/Pedography scan. There is a difference between FC and COG. This expected finding was quantified with this study. There is a typical/standard shift between COG and FC in the investigated 32 subjects / 64 feet (26 mm distally and 3 mm laterally on average) which might allow for prediction of COG based on FC without additional pedography. Definition of COG might be taken into consideration for planning and followup for corrections/fusion around the hindfoot and for total ankle replacement

3D biometrics for hindfoot alignment using Weight Bearing CT

Category: Hindfoot Introduction/Purpose: Hindfoot alignment is an important reference for foot and ankle surgery, and the Foot Ankle Offset (FAO) using semi-automatic software has been reported as a valuable hindfoot alignment measurement in weightbearing CT(WBCT). The objective was to assess the clinical relevance and reproducibility of the FAO value for hindfoot alignment and compare it with previous findings. Methods: A prospective study was conducted, with ethics committee approval. Patients were included, clinically examined and divided into 3 groups: normal alignment (Group 1), valgus (Group 2), varus (Group 3). A continuous series of 140 feet (71 patients) were referred from September to December 2017 (65 normal, 41 valgus, and 34 varus). All patients had a bilateral weight bearing CT, and the FAO values were recorded. The long axial view angle(HAct)was measured on Digitally Reconstructed Radiographs (DRR) as comparison. All values were measured and compared by two different investigators. The reproducibility of FAO and HAct were calculated using intraclass correlation coefficients(ICCs) and regression analysis was conducted to study the correlation between the two methods. Results: In Group 1, the mean value for FAO/HAct was 1.69%±2.58%/4.13±2.67, in Group 2, the FAO/HAct was 7.46%±3.18%/9.00±3.43; in Group 3 the values were -6.11%±4.55%/-7.49±6.06. The intra- and interobserver reliability were 0.991/0.992 and 0.976/0.976. There was a good linear correlation between HAct and FAO (R2=0.778, and the regression slope was 1.083. Conclusion: The use of weightbearing CT can help characterize hindfoot alignment objectively using WBCT. The present study is the first prospective comparative assessment of this technology and shows that FAO has good repeatability, and it correlates well with clinical examination,, X ray findings and previous literature. The FAO is a clinically relevant and reproducible method for measuring hindfoot alignment

Benefit of weight-bearing CT - what have we learned from more than 8,000 scans at a foot and ankle center

Category: Other Introduction/Purpose: Weight-bearing CT (WBCT) has been proven to allow for more precise and valid measurement of bone position than conventional weight-bearing radiographs (R) and conventional CT without weight-bearing (CT). Time spent for image acquisition has been shown to be lower for WBCT than for R and CT2. Radiation dose for WBCT has been shown to be lower for WBCT than for CT. A WBCT device (PedCAT, Curvebeam, Warrington, PA, USA) had been brought on line July 1, 2013 in the first author´s foot and ankle department. The purpose of this study was to assess the benefit of using WBCT instead of R and/or CT in a foot and ankle center regarding time spent for image acquisition, radiation dose, disturbances, and cost effectiveness. Methods: All patients who obtained WBCT July 1, 2013 until December 31, 2017 were included in the study. Age, sex and primary pathology were analyzed. The time spent for image acquisition (T) was calculated based on an analysis of a previous study as follows: R (bilateral feet dorsoplantar and lateral, metatarsal head skyline view), 902 seconds; CT (bilateral feet and ankle), 415 seconds; WBCT (bilateral), 207 seconds. Radiation dose (RD) per patient was calculated based on previous phantom measurements as follows: R, 1.4 uSV; CT, 25 uSv; WBCT 4.2 uSv. For analysis of cost effectiveness device cost, reimbursement and working time cost of radiology technicians were taken into consideration within the local circumstances. All parameters were compared between the time period using WBCT (yearly average) with the parameters from 2012, i.e. before availability of WBCT. Results: 8,129 WBCT scans were obtained in 3,874 patients (3,874 (48%) preoperatively, 4,255 (52%) follow-up; mean age, 52.2; 39% male). Primary pathologies were forefoot deformities (n=728 (19%) and ankle osteoarthritis/cartilage defect (n=412 (11%)). 1,804 WBCT scans were obtained on average yearly, and 10 CTs (WBCT group). In 2012, 1,750 R and 250 CTs were obtained (R(+CT) group). Yearly RD was 4.3 uSv for WBCT group and 5.0 uSv for R(+CT) group (difference 0.6 uSv decrease with WBCT 13%, p<0.01). Yearly T was 105 hours in total (3.5 minutes per patient) for WBCT group and 961 hours in total (16.0 minutes per patient) for R(+CT) group (difference, 752.0 hours, decrease with WBCT, 78%, p<0.01). Yearly profit was 34,300 Euro for WBCT group, -846 Euro for R(+CT) group. Conclusion: 8,129 WBCT scans in 3,874 patients as substitution of R(+CT) over a 4.5 year period at a foot and ankle center resulted in 13% decreased RD (minus 0.7 uSV on average per patient). Yearly T decreased 752 hours (78%) in total (12.5 minutes per patient). Yearly financial profit increased 35,000 Euro in total (19 Euro per patient). RD decreased despite higher radiation dose for WBCT than for R alone, based on substitution of a high number of CTs by WBCT. Other centers with low usage of CT might not decrease RD by substituting R alone by WBCT

Comparison between Weight Bearing Radiographs and Weight Bearing ConeBeam CT Examinations in the Assessment of Adult Acquired Flatfoot Deformity

Category: Hindfoot Introduction/Purpose: Adult acquired flatfoot deformity (AAFD) represents a biomechanical derangement involving the three- dimensional (3D) midfoot and hindfoot osseous complex, and can be challenging to optimally characterize using conventional two- dimensional (2D) plain radiographs. Weightbearing (WB) ConeBeam CT (CBCT) can better demonstrate the deformity of the 3D structures during WB. Therefore, we compared validated AAFD measurements between WB conventional radiographs and WB CBCT images. Methods: In this prospective, IRB approved and HIPAA compliant study, 20 patients (20 feet, 15 right and 5 left) with clinical diagnosis of flexible AAFD were included, 12 males and 8 females, with a mean age of 52.2 years (range, 20 to 88 years of age), and average BMI of 30.35 kg/m2 (range, 19.00 to 46.09 kg/m2). Involved feet underwent standing (WB) anteroposterior (AP) and lateral radiographs, and were also scanned by WB CBCTs. Both imaging modalities were assessed with traditional AAFD measurements obtained at sagittal (lateral view on radiograph) and axial (anteroposterior view on radiograph) planes using predefined anatomical landmarks, by two independent and blinded foot and ankle fellowship-trained observers. Intra- and Inter- observer reliabilities for both imaging modalities were calculated using Pearson correlation. WB radiograph and WB CBCT measurements were compared by T-Test of the means. P- values < 0.05 were considered significant. Results: There was good to excellent intra and inter-observer agreements for most of the measurements on both radiographs and WB CBCT images, with slightly better results favoring WBCT measurements. When comparing WB radiographs and WB CBCT images, we found significant differences in the mean values for some of the measurements, including: talus-first metatarsal angle in the sagittal plane (11.34° x 21.73°, p<0.0001), navicular-medial cuneiform angle (13.19° x 7.63°, p<0.0004), medial cuneiform to floor distance (6.70 mm x 5.50 mm, p<0.0003) and navicular to floor distance (31.34 mm x 23.22 mm, p<0.0001). No significant differences were found when measuring: talus-first metatarsal angle in the axial plane, talar uncoverage angle, cuboid to floor distance and calcaneal inclination angle. Conclusion: Traditional adult acquired flatfoot deformity radiographic measurements are obtainable using high resolution 3D WB CBCT imaging. Measurements performed on WB CBCT have similar intra-observer and overall higher inter-observer reliability when compared to WB radiographs. The statistically significant differences found in some of the measurements, when comparing both imaging techniques, might be related to a better characterization of the three-dimensional deformity on WB CBCT images

Weightbearing CT Analysis of Hindfoot Alignment in Chronic Lateral Ankle Instability

Category: Ankle, Hindfoot, Imaging, Ankle Instability Introduction/Purpose: Varus hindfoot deformity may increase the risk of chronic ankle instability (CAI).Weightbearing CT (WBCT) semi-automated measurements and built-in databases may contribute to investigate the relationship between clinical and radiographic data. The objective of this study was to analyze hindfoot alignment (HA) in relation with CAI in a series of patients using these new tools. We hypothesized that there would be a positive correlation between a varus morphotype and a history of CAI. Methods: This is a Level 3 retrospective comparative study of a continuous series of 124 feet (63 patients) referred from July to December 2016. and subsequently assessed by WBCT (PedCAT®, CurveBeam LLC). The measurement software (Talas®, Curvebeam LLC), gave HA as a value of Foot and Ankle Offset (FAO). This measures the offset between the center of the ankle joint and the median line of the foot joining the centers of the calcaneus and forefoot weight bearing surfaces. Data was prospectively saved in a database (CubeView®, CurveBeam, PA, USA). The definition of CAI was a history of at least 3 ankle sprains during a 6 months period. Exclusion criteria were medial instability and syndesmotic injuries (2 cases).A univariate analysis was conducted to study CAI against the following variables: gender (Fisher), BMI and FAO (Kurskal-Wallis). The significant variables were subsequently included in a multivariate logistic model. Results: Nineteen feet had CAI, in 12 patients. Gender (p=0.0467 –the proportion of women for patients with CAI was 72.3%, compared to 33.3% without CAI) and FAO (p=0 .0002) were significant in the univariate analysis. The mean FAO was respectively -1.40 (SD: 5.50) and 3.56 (SD: 5.31) with and without a history of CAI. No significant difference of age or BMI was shown. After verification of log-linearity between odds of CAI and FAO, the multivariate logistic regression adjusted for gender demonstrated a 15% increase of odds of CAI per unit increase of varus (adjusted Odds Ratio (CI95%): 0.858 (0.771-0.943) p=0.003), and no more significant effect of gender after adjustment on FAO (Odds ratio (CI95%) Female versus Male: 0.548 (0.185 -1.669) p=0.277). Conclusion: A positive linear relationship was found between Varus Hindfoot Alignment measured using a semi-automatic tool in WBCT and the odds ratio for Chronic Ankle Instability, thus confirming and quantifying previous findings. The recent development of semi-automatic measurements and prospective databases opens future perspectives for big data and multivariate analysis in foot and ankle pathology

Foot Alignment Profile in Injured Professional Basketball and Football Athletes

Category: Sports Introduction/Purpose: Adequate evaluation of foot and ankle problems in elite athletes is paramount for planning the correct treatment, predicting clinical prognosis and supporting decision making. A complete physical examination that includes the assessment of foot alignment during weightbearing is mandatory. The three-dimensional evaluation provided by weightbearing CT imaging (WBCT) represent an important diagnostic tool for foot and ankle surgeons when dealing with these extremely physically active patients. The purpose of this study was to assess different WBCT measurements of hindfoot and forefoot alignment in injured high-level football and basketball players. We hypothesized that specific patterns of hindfoot alignment and height of the longitudinal arch of the foot could be identified. Methods: In this single center retrospective comparative study, 80 professional male athletes - 47 basketball and 33 American football players from College, NBA and NFL leagues - that underwent WBCT as part of the clinical investigation for different injuries of the foot and ankle were included in the study. WBCTs images were evaluated by a blinded board-certified foot and ankle orthopedic surgeon. Multiple measurements used for assessment of hindfoot valgus and longitudinal arch height were assessed and included: foot and ankle offset (%), calcaneal offset (mm), hindfoot alignment angle (°), navicular-floor distance (mm), medial cuneiform-floor distance (mm), forefoot arch angle (°), inferior talar-superior talar angle (°), and subtalar horizontal angle (°). An unpaired Student’s t test was performed to evaluate any differences in the measurements when comparing professional basketball and football patients. P-values less than 0.05 were considered significant. Results: A summary of demographic characteristics and each measurement’s distributions and standard deviations, as well as p-values for the analysis between groups, is given in table 1. No significant differences were found between basketball and American football elite athletes when comparing the mean values of measurements evaluated (mean differences): foot and ankle offset (0.26%), calcaneal offset (0.58 mm), hindfoot alignment angle (0.73°), navicular-floor (0.35 mm) and medical cuneiform-floor distances (0.38 mm), forefoot arch angle (0.74°), inferior talar–superior talar angle (0.83°) and subtalar horizontal angle (0.1°). Conclusion: Although we did not find significant differences in foot alignment when comparing basketball and American football professional athletes, the results of our study highlight some of the important foot alignment parameters and establish distributions in an extreme but important population. Further studies correlating foot alignment with the incidence of some of the most common pathologies diagnosed in elite athletes, such as the ones reported in our study, can help in the understanding and prevention of those injuries

A Case-control Study of 3D versus 2D Weight Bearing CT Measurements of the M1-M2 Intermetatarsal Angle in Hallux Valgus

Category: Midfoot/Forefoot Introduction/Purpose: Surgical planning based on angular measurements obtained on conventional radiographs is challenging due to perspective distortion and operator bias. Novel weightbearing CT (WBCT) three-dimensional (3D) measurements using coordinate systems may represent a more reliable and accurate evaluation of this 3D deformity. The objective of this study was to compare the M1-M2 intermetatarsal angle (IMA) obtained manually on WBCT digitally reconstructed 2D radiographs versus a set of coordinates from the full 3D dataset, in patients with hallux valgus (HV) deformity and in healthy controls. We hypothesised that the 3D measurements would be more reliably obtained, demonstrating different values when compared to 2D radiographic measurements. Methods: In this multicenter retrospective comparative study, 83 feet that underwent WBCT of the foot were included (41 HV: mean age 59, 81% female, 42 controls: mean age 52, 80% female). Datasets were analysed by three independent trained foot and ankle surgeons using the same protocol. Coordinates in three planes (x, y, z) of four different landmark points were harvested: center of the heads and midpoint of the proximal metaphysis of the 1st and 2nd metatarsal. The IMA measurements were then performed in reconstructed radiographic images (DRR-IMA). The data collected was then analyzed by a single 4th independent and blinded investigator who calculated the 3D angle (3D-IMA) and its projection on the weightbearing plane (2D-IMA). Intra-observer realiability was assessed by Pearson/Spearman’s correlation. Intermethod correlation was evaluated by intraclass correlation coefficient (ICC). Mean values for measures were comparared by One-way ANOVA. P-values of less than 0.05 were considered significant. Results: Intraobserver reliability was excellent for radiographic DRR-IMA (0.95) and 3D coordinates assessment (0.99). Intermethod correlation between the three different imaging modalities (DDR, 2D and 3D), considering bias and interactions, were respectively 0.71 and 0.51 in control and HV patients. IMA measurements were found to be similar when measured in DRR, 2D and 3D WBCT images, for both controls and HV patients. Mean values and confidence intervals (CI) for controls were 8.8 degrees (CI, 7.9-9.7) in DDR images, 9.8 degrees (CI, 8.7-10.9) in 2D images and 10.6 degrees (CI, 9.5-11.8) in 3D images. When compared to controls, HV patients demonstraded significantly increased IMA (p<0.05): 13.06 degrees (CI, 11.8-14.3) in DDR images, 12.1 degrees (CI, 10.8-13.3) in 2D images and 13.3 degrees (CI, 12.3-14.3) in 3D images. Conclusion: We found that similar values for IMA were measured in 2D reconstructed radiographs, WBCT 3D and 2D projected images. When compared to controls, HV patients were found to have increased IMA in all three different imaging types used (DDR, 2D and 3D). Intermethod correlation was higher for IMA performed in controls. Intraobserver reliability was excellent for both radiographic IMA measurements and WBCT 3D coordinates. Our study is the first study to evaluate measurements of the 3D-IMA in HV and control patients. Further investigations are required before guidelines for its clinical use can be formulated