Measuring physiological and pathological femoral anteversion using a biplanar low-dose X-ray system: validity, reliability, and discriminative ability in cerebral palsy

Validity of measurement of femoral anteversion angle using FEMORA® software based on two-dimensional radiographic imaging examination femur in children with cerebral palsy in Indonesia

Introduction

Children with spastic cerebral palsy (CP) often show an increase in femoral anteversion angle (FAA). Computed tomography (CT) scan is the main modality for evaluating FAA in these patients, however, due to significant radiation exposure, it carries a high carcinogenic risk. FEMORA® software is expected to be able to accurately assess FAA even with conventional X-ray images that only require low radiation exposure. However, its validity has not been tested in various populations or CT devices. This study aimed to validate the FEMORA® software by comparing it to CT scans done on an Indonesian population.

Material and methods

All spastic CP patients of the outpatient clinic at Dr. Soetomo Hospital between March and November 2022, were included. The FEMORA® Software evaluation was performed by three examiners. The calculation results were averaged and compared with those of the CT scan. Intraclass correlation coefficient (ICC), reliability, and correlation were be assessed.

Results

There were 36 patients included in this study. Most were female (n = 22; 61,1 %) and the average age was 7,28 years old. Interobserver preoperative analysis using ICC showed good outcomes (p = 0.918; 95 % CI, 0.858-0.955). FAA measurement results using FEMORA® and CT scans were 41,71 ± 12,90 and 32,68 ± 11,85, respectively. Correlation coefficient between the two values is 0.634 (p < 0.001).

Conclusion

FEMORA® software demonstrates a good and significant correlation with FAA measurement using CT scan.

Reliability and validity of a mobile application for femoral anteversion measurement in adult patients

BACKGROUND

Femoral torsion is primarily measured by computed tomography (CT), which has cost and radiation exposure concerns. Recently, femoral anteversion measurement by a simple radiograph-based mobile application was developed for patients with cerebral palsy. This study aimed to validate the use of a mobile application that can reconstruct a three-dimensional model of the femur from conventional radiographs for adults.

METHODS

Medical records of 76 patients undergoing conventional femur anteroposterior/lateral radiography and femur CT were reviewed. To measure femoral anteversion on the reconstructed 3-dimensional images from both the mobile application and CT, we drew a line which connects the posterior margins of each femoral condyle and another line which passes through the center of the femoral head and the midpoint of the femoral neck. After the reliability test, a single examiner measured femoral anteversion on the mobile application and CT. Pearson's correlation analysis was used to assess the correlation between anteversion on the mobile application and CT.

RESULTS

Femoral anteversion measured on both CT and the mobile application showed excellent reliability (intraclass correlation coefficients: 0.808-0.910). The correlation coefficient between femoral anteversion measured using CT and the mobile application was 0.933 (p < 0.001). The correlation of femoral anteversion between CT and the mobile application was relatively higher in the absence of metallic implants (correlation coefficient: 0.963, p < 0.001) than in the presence of metallic implants (correlation coefficient: 0.878, p < 0.001).

CONCLUSIONS

Using two simple radiographs, the mobile application showed excellent validity and reliability for femoral anteversion measurement in adults as compared to CT. With the high accessibility and cost-effectiveness of this mobile application, femoral torsion measurement might be easily performed with simple radiography in clinical settings in the near future.

Torsion Tool: An automated tool for personalising femoral and tibial geometries in OpenSim musculoskeletal models

Common practice in musculoskeletal modelling is to use scaled musculoskeletal models based on a healthy adult, but this does not consider subject-specific geometry, such as tibial torsion and femoral neck-shaft and anteversion angles (NSA and AVA). The aims of this study were to (1) develop an automated tool for creating OpenSim models with subject-specific tibial torsion and femoral NSA and AVA, (2) evaluate the femoral component, and (3) release the tool open-source. The Torsion Tool (https://simtk.org/projects/torsiontool) is a MATLAB-based tool that requires an individual's tibial torsion, NSA and AVA estimates as input and rotates corresponding bones and associated muscle points of a generic musculoskeletal model. Performance of the Torsion Tool was evaluated comparing femur bones as personalised with the Torsion Tool and scaled generic femurs with manually segmented bones as golden standard for six typically developing children and thirteen children with cerebral palsy. The tool generated femur geometries closer to the segmentations, with lower maximum (-19%) and root mean square (-18%) errors and higher Jaccard indices (+9%) compared to generic femurs. Furthermore, the tool resulted in larger improvements for participants with higher NSA and AVA deviations. The Torsion Tool allows an automatic, fast, and user-friendly way of personalising femoral and tibial geometry in an OpenSim musculoskeletal model. Personalisation is expected to be particularly relevant in pathological populations, as will be further investigated by evaluating the effects on simulation outcomes.

Reliability of Low-dose Biplanar Radiography in Assessing Pediatric Torsional Pathology

BACKGROUND

Low-dose biplanar radiographs (LDBRs) significantly reduce ionizing radiation exposure and may be of use in evaluating lower extremity torsion in children. In this study, we evaluated how well femoral and tibial torsional profiles obtained by LDBR correspond with 3-dimensional (3D) computed tomography (CT) and magnetic resonance axial imaging (MRI) in pediatric patients with suspected rotational abnormalities.

METHODS

Patients who had both LDBR and CT/MRI studies performed for suspected lower extremity rotational deformities were included. Unlike previous publications, this study focused on patients with lower extremity torsional pathology, and bilateral lower extremities of 17 patients were included. CT/MRI torsion was measured using the Reikerås method, after conversion to 3D reconstructions. The LDBRs were deidentified and sent to the software division of EOS imaging, who created 3D reconstructions and evaluated each reconstruction for the torsional quantification of the femurs and tibiae. These imaging modalities were compared using correlation statistics and Bland-Altman analyses.

RESULTS

The mean age of the cohort was 12.1±1.7 years old. Torsional values of the femur were significantly lower in LDBRs versus 3D CT/MRIs at 17.7±15.1 and 23.3±17.3, respectively (P=0.001). Torsional values of the tibia were similar in LDBRs versus 3D CT/MRIs at 23.6±10.6 and 25.3±11.2, respectively (P=0.503). There was a good intermodality agreement between LDBR and 3D CT/MRI torsional values in the femur (intraclass correlation coefficient=0.807) and tibia (intraclass correlation coefficient=0.768). Bland-Altman analyses showed a fixed bias with a mean difference of -5.6±8.8 degrees between femoral torsion measurements in LDBRs versus 3D CT/MRIs (P=0.001); 15% (5/34) of femurs had a clinically significant measurement discrepancy. Fixed bias for LDBR measurements compared with 3D CT/MRIs for the tibia was not observed (P=0.193), however, 12% (4/34) of tibias had a clinically significant measurement discrepancy.

CONCLUSION

Although we found strong correlations between torsional values of the femur and tibia measured from LDBRs and 3D CT/MRIs, torsional values of the femur produced from LDBRs were significantly lower than values obtained from 3D CT/MRIs with some notable outliers.

LEVEL OF EVIDENCE

Level III.

What's New in the Orthopaedic Treatment of Ambulatory Children With Cerebral Palsy Using Gait Analysis

BACKGROUND

Limb deformities in ambulatory children with cerebral palsy (CP) are common. The natural history of lower extremity deformities is variable and the impact on gait is managed with many treatment modalities. Effective interventions must consider the underlying pathophysiology, patient-specific goals, and incorporate objective outcome assessment. Evaluation and treatment include observation, tone management multilevel orthopaedic surgery to address muscle contractures and bony deformities, and the use of gait analysis for preoperative and postoperative assessment.

METHODS

A PubMed search of the orthopaedic literature for studies published between January 2016 and February 2019 was performed. Eligible abstracts included the use of 3-dimensional instrumented gait analysis in the evaluation and treatment of the lower extremities in ambulatory children with CP. Seven hundred twenty abstracts were reviewed, with 84 papers identified as eligible, of which 45 full manuscripts were included for detailed review.

RESULTS

The review summarized recent advances regarding the treatment of torsional alignment, knee deformities and clinical gait evaluation with visual assessment tools compared with instrumented gait analysis.

CONCLUSIONS

Gait analysis of ambulatory children with CP remains essential to evaluation and surgical decision-making. Promising results have been reported with the goal of maintaining or reaching a higher level of function and increased endurance.

LEVEL OF EVIDENCE

Level IV-literature review.

Development and Validation of a Mobile Application for Measuring Femoral Anteversion in Patients With Cerebral Palsy

BACKGROUND

Computed tomography (CT) provides benefits for 3-dimensional (3D) visualization of femur deformities. However, the potential adverse effects of radiation exposure have become a concern. Consequently, a biplanar imaging system EOS has been proposed to enable reconstruction of the 3D model of the femur. However, this system requires a calibrated apparatus, the cost of which is high, and the area occupied by it is substantial. The purpose of this study was to develop a mobile application that included a new method of 3D reconstruction of the femur from conventional radiographic images and to evaluate the validity and reliability of mobile the application when measuring femoral anteversion.

METHODS

The statistical shape model, graph-cut algorithm, and iterative Perspective-n-Point algorithm were utilized to develop the application. The anteroposterior and lateral images of a femur can be input using the embedded camera or by file transfer, and the touch interface aids accurate contouring of the femur. Regarding validation, the CT scans and conventional radiographic images of 36 patients with cerebral palsy were used. To evaluate concurrent validity, the femoral anteversion measurements on the images reconstructed from the mobile application were compared with those from the 3D CT images. Three clinicians assessed interobserver reliability.

RESULTS

The mobile application, which reconstructs the 3D image from conventional radiographs, was successfully developed. Regarding concurrent validity, the correlation coefficient between femoral anteversion measured using 3D CT and the mobile application was 0.968 (P<0.001). In terms of interobserver reliability, the intraclass correlation coefficient among the 3 clinicians was 0.953.

CONCLUSIONS

The measurement of femoral anteversion with the mobile application showed excellent concurrent validity and reliability in patients with cerebral palsy. The proposed mobile application can be used with conventional radiographs and does not require additional apparatus. It can be used as a convenient technique in hospitals that cannot afford a CT machine or an EOS system.

LEVEL OF EVIDENCE

Level III-diagnostic.

3-D lower extremity bone morphology in ambulant children with cerebral palsy and its relation to gait

Changes in lower-extremity bone morphology are potential mid- to long-term secondary consequences of cerebral palsy (CP), affecting activity. Little is known about the 3-D morphology of lower-extremity bones in children with CP and the association with gait deviations. The main aim of this study was to describe and compare 3-D lower-extremity bone morphology in ambulant children with unilateral or bilateral CP. Secondary aims were to determine whether certain bone parameters were related to the unilateral or bilateral CP and to quantify the association between bone parameters and gait deviations. Among 105 ambulant children with CP (aged 3 to 17 years), 48 had bilateral CP (Bilat-CP) and 57 had unilateral CP (Unilat-CP); the unaffected limb of children with Unilat-CP was used as control limbs. Fifteen bone parameters were calculated by EOS® biplanar radiography, and the Gait Deviation Index (GDI) was calculated by 3-D gait analysis. Data were compared by descriptive and comparative statistical analysis (Anova, principal component analysis [PCA] and focused-PCA). Mean (SD) neck shaft angle was significantly greater for Unilat-CP than control limbs (134.9° [5.9] vs. 131.3° [5]). Mean mechanical tibial angle was significantly smaller (85.8° [6.7] vs. 89° [4.6]) and mean femoral torsion was significantly greater (29.4° [1.6] vs. 19.1° [11.8]) for Bilat-CP than control limbs. On PCA of the main determinants of 3-D bone morphology, bone shape was more complex with Bilat-CP, with changes in all 3 dimensions of space, than Unilat-CP and control limbs. Few bone parameters were correlated with the GDI in any limbs. In ambulant children with CP, femoral and tibial growth are not affected by the condition. The unilateral or bilateral nature of CP must be considered during treatment to prevent bone deformities and bone morphology affecting gait quality.

Femoral anteversion assessment: Comparison of physical examination, gait analysis, and EOS biplanar radiography

BACKGROUND

Multiple measurement methods are available to assess transverse plane alignment of the lower extremity.

RESEARCH QUESTION

This study was performed to determine the extent of correlation between femoral anteversion assessment using simultaneous biplanar radiographs and three-dimensional modeling (EOS imaging), clinical hip rotation by physical examination, and dynamic hip rotation assessed by gait analysis.

METHODS

Seventy-seven patients with cerebral palsy (GMFCS Level I and II) and 33 neurologically typical children with torsional abnormalities completed a comprehensive gait analysis with same day biplanar anterior-posterior and lateral radiographs and three-dimensional transverse plane assessment of femoral anteversion. Correlations were determined between physical exam of hip rotation, EOS imaging of femoral anteversion, and transverse plane hip kinematics for this retrospective review study.

RESULTS

Linear regression analysis revealed a weak relationship between physical examination measures of hip rotation and biplanar radiographic assessment of femoral anteversion. Similarly, poor correlation was found between clinical evaluation of femoral anteversion and motion assessment of dynamic hip rotation. Correlations were better in neurologically typical children with torsional abnormalities compared to children with gait dysfunction secondary to cerebral palsy.

SIGNIFICANCE

Dynamic hip rotation cannot be predicted by physical examination measures of hip range of motion or from three-dimensional assessment of femoral anteversion derived from biplanar radiographs.

Three-dimensional evaluation of skeletal deformities of the pelvis and lower limbs in ambulant children with cerebral palsy

Skeletal abnormalities, affecting posture and walking pattern, increase with motor impairment in children with cerebral palsy (CP). However, it is not known whether these skeletal malalignments occur in children with slight motor impairment. Our aim was to evaluate skeletal malalignment at the level of the pelvis and lower limbs in ambulant children with CP, with slight motor impairment, using a low dose biplanar X-ray technique. Twenty-seven children with spastic CP (mean age: 10.9±4years, 7 Hemiplegia, 20 Diplegia, GMFCS levels I:17, II:10), with no previous treatments at the hips and knees, underwent EOS(®) biplanar X-rays. A control group consisting of 22 typically developing children was also included. Three-dimensional reconstructions of the pelvis and lower limbs were performed in order to calculate 11 radiological parameters related to the pelvis, acetabulum and lower limbs. Pelvic incidence and sacral slope were significantly increased in children with CP compared to TD children (48°±7° vs. 43°±8°, 42°±7° vs. 38°±5°, respectively, p=0.003). Acetabular parameters did not significantly differ between the two groups. Femoral anteversion and neck shaft angle were significantly increased in children with CP (25°±12° vs. 14°±7°, p<0.001; 134°±5° vs. 131°±5°, p=0.005 respectively). No difference was found for tibial torsion. This study showed that even slightly impaired children with CP have an anteverted and abducted femur and present positional and morphological changes of the pelvis in the sagittal plane. The orientation of the acetabulum in 3D seems to not be affected when children with CP present slight motor impairment.