Foot Ankle Offset Research Articles

Changes in the Subtalar Joint Alignment after Supramalleolar Osteotomy for Varus Ankle Arthritis

Category: Ankle; Hindfoot Introduction/Purpose: The subtalar joint may compensate for tibio-talar deformity, but what would happen to the joint after the deformity was corrected is not well known. Supramalleolar osteotomy (SMOT) is an effective procedure for the treatment of varus deformity of ankle arthritis. The objective of this study was to investigate the subtalar joint alignment pre and postoperatively following SMOT, and the factors which influenced the alignment of the subtalar joint. Methods: Thirty-one patients with varus ankle arthritis (Takakura stage 2, 3a and 3b) who were treated using SMOT were retrospectively reviewed. The subtalar and ankle joint alignment was measured on weightbearing radiograph and weightbearing computerized tomography (WBCT). Results: The foot ankle offset (FAO), tibial articular surface angle (TAS), tibio-talar surface angle (TTS), subtalar vertical angle (SVA) and subtalar inclination angle (SIA) were significantly corrected (P<0.05). There were 19 cases with the subtalar joints shifted medially after surgery (ΔSIA=-4.27±3.23°), and the other 12 cases with the subtalar joints moved to the lateral side (ΔSIA=2.79±1.68°). The shift of subtalar joint (ΔSIA) showed an inverse correlation with the preoperative FAO (P<0.001, r=-0.621). Conclusion: The shift of subtalar joint after SMOT could maintain the neutral position of the hindfoot and showed a negative correlation with the preoperative FAO. The ΔSIA was greater in the severer preoperative hindfoot deformity. Figure 1 The varus deformation of the ankle joint was corrected by the supramalleolar osteotomy, and the increased SIA after surgery resulted in the stenosis of the lateral joint space. (A and C, preoperative; B and D, postoperative, the pre and postoperatively SIA were 3 degrees and 10 degrees; the pre and postoperatively FAO were -5.77% and -1.89%). Abbreviations: TAS, tibia articular surface angle; SIA, subtalar inclination ankle; FAO, foot ankle offset.

3D Weight-Bearing CT Imaging Analysis of Foot Mechanics: Bridging High Heels and Hallux Valgus

Introduction/Purpose: Evidence in the literature suggests the negative effects of using High Heels (HH), becoming a challenge for clinicians and researchers since they are welcomed by women worldwide, mainly due to the subjective power of attractiveness given to them. Although some people blame HH as one of the causes of Hallux Valgus (HV), until now, there are no studies in the literature that effectively prove a cause-effect relationship between HH and HV. The objectives of this study are: (1) to analyze whether the increase in heel height can lead to HV and (2) to evaluate whether HV can increase in severity with increasing heels. We hypothesized that an increase in heel height could cause and increase the severity of HV deformity. Methods: Comparative cross-sectional study. Forty-one feet from twenty-one participants (11 males and 10 females, aged 30.8 ± 8.9 years, and with Body Mass Index 25.5 ± 2.0 m kg2) were recruited. HH shoes were designed for this study with three heights for each participant: 3, 6, and 9 cm. The inclusion criteria were: no regular wearing of heels. The exclusion criteria were: Hallux Valgus diagnosis and/or any orthopedic conditions that affect the Foot and Ankle joints. Hallux Valgus Angle (HVA), Intermetatarsal Angle (IMA), First-Metatarsal Phalangeal Angle, 1st-to-5th Intermetatarsal Angle, First Tarsometatarsal Angle (axial), Second tarsometatarsal angle (axial), Hindfoot Moment Arm (HMA) (mm), Saltzman 45 angle and, Foot Ankle Offset (FAO) were measurement using semiautomated software analysis. Multiple comparisons were performed (Bonferroni's for normal distributions and Wilcoxon test for no normal distributions) when there was a main effect on an outcome (p < 0.05). Results: With the increase in HH, we noticed a progressive increase in HVA (p < 0.001), IMA (p < 0.001), First-Metatarsal Phalangeal Angle (p < 0.001), First Tarsometatarsal Angle (axial) (p < 0.001), and the Second tarsometatarsal angle (axial) (p < 0.001). The Hindfoot Moment Arm (HMA) (mm), Saltzman 45 angle, and Foot Ankle Offset (FAO) had hindfoot varization behavior. When we stratified the groups and compared them, we noticed that an increase of 3 cm in heels slightly increased HVA and IMA (p > 0.05). However, heel increases above 6 cm significantly increased HVA and IMA (p > 0.001). Based on Coughlin's classification, a 3 cm heel increase promoted a mild HV and increases above 6 cm caused a moderate HV. Conclusion: Based on data from our study with patients without Hallux Valgus through analysis with WBCT versus high heels, we conclude that increasing heel height can lead to Hallux Valgus and can progressively increase the severity with increasing high heels. High heels above 6 cm can lead to moderate Hallux Valgus. These findings may be an essential step toward a better understanding of the effects of increasing high heels on Hallux Valgus pathology.

The Impact of 3D Foot Alignment on Detection of Distal Tibiofibular Syndesmotic Widening after Injury using Comparative Contralateral Distance Mapping

Category: Ankle; Trauma Introduction/ Purpose: Previous studies identified a link between increased hindfoot valgus and distal tibiofibular syndesmosis (DTFS) widening in patients with flatfoot deformity using foot-ankle offset (FAO). However, it is not known what the impact of 3D foot alignment is on the DTFS in the presence of a known syndesmotic injury, particularly in varus. Weight-bearing Computed Tomography (WBCT) has emerged as a highly precise tool for diagnosing deformities of the foot and ankle. Under weight-bearing, it is possible to precisely detect deviations in DTFS stability. The objective of this cadaveric study was to determine the relationship between hindfoot alignment, measured by FAO, and DTFS widening in specimens with complete DTFS ligamentous injury. We hypothesized that DTFS widening would be significantly greater in specimens with increased hindfoot valgus. Methods: Two WBCT scans of the foot and ankle were obtained for each of 17 matched pairs (34 legs) of through-knee cadaveric specimens in a radiolucent frame under 80lbs of load to simulate double legged stance, a baseline scan with intact syndesmotic ligaments and a second after surgical ligament sectioning. All syndesmotic ligaments were released through a direct lateral approach to the distal fibula. Models of the bones were created from scans using Disior Bonelogic. Distance mapping was used to evaluate DTFS widening over the entire DTFS interface, as well as the anterior/posterior sections, in the first 1cm, 3cm, and 5cm from the joint after injury. Post-injury distance maps were compared to the contralateral baseline normal scan as a control. FAO was measured post-injury and compared to the difference in DFTS widening between the injured leg and its contralateral, healthy control. Linear regression and Spearman’s correlations were used to evaluate relationships. Results: Significant correlations between hindfoot alignment and DTFS widening were identified at every level in the syndesmosis. The Spearman’s rho values for the entire DTFS interface at 1cm, 3cm, and 5cm were 0.393 (p = 0.0316), 0.458 (p = 0.0101), and 0.369 (p = 0.0446), respectively. Anterior Spearman’s rho values at 1cm and 3cm were 0.453 (p = 0.0119) and 0.420 (p = 0.0209), respectively. Inter-observer variability of the FAO measurements showed no statistical difference (p = 0.4248). Extremely varus FAO measurements (FAO < -10%) showed negligible changes in syndesmotic opening. Linear regression also demonstrates a positive trend. The R2 values for the entire interface at 1cm, 3cm, and 5cm were 0.127, 0.213, and 0.158. Anterior R2 values at 1cm and 1cm were 0.133 and 0.1583. Conclusion: In this cadaveric study, we confirmed our hypothesis showing that valgus FAO was correlated with syndesmosis opening from an uninjured to an injured site. These data are in accord with prior findings relating FAO and DTFS opening in flatfeet and additionally demonstrate a stronger positive trend in the presence of known injury with smaller changes in tibiofibular distances after injury for extreme varus alignments. This study provides important context to the clinically relevant comparison of contralateral feet. The trend in our data allows for predictable results for the degree of injury in patients with valgus foot alignment.

Bone Mineral Density Distribution in the Foot Bones and Correlation with Hindfoot Alignment

Category: Basic Sciences/Biologics; Hindfoot Introduction/Purpose: Weight-bearing CT (WBCT) enables accurate 3D hindfoot alignment (HA) measurements such as the Foot Ankle Offset (FAO). However, this uses anatomical landmarks and oversimplifies anatomy. Stress distribution influences bone mineral density (BMD). Hounsfield units (HU) are the tomographic measurement unit for BMD. We aim to analyze the distribution of BMD in the foot bones, relative to the long axis of the second metatarsal (M2), an accepted landmark for foot orientation, and its correlation with HA. Methods: In this retrospective study, 81 feet (27 per HA group : normal, valgus or varus) were included from our database after ethics approval. After 3D segmentation, a HU-weighted map (HUM) of the foot was projected on the ground plane with orientation defined by the longitudinal axis of the 2nd metatarsal. A HU Curve (HUC) was drawn, corresponding to the center of mass of the HUM in the coronal plane. We studied the HU angle (HUA) formed by HU Line (HUL) (linear regression of the HUC) and M2 longitudinal axis. Results: The groups were comparable by age, sex and BMI. A positive correlation between FAO and HU angle was found (r =0.75, p< 0.001). HUA were -0.4° ± 5.5° in varus, 3.5° ± 6.8° in normals, 13.4° ± 5.1° in valgus (F=39.7 and p< 0.001). HUA differences were significant between normals and varus (p < 0.05), and between normals and valgus (p < 0.001). FAO and HUA were significantly correlated in valgus (rho=0.437, p=0.002) and varus (rho=0.540, p=0.004). Conclusion: We found altered distributions in misaligned cases, and BMD was correlated with HA. The HUL could be an interesting new tool to analyse the topography of bone distribution in WBCT.

Relationship between High Heels and Hallux Valgus Deformity. Fact or Fiction? A 3-Dimensional Weight-bearing CT Assessment

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: Evidence in the literature suggests the negative effects of using High Heels (HH), becoming a challenge for clinicians and researchers since they are welcomed by women worldwide, mainly due to the subjective power of attractiveness given to them. Although some people blame HH as one of the causes of Hallux Valgus (HV), until now, there are no studies in the literature that effectively prove a cause-effect relationship between HH and HV. The objectives of this study are: (1) to analyze whether the increase in heel height can lead to HV and (2) to evaluate whether HV can increase in severity with increasing heels. We hypothesized that an increase in heel height could cause and increase the severity of HV deformity radiographically. Methods: Comparative cross-section4-one feet from twenty-one participants (11 males and 10 females, aged 30.8 ± 8.9 years, and with Body Mass Index 25.5 ± 2.0 m kg2) were recruited. HH shoes were designed for this study with three heights for each participant: 3, 6, and 9 cm. The inclusion criteria were: no regular wearing of heels. The exclusion criteria were: Hallux Valgus diagnosis and/or any orthopedic conditions that affect the Foot and Ankle joints. Hallux Valgus Angle (HVA), Intermetatarsal Angle (IMA), First-Metatarsal Phalangeal Angle, 1st-to-5th Intermetatarsal Angle, First Tarsometatarsal Angle (axial), Second tarsometatarsal angle (axial), Hindfoot Moment Arm (HMA) (mm), Saltzman 45 angle and, Foot Ankle Offset (FAO) were measurement using semiautomated software analysis. Multiple comparisons were performed (Bonferroni's for normal distributions and Wilcoxon test for no normal distributions) when there was a main effect on an outcome (p < 0.05). Results: With the increase in HH, we noticed a progressive increase in HVA (p < 0.001), IMA (p < 0.001), First-Metatarsal Phalangeal Angle (p < 0.001), First Tarsometatarsal Angle (axial) (p < 0.001), and the Second tarsometatarsal angle (axial) (p < 0.001). The Hindfoot Moment Arm (HMA) (mm), Saltzman 45 angle, and Foot Ankle Offset (FAO) had hindfoot varus behavior. When we stratified the groups and compared them, we noticed that an increase of 3 cm in heels slightly increased HVA and IMA (p > 0.05). However, heel increases above 6 cm significantly increased HVA and IMA (p > 0.001). Based on Coughlin's classification, a 3 cm heel increase promoted a mild HV, and increases above 6 cm caused a moderate HV. Conclusion: Based on data from our study with patients without Hallux Valgus through analysis with WBCT versus High Heels, we conclude that increasing heel height can radiographically lead to Hallux Valgus deformity and progressively increase the severity. High heels above 6 cm can lead to radiographically moderate Hallux Valgus. These findings may be an essential step toward a better understanding the effects of increasing high heels on Hallux Valgus pathology. More studies are needed to support this data clinically.

Decreased Peritalar Subluxation in Progressive Collapsing Foot Deformity with Ankle Valgus Tilting.

Middle facet subluxation (MFS) has been established as an early indicator of peritalar subluxation. However, when progressive collapsing foot deformity (PCFD) affects the ankle leading to a valgus talar tilt (Class E), structures and anatomic relationships distal to the ankle joint may be affected. Therefore, this study aimed to assess radiographic parameters of peritalar subluxation in patients with PCFD who either did or did not have a valgus ankle. Our hypothesis was that these parameters would differ in Class E patients, upsetting their capability to quantify deformity. We performed a prospective comparative study utilizing weight-bearing computed tomography (WBCT) images of 21 feet with PCFD and with valgus of the ankle and 64 with flexible PCFD without ankle involvement. Parameters including MFS, the medial cuneiform-to-floor distance, the forefoot arch angle, the talonavicular coverage angle, the hindfoot moment arm (HMA), the foot-ankle offset (FAO), and the talar tilt angle (TTA) were measured and compared. Variables that influence the presence of ankle valgus and overall alignment were assessed by multivariable regression models. Patients with PCFD and ankle valgus demonstrated a higher mean HMA (20.79 mm [95% confidence interval (CI), 17.56 to 24.02 mm] versus 8.94 mm [95% CI, 7.09 to 10.79 mm]), FAO (14.89% [95% CI, 12.51% to 17.26%] versus 6.32% [95% CI, 4.96% to 7.68%]) and TTA (95% CI, 17.10° [14.75° to 19.46°] versus 2.30° [95% CI, 0.94° to 3.65°]) and lower mean MFS (21.84% [95% CI, 15.04% to 28.63%] versus 38.45% [95% CI, 34.55% to 42.34%]) compared with the group without ankle valgus (p < 0.0001 for all). The FAO was influenced by MFS in the group without ankle valgus (p <0.0001) but not in the group with ankle valgus (p = 0.9161). FAO values of ≥12.14% were a strong predictor (79.2%) of ankle valgus deformity. Subluxation of the middle facet was not as severe and did not influence the overall alignment in patients with PCFD who had valgus of the ankle (Class E). These findings suggest a distal peritalar reduction in the presence of a proximal deformity, making MFS an imprecise disease parameter in this scenario. An FAO value of ≥12.14% was a strong indicator of ankle deformity in patients with PCFD. Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Peritalar Configuration Following Fusion in Varus Ankle Osteoarthritis: A 3D Weight Bearing CT Analysis

Category: Ankle Arthritis; Ankle Introduction/Purpose: In varus-type osteoarthritis of the ankle (VAOA), it is known that the subtalar joint compensates in valgus/eversion for the malalignment of the tibiotalar joint. However, previous studies were mainly based on X-ray measurements and did not take into account peri-talar changes that extend to the subtalar and Chopart joints. Furthermore, the effect on peritalar compensation when tibio-talar arthrodesis is performed is still unclear. Distance Mapping (DM) is a technology that can produce a 3D point-to-point distance map of joint interactions from cone beam weight bearing CT (WBCT) images. The purpose of this study was to quantify the peri-talar changes that occur when the tibiotalar joint is fused. We hypothesized that talar varus would improve and that the Chopart/Subtalar joint complex would present compensatory varus/inversion. Methods: The subjects were 14 patients (15 feet) who underwent arthrodesis for VAOA at our institution. The average postoperative follow-up period was 6.6 months. Foot alignment (Foot Ankle Offset (FAO)) was measured from WBCT datasets pre and postoperatively. The pre to post op shift vectors of the weighted distance maps center points were measured for the tibiotalar, subtalar, calcaneocuboid and talonavicular joints. Statistical analysis was performed by paired T-test, and the significance level set at p&lt;0.05. Results: FAO improved significantly from preoperative -12.9 +-7.4 % to postoperative -6.4 +-3.9 %. The DM vectors were 4.9 +-2.8 mm (lateral direction) for the tibiotalar joint, 0.86 +-0.93 mm (posterior) for the subtalar joint and 4.9 +-2.6 mm (plantar- medial) for the talonavicular joint. Conclusion: The main finding in this study was that foot alignment was improved following tibiotalar arthrodesis with peritalar compensation, more so in the talonavicular than in the subtalar joint and not in the calcaneocuboid joint. The limitations of this study include the small number of cases and the short postoperative follow-up. Our results suggest that the flexibility of the talonavicular joint may be necessary when arthrodesis is performed on VAOA to contribute to the alignment correction. If it is not the case, TAR could be considered an alternative.

Distribution of Bone Mineral Density in the Ankle Joint: Correlation with Hindfoot Alignment

Category: Ankle; Basic Sciences/Biologics; Hindfoot Introduction/Purpose: Abnormal Hindfoot Alignment (HA) has been correlated with increased complication rates in ankle fusion or replacement. Altered Bone Mineral Density (BMD) due to abnormal stress distribution could be predisposing factor for those unwanted outcomes. The objective of this study was to assess spatial distribution of BMD around the ankle joint in patients with normal or abnormal HA using cone beam Weight Bearing CT. Methods: Retrospective comparative study including 81 ankles allocated into 3 groups based on the Foot Ankle Offset (FAO): 27 normal (0%5%). groups were comparable by age (p=0.967), Body Mass Idex (p=0.669), sex (p=0.820) and side (p=0.708). Semi- automatic segmentation (BoneLogic, Disior) was applied to identify bones. Tibia and talus were digitally compartmented in medial (M) and lateral (L) volumes relative to the median sagittal plane. Mean Hounsfield Unit (HU) value per compartment was used to assess BMD and to calculate the Medial over Lateral HU ratio (M/L-HU). Comparisons among the three groups were performed using one-way ANOVA, Kruskal-Wallis and Chi2 tests. Results: Mean +- standard deviation HU values in the compartments in normal cases were 495.2+-110 (medial tibia), 495.6+- 108.1 (lateral tibia), 368.9+-80.3 (medial talus), 448.2+-90.6 (lateral talus) and 686.7+-120.4 (fibula). Upon comparison of the mean BMD value for each compartment in the three groups, the difference did not achieve statistical significance. Conversely, the tibia HU-M/L ratio (0.88+-0.14 in valgus cases, 0.99 +- 0.08 in normally-aligned cases and 1.04+-0.08 in varus cases) and the talar HU- M/L ratio (0.68+-0.18 in valgus cases, 0.82+-0.08 in normally-aligned cases and 0.96+-0.20 in varus cases) were significantly different in the three groups (p&lt;0.001). Conclusion: We found that the BMD in distal tibia, fibula and the talus varies with hindfoot alignment. The increased HU medio- lateral ratio in varus cases was consistent with a greater medial bone density in the tibia and talus, while the decreased ratio found in valgus cases suggested a more lateral concentration in both bones. This data supports the role of WBCT in analyzing BMD distribution. This method could be clinically useful in ankle OA to evaluate bone quality for such considerations as surgical indications or implant positioning.

Hindfoot alignment assessment by the foot-ankle offset: a diagnostic study.

Foot-ankle offset (FAO) is a three-dimensional (3D) biometric measurement of hindfoot alignment (HA) measured on images from weight-bearing computed tomography (WBCT). Our aim was to investigate its distribution in a large cohort of patients, hypothesizing that threshold FAO values in valgus or varus could be identified as markers for increased risk of associated pathologies. Prospective, monocentric, level II study including 125 subjects (250 feet) undergoing bilateral WBCT [58.4% female; mean age, 54years (18-84)]. Patients were clinically assessed and pathologies were classified according to anatomic location (valgus- or varus associated). HA was measured using FAO on 3D datasets and tibio-calcaneal angles (TCA) on two-dimensional Saltzman-El-Khoury views. Threshold FAO values and area under the receiver operating characteristics curve (AUC) were calculated for predicting increased risk of medial or lateral pathologies. Mean FAO was 1.65% ± 4.72 and mean TCA was 4.15° ± 7.67. Clinically, 167 feet were normal, 33 varus and 50 valgus with FAO values of 1.71% ± 3.16, -4.96% ± 5.30 and 5.79% ± 3.77, respectively. Mean FAO was 0.99% ± 3.26 for non-pathological feet, -2.53% ± 5.05 for lateral and 6.81% ± 2.70 for medial pathologies. Threshold FAO values of -1.64% (51.4% sensitivity, 85.1% specificity, AUC = 0.72) and 2.71% (95% sensitivity, 82.8% specificity, AUC = 0.93) best predicted the risk of lateral and medial pathology, respectively. Patients with FAO between -1.64% and 2.71% had the least risk of degenerative foot and ankle pathology. This interval could be considered a target for patients undergoing realignment procedures. A "safe zone" for Foot Ankle Offset was described between -1.64% and 2.71%, for which the risk of foot and ankle pathologies is lower. II-Diagnostic study.

Diagnostic accuracy of measurements in progressive collapsing foot deformity using weight bearing computed tomography: A matched case-control study

BackgroundWe aimed to investigate the diagnostic accuracy of known two-dimensional (2D) and three-dimensional (3D) measurements for Progressive Collapsing Foot Deformity (PCFD) in weight-bearing computed tomography (WBCT). We hypothesized that 3D biometrics would have better specificity and sensitivity for PCFD diagnosis than 2D measurements. MethodsThis was a retrospective case-control study, including 28 PCFD feet and 28 controls matched for age, sex and Body Mass Index. Two-dimensional measurements included: axial and sagittal talus-first metatarsal angles (TM1A and TM1S), talonavicular coverage angle (TNCA), forefoot arch angle (FFAA), middle facet incongruence angle (MF°) and uncoverage percentage (MF%). The 3D Foot Ankle Offset (FAO) was obtained using dedicated semi-automatic software. Intra and interobserver reliabilities were assessed. Receiver Operating Characteristic (ROC) curves were calculated to determine diagnostic accuracy (Area Under the Curve (AUC)), sensitivity and specificity. ResultsIn PCFD, mean MF% and MF° were respectively 47.2% ± 15.4 and 13.3° ± 5.3 compared with 13.5% ± 8.7 and 5.6° ± 2.9 in controls (p < 0.001). The FAO was 8.1% ± 3.8 in PCFD and 1.4% ± 1.7 in controls (p < 0.001). AUCs were 0.99 (95%CI, 0.98–1) for MF%, 0.96 (95%CI, 0.9–1) for FAO, 0.90 (95%CI, 0.81–0.98) for MF°. For MF%, a threshold value equal or greater than 28.7% had a sensitivity of 100% and specificity of 92.8%. Conversely, a FAO value equal or greater than 4.6% had a specificity of 100% and a sensitivity of 89.2%. All other 2D measurements were significantly different in PCFD and controls (p < 0.001). ConclusionsMF% and FAO were both accurate measurements for PCFD. MF% demonstrated slightly better specificity. FAO better sensitivity. A combination of threshold values of 28.7% for MF% and 4.6% for FAO yielded 100% sensitivity and specificity.

Distribution of Bone Mineral Density in the Ankle Joint: Correlation with Hindfoot Alignment

Category:Ankle; Basic Sciences/Biologics; HindfootIntroduction/Purpose:Abnormal Hindfoot Alignment (HA) has been correlated with increased failure rates in ankle fusion or replacement for osteoarthritis (OA). An altered stress distribution in the surrounding bone and abnormal Bone Mineral Density (BMD) around the native ankle may be predisposing factors for those unwanted outcomes. Cone Beam Weight Bearing CT (WBCT) has recently been used to investigate BMD and to correlate the localization of periprosthetic cysts and alignment in ankle arthroplasty. The objective of this study was to assess the spatial distribution of BMD around the ankle joint in patients with normal or abnormal HA. We hypothesized that BMD would be evenly distributed in normally-aligned ankles whilst increased medially in varus and laterally in valgus configurations.Methods:In this retrospective comparative Level III study, 60 ankles (41 adults),without any trauma or surgery affecting HA, with WBCT datasets (PedCat, Curvebeam LLC, PA-USA) were allocated to 3 groups (comparable by age, p=0.79; BMI, p=0.24; and side, p=0.93), based on the Foot Ankle Offset (FAO) values: 20 normal (0%-2), 20 varus (FAO< 0%; 35% female, age 48.8+-13 years, BMI 26.2+-2.9 kg.m-2), and 20 valgus (FAO>5%; 40% female, age 58.9+-14.6 years, BMI 28.6+-4.2 kg.m-2). Semi-Automatic Segmentation (BoneLogic, Disior Oy, Helsinki-Finland) was applied to identify bones of interest. The tibia and talus were digitally compartmented in medial (M) and lateral (L) volumes relative to the median sagittal plane. Mean Hounsfield Unit (HU) value per compartment was used to assess BMD. The primary outcome measure was the Medial over Lateral HU ratio (M/L-HU). Comparisons were performed using one-way ANOVA, Kruskal-Wallis and Chi2 tests.Results:All values of BMD were normally distributed but M/L-HU ratios were not. Mean +- standard deviation HU values in the compartments in normal cases were 523+-103 (medial tibia), 519+-115 (lateral tibia) 421+-81 (medial talus), 470+-92 (lateral talus) and 725+-109 (fibula). The mean BMD was significantly lower in all compartments in valgus cases compared to normal (all p<0.05). It was decreased in valgus vs varus in the talus (p<0.04), specifically in the medial compartment (p<0.01). The tibia M/L- HU ratio was decreased in valgus vs normal (0.87+-0.16 vs 1.01+-0.07; p=0.001) and vs varus (1.04+-0.09; p<0.001). The talus M/L-HU ratio was increased in varus cases vs normal (1+-0.22 vs 0.83+-0.09; p<0.01) and valgus (0.07+-0.19; p<0.001).Conclusion:We found that BMD in distal tibia, fibula and the talus varies with hindfoot alignment. In valgus configuration, all bone compartments were less dense compared to normal and varus. The medio-lateral ratio increased in the tibia and in the talus in varus cases, suggesting medial concentration of bone, and decreased in valgus cases, suggesting a more lateral concentration. This data supports the role of WBCT in analyzing BMD distribution. This method could be clinically useful in ankle OA to evaluate bone quality for such considerations as surgical indications or implant positioning.

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; OtherIntroduction/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.

Comparison of Change in Hindfoot Alignment with Coleman Block Testing Using Clinical Exam, X-ray, and Weight-bearing CT

Category:Hindfoot; Midfoot/ForefootIntroduction/Purpose:The Coleman block test has traditionally been used to distinguish between forefoot- and hindfoot-driven deformity as well as flexibility of cavovarus deformity. However, there has been no validation of the Coleman block test using x- rays or weightbearing CT scan. The purpose of this study was to compare hindfoot alignment in cavovarus feet with and without the Coleman block using clinical exam, x-ray, and weightbearing CT scan.Methods:We retrospectively evaluated 7 feet in 7 patients. The average age was 57, there were 5 males, and the average BMI was 34.7. Average calcaneal pitch was 30 degrees. Clinical measurements were made using standing talocalcaneal angle (STCA) and resting calcaneal stance position (RCSP) with and without a Coleman block using a camera positioned at 0 degrees to the heels.Hindfoot angle (HFA) was measured off of Saltzman-view x-rays and off of weightbearing CT coronal reconstructions with and without the Coleman block. Finally, foot ankle offset (FAO) was measured with and without the Coleman block from weightbearing CT using Cubeview TALAS software. Differences before and after Coleman block were measured using paired t- testing and correlations between different hindfoot alignment measurements were made using Pearson correlation coefficients.Results::The average change in STCA before and after Coleman block placement was 2.9 degrees (7.14 varus without block, 4.28 degrees of varus with block; p<0.05). The average change in hindfoot angle before and after Coleman block using X-ray was 7.4 degrees (14 degrees varus without block, 6 degrees varus with block; p=0.08), and using CT was 3.9 degrees (14 degrees varus without block, 10 degrees varus with block; p= 0.06). There was no significant change in FAO before and after Coleman block testing. STCA was best-correlated with FAO (R= 0.7, p<0.05). CT HFA was also well-correlated with FAO (R=0.68, p<0.05).There was lesser correlation between X-ray HFA and FAO (R=0.608, p<0.05) and X-ray HFA and SCTA (p=0.63, p<0.05).Conclusion::Although Coleman block testing resulted in a decrease in varus, no patient had full re-constitution of physiologic hindfoot valgus with any measurement method. This suggests that either the forefoot was a partial (but never a complete) ‘driver’ of hindfoot varus deformity, or that there was some degree of rigidity in all patients tested. FAO did not demonstrate a statistically significant difference with and without Coleman block on this small sample size. FAO was best correlated with both clinical exam and CT HFA measurements. Clinical exam and weightbearing CT may be more reliable than radiographs in measuring cavovarus hindfoot alignment.Figure 1.

3D Imaging for Hindfoot Alignment: A Comparative Study between MRI and Weight Bearing CT

Category:Hindfoot; OtherIntroduction/Purpose:Hindfoot malalignment is a common finding in multiple foot and ankle pathologies. In clinical practice, it is usually quantified through traditional weight bearing radiographs or, more recently, through cone beam weight bearing CT (CB- WBCT), which overcomes issues related to two-dimensional imaging. Interestingly, a few studies have suggested that hindfoot alignment can also be accurately assessed using non-weight bearing magnetic resonance imaging (MRI). The purpose of this study was to compare measurements of hindfoot alignment on non-weight bearing ankle MRI and CB-WBCT and to establish if there was any correlation.Methods:In this Level III retrospective comparative study, a database review identified 51 feet in 47 patients (27 males, 20 females; mean age of 45 (range 13-79)) which had both CB-WBCT and MRI scans on the same day as part of standard care at our specialist tertiary referral Foot and Ankle Unit. Hindfoot alignment was assessed by independent Consultant Musculoskeletal specialists. The foot ankle offset (FAO), calcaneal offset (CO) and hindfoot alignment angle (HA) were assessed on CB-WBCT using dedicated software. The tibiocalcaneal angle (TCA) and calcaneofibular ligament angle (CFLA) were assessed on non-weight bearing MRI. Pearson correlation was used to evaluate the correlation between these measurements.Results:We found a statistically significant positive correlation between TCA on non-weight bearing MRI and each measurement on CB-WBCT (Pearson correlation for TCA and FAO: 0.42, p=0.003; for TCA and CO: 0.46, p=0.001; and for TCA and HA: 0.40, p=0.005).We also demonstrated a moderate-to-low negative but significant correlation between CFLA and CO (Pearson correlation: -0.35; p=0.03). Conversely, the negative correlation between CFL and FAO (Pearson correlation: -0.29; p=0.07) and CFL with HA (Pearson correlation: -0.26; p=0.11) did not reach statistical significance.Conclusion:Weight bearing three-dimensional imaging has shown high degrees of accuracy and reproducibility for hindfoot alignment. The significant correlation between TCA on non-weight bearing MRI and hindfoot alignment measurements on CB- WBCT suggests that TCA should be reported during routine ankle MRI in order to put into context some of the soft-tissue findings. The CFLA shows a less significant negative correlation.

3D imaging for hindfoot alignment assessment: a comparative study between non-weight-bearing MRI and weight-bearing CT.

The authors compared measurements of hindfoot alignment on MR imaging with weight-bearing CT (WB-CT) to establish the degree of correlation. Forty-seven feet in 44 patients had weight-bearing CT and MRI studies performed on the same day. Hindfoot alignment on MRI was assessed by two radiologists who calculated tibiocalcaneal angle (TCA) and calcaneofibular ligament angle (CFLA). On WB-CT, foot ankle offset (FAO), calcaneal offset (CO) and hindfoot angle (HA) were assessed by a senior Foot and Ankle Surgeon using dedicated software. Pearson correlation coefficient was used to evaluate the correlation between these measurements. The study group comprised 27 males and 17 females with a mean age of 45years (range 13-79years). A statistically significant positive correlation was identified between TCA on MRI and all measurements of hindfoot alignment on WB-CT (p = 0.001-0.005). The CFLA on MRI only had significant correlation with CO on WB-CT (p = 0.03). A significant negative correlation was observed between both MRI parameters (p < 0.001). A highly significant correlation between tibiocalcaneal angle on non-weight-bearing ankle MR imaging and hindfoot alignment measurements on weight-bearing CT was identified.

2019 IFFAS Award for Excellence Winner: Peri-Prosthetic Cysts and Alignment in Total Ankle Replacement: A 3-D, Weight Bearing Topographical Study

Category:Ankle, Ankle ArthritisIntroduction/Purpose:Peri-prosthetic cysts (PPC) in Total Ankle Replacement (TAR) are a common failure cause but the mechanisms of their development remains unclear. One possible explanation could be hindfoot malalignment and subsequent unequal distribution of load inside the joint. However, how residual malalignment influences the evolution of PPC remains unclear. Computed tomography (CT) has demonstrated superiority on conventional radiography in the follow up of PPC. Weight Bearing CT (WBCT), by combining 3D imaging and weight bearing measurements seems a valid tool to investigate this further. The objective for this work was to study the effects of residual hindfoot deformity on the distribution of PPC in the coronal plane. We hypothesized that cysts would be found predominantly medially in varus configuration, and laterally in valgus configuration.Methods:Retrospective comparative study, ethics committee approved. Forty-eight cases of TAR were included, with relevant demographics. Inclusion criteria were cases of primary TAR with available WBCT imaging of their ankle as part of normal follow up. Exclusion criteria were subsequent implant revision or cyst grafting. In each case, the localization and size of PPC’s were documented and their volume calculated by approximation of the closest ellipsoid. Hindfoot alignment was evaluated by the percentage Foot Ankle Offset (FAO) (foot-length normalized 3D ratio between the midline of the foot and the center of the ankle) using a WBCT dedicated semi-automatic software. The mean FAO value with 95%CI for the population was calculated. The difference in medial and lateral cyst volume defined by their position relative to the median axis in the coronal plane was compared in varus and valgus cases by a Mann-Whitney non-parametric test for unpaired samples.Results:Demographic distributions of the series were 32% female, mean age 65 (45-85) years. Mean FAO value was 0.12% (95%CI -1.09 to 1.33). Mean follow up was 43 months (6 to 239). The mean total cyst volume per case was 1190,7 mm3. In varus cases (defined by FAO<-1.09%), the volume of medial cysts was greater than laterally by a mean 197 mm3, whereas in valgus cases (defined by FAO>1.33%), the volume of lateral cysts was greater than medially by a mean 332 mm3. The difference was statistically significant (p<0.05). There was a weak, significant positive correlation (r=0.25, p<0,001) between FAO and total cyst volume and a moderate, significant correlation (r=0,56, p<0,001) between time to follow up and total cyst volume.Conclusion:Our hypothesis was confirmed. Periprosthetic cysts volume in this series of primary TAR was found to be relatively greater medially in postoperative varus configurations and vice-versa laterally in valgus. This confirms a possible correlation between the direction of residual hindfoot malalignment and the coronal localization of PPC in TAR, although this is certainly not the only pathophysiologic factor involved in PPC onset. Weightbearing CT may be helpful in Total Ankle Replacement follow up, in order to early detect PPC development and possibly to identify situations at risk of a more rapid evolution.

Intraobserver and interobserver reliability of cone beam weightbearing semi-automatic three-dimensional measurements in symptomatic pes cavovarus

IntroductionPes cavovarus is a three-dimensional (3D) foot deformity. New 3D semi-automatic measurements utilising weightbearing computerised topography (WBCT) images have recently been proposed to assess hindfoot alignment, but reliability in pes cavovarus has never been investigated. The aim of this study was to assess intraobserver and interobserver reliability of the foot ankle offset (FAO), calcaneal offset (CO) and hindfoot alignment angle (HAA) in pes cavovarus. MethodsAnonymised WBCT datasets from 51 feet (17 Charcot-Marie-Tooth related cavovarus, 17 idiopathic cavovarus and 17 controls) were retrospectively reviewed. Three observers (two senior foot and ankle fellows and one orthopaedic resident) independently measured FAO, CO and HAA using dedicated software, with measurements repeated two weeks apart. Subgroup analysis was performed to assess whether aetiology or severity of varus deformity and level of seniority affected reliability. ResultsMean values for intra and interobserver reliability for FAO (r=0.98; ICC: 0.99), CO (r=0.97; ICC: 0.98) and HAA measurements (r=0.97; ICC: 0.98) were excellent. Subgroup analyses showed that FAO, CO and HAA's intra (r/ρ range, 0.77–0.95) and interobserver (ICC range, 0.88–0.98) reliability remained excellent in patients with Charcot-Marie-Tooth related cavovarus, idiopathic pes cavovarus and normal feet, regardless of the severity of deformity. No difference was found in FAO, CO and HAA mean values from three observers (p>0.05 in all cases). DiscussionThis study demonstrates that 3D semi-automatic measurements of WBCT images have excellent intra and interobserver reliability in the assessment of hindfoot alignment in pes cavovarus. Aetiology and severity of deformity, and level of seniority do not affect reliability of these measurements. Level of evidenceLevel III, retrospective comparative study.

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.

How Are Coronal Alignments of the Knee and Hindfoot Correlated?

Category: Hindfoot Introduction/Purpose: Hindfoot and knee coronal alignments have shown to be related in previous literature suggesting that there might be some degree of compensation between the two. However, previous studies have focused on the effects of knee surgery on hindfoot alignment, not on the preoperative relationship. Recent 3D weight bearing imaging technology may help to investigate this. The objective of this study was to analyse the preoperative relationships between knee and hindfoot coronal alignments using bilateral weight bearing CT (WBCT) and biplanar low dose radiography (BLDR). We hypothesized that hindfoot valgus and varus respectively compensates knee varus and valgus. Methods: Relevant ethical approval was obtained for this retrospective comparative level 3 study including 124 limbs in 62 patients (32 female, 30 male), mean age 56 (23-84). Mean BMI was 27 (20-38). Cases included had been referred continuously according to diagnostic protocols in our institution, for a combined WBCT and BLDR investigation. Age, gender and BMI were recorded. Cases with a history of trauma or surgery, which may have caused a change in lower limb alignment, were excluded. Hindfoot alignment was measured using a semi automatic software (TALAS, Curvebeam, Warrington PA, USA) and given as Foot Ankle Offset (FAO). Knee alignment was measured using the EOS platform (EOS Imaging, Paris, France) and given as HKA. Distribution and demographics of hindfoot alignment in the varus and valgus knee groups were studied. Correlations were investigated using linear regression and Bland and Altman plots. Results: Incidence of Varus hindfeet was 15.8% in the Valgus knee group and 25.5% in the Varus knee group but the difference was not significant (p=0.82). Bland and Altman plots did not yield any additional result. No linear correlation was found between hindfoot and knee coronal alignments in the study population. Conclusion: Our results do not confirm prior findings regarding compensatory valgus in varus knees, and do not confirm the hypothesis according to which linear compensatory mechanisms may relate knee and hindfoot alignments. In practice, these results suggest that in cases where knee and hindfoot misalignments are associated, the causes for each should be analyzed independently before any assumption is made as to hypothetical interactions. Furthermore, subsequent studies are warranted to investigate whether other kinds of non-linear correlations way be found in selected populations.

Reliability of Hindfoot Alignment Using Weightbearing CT Semi Automatic Software

Category: Ankle, Hindfoot, Imaging Introduction/Purpose: Hindfoot Alignment (HA) on 2D radiographs presents anatomical and operator-related bias. In this study, weightbearing CT (WBCT) was used to measure HA using a semi-automatic software which gives HA as a value of Foot Ankle Offset (FAO) after selecting four landmarks (weight bearing points of first and fifth Metatarsals, Calcaneus and center of the ankle joint). We assessed the intra and interobserver reproducibility and the distribution of FAO values in a series of datasets from clinically normal, varus and valgus cases. We hypothesized that reproducibility would be excellent. Furthermore, FAO in normals should have a Gaussian distribution and be significantly different to the varus and valgus groups. Methods: In this level 3, retrospective comparative study, WBCT (PedCAT ®, CurveBeam LLC, Warrington, PA, USA) datasets were obtained from an existing database. The 135 feet were assessed by a senior foot and ankle surgeon as normal, varus or valgus (57, 38 and 40 respectively). Two surgeon investigators (one senior and one trainee) independently analyzed each case using a semi-automatic HA measurement tool (TALAS ™, CurveBeam LLC, Warrington, PA, USA). A third, independent investigator conducted the statistical analysis using Stata® Software. Results: The overall intraoberver and interobserver reliability were 0.99 ± 0.002 and 0.97 ± 0.02 respectively. In normal cases, mean value for FAO was 2.38% ± 2.96, whereas in varus and valgus cases mean was -11.67% ± 6.90 and 11.47% ± 5.79, respectively (p&lt;0.001). The normal population had a Gaussian distribution with a Kolmogorov-Smirnov test &gt; 0.8 Conclusion: This study reports excellent reliability and discriminative power of a semi-automatic 3D measurement tool for Hindfoot Alignment in WBCT.