Results of more than 11,000 scans with weightbearing CT : impact on costs, radiation exposure, and procedure time

Background: Weightbearing CT (WBCT) has been proven to more precisely measure bone position than conventional weightbearing radiographic series (R) and conventional CT (CT). The purpose of this study was to assess the benefit of using WBCT instead of R and/or CT as the standard imaging modality, evaluating image acquisition time, radiation dose, and cost-effectiveness. Methods: All patients who obtained a WBCT as part of standard of care from July 1, 2013 until March 15, 2019 were included in the study. Image acquisition time (T), radiation dose (RD) per patient, and costeffectiveness were analyzed and compared between the time period using WBCT (yearly average) and the parameters from 2012, i.e. before the availability of WBCT (RCT group). Results: 11,009 WBCT scans were obtained from 4987 patients (4,987 scans (45%) before treatment; 6,022 scans (55%) at follow-up). On a yearly average, 1,957 WBCTs (bilateral scans) and an additional 10.6 CTs (bilateral feet and ankles) were obtained (WBCT group). In 2012, 1,850 Rs (bilateral feet, dorsoplantar and lateral, metatarsal head skyline view) and 254 CTs were obtained from 885 patients (RCT group). The mean yearly RD was 4.3/4.8uSv for the WBCT/RCT groups (mean difference of .5 uSv; a decrease of 10% for the WBCT group; p < .01). Yearly mean T was 114/493 h in total (3.3/16.0 min per patient) for WBCT/RCT groups (mean difference of 379 h; a 77% decrease for the WBCT group; p < .01). Yearly cost-effectiveness was a mean profit of 43,959/-723 Euros for WBCT/RCT groups. Conclusions: 11,009 WBCT scans from 4,987 patients over a period of 5.6 years at a foot and ankle department resulted in 10% decreased RD, 77% decreased T, and increased financial profit (51 Euros per patient) for the institution. (c) 2019 The Author(s). Published by Elsevier Ltd on behalf of European Foot and Ankle Society

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

Do the Number of Screws and the Use of a Lateral Fibular Autograft Influence the Union Rate in Ankle Arthrodesis? A Systematic Review

CATEGORY: Ankle Arthritis; Ankle INTRODUCTION/PURPOSE: Ankle arthrodesis, well-known as a reliable option to treat end-stage ankle osteoarthritis (AO), may be fixed using screws in various configurations. The purpose of this study was to determine whether the number of screws and the use of a lateral distal fibular autograft during the procedure might influence the union and complication rate. We hypothesized that a greater number of screws and the use of a fibular autograft might increase the union rate and reduce the number of complications. METHODS: Following the PRISMA-compliant PROSPERO-registered checklist, the Medline, Scopus, Web of Science and Cochrane databases were searched, including studies reporting patients affected by AO and undergone Ankle Arthrodesis (AA) using screws as exclusive fixation method. Data were harvested regarding the cohort (sample size, age, sex, etiology), the study design (type of study, level of evidence), the surgical technique (open/arthroscopic procedure, the number of screws, the use of autograft) and the final outcome (union, complication and reoperation rate) at the longest follow-up. The risk of bias was assessed using the modified Coleman Methodology Score (mCMS) was used to assess the methodological quality of studies. Three groups were built based on the type of fixation: arthrodeses fixed with 2 screws (Group 1, G1), with 3 screws (Group 2, G2), and those augmented with a lateral fibular autograft (Group 3, G3). RESULTS: Twenty series of patients from nineteen studies (732 ankles) were selected (G1=252 ankles, G2=209, G3=271). The pooled proportion estimate revealed a similar nonunion rate in the 2-screw group as compared to the 3-screw group (6% vs 1%; p=0.43) The pooled proportion of complications appeared higher in G1 (18%) than in G2 (8%) but it was not significantly different either (p=0.27). After exclusion of 'symptomatic hardware and screw removal' the difference was still not significant (p=0.62) although it resulted lower in G1 than in G2 (3% vs 8%, respectively). The pooled proportion of nonunions (p=0.48) and complications (p=0.76) did not differ between the AA performed without or with a fibular autograft. CONCLUSION: Fixation of Ankle Arthrodesis using three screws as compared to two screws seems to be advantageous in terms of reduced risk of nonunion and complications, although the difference did not achieve statistical significance in this study. The use of an adjuvant lateral distal fibular autograft does not seem to significantly increase the chances of fusion as compared to a no- autograft construct. The evidence provided so far is based on retrospective and short-term follow-up studies of moderate methodological quality. Further comparative and prospective analyses are warranted to define how to achieve the best outcome in Ankle Arthrodesis stabilized using screws

Results of a 5 year, 10,000 scans experience with weight-bearing CT : impact on costs, radiation exposure and time spent

CATEGORY: Radiolography 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 CT. 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 (PedCAT)from July 1, 2013 until September 30, 2018 were included in the study. Age, sex, primary pathology were analyzed. The time spent for image acquisition (T) was calculated based on an analysis of 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 uSv1. For analysis 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: 10,087 WBCT scans were obtained in 4,702 patients (4,702 (47%) before treatment; 5,385 (53%) follow-up; mean age, 52.0; 40% male). Primary pathologies were forefoot deformities (n=916 (20%) and ankle instability/cartilage defect (n=534 (13%)), and hindfoot deformity (n=480 (10%)). 1,940 WBCT scans were obtained on average yearly, and 10.4 CTs (WBCT group). In 2012, 1,850 R and 254 CTs were obtained (R(+CT) group). Yearly RD was 4.4 uSv for WBCT group and 4.8 uSv for R(+CT) group (difference 0.4 uSv decrease with WBCT 8%, p<0.01). Yearly T was 127 hours in total (3.6 minutes per patient) for WBCT group and 959 hours in total (15.6 minutes per patient) for R(+CT) group (difference, 832 hours, decrease with WBCT, 87%, p<0.01). Yearly profit was 47,545/-816 Euro for WBCT/R+(CT). CONCLUSION: 10,087 WBCT scans in 4,702 patients as substitution of R(+CT) over a 5.3 year period at a foot and ankle center resulted in 8% decreased RD (minus 0.4 uSV on average per patient). Yearly T decreased 832 hours (87%) in total (12.0 minutes per patient). Yearly financial income increased more than 48,000 Euro in total (24 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

Weightbearing CT Assessment of Foot and Ankle Joints in Pes Planovalgus Using Distance Mapping

The goal of this study was to describe the abnormal joint surface interaction at the ankle, hindfoot and midfoot joints in patients presenting with Pes Planovalgus (PPV) using three-dimensional (3D) distance mapping on weightbearing computed tomography (WBCT) images by comparing a series of PPVs to a series of normally-aligned feet. We hypothesized that in PPVs joint interactions would reveal significantly increased spaces in the medial side of the ankle, hindfoot and midfoot joints

Three-Dimensional Weightbearing Assessment of the First Ray in Hallux Valgus: A Case-Control Study

CATEGORY: Bunion INTRODUCTION/PURPOSE: Coronal plane rotational deformity of the first ray has been implicated with the developmental pathologic process of hallux valgus (HV). Weight Bearing CT (WBCT) is an imaging technology that can support the assessment of this complex three-dimensional (3D) deformity. The objective of the study was to analyze the 3D architecture of the first ray in patients with HV when compared to controls using WBCT images and a 3D biometric algorithm analyzing the deformity in all three planes. We hypothesized that WBCT would confirm the rotational deformity in HV patients, and that the 3D algorithm would demonstrate increased specificity and sensitivity for the pathology when compared to traditional two-dimensional (2D) HV measurements such as the 1-2 intermetatarsal angle. METHODS: Retrospective case-control study, ethics committee approved. Twenty-one feet of patients with clinically symptomatic HV and 20 feet of asymptomatic controls were included. Exclusion criteria applied were previous trauma or surgery affecting first ray or forefoot morphology. All patients were assessed using WBCT. First ray 3D coordinates (x, y, z) were harvested including: center-points of the heads and bases of the first and second metatarsals, center-point of the medial and lateral sesamoids, distal condyles of the proximal phalanx (PP) of the first toe, as well as the medial and lateral borders of the first metatarsal head and diaphysis. The 2D measurements (dorsoplantar 1-2 intermetatarsal (IMA) and metatarsophalangeal (MPA) angles) were obtained using digitally reconstructed radiographs (DRR). The Sesamoid Rotation Angle (SRA) was measured in the coronal plane. Using these coordinates, all 2D, 3D axes, distances, angulations and 3D biometric for HV (HV-3DB) could be calculated. RESULTS: Mean ages were respectively 62.2y in the HV group and 48.8y in the control group (p<0.05). In 2D, the mean IMA and MPA for HV/controls were respectively 14.9/9.3 (p<0.001) and 30.1/13.1 (p<0.001). The SRA were respectively 29.1/7.1 (p<0.001). We found an almost perfect positive correlation between P1 rotation and sesamoid rotation, good correlation between IMA, MPA and SRA angles. There was poor correlation between pronation angles of the 1st phalanx and the 1st metatarsal. The 3D biometric algorithm combining IMA, MPA and SRA had a sensitivity of 95% and a specificity of 95.2% for the diagnosis of HV, compared to 90%/85.6% for the IMA and 90%/90.5% for the SRA. CONCLUSION: This original study confirmed our hypotheses. Weight Bearing CT efficiently analyzed the 3D architecture of the 1st ray in HV patients compared to asymptomatic controls. We concur with previous findings described in the literature concerning increased pronation of the 1st ray in HV. A novel biometric for HV using a specific multidimensional algorithm which combined IMA, HVA and SRA in a single 3D measurement, demonstrated increased sensitivity and specificity compared to the conventional 2D 1-2 intermetatarsal angle for the diagnosis of HV

Redefining Hindfoot Alignment Based on Pathology rather than Morphology: A Prospective Observational Diagnostic Study on 250 Feet

CATEGORY: Ankle; Ankle Arthritis; Bunion; Hindfoot; Midfoot/Forefoot; Other INTRODUCTION/PURPOSE: The analysis of the hindfoot alignment (HA) is important in the management of various foot and ankle pathologies. Foot Ankle Offset (FAO), measured using Weight Bearing CT (WBCT) scans is a 3D biometric measurement of HA described in the literature, however only with relation to the clinical morphology of the hindfoot or previously known 2D biometrics such as the hindfoot angle. The aim of this study was to observe the FAO distribution on a continuous, large population of patients and to analyze its discriminating power between pathological and non-pathological cases. We hypothesized that threshold values could be determined for the normal range of FAO in terms of risk of presenting with different pathologies in varus or valgus configurations. METHODS: Prospective, IRB approved (COS-RGDS-2016-06-008-P-LINTZ-F, Clinical Trials NCT 04134962), level II study. 125 patients (250 feet) with bilateral WBCT as standard follow-up were included at a single institution. Mean age was 54 years (18-84), 58.4 % were female. Each patient was clinically evaluated, scans analyzed by a fellowship-trained foot and ankle surgeon and all degenerative pathologies classified depending on their anatomical location (medial or lateral). HA was measured using FAO on 3D datasets and Tibio-Calcaneal Angle (TCA) on 2D Saltzman-El-Khoury views. All scans were analyzed a second time by a radiology MD. FAO and TCA Intraclass Correlation Coefficient (ICCs) and Spearman’s correlation coefficient were calculated. Mean FAO values were calculated for all, normal, varus and valgus cases, and each pathology group. Receiver operating Curves (ROC), threshold values of FAO and area under the curve (AUC) were established for predicting an increased risk of medial or lateral pathologies. RESULTS: A threshold FAO value of -1.64% was found to best predict the risk of lateral pathology (51.4% sensitivity, 85.1% specificity, AUC=0.72) and 2.71% (95% sensitivity, 82.8% specificity, AUC=0.93) for medial pathology, both versus no pathology. Mean FAO value was 1.65% +-4.72% and mean TCA was 4.15° +-7.67°. Interobserver reproducibility for FAO and TCA was respectively 0.96 [95% CI 0.95-0.97] and 0.95 [95% CI 0.94-0.96]. Spearman’s correlation coefficient between FAO and TCA was 0.697. Clinical assessment rated 167 feet as normal, 33 varus, and 50 valgus. Mean FAO values were respectively 0.99 +-3.26%, - 2.53+-5.05 % and 6.81+-2.70%. We found that the mean FAO was 0.42+-3.19 % for non-pathologic feet, -2.30+-4.58 for lateral pathologies, 6.62+-2.77 for medial pathologies. CONCLUSION: The most important finding in this prospective clinical trial is the description of normal HA as the FAO range in which the risk for degenerative Foot and Ankle pathology is the least: -1.64% to 2.71%. This new, pathology based prognostic approach to HA is different to the traditional morphological approach. The potential of WBCT to provide computerized, data- based and biomechanically meaningful 3D measurement tools could improve the prognostic potential of biometrics such as HA. Results will be refined in the future by increasing the size of study population