Department of Orthopaedics and Rehabilitation, University of Iowa, Iowa City, IA, USA.
Foot and Ankle Surgery, Hospital for Special Surgery, New York, NY, USA.
Foot Ankle Int. 2020 Jul;41(7):839-848. doi: 10.1177/1071100720920274. Epub 2020 May 22.
Semiautomatic 3-dimensional (3D) biometric weightbearing computed tomography (WBCT) tools have been shown to adequately demonstrate the relationship between the center of the ankle joint and the tripod of the foot. The measurement of the foot and ankle offset (FAO) represents an optimized biomechanical assessment of foot alignment. The objective of this study was to evaluate the correlation between FAO and traditional adult acquired flatfoot deformity (AAFD) markers, measured in different planes. We hypothesized that the FAO would significantly correlate with other radiographic markers of pronounced AAFD.
In this retrospective comparative study, we included 113 patients with stage II AAFD, 43 men and 70 women, mean age of 53.5 (range, 20-86) years. 3D coordinates (x, y, and z planes) of the foot tripod (most plantar voxel of the first and fifth metatarsal heads, and calcaneal tuberosity) and the center of the ankle joint (most proximal and central voxel of the talar dome) were assessed by 2 blinded and independent fellowship-trained orthopedic foot and ankle surgeons. The FAO was automatically calculated using the 3D coordinates by dedicated software. Multiple WBCT parameters related to the severity of the deformity in the coronal, sagittal, and transverse planes were manually measured.
We found overall good to excellent intra- (range, 0.75-0.99) and interobserver (range, 0.73-0.99) reliability for manual AAFD measurements. FAO semiautomatic measurements demonstrated excellent intra- (0.99) and interobserver (0.99) reliabilities. Hindfoot moment arm (HMA) ( < .00001), subtalar horizontal angle ( < .00001), talonavicular coverage angle ( = .00004), and forefoot arch angle ( = .0001) were the only variables found to significantly influence and correlate with FAO measurements, with an value of 0.79. An HMA value of 19.8 mm was found to be a strong threshold predictor of increased values of FAO, with mean values of FAO of 6.5 when the HMA was lower than 19.8 mm and 14.6 when the HMA was equal to or higher than 19.8 mm.
We found that 3D WBCT semiautomatic measurements of FAO significantly correlated with some traditional markers of pronounced AAFD. Measurements of FAO were also found to be slightly more reliable than the manual measurements. The FAO offers a simple and more complete biomechanical and multiplanar assessment of the AAFD, representing in a single measurement the 3D components of the deformity.
Level III, retrospective comparative study.
半自动三维（3D）生物力学负重计算机断层扫描（WBCT）工具已被证明可充分显示踝关节中心与足部三脚架之间的关系。足踝偏移量（FAO）的测量是对足弓对线进行优化的生物力学评估。本研究的目的是评估 FAO 与不同平面测量的传统成人获得性扁平足畸形（AAFD）标志物之间的相关性。我们假设 FAO 与其他明显 AAFD 的影像学标志物有显著相关性。
在这项回顾性比较研究中，我们纳入了 113 名 II 期 AAFD 患者，其中男 43 例，女 70 例，平均年龄 53.5（范围 20-86）岁。由 2 名经过足踝矫形外科专业培训的盲法独立研究员评估足部三脚架（第一和第五跖骨头最跖侧像素和跟骨结节）和踝关节中心（距骨穹顶最近端和中央像素）的 3D 坐标（x、y 和 z 平面）。FAO 由专用软件通过 3D 坐标自动计算。手动测量冠状面、矢状面和横断面与畸形严重程度相关的多个 WBCT 参数。
我们发现手动 AAFD 测量的内部（范围 0.75-0.99）和观察者间（范围 0.73-0.99）可靠性总体较好到优秀。FAO 半自动测量具有极好的内部（0.99）和观察者间（0.99）可靠性。距下关节力臂（HMA）（<0.00001）、距下关节水平角（<0.00001）、距舟关节覆盖角（=0.00004）和前足弓角（=0.0001）是唯一发现与 FAO 测量显著相关并具有相关性的变量，相关系数为 0.79。HMA 值为 19.8mm 时，FAO 值明显升高，当 HMA 值低于 19.8mm 时，FAO 的平均值为 6.5，当 HMA 值等于或高于 19.8mm 时，FAO 的平均值为 14.6。
我们发现，3D WBCT 半自动 FAO 测量与明显 AAFD 的一些传统标志物显著相关。FAO 的测量也被发现比手动测量更可靠。FAO 提供了对 AAFD 的简单而更完整的生物力学和多平面评估，通过单次测量即可代表畸形的 3D 成分。
III 级，回顾性比较研究。
