Direct assessment of 3D foot bone kinematics using biplanar X‐ray fluoroscopy and an automatic model registration method

Abstract

BackgroundQuantifying detailed 3-dimensional (3D) kinematics of the foot in contact with the ground during locomotion is crucial for understanding the biomechanical functions of the complex musculoskeletal structure of the foot. Biplanar X-ray fluoroscopic systems and model-based registration techniques have recently been employed to capture and visualise 3D foot bone movements in vivo, but such techniques have generally been performed manually. In the present study, we developed an automatic model-registration method with biplanar fluoroscopy for accurate measurement of 3D movements of the skeletal foot.MethodsThree-dimensional surface models of foot bones were generated prior to motion measurement based on computed tomography. The bone models generated were then registered to biplanar fluoroscopic images in a frame-by-frame manner using an optimisation technique, to maximise similarity measures between occluding contours of the bone surface models with edge-enhanced fluoroscopic images, while avoiding mutual penetration of bones. A template-matching method was also introduced to estimate the amount of bone translation and rotation prior to automatic registration.ResultsWe analysed 3D skeletal movements of a cadaver foot mobilized by a robotic gait simulator. The 3D kinematics of the calcaneus, talus, navicular and cuboid in the stance phase of the gait were successfully reconstructed and quantified using the proposed model-registration method. The accuracy of bone registration was evaluated as 0.27 ± 0.19 mm and 0.24 ± 0.19° (mean ± standard deviation) in translation and rotation, respectively, under static conditions, and 0.36 ± 0.19 mm and 0.42 ± 0.30° in translation and rotation, respectively, under dynamic conditions.ConclusionsThe measurement was confirmed to be sufficiently accurate for actual analysis of foot kinematics. The proposed method may serve as an effective tool for understanding the biomechanical function of the human foot during locomotion.

A model‐based tracking method for measuring 3D dynamic joint motion using an alternating biplane x‐ray imaging system

“…The image frames that failed during the registration were those with incomplete bone images as a result of overlapping of bones or out‐of‐detector views, leading to far from correct bone poses at the first stage, erroneous motion vectors at the second stage, and finally, bone poses with mTRE greater than the 2.5 mm threshold. The new MCPI‐based tracking method using alternating biplane x‐ray image systems gave accuracy values that were well within those obtained by other model‐based tracking methods using custom‐built synchronized biplane x‐ray imaging systems, mostly with submillimeter and subdegree accuracy . While a direct comparison between these results and the current study may not be feasible considering the different scanners used, specimen status, accuracy representations, and experimental conditions and protocols, the reported values provide a possible range of accuracy for custom‐built synchronized biplane x‐ray image systems.…”

“…and subdegree accuracy. 24,25,38,61,62 While a direct comparison between these results and the current study may not be feasible considering the different scanners used, specimen status, accuracy representations, and experimental conditions and protocols, the reported values provide a possible range of accuracy for custom-built synchronized biplane x-ray image systems. With alternating biplane systems, the new modelbased tracking method showed standard deviations of errors (precision) of less than 0.84°in rotations and 0.38 mm in translations for the knee bones, which were well within the reported ranges of 0.65-0.91°and 0.18-0.7 mm, respectively.…”

“…Biplane dynamic x ray has been used to address the issue, as the simultaneous incorporation of an additional x‐ray image plane enables a better determination of all six degrees‐of‐freedom (6‐DOF) of individual bones. Such methods have been validated in vitro for their accuracy in measurements of kinematics of various joints, and have also been applied to measure rigid‐body and intra‐articular surface kinematics in various joints during quasistatic and dynamic activities …”

“…35,36 Biplane dynamic x ray has been used to address the issue, as the simultaneous incorporation of an additional x-ray image plane enables a better determination of all six degrees-offreedom (6-DOF) of individual bones. Such methods have been validated in vitro for their accuracy in measurements of kinematics of various joints, [24][25][26][36][37][38][39] and have also been applied to measure rigid-body and intra-articular surface kinematics in various joints during quasistatic 40,41 and dynamic activities. [42][43][44][45] By definition, biplane dynamic x ray-based methods require synchronized imaging by the two x-ray units, which can be achieved only on custom-built biplane systems or by integrating two single-plane C-arm fluoroscopes.…”

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

“…It is difficult to assess the kinematic change of the AJC under the weightbearing condition using 2D radiography because of the complex bony shapes of the joint. Thus, the 2D-3D registration technique was developed to measure foot bone and AJC kinematics of patients [1,2] or asymptomatic volunteers [3][4][5][6]. Although the accuracy of the 2D-3D registration technique is below 1.0 mm and 1.0°, the number of steps is required to achieve accuracy.…”