Three-Dimensional Evaluation of Similarity of Right and Left Knee Joints

Only 26% of Native Knees Show an Identical Coronal Functional Knee Phenotype in the Contralateral Knee

BACKGROUND

A comprehensive exploration evaluating left-to-right knee symmetry across all anatomical planes utilizing three-dimensional (3D) scans stands absent from the existing body of research. Therefore, the primary objectives of this investigation involved examining potential differences and resemblances in alignment and structure between left and right non-osteoarthritic (native) knees in various planes (coronal, sagittal, and axial) using three-dimensional single-photon emission computed tomography/computed tomography (SPECT/CT) images.

METHODS

A total of 282 native knees from 141 patients were retrospectively gathered from the hospital's records. Patients, aged between 16 and 45, who underwent Tc99m-methyl diphosphonate SPECT/CT scans for both knees, adhering to the Imperial Knee Protocol, were included. A statistical analysis was conducted, including 23 knee morphometric parameters, comparing left and right knees, and classifying them based on functional knee phenotypes across the coronal, sagittal, and axial planes.

RESULTS

Regarding the functional coronal knee phenotype, 26% of patients (n = 37) exhibited identical phenotypes in both knees (p < 0.001). Significant correlated similarities between the left and right knees were observed in the coronal plane (Pearson's r = 0.76, 0.68, 0.76, 0.76, p < 0.001) and in several morphometric measures in the sagittal plane (Pearson's r = 0.92, 0.72, 0.64, p < 0.001). Moderately correlated similarities were noted in the axial plane (Pearson's r = 0.43, 0.44, 0.43, p < 0.001).

CONCLUSIONS

Only 26% of native knees exhibit an identical coronal phenotype in their contralateral knee, whereas 67% have the adjacent coronal phenotype. Strongly correlated resemblances were established across various left and right knee morphometric parameters in the coronal, sagittal, and axial planes. These findings could enhance decisions in procedures like total knee arthroplasties or osteotomies, where alignment is key to outcomes, and reveal a potential for future artificial intelligence-driven models to improve our understanding and improve personalized treatment strategies for knee osteoarthritis.

The symmetry of the left and right tibial plateau: a comparison of 200 tibial plateaus

PURPOSE

This study aims to investigate the symmetry of the left and right tibial plateau in young healthy individuals to determine whether left-right mirroring can be reliably used to optimize preoperative 3D virtual planning for patients with tibial plateau fractures.

METHODS

One hundred healthy subjects, without previous knee surgery, severe knee trauma, or signs of osteoarthritis were included for a previous dynamic imaging study of the knee. The subjects underwent a CT scan, scanning the left and right knee with a slice thickness of 0.8 mm. 3D surface models of the femur, patella, and tibia were created using a convolutional neural network. The 3D models of the left and right tibias were exported to MATLAB © and the tibias were mirrored. The mirrored tibias were superimposed on the contralateral tibia using a coherent point drift surface matching algorithm. Correspondence points on both surfaces were established, the mean root squared distance was calculated and visualized in a boxplot and heatmaps.

RESULTS

The overall mean difference between correspondence points on the left and right tibial plateau is 0.6276 ± 0.0343 mm. The greatest differences between correspondence points were seen around two specific surfaces on the outside of the tibial plateau; where the distal tibia was cut 15 mm below the tibial plateau and around the tibiofibular joint.

CONCLUSIONS

The differences between the left and right tibial plateau are small and therefore, we can be confident that the mirrored contralateral, unfractured, tibial plateau can be used as a template for 3D virtual preoperative planning for young patients without previous damage to the knee.

Asymmetric transepicondylar axis between varus and valgus osteoarthritic knees in windswept deformity can be predicted by hip-knee-ankle angle difference

PURPOSE

Studies regarding the best strategy to determine appropriate femoral component rotation during bilateral total knee arthroplasty (TKA) in wind swept deformities (WSD) are very limited. The purpose of this study was (1) to evaluate whether femoral rotational profiles differ between varus and valgus osteoarthritic knees in WSD and (2) to analyze the correlation between femoral rotational profiles and coronal radiologic parameters.

METHODS

A total of 40 patients who were diagnosed with bilateral knee osteoarthritis with WSD between January 2010 and December 2020 at a single institution were retrospectively reviewed. On axial computed tomography scans, femoral rotational profile parameters such as the clinical transepicondylar axis (cTEA) and anterior-posterior (AP) axis were compared between valgus and varus osteoarthritic knees. In standing full-limb AP radiographs, coronal radiographic parameters including hip-knee-ankle angle (HKA), valgus correction angle (VCA), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), and joint line convergence angle (JLCA) were measured in both knees. The correlation between the varus-valgus cTEA difference, and differences in coronal radiologic parameters was analyzed.

RESULTS

In valgus osteoarthritic knees, cTEA was significantly increased compared to varus osteoarthritic knees by 1.5° (valgus: 7.65° ± 1.82°, varus: 6.15° ± 1.58°, p < 0.001). All coronal radiologic parameters, including HKA, LDFA, MPTA, JLCA, and VCA, were significantly different between valgus and varus knees. In correlation analysis, the varus-valgus cTEA difference was significantly correlated with LDFA (r = 0.365, p = 0.021), MPTA (r = 0.442, p = 0.004), and HKA differences (r = 0.693, p < 0.001), with the HKA difference showing the strongest correlation with the cTEA difference.

CONCLUSION

In bilateral knee osteoarthritis with WSD, valgus knees showed significantly increased cTEA compared to varus knees, and the cTEA difference positively correlated with the HKA difference between valgus and varus knees. To determine the optimal femoral component rotation during TKA in WSD, assessment of cTEA with pre-operative CT scans or careful intra-operative measurement is recommended, especially in patients with large HKA difference.

LEVEL OF EVIDENCE

III, Retrospective cohort study.

Radiographic Templating for Calcaneus Operative Fixation: How Similar Is Side-to-Side Comparison?

OBJECTIVES

Calcaneal fractures often require contralateral, uninjured calcaneus radiographs as a template. The purpose of this study was to establish mean values for calcaneal radiographic parameters in an uninjured urban American population and perform side-by-side comparison with respect to age, sex, laterality, and radiograph obliquity (XRO).

DESIGN

Retrospective analysis of consecutive patients.

SETTING

Fourteen hospitals including Level 1 trauma center.

PATIENTS/PARTICIPANTS

Retrospective review of >800 uninjured patients with bilateral foot and calcaneus radiographs obtained between June and December 2019 was performed. Inclusion criteria were the following: age 18-89 years without fracture; previous foot surgical procedures; radiographic evidence of arthrosis in ankle, hindfoot, or midfoot; osteomyelitis; tumor; or foot deformities.

INTERVENTION

The lateral radiographs were independently reviewed by 3 observers, measuring Böhler angle (BA), crucial angle of Gissane (CAG), calcaneal length (CL), calcaneal height (CH), calcaneotalar ratio (CTR), and XRO.

MAIN OUTCOME MEASUREMENTS

The mean values of BA, CAG, CL, CH, and CTR were established. Side-by-side comparisons were completed with respect to age, sex, laterality, and XRO.

RESULTS

There were no statistically significant differences in side-by-side measurements of the BA, CAG, CL, or CH. XRO had significant effects on the measurements of BA, CAG, CH, and CTR. Side-by-side comparisons showed greater intersubject variability than within-subject differences.

CONCLUSIONS

We did not observe any differences in commonly measured calcaneal radiographic parameters. CAG is not a reliable parameter for diagnostic and operative planning purposes. We conclude that the use of contralateral calcaneus radiographs as templates for calcaneus fractures is a valid technique.

Wearable Dual Polarized Electromagnetic Knee Imaging System

With the increasing uptake of sport activities, onsite detection of associated knee injuries at early stages is in high demand to avoid severe ligament tear and long treatment period. Portable electromagnetic imaging (EMI) systems have the potential to meet that demand, but there are challenges. For example, EMI is based on the contrast in the dielectric properties due to the accumulated fluid after knee injury. However, that fluid can be in any shape and orientation. Therefore, to capture enough data for processing, EMI should operate as a dual-polarized wearable system with compact antennas. Thus, the proposed system is a textile brace worn on the knee and consists of an 8-element dual-polarized aperture antenna array, which is matched with the knee. Each of the utilized antennas is fed by two orthogonal coaxial feed, occupies a small size of 36 ×36 ×3.1 mm³, and is backed by a full ground plane for unidirectional radiation. The antenna covers the band 0.7-3.3 GHz (130%), with front to back ratio of more than 10 dB. The textile wool-felt is used as the substrate to enable building flexible brace system. The system's capability to reconstruct knee images with different injuries is verified on realistic knee models and phantoms. The double stage delay, multiply and sum algorithm (DS-DMAS) is used to reconstruct those images, which demonstrate the efficiency of the dual-polarized system and its superiority over single-polarized systems.

The contralateral limb is no reliable reference to restore coronal alignment in TKA

PURPOSE

Implementation of morphometric reference data from the contralateral, unaffected lower limb is suggested when reconstructing the coronal plane alignment in TKA. Limited information, however, is available which confirms this left-to-right symmetry in coronal alignment based upon radiographs. The purpose of the study was, therefore, (1) to verify if a left-to-right symmetry is present and (2) to assess whether the contralateral lower limb would be a reliable reference for reconstructing the frontal plane alignment.

METHODS

Full-leg standing radiographs of 250 volunteers (male, 125; female,125) were reviewed for three alignment parameters (Hip-Knee-Ankle angle (HKA), Femoral Mechanical Angle (FMA) and Tibial Mechanical Angle (TMA)). Evaluation of assumed left-to-right symmetry was performed according to two coronal alignment classifications (HKA subdivisions (HKA) and limb, femoral and tibial phenotypes (HKA, FMA and TMA)). Inter- and within-subject variability was calculated, along with correlations coefficients (r) and coefficients of determination (r²). Reliability of the contralateral limb as a personalized reference to reconstruct the constitutional alignment was investigated by intervals, expanding by 1° increments (0.5° increment both to varus and valgus) around the right knee alignment parameters. Subsequently, it was verified whether or not the left knee parameters fell within this interval.

RESULTS

Symmetrical distribution in coronal alignment was found in 79% (HKA subdivision) and 59% (limb phenotype) of the cohort. Gender differences were present for the most common symmetric limb phenotypes (VAR_HKA3° (23.2%) in males and NEU_HKA0° (38.4%) in females). Inter-subject variability was more prominent than the within-subject side differences for all parameters. Correlations analyses revealed mostly moderate correlations between the alignment measurements. Coefficients of determination showed overall weak left-to-right relationship, except for a moderate predictability for HKA (r² = 0.538, p < 0.001) and FMA (r² = 0.618, p < 0.001) in females. FMA and TMA marked weak predictive values for contralateral HKA. Only 60% of left knees were referenced within a 3° interval around the right knee.

CONCLUSION

No strict left-to-right symmetry was observed in coronal alignment measurements. There is insufficient left-to-right agreement to consider the concept of the contralateral unaffected limb as an idealized reference for frontal plane alignment reconstruction based upon full-leg standing radiographs.

LEVEL OF EVIDENCE

I.

Feasibility of Electromagnetic Knee Imaging Verified on ex-vivo Pig Knees

OBJECTIVE

The potential of electromagnetic (EM) knee imaging system verified on ex-vivo pig knee joint as an essential step before clinical trials is demonstrated. The system, which includes an antenna array of eight printed biconical elements operating at the band 0.7-2.2 GHz, is portable and cost-effective. Importantly, it can provide daily monitoring and onsite real-time examinations imaging tool for knee injuries.

METHODS

Six healthy hind legs from three dead adult pigs were removed at the hip and suspended in the developed system. For each pig, the right- and left-knee were scanning sequentially. Then ligament tear was emulated by injecting distilled water into the left knee joint of each pig for early (5 mL water) and mid-stage (10 mL water) injuries. The injured left knees were re-scanned. A modified multi-static fast delay, multiply and sum algorithm (MS-FDMAS) is used to reconstruct imaging of the knee. All knees connective tissues, such as anterior and posterior cruciate ligaments (ACL, PCL), lateral and medial collateral ligaments (LCL, MCL), tendons, and meniscus, are extracted from a healthy hind leg along with collected synovial fluid. The extracted tissues and fluid were characterized and modelled as their data are not available in the literature, then imported to build an equivalent model for pig knee of 1 mm3 resolution in a realistic simulation environment.

RESULTS

The obtained results proved potential of the proposed system to detect ligament/tendon tears.

CONCLUSION

The proposed system has the potential to detect early knee injuries in a realistic environment.

SIGNIFICANCE

Contactless EM knee imaging system verified on ex-vivo pig joints confirms its potential to reconstruct knee images. This work lays the groundwork for clinical EM system for detecting and monitoring knee injuries.

Textile Electromagnetic Brace for Knee Imaging

A wearable textile brace is introduced as an electromagnetic imaging system that breaks hospital boundaries to real-time onsite scanning for knee injuries. The proposed brace consists of a 12-element textile slot loop antenna array, which is designed to match the human knee for enhanced electromagnetic wave penetration. Wool felt and conductive fabric are used to fabricate the antenna array thanks to their flexibility and proper dielectric properties. Each antenna element has a compact footprint of 42 ×24 ×3.22 mm³ and achieves unidirectional radiation, high front-to-back ratio of 14 dB, wide bandwidth of 81% at 0.7-1.7 GHz, and safe SAR levels. A modified double-stage delay, multiply, and sum (DS-DMAS) algorithm is used to process the collected signals from the antenna array based on differential left/right knee imaging. The reconstructed images numerically and experimentally on realistic phantoms demonstrate the potential of the brace system for onsite detection of different types of ligaments/tendon tears.

Anatomical Variation of the Tibia - a Principal Component Analysis

Conventional anatomically contoured plates do not adequately fit most tibiae. This emphasizes the need for a more thorough morphological study. Statistical shape models are promising tools to display anatomical variations within a population. Herein, we aim to provide a better insight into the anatomical variations of the tibia and tibia plateau. Seventy-nine CT scans of tibiae were segmented, and a principal component analysis was performed. Five morphologically important parameters were measured on the 3D models of the mean tibial shapes as well as the −3SD and +3 SD tibial shapes of the first five components. Longer, wider tibiae are related to a more rounded course of the posterior column, a less prominent tip of the medial malleolus, and a more posteriorly directed fibular notch. Varus/valgus deformations and the angulation of the posterior tibia plateau represent only a small percentage of the total variation. Right and left tibiae are not always perfectly symmetrical, especially not at the level of the tibia plateau. The largest degree of anatomical variation of the tibia is found in its length and around the tibia plateau. Because of the large variation in the anatomy, a more patient-specific approach could improve implant fit, anatomical reduction, biomechanical stability and hardware-related complications.