Surgical Epicondylar Axis of the Knee and Its Relationship to the Axial Tibia Alignment in Knee Osteoarthritis: The Concept of Proximal Twist Tibia

The proximal tibia and distal femur are intimately linked with the biomechanics of the knee and they are to be considered in total knee arthroplasty (TKA). The aim of the present study was to evaluate the proximal tibial torsion (PTT) in relation to surgical epicondylar axis (SEA) in a healthy cohort and a pathological cohort affected by knee osteoarthritis (OA). We retrospectively analyzed computed tomography of OA knee of 59 patients before they underwent TKA and nonarthritic knee of 39 patients as control. Posterior condylar angle (PCAn), femoral tibial torsion (SEA-proximal tibial condyle [PTC] and SEA-PTT), PTT (PTC-PTT and posterior condylar axes [PCAx]-PTC), and distance between tibial tuberosity and the trochlear groove (TT-TG) were measured. No differences were found for gender, age, TT-TG, and PCAn angles. Statistically significant differences were found for all the other angles considered. Significant correlation was found between tibial torsion and SEA-PTT angles, between PCAx-PTC and SEA-PTC, between SEA-PTT and SEA-PTC, and between PCAx-PTC and SEA-PTT. All measures, except TT-TG and PCAn angles, showed high validity (area under the curve [AUC] > 75%) in associating with OA, with SEA-PTT displaying the highest validity with an AUC of 94.38%. This is the first study to find significant differences in terms of proximal tibia geometry and anatomy between nonarthritic and OA knees. From our results, we reported that OA group was characterized by a greater internal rotation of tibia with respect to SEAs compared with control group. Since the design of the study cannot evaluate a cause–effect relationship, further studies need to be performed to assess the potential implications of these anatomic differences for knee OA and arthroplasty surgeries.

Artificial intelligence-based automatic assessment of lower limb torsion on MRI

Abnormal torsion of the lower limbs may adversely affect joint health. This study developed and validated a deep learning-based method for automatic measurement of femoral and tibial torsion on MRI. Axial T2-weighted sequences acquired of the hips, knees, and ankles of 93 patients (mean age, 13 ± 5 years; 52 males) were included and allocated to training (n = 60), validation (n = 9), and test sets (n = 24). A U-net convolutional neural network was trained to segment both femur and tibia, identify osseous anatomic landmarks, define pertinent reference lines, and quantify femoral and tibial torsion. Manual measurements by two radiologists provided the reference standard. Inter-reader comparisons were performed using repeated-measures ANOVA, Pearson’s r, and the intraclass correlation coefficient (ICC). Mean Sørensen-Dice coefficients for segmentation accuracy ranged between 0.89 and 0.93 and erroneous segmentations were scarce. Ranges of torsion as measured by both readers and the algorithm on the same axial image were 15.8°–18.0° (femur) and 33.9°–35.2° (tibia). Correlation coefficients (ranges, .968 ≤ r ≤ .984 [femur]; .867 ≤ r ≤ .904 [tibia]) and ICCs (ranges, .963 ≤ ICC ≤ .974 [femur]; .867 ≤ ICC ≤ .894 [tibia]) indicated excellent inter-reader agreement. Algorithm-based analysis was faster than manual analysis (7 vs 207 vs 230 s, p < .001). In conclusion, fully automatic measurement of torsional alignment is accurate, reliable, and sufficiently fast for clinical workflows.

Evaluation of the reliability of lower extremity alignment measurements using EOS imaging system while standing in an even weight-bearing posture

This study aimed to analyze the reproducibility and reliability of the alignment parameters measured using the EOS image system in both limbs while standing with an even weight-bearing posture. Overall, 104 lower extremities in 52 patients were analyzed retrospectively. The patients stood with an even load over both lower extremities then rotated 15° in both directions. Two EOS images were acquired and 104 pairs of lower extremities were compared according to the position of the indexed lower extremities. Then, the inter-observer reliability of the EOS system and the inter-modality reliability between EOS and computed tomography (CT) were evaluated. Femoro-tibial rotation (FTR) and tibial torsion demonstrated a significant difference between the anterior and posterior positions of the indexed lower extremity. In the inter-observer reliability analysis, all values except for FTR and tibial torsion demonstrated good or very good reliability. In the anterior position, FTR demonstrated moderate, and tibial torsion demonstrated poor reliability. In the posterior position, both FTR and tibial torsion demonstrated poor reliability. In the reliability analysis between the three-dimensional (3D) EOS model and 3D CT images, all measurements of the femur demonstrated very good reliability, but measurements of the tibia did not. For the coronal and sagittal alignment parameters measured by the EOS 3D system with rotated standing posture, except for the measurement including tibial torsion., there were no significant difference for either position of the indexed extremities with high agreement between the observers as well as with the CT 3D model.

Evaluation of the Reliability of Lower Extremity Alignment Measurements Using EOS Imaging System While Standing in an Even Weight-Bearing Posture

Purpose: This study aimed to analyze the reproducibility and reliability of the alignment parameters measured using the EOS image system in both limbs while standing with an even weight-bearing posture.Methods: Overall, 104 lower extremities in 52 patients were analyzed retrospectively. The patients stood with an even load over both lower extremities then rotated 15° in both directions. Two EOS images were acquired and 104 pairs of lower extremities were compared according to the position of the indexed lower extremities. Then, the inter-observer reliability of the EOS system and the inter-modality reliability between EOS and computed tomography (CT) were evaluated.Results: Femoro-tibial rotation (FTR) and tibial torsion demonstrated a significant difference between the anterior and posterior positions of the indexed lower extremity. All values except for FTR and tibial torsion demonstrated good or very good reliability. In the anterior position, FTR demonstrated moderate, and tibial torsion demonstrated poor reliability. In the posterior position, both FTR and tibial torsion demonstrated poor reliability. In the reliability analysis between the three-dimensional (3D) EOS model and 3D CT images, all measurements of the femur demonstrated very good reliability, but measurements of the tibia did not.Conclusions: For the coronal and sagittal alignment parameters measured by the EOS 3D system with rotated standing posture, except for the measurement including tibial torsion., there were no significant difference for either position of the indexed extremities with high agreement between the observers as well as with the CT 3D model.

A New Factor Predicting Excessive Femoral Anteversion in Patients with Recurrent Patellar Dislocation

Purpose Determining a new imaging method on full-leg standing lower limb radiographs to predict excessive femoral anteversion in patients with patellar dislocation.Methods This study included 119 patients with patellar dislocation from January 2014 to January 2021. The femoral anteversion and tibial torsion were measured by CT scanning. The medial condylar angle was measured by the full-leg standing lower limb radiographs. Pearson correlation coefficient was used to evaluate the correlation between rotation parameters and medial condylar angle.Results Included patients were divided into DFO group and control group according to whether they received derotational femoral osteotomy (DFO) operation or not. There were significant statistical differences in femoral anteversion, tibial torsion and medial condylar angle between DFO group and control group (P < 0.05). This showed that there was a smaller medial condylar angle in patients undergoing DFO operation. Correlation analysis showed that the values of femoral anteversion were significantly correlated with medial condylar angle (r= -0.719, P < 0.001). Conclusion This study showed that medial condylar angle had a negative correlation with excessive femoral anteversion on the full-leg standing lower limb radiographs. The medial condylar angle can be a good predictor of femoral anteversion and can be used to guide the performance of DFO to treat patellar dislocation in clinical practice.

Evaluation of factors affecting external tibial torsion in patients with cerebral palsy

Background Gait deviation and associated torsional problems are common in patients with cerebral palsy (CP). Although femoral anteversion in CP has been extensively reviewed in previous studies, only a few studies have focused on tibial torsion. Therefore, this study aimed to evaluate tibial torsion in patients with CP and investigate the affecting factors. Methods Consecutive patients with cerebral palsy who underwent 3-dimensional computed tomography for the assessment of rotational profiles were reviewed. Femoral anteversion and tibial torsion were measured, and the demographic characteristics of the patients were recorded. A linear mixed model was implemented to overcome the retrospective nature of the study. Results After the implementation of inclusion and exclusion criteria, 472 patients were enrolled for this study. With age, external tibial torsion increased, while femoral anteversion decreased. The factors affecting external tibial torsion were increased femoral anteversion (p = 0.0057), increased age (p < 0.0001), higher Gross Motor Function Classification System (GMFCS) level (p < 0.0001), and involved/uninvolved limbs of hemiplegia (p = 0.0471/p = 0.0047). Conclusions Older age, GMFCS level IV/V, hemiplegia, and increased femoral anteversion were the independent risk factors of increased external tibial torsion; therefore, performing an imaging study is recommended for assessing the extent of tibial torsion in patients with such characteristics.