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

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.

What is the most reliable radiographic method to evaluate the longitudinal foot arch? Application in subjects with Adolescent Idiopathic Scoliosis

BACKGROUND

The foot arch is known to be altered in subjects with postural malalignment. Foot arch morphology can be studied simultaneously with body's balance by measuring foot radiographic parameters on full-body biplanar x-rays. There is no consensus on which is the most reliable method to use to draw the foot axes. The aim was to determine the most reliable methods to draw the main foot axes and apply these findings in order to study the difference of foot parameters between AIS and control subjects.

HYPOTHESES

(1) distant and clear anatomical landmarks are needed to draw the foot axes accurately; (2) foot longitudinal arch parameters differ between AIS and controls.

METHODS

Ninety AIS patients and 36 controls have undergone full body biplanar X-rays from which 3D spino-pelvic and postural parameters were collected for each patient. Six radiological foot angles were evaluated on the 2D lateral radiographs: calcaneal pitch (CPA), talar declination (TDA), first metatarsal declination (FMDA), talo-calcaneal (TCA), calcaneal first metatarsal (CFMA) and Meary. Angles were calculated based on three major axes of the foot: talar, calcaneal, and first metatarsal. Two to three methods were used to draw each axis and the reliability of each method was assessed (three operators, 2-times each). Then, differences of the foot parameters between AIS and controls, and determinants of these differences among 3D spino-pelvic and postural parameters were evaluated.

RESULTS

The most reliable methods for drawing the three axes of the foot were those using distant and clear anatomical landmarks on talus, calcaneum and first metatarsal and used for the subsequent analysis. The AIS group showed a significantly lower TDA (22° vs. 24°, p=0.014) and CFMA (141° vs. 144°, p=0.045), and higher FMDA (18° vs. 15°, p=0.008) and Meary's angle (-5° vs. -9°, p=0.005) when compared to controls. Differences were found to be determined mainly by the center of auditory meatus sagittal plumbline.

DISCUSSION

This is the first study to evaluate the most reliable method to draw foot axes on the lateral radiograph of biplanar X-rays in order to assess radiological foot arch parameters. AIS patients were shown to have more elevated foot arch compared to controls.

Midterm assessment of subtalar arthroereisis for correction of flexible flatfeet in children

BACKGROUND

The role of subtalar arthroereisis (STA) for treating flexible flatfoot (FFF) in children is controversial. We hypothesized that (1) STA provided significant radiographic correction of low longitudinal arch and forefoot abduction in paediatric FFF and that (2) mid-term clinical outcomes were satisfactory and comparable to a normal population.

METHODS

A retrospective comparative study was performed of paediatric patients with symptomatic FFF who underwent STA between 2012 and 2015. Multiple measurements on preoperative and latest follow-up radiographs were recorded by two observers and compared to assess for correction of the FFF. Intra- and inter-observer reliability was also assessed. Ankle and hindfoot range of motion (ROM), AOFAS hindfoot score and VAS-FA score were compared with controls without foot symptoms or deformity. From 70 consecutive feet, 62 (31 patients) treated at 10.5 years of age were identified and compared to 48 controls (24 patients). Mean follow-up was 62 months.

RESULTS

Intra- and inter-observer reliability was excellent for all angles (range, 0.81-0.97). Radiographic measurements demonstrated significant improvement after surgery (p<0.001) but significance was not reached in talonavicular coverage angle (p=0.49) and calcaneo-fifth metatarsal angle (p=0.53) on dorsoplantar view. At latest follow-up, patients had less hindfoot inversion than controls (15.1̊ vs. 19.3̊, p=0.03), lower AOFAS scores (94.1 vs. 99.6 points, p=0.01), due to pain (p=0.01) and alignment (p=0.006) subscores. Using the VAS-FA score, patients were found to demonstrate higher pain at rest (prange, 0.02-0.03) and during activity (p=0.009), and felt limited when standing on one leg (p range, 0.01-0.03) and running (p=0.04). No loss of correction was found after removal of the implant.

CONCLUSION

This study showed that STA corrected the low longitudinal arch in symptomatic paediatric FFF, but did not correct forefoot abduction in relation to the hindfoot. Mid-term assessment revealed STA provided satisfactory ankle and hindfoot ROM, pain and function levels, but limitations are witnessed compared to unaffected individuals. This aspect should be considered when counselling patients and their parents or caregivers to allow for realistic expectations.

LEVEL OF EVIDENCE

III, retrospective comparative study.