Foot And Ankle Offset Research Articles

Assessment of Posterior and Middle Facet Subluxation of the Subtalar Joint in Progressive Flatfoot Deformity.

Adult acquired flatfoot deformity (AAFD) is a complex 3-dimensional pathology characterized by peritalar subluxation (PTS) of the hindfoot. For many years, PTS was measured at the posterior facet of the subtalar joint. More recently, subluxation of the middle facet has been proposed as a more accurate and reliable marker of symptomatic AAFD, enabling earlier detection. The objective of this study was to compare the amount of subluxation between the medial and posterior facets in patients with AAFD. In this institutional review board-approved retrospective comparative study, a total of 76 patients with AAFD (87 feet) who underwent standing weightbearing computed tomography (WBCT) as a standard baseline assessment of their foot deformity were analyzed. Two blinded fellowship-trained orthopedic foot and ankle surgeons with >10 years of experience measured subtalar joint subluxation (as a percentage of joint uncoverage) at the both posterior and middle facets. One of the readers also measured the foot and ankle offset (FAO). PTS measurements were performed at the sagittal midpoint of the articular facets using coronal plane WBCT images. Intra- and interobserver agreement was measured for PTS measurements using the intraclass correlation coefficient (ICC). The intermethod agreement between the posterior and middle facet subluxation was assessed using Spearman's correlation and bivariate analysis. Paired comparison of the measurements was performed using the Wilcoxon test. A multivariate analysis and a partition prediction model were used to assess influence of PTS measurements on FAO values. P values of <.05 were considered significant. ICCs for intra- and interobserver reliabilities were 0.97 and 0.93, respectively, for posterior and 0.99 and 0.97, respectively, for middle facet subluxation. The intermethod Spearman's correlation between subluxation of the posterior and middle facets was measured at 0.61. In a bivariate analysis, both measurements were found to be significantly and linearly correlated (P < .0001; R2 = 0.42). Measurements of middle facet subluxation were found to be significantly higher than those for posterior facet subluxation, with a median difference (using the Hodges-Lehman factor) of 17.7% (P < .001; 95% CI, 10.9%-23.6%). We also found that for every 1% increase in posterior facet subluxation there was a corresponding 1.6-fold increase in middle facet subluxation. Only middle facet subluxation measurements were found to significantly influence FAO calculations (P = .003). The partition prediction model demonstrated that a middle facet subluxation value of 43.8% represented an important threshold for increased FAO. This study is the first to compare WBCT measurements of subtalar joint subluxation at the posterior and middle facets as markers of PTS in patients with AAFD. We found a positive linear correlation between the measurements, with subluxation of the middle facet being significantly more pronounced than that of the posterior facet by an average of almost 18%. This suggests that middle facet subluxation may provide an earlier and more pronounced marker of progressive PTS in patients with AAFD. Level III, retrospective comparative cohort study.

Intraobserver and Interobserver Reliability of Cone Beam Weightbearing Semiautomatic Three- Dimensional Measurements in Symptomatic Pes Cavovarus

Category:Basic Sciences/Biologics, HindfootIntroduction/Purpose:Pes cavovarus is a three-dimensional complex foot deformity variably involving a varus hindfoot, high longitudinal arch and forefoot adduction. Two-dimensional radiographs may be flawed by rotational bias and operator-related bias, while standard computed tomography (CT) cannot be perfomed in loading conditions. Three-dimensional (3D) cone beam weightbearing computed tomography (WBCT) may overcome these drawbacks, obtaining physiological weightbearing images with low-dose radiation. New 3D semiautomatic tools have been proposed to measure hindfoot alignment, but reliability in pes cavovarus has never been tested. The aim of this study was to assess intra and interobserver reliability of 3D biometrics on WBCT imaging in pes cavovarus. Our hypothesis was that foot and ankle offset, calcaneal offset and hindfoot angle were reliable measures regardless of type and severity of deformity.Methods:Cone beam WBCT anonymised datasets from 34 pes cavovarus (PC) (17 neurological, 17 non-neurological) and 17 normal feet were retrospectively reviewed. All WBCTs were performed during routine investigation. Inclusion criteria consisted of no previous ipsilateral foot/ankle surgery and ability to heel weightbear. Three foot and ankle surgeons (blinded to patient diagnosis) independently measured the following variables on 51 feet: foot and ankle offset (FAO), calcaneal offset (CO) and hindfoot angle (HA) using dedicated software. Each observer repeated all measurements two-weeks apart. The Shapiro–Wilk test was used to assess normality of data distribution. The Pearson or Spearman correlation test and Intraclass Correlation Coefficients (ICCs) and were used to assess intra and interobserver reliability, respectively. Subgroup analysis was performed to assess whether clinical diagnosis (neurological PC, non-neurological PC, normal controls) or severity of varus deformity (4 groups based on FAOs 25th, 50th and 75th centiles) could affect reliability of FAO measurements.Results:Intra and interobserver reliability for FAO (r= 0.98; ICC: 0.98), CO (r=0.94; ICC 0.89) and HA measurements (r=0.93; ICC:0.89) were excellent. Subgroup analysis showed that FAOs intra and interobserver reliability remained excellent in neurological PC (r= 0.96; ICC: 0.97), non-neurological PC (r=0.95; ICC: 0.96) and normal feet (r=-0.97; ICC: 0.94). Also, intraobserver (r=0.95, r=0.76, r=0.82 and r=0.92 for FAO >0%, from -7% to 0%, from -13% to -7%, and <-13%, respectively) and interobserver reliability for FAO measurements (ICC: 0.78, ICC: 0.76, ICC: 0.85 and ICC: 0.92) scored excellent regardless of the deformity.Conclusion:This study confirms that three-dimensional semiautomatic tools used on weightbearing CT datasets have excellent intra and interobserver reliability in the assessment of hindfoot alignment in pes cavovarus. The nature and severity of the deformity does not affect the reliability of the measurements. This infers that these 3D biometric tools on WBCT images can be reliably used in severe neurological cavovarus feet to evaluate and monitor cavovarus deformity and assess response to intervention.

Pes Cavovarus in Charcot-Marie-Tooth Compared to the Idiopathic Cavovarus Foot: A Preliminary Weightbearing CT Analysis

Category:Ankle, HindfootIntroduction/Purpose:Charcot-Marie-Tooth disease (CMT) is an inherited sensory motor peripheral neuropathy progressively leading to cavovarus deformity of the foot. Conversely, the idiopathic cavovarus foot represents a non-neurological condition, with a spectrum from subtle to markedly deformed. Our aim was to investigate morphological differences between CMT pes cavovarus (CMT-PC), idiopathic pes cavovarus (I-PC) and normally aligned feet using three-dimensional (3D) cone beam weightbearing computed tomography (WBCT) measurements. We hypothesised that the hindfoot alignment was significantly different between the three groups.Methods:Retrospectively, we compared 17 CMT-PC (15 patients) with 24 I-PC and 24 clinically normally aligned feet. Patients were comparable by age, sex and body mass index. All WBCTs were performed during routine investigation. Exclusion criteria included previous ipsilateral foot/ankle surgery and inability to heel weightbear. Three measurements were made by one orthopaedic surgeon: foot and ankle offset (FAO), a three-dimensional calculation describing the relationship between the centre of gravity of the tripod of the foot and the centre of the ankle; calcaneal offset (CO), measuring the distance between a theoretically neutral position of the calcaneus and its true position; and hindfoot angle (HA), an estimative of coronal angular hindfoot alignment. These measurements were all repeated twice for intraobsever reliability calculation (Pearson correlation). The mean values were compared using one-way ANOVA (values normally distributed after Shapiro-Wilk test) with the Bonferroni test.Results:Intraobserver reliability was excellent for all the three measurements (r=0.98 for FAO, CO and HA). Mean FAO value ± standard deviation in CMT-PC group (-14.1% ± 7.2) and in I-PC group (-9.6% ± 5.2) both differed from normal feet (1.6% ± 3.3) (p< .001). Of note, a difference was found between mean FAO in CMT-PC and I-PC feet (p .025). Furthermore, the mean CO (- 23.6 mm ± 11.3 in CMT-PC, -16.7 mm ± 8.2 in I-PC and 3.1 mm ± 6 in normal feet) and the mean HA (-44.9° ± 21.7 in CMT-PC; - 30.3° ± 16.9 in I-PC; 5.1° ± 10.1 in normal feet) significantly differed in three groups (p< .001) and specifically between CMT-PC and I-PC feet (p .032 and p .02 for CO and HA, respectively).Conclusion:This study confirms our hypothesis. Hindfoot alignment in patients diagnosed with CMT cavovarus and idiopathic cavovarus feet significantly differed between them and from normal controls, with a more accentuated varus deformity in CMT patients. This probably reflects the presence of a known neuromuscular imbalance driving the deformity over time in CMT feet. We therefore propose using a reliable method of quantifying heel varus and seeking a potential neurological diagnosis in the more severe.

The Use of Three-Dimensional (3D) Biometric Measurements to Predict Additional Alignment Procedures in Total Ankle Replacement

Category:Ankle ArthritisIntroduction/Purpose:Preoperative evaluation of ankle and hindfoot deformities in patients undergoing total ankle replacement (TAR) is challenging. Characterizing deformity based on conventional radiographs is limited by its two-dimensional (2D) nature and is influenced by anatomical and operator-related bias. The final decision to perform associated corrective alignment procedures, that include calcaneal osteotomies, midfoot and forefoot osteotomies/fusions, and soft tissue balancing, is made intraoperatively following insertion of the TAR components. The use of weightbearing cone beam CT (WB CBCT) images and three-dimensional (3D) biometric tools, encompassing the hindfoot alignment, foot tripod, and center of the ankle joint, may be an effective surgical planning instrument. In this retrospective study, we assessed the ability of these tools to predict additional procedures performed at the time of TAR.Methods:In this retrospective study, we enrolled 22 patients that underwent TAR and had preoperative WB CBCT studies. We excluded seven patients with isolated ankle CBCT images and three with metallic hindfoot implants. Patients demographics, type and number of additional alignment procedures were noted. The WB CBCT data sets were screened using built-in semi-automatic measurement software. 3D coordinates (x/y/z) were identified for the specific anatomical landmarks required to calculate Foot and Ankle Offset (FAO), which included the WB points of the first, fifth metatarsal heads and calcaneus, as well as the highest point of the talar dome. FAO is a representation of the torque (offset) between the hindfoot/forefoot midline and the center of the talus, and is given as a percentage of foot-length. Patients were then divided into varus and valgus hindfoot alignment groups accordingly to their measured FAO, using available literature FAO values for normally aligned feet (2.3%, ±2.9%).Results:We included 12 patients (6F/6 M), mean age 65 (range, 47-80). The mean preoperative FAO was 5.73 (CI -0.99 - 12.55). Seven patients had valgus and 5 patients had varus alignment of the hindfoot. The mean number of additional procedures was 2 (range, 0 to 5), and included: calcaneal osteotomy (58%), Achilles lengthening/Gastroc recession (58%), Cotton osteotomy (25%), First TMT fusion (17%), talonavicular fusion, naviculo-cuneiform fusion, and Brostrom procedure (8%). The FAO positively correlated with occurrence of additional alignment procedures (p=0.003). Patients with valgus hindfoot alignment had significantly increased number of additional procedures (2.7; CI 1.6 – 3.8) when compared to varus alignment patients (1.2; CI -0.1 – 2.5) (p=0.03), and were found to have a 1.8 fold greater chance to have a calcaneal osteotomy.Conclusion:This is the first study to evaluate the role of 3D biometric tools and semi-automatic WB CBCT measurements in the preoperative assessment of foot alignment in patients undergoing TAR. We found that increased Foot and Ankle Offset (FAO) significantly predicts the occurrence and number of additional alignment procedures, including calcaneal osteotomies. We believe that the use of biometrics and semi-automatic measurements, which account for the relationship between the center of the ankle and the tripod of the foot, can enhance the preoperative assessment, surgical planning and outcomes of TAR patients. Prospective and postoperative studies demonstrating correction are needed.

Foot Alignment in Symptomatic National Basketball Association Players Using Weightbearing Cone Beam Computed Tomography.

Background:Weightbearing cone beam computed tomography (WB CBCT) allows detailed 3-dimensional imaging of the foot and ankle in a weightbearing state and provides improved accuracy and reliability of foot alignment measures, especially when compared with conventional radiographic views.Purpose:To describe the foot alignment in National Basketball Association (NBA) players with different symptomatic foot and ankle injuries using WB CBCT and to determine if any predominant morphotype would be identified.Study Design:Cross-sectional study; Level of evidence, 3.Methods:A total of 45 active NBA players (mean age, 24.4 years [range, 20-34 years]; N = 54 feet [29 right, 25 left]) were assessed using WB CBCT. Measurements included the following: (1) foot and ankle offset (FAO), (2) calcaneal offset (CO), (3) hindfoot alignment angle (HAA), (4) angle between the inferior and superior facets of the talus (Inftal-Suptal), (5) angle between the inferior facet of the talus and the horizontal floor line (Inftal-Hor), (6) forefoot arch angle (FAA), (7) navicular-to-floor distance, and (8) medial cuneiform–to-floor distance. Measurements were then compared with values available in the literature for a “normal” foot morphotype.Results:Among the 54 feet, the mean FAO was 0.48% (95% CI, –0.25% to 1.21%), the mean CO was 1.18 mm (95% CI, –0.50 to 2.87 mm), and the mean HAA was 1.42° (95% CI, –0.80° to 3.65°). The mean Inftal-Suptal angle was 5.31° (95% CI, 3.50°-7.12°), while the mean Inftal-Hor angle was 4.04° (95% CI, 2.56°-5.51°). The mean FAA was 15.84° (95% CI, 14.73°-16.92°), the mean navicular-to-floor distance was 38.30 mm (95% CI, 36.19-40.42 mm), and the mean medial cuneiform–to-floor distance was 26.79 mm (95% CI, 25.30-28.28 mm). None of these values were found to be significantly different when comparing forwards, guards, and centers.Conclusion:NBA players presenting with symptomatic foot and ankle injuries had a fairly “normal” foot morphology, with a tendency toward a varus hindfoot and a high-arched morphotype. No significant differences were found between players based on their position on the court. WB CBCT may help to shed light on anatomic risk factors for common injuries in professional players and may aid in the planning of specific prevention programs.

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.

3D Biometrics for Hindfoot Alignment Using Weightbearing CT.

Hindfoot alignment on 2D radiographs can present anatomical and operator-related bias. In this study, software designed for weightbearing computed tomography (WBCT) was used to calculate a new 3D biometric tool: the Foot and Ankle Offset (FAO). We described the distribution of FAO in a series of data sets from clinically normal, varus, and valgus cases, hypothesizing that FAO values would be significantly different in the 3 groups. In this retrospective cohort study, 135 data sets (57 normal, 38 varus, 40 valgus) from WBCT (PedCAT; CurveBeam LLC, Warrington, PA) were obtained from a specialized foot and ankle unit. 3D coordinates of specific anatomical landmarks (weightbearing points of the calcaneus, of the first and fifth metatarsal heads and the highest and centermost point on the talar dome) were collected. These data were processed with the TALAS system (CurveBeam), which resulted in an FAO value for each case. Intraobserver and interobserver reliability were also assessed. In normal cases, the mean value for FAO was 2.3% ± 2.9%, whereas in varus and valgus cases, the mean was -11.6% ± 6.9% and 11.4% ± 5.7%, respectively, with a statistically significant difference among groups ( P < .001). The distribution of the normal population was Gaussian. The inter- and intraobserver reliability were 0.99 +/- 0.00 and 0.97 +/-0.02 Conclusions: This pilot study suggests that the FAO is an efficient tool for measuring hindfoot alignment using WBCT. Previously published research in this field has looked at WBCT by adapting 2D biometrics. The present study introduces the concept of 3D biometrics and describes an efficient, semiautomatic tool for measuring hindfoot alignment. Level III, retrospective comparative study.