Three-Dimensional Reconstruction of Foot in the Weightbearing Position From Biplanar Radiographs: Evaluation of Accuracy and Reliability

A New Paradigm in Foot and Ankle Outcomes?: Away From Radiographs and Toward Patient-Centered Outcomes

Having reasonable outcome measures is essential to unbiased research. For years, provider-measured outcomes have been valued as they are more objective and convenient for investigators. However, with the popularity of patient-centered medical care delivery, patient-reported outcome measures are appropriately becoming more popular in foot and ankle research.

Three-dimensional reconstruction of the hand from biplanar X-rays: Assessment of accuracy and reliability

BACKGROUND

Functional disorders of the hand are generally investigated first using conventional radiographic imaging. However, X-rays (two-dimensional (2D)) provide limited information and the information may be reduced by overlapping bones and projection bias. This work presents a three-dimensional (3D) hand reconstruction method from biplanar X-rays.

METHOD

This approach consists of the deformation of a generic hand model on biplanar X-rays by manual and automatic processes. The reference examination being the manual CT segmentation, the precision of the method was evaluated by a comparison between the reconstructions from biplanar X-rays and the corresponding reconstructions from the CT scan (0.3mm section thickness). To assess the reproducibility of the method, 6 healthy hands (6 subjects, 3 left, 3 men) were considered. Two operators repeated each reconstruction from biplanar X-rays three times to study inter- and intra-operator variability. Three anatomical parameters that could be calculated automatically from the reconstructions were considered from the bone surfaces: the length of the scaphoid, the depth of the distal end of the radius and the height of the trapezius.

RESULTS

Double the root mean square error (2 Root Mean Square, 2RMS) at the point/area difference between biplanar X-rays and computed tomography reconstructions ranged from 0.46mm for the distal phalanges to 1.55mm for the bones of the distal carpals. The inter-intra-observer variability showed precision with a 95% confidence interval of less than 1.32mm for the anatomical parameters, and 2.12mm for the bone centroids.

DISCUSSION

The current method allows to obtain an accurate 3D reconstruction of the hand and wrist compared to the traditional segmented CT scan. By improving the automation of the method, objective information about the position of the bones in space could be obtained quickly. The value of this method lies in the early diagnosis of certain ligament pathologies (carpal instability) and it also has implications for surgical planning and personalized finite element modeling.

LEVEL OF PROOF

Basic sciences.

Combined 3D analysis of lower-limb morphology and function in children with idiopathic equinovarus clubfoot: A preliminary study

INTRODUCTION

In children treated for idiopathic equinovarus clubfoot (EVCF), the relation between morphologic defects on clinical examination and standard X-ray on the one hand and functional abnormalities on the other is difficult to objectify. The aim of the present study was to demonstrate the feasibility of combined 3D analysis of the foot and lower limb based on biplanar EOS radiographs and gait analysis. The study hypothesis was that this provides better understanding of abnormalities in form and function.

METHODS

Ten children with unilateral EVCF and "very good" clinical results were included. They underwent gait analysis on the Rizzoli Institute multisegment foot model. Kinematic data were collected for the hip, knee, ankle and foot (hindfoot/midfoot, midfoot/forefoot and hindfoot/forefoot). Biplanar EOS radiographs were taken to determine anatomic landmarks and radiological parameters.

RESULTS

Complete acquisition time was around 2hours per patient. No significant differences were found between EVCF and healthy feet except for calcaneal incidence, tibiocalcaneal angle and hindfoot/midfoot and hindfoot/forefoot inversion.

DISCUSSION

The feasibility of the combined analysis was confirmed. There were no differences in range of motion, moment or power between EVCF and healthy feet in this series of patients with very good results. The functional results are related to radiological results within the normal range. The protocol provided anatomic and kinematic reference data. A larger-scale study could more objectively assess the contribution of EOS radiography using optoelectronic markers.

LEVEL OF EVIDENCE

II, low-power prospective study.

Understanding the foot's functional anatomy in physiological and pathological conditions: the calcaneopedal unit concept

BACKGROUND

A thorough review of the available orthopaedic literature shows significant controversies, inconsistencies and sparse data regarding the terminology used to describe foot deformities. This lack of consensus on terminology creates confusion in professional discussions of foot anatomy, pathoanatomy and treatment of deformities. The controversies apply to joint movements as well as static relationships between the bones.

DESCRIPTION

The calcaneopedal unit (CPU) is a specific anatomical and physiological entity, represented by the entire foot excepted the talus. The calcaneus, midfoot and forefoot are solidly bound by three strong ligaments that create a unit that articulates with the talus. The movement of the CPU is complex, as it rotates under the talus, around the axis of Henke that coincides with the talo-calcaneal ligament of Farabeuf.This calcaneopedal unit is deformable. It is compared with a twisted plate, able to adapt to many physiological situations in standing position, in order to acheive a plantigrade position.Moreover, the calcaneopedal unit and the talo-tibiofibular complex are interdependent; rotation of the latter produces morphologic modifications inside the former and vice versa.

PURPOSE

This paper is a review article of this concept and of its physiopathological applications.

Assessing 3D paediatric foot morphology using low-dose biplanar radiography: Parameter reproducibility and preliminary values

BACKGROUND

The physical examination and weight-bearing radiography are the two main available methods for assessing the feet and lower limbs. The anatomy and function of these two structures interact with each other. These two assessment methods are affected by subjectivity and projection bias. Low-dose biplanar radiography (LDBR) is now a promising alternative for evaluating the lower limbs in children. At present, however, the foot cannot be assessed using LDBR. The objective of this study was to work towards developing a new method for 3D radiographic analysis of the paediatric foot during weight-bearing, first by determining the reproducibility of landmarks defined by LDBR then by reporting the values of the calculated radiographic parameters.

HYPOTHESIS

A new radiographic method based on LDBR can be used to obtain a 3D evaluation of the foot in paediatric patients.

PATIENTS AND METHODS

Two biplanar radiographs in perpendicular planes were obtained simultaneously in a standardised position using the EOS system (EOS^® Imaging, Paris, France) in each of 10 healthy children. To assess measurement uncertainty, two observers performed 3D reconstructions of each of the 10 feet three times (60 reconstructions). The standard error of reproducibility of the anatomic landmarks and clinical parameters was computed. Measurement uncertainty was then estimated based on the 95% confidence interval (95%CI). To obtain reference values, the mean±SD of each variable was computed after checking that the data were normally distributed.

RESULTS

Reproducibility was high for the anatomical landmarks of interest, calcaneal pitch angle, tibio-calcaneal angle on the lateral view, and first metatarsal pitch angle (95%CI<5%). The values of these angles in the study population are reported.

DISCUSSION AND CONCLUSION

The data reported here pave the way towards developing new parameters for describing 3D foot morphology and for simultaneously assessing the lower limb and foot in the standing position.

LEVEL OF EVIDENCE

I.