3D Biometrics for Hindfoot Alignment Using Weightbearing CT

Abstract

Background: 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. Methods: 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. Results: 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 of Evidence: Level III, retrospective comparative study.

Weight-bearing CT Technology in Musculoskeletal Pathologies of the Lower Limbs: Techniques, Initial Applications, and Preliminary Combinations with Gait-Analysis Measurements at the Istituto Ortopedico Rizzoli

“…Other original measurements are expected to be developed, as already shown in a preliminary way. 62,63 Integration of these novel 3D measures of bone morphology with current kinematics or baropodometric analyses definitely has great potential, particularly for their synergy, and they will contribute to shed more light on the biomechanical status of these anatomical areas.…”

Three-dimensional kinematic change of hindfoot during full weightbearing in standing: an analysis using upright computed tomography and 3D-3D surface registration

“…Second, only minor motion artifacts were found in AJC images with upright CT in the present study (Table 1). Changes in hindfoot alignment have been assessed using upright cone beam CT [16][17][18][19][20][21][22][23], but it takes as long as 20 to 48 s to acquire images, and it is necessary for participants to support the body to reduce artifacts. In fact, moderate to severe motion artifacts were observed in the cone beam CT images of the knee and ankle [27].…”

“…Many studies have analyzed the effect of weightbearing on the hindfoot using magnetic resonance imaging [1] or conventional CT with loading devices [7][8][9][10][11][12][13][14][15] or upright cone beam CT [16][17][18][19][20][21][22][23]. However, the effect of natural full weightbearing in a standing position has not been evaluated due to limitations of acquiring foot images under a physiological weightbearing condition using those imaging modalities.…”

Commentary on the paper: “Hindfoot malalignment in adults with haemophilic ankle arthropathy: The importance of early detection and orthotic treatment”

“…In the last decade, weightbearing computed tomography (WBCT) has increased in use for preoperative and postoperative assessment of patients with hindfoot disorders . This novel imaging modality improves the assessment of joint alignment and degeneration under weightbearing conditions (Figures and ) …”

“…19 This novel imaging modality improves the assessment of joint alignment and degeneration under weightbearing conditions (Figures 1 and 4). 15,19,20 In summary, evaluation of clinical hindfoot alignment represents an undoubtedly crucial step in the overall assessment of patients with foot and ankle pathologies. However, assessment of hindfoot deformities should not be limited to visual inspection.…”