Ultrasonographic Assessment of Femoral Torsion Angle Based on Tilting Angles of Femoral Neck and Condylar Axis

Validity and reliability of ultrasonographic assessment of femoral and tibial torsion in children and adolescents: a systematic review

Torsional disorders of the lower limb are common in childhood, and they are one of the primary reasons parents seek consultation with healthcare providers. While clinical manoeuvres can assess femoral and tibial torsion, their reliability is medium to low. Various imaging-based techniques, including computed tomography, magnetic resonance imaging, fluoroscopy, biplanar radiology and ultrasonography, have been used to evaluate torsional alterations of the lower extremity. Among these, ultrasound assessment offers certain advantages: it is a low-cost, non-irradiating technique, which allows the follow-up of children's torsional development. However, to the best of the authors' knowledge, its validity and reliability have not been summarised in a systematic review. This study aims to analyse the validity and reliability of ultrasonography in determining femoral and tibial torsion in children and adolescents. A search from Medline (via PubMed), Web of Science, Scopus and CINAHL databases were performed from inception to 16 March 2023. No restrictions were placed on the publication year or language. The methodological quality of all eligible studies was independently reviewed by two authors using QUADAS and STARD checklists. Overall, 1546 articles were identified through the searches; 30 were considered eligible for full-text screening; and 8 studies were finally included in this review. The included studies were conducted in Germany, Norway and the UK. Among them, 7 studies analysed the validity of ultrasonography compared with other imaging techniques such as computed tomography, magnetic resonance imaging and biplanar X-ray, and 4 studies assessed intra- and inter-observer reliability. All the studies assessed femoral torsion, but only one of them also included tibial torsion.     Conclusion: Ultrasound is a good alternative for routine evaluation and follow-up of femoral torsional alterations in children and adolescents due to its safety, accessibility and immediate results in the clinical examination room. Although ultrasound has good accuracy and reliability for routine evaluations, there is controversy about whether it is sufficient for surgical planning. In cases where greater accuracy is required, magnetic resonance imaging and biplanar radiography are the preferred imaging techniques. What is Known: • Several imaging-based techniques have been described for the assessment of torsional alterations of the lower extremity. • Computed tomography, magnetic resonance imaging, biplanar radiology and ultrasonography are the most used and studied methods. What is New: • Ultrasonography represents a good alternative for the assessment of femoral and tibial torsional alterations in children and adolescents, given its safety, accessibility and immediacy of results in the consultation room. • Its accuracy and reliability are good but not sufficient for surgical planning, in which case MRI and biplanar X-ray will be the preferred choices.

Virtual 3D femur model to assess femoral version: comparison to the 2D axial slice approach

BACKGROUND

Quantifying femoral version is crucial in diagnosing femoral version abnormalities and for accurate pre-surgical planning. There are numerous methods for measuring femoral version, however, reliability studies for most of these methods excluded children with hip deformities.

OBJECTIVE

To propose a method of measuring femoral version based on a virtual 3D femur model, and systematically compare its reliability to the widely used Murphy's 2D axial slice technique.

MATERIALS AND METHODS

We searched our imaging database to identify hip/femur CTs performed on children (<18 years old) with a clinical indication of femoral version measurement (September 2021-August 2022). Exclusion criteria were prior hip surgery, and inadequate image quality or field-of-view. Two blinded radiologists independently measured femoral version using the virtual 3D femur model and Murphy's 2D axial slice method. To assess intrareader variability, we randomly selected 20% of the study sample for re-measurements by the two radiologists >2 weeks later. We analyzed the reliability and correlation of these techniques via intraclass correlation coefficient (ICC), Bland-Altman analysis, and deformity subgroup analysis.

RESULTS

Our study sample consisted of 142 femurs from 71 patients (10.6±4.4 years, male=31). Intra- and inter-reader correlations for both techniques were excellent (ICC≥0.91). However, Bland-Altman analysis revealed that the standard deviation (SD) of the absolute difference between the two radiologists for the Murphy method (mean 13.7°) was larger than that of the 3D femur model technique (mean 4.8°), indicating higher reader variability. In femurs with hip flexion deformity, the SD of the absolute difference for the Murphy technique was 17°, compared to 6.5° for the 3D femur model technique. In femurs with apparent coxa valga deformity, the SD of the absolute difference for the Murphy technique was 10.4°, compared to 5.2° for the 3D femur model technique.

CONCLUSION

The 3D femur model technique is more reliable than the Murphy's 2D axial slice technique in measuring femoral version, especially in children with hip flexion and apparent coxa valga deformities.

Online Instruction to Measure Axial Alignment with the Bonesetter App

Background and objectives: Alignment of the lower extremity is important when treating congenital deformities, fractures, and joint replacement. During the COVID-19 pandemic, AO North America offered an online course on deformity measurement and planning. The Bonesetter app is a deformity planning tool that is freely available online. The purpose of this study was to see how effective an online course was in teaching axial alignment measurement and to assess that skill using an online digital planning tool, the Bonesetter app. Materials and Methods: An online module on axial alignment was provided during the AONA osteotomy course as well as a tutorial on how to use an online digital planning tool (Bonesetter app). The tools within the Bonesetter app allow users to draw digital lines directly on the CT images and measure the exact angle between two planes. Participants in this study were directed to perform these measurements in four different cases that tested different variations of deformity. Results: The measurements were completed correctly in case 1 = 56%, case 2 = 61%, case 3 = 84%, and case 4 = 76%. The standard deviation of angular digital measurements between individuals was ±4.26 degrees. Measuring the angle directly vs. drawing angles to a horizontal line had smaller standard deviations per case (p < 0.005) and less incidents outside 1 standard deviation for each measurement. Errors in adding and subtracting were the most common errors, particularly in relation to femoral anteversion or retroversion. Conclusions: The online course successfully instructed a group of orthopedic surgeons to measure alignment and malalignment of lower limb axial deformities. The Bonesetter app helped participants to learn this skill and identify errors in measurement. The inability to differentiate between anteversion and retroversion of the femur is a common source of error when it occurs and should be a focus of instruction.

Morphological Parameters of the Hip Joint and Its Relation to Gender, Joint Side and Age-A CT-Based Study

Background: Physiological reference values for morphological parameters of the hip (MPH) are of clinical importance for the treatment of painful, degenerated or fractured hip joints, as well as to detect morphological deformities, which could result in early osteoarthritis of the hip. Currently, sufficient data for MPH are lacking. Therefore, it remains unclear if age-dependent alterations in adult hip morphology are physiological and if there are side- and gender-dependent differences. The aim of the study was to analyze MPH according to gender, side and age in a large-scaled cohort by CT scans. Methods: A total of 1576 hip joints from 788 patients (female: 257, male: 531; mean age: 58.3 years (±18.9; 18−92 years)) were analyzed by CT. For all hips, acetabular anteversion (AcetAV); lateral centrum edge angle (LCE); acetabular index (AI); femoral neck version (FNV); centrum-collum-diaphyseal angle (CCD); and anterior alpha angle (AαA) were measured. Results: The mean values in this cohort were: AcetAV 20.5° (±6.9); LCE 40.8° (±8.8); AI 0.3° (±5.3); FNV 11.0° (±9.8); CCD 129.9° (±7.4); and AαA 41.2° (±7.7). There was a detectable side-specific difference for AcetAV (p = 0.001); LCE (p < 0.001); CCD (p < 0.001); and AαA (p < 0.001). All the analyzed parameters showed a significant gender-specific difference, except for AI (p = 0.37). There was a significant correlation between age and AcetAV (r = 0.17; p < 0.001); LCE (r = 0.39; p < 0.001); AI (r = −0.25; p < 0.001); CCD (r = −0.15; p < 0.001); and AαA (r = 0.09; p < 0.001), except FNV (p = 0.79). Conclusions: There are side-, gender- and age-specific alterations in hip morphology, which have to be considered in treating hip joint pathologies.

Characteristics of Femoral Torsion Angles and Relationships Between Femoral Torsion Angles and Hip Rotational Motion Variables in Adult Baseball Players

Background:

Abnormalities in hip rotational motion (HRM) are risk factors for throwing injuries. To evaluate hip rotational motion, it is necessary to assess the torsion angle. However, no studies have investigated the femoral torsion angle (FTA) in baseball players.

Purpose:

To investigate differences in hip FTA of adult baseball players through use of ultrasonography to evaluate the relationship between the FTA and HRM.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

A total of 149 elite male baseball players (mean age, 20.0 ± 1.8 years; 64 pitchers, 85 position players) were enrolled in this study. Ultrasonographic assessment of FTA was performed based on the tilting angles of the anterior surface of the femoral neck and condylar axis. The hip internal rotation (HIR) and hip external rotation (HER) were assessed at 0° and 90° of flexion. Data related to FTA and HRM were compared between hips and between pitchers and position players.

Results:

No significant difference was observed in the FTAs between hips for any player (lead hip, 20.5° ± 9.2°; trail hip, 19.6° ± 9.8°; P = .276). No significant difference was observed in FTAs of both hips between pitchers and position players (lead hip, 20.1° ± 9.4° and 20.9° ± 9.0°, respectively, P = .957; trail hip, 19.5° ± 9.8° and 19.7° ± 9.8°, P = .999). In terms of HER in 90° of hip flexion in both hips, significant differences were observed in HRM variables between pitchers and position players (lead hip, 33.0° ± 8.9° and 37.5° ± 9.8°, respectively, P = .024; trail hip, 35.6° ± 9.6° and 40.4° ± 10.2°, P = .035). Linear regression analysis revealed a significant agreement between the FTA and HIR at both 0° (R = 0.298, P < .001) and 90° of hip flexion (R = 0.279, P < .001).

Conclusion:

Our findings indicated that FTAs were not different between the hips of elite baseball players. Abnormalities of the HRM are not caused by differences in the FTA but rather involve soft tissue tightness around the hip area or other bony morphologic factors in the hip joint.