Characterization of the mid-coronal plane method for measurement of radiographic change in knee joint space width across different levels of image parallax

Minimal impact of beam projection angle deviations in skyline (Laurin) view and the efficacy of the anterior border of proximal tibia as a guiding landmark

OBJECTIVE

Obtaining an optimal knee skyline view is challenging due to inaccuracies in beam projection angles (BPAs) and soft tissue obscuring bony landmarks. This study aimed to assess the impact of BPA deviations on patellofemoral index measurements and assessed the anterior border of the proximal tibia as an anatomic landmark for guiding BPAs.

MATERIALS AND METHODS

This retrospective study consisted of three parts. The first was a simulation study using 52 CT scans of knees with a 20° flexion contracture to replicate the skyline (Laurin) view. Digitally reconstructed radiographs simulated neutral, 5° downward, and 5° upward tilt BPAs. Five patellofemoral indices (sulcus angle, congruence angle, patellar tilt angle, lateral facet angle, and bisect ratio) were measured and compared. The second part was a proof of concept study on 162 knees to examine patellar indices differences across these BPAs. Lastly, the alignment of the anterior border of the proximal tibia with the BPA tangential to the patellar articular surface was tested from the CT scans.

RESULTS

No significant differences in patellofemoral indices were found across various BPAs in both the simulation and proof of concept studies (all p > 0.05). The angle between the anterior border of the proximal tibia and the patellar articular surface was 1.5 ± 5.3°, a statistically significant (p = 0.037) yet clinically acceptable deviation.

CONCLUSION

Patellofemoral indices in skyline view remained consistent regardless of BPA deviations. The anterior border of the proximal tibia proved to be an effective landmark for accurate beam projection.

Fibrocyte Phenotype of ENTPD1+CD55+ Cells and Its Association with Pain in Osteoarthritic Synovium

Osteoarthritis (OA) is a prevalent degenerative joint disorder characterized by cartilage erosion, structural changes, and inflammation. Synovial fibroblasts play a crucial role in OA pathophysiology, with abnormal fibroblastic cells contributing significantly to joint pathology. Fibrocytes, expressing markers of both hematopoietic and stromal cells, are implicated in inflammation and fibrosis, yet their marker and role in OA remain unclear. ENTPD1, an ectonucleotidase involved in purinergic signaling and expressed in specific fibroblasts in fibrotic conditions, led us to speculate that ENTPD1 plays a role in OA pathology by being expressed in fibrocytes. This study aimed to investigate the phenotype of ENTPD1+CD55+ and ENTPD1-CD55+ synovial fibroblasts in OA patients. Proteomic analysis revealed a distinct molecular profile in ENTPD1+CD55+ cells, including the upregulation of fibrocyte markers and extracellular matrix-related proteins. Pathway analysis suggested shared mechanisms between OA and rheumatoid arthritis. Correlation analysis revealed an association between ENTPD1+CD55+ fibrocytes and resting pain in OA. These findings highlight the potential involvement of ENTPD1 in OA pain and suggest avenues for targeted therapeutic strategies. Further research is needed to elucidate the underlying molecular mechanisms and validate potential therapeutic targets.

An accurate method for measuring knee joint space width despite variations in beam projection angles

BACKGROUND

Assessing knee osteoarthritis (OA) severity through joint space width (JSW) measurements can be difficult due to anatomical variations, beam projection angle (BPA) errors, and patient posture during X-rays. Although various methods address these issues, a consensus on the reference point for accurate measurement is lacking. Therefore, establishing a precise evaluation method for JSW is imperative.

METHODS

Simulation on 30 knees with advanced OA to measure the JSW using digital reconstruction radiographs from computed tomography (CT) images was conducted. The distance between the medial femoral condyle and the anterior and posterior borders of the medial tibial plateau (represented by DAB and DPB, respectively) and their average (AVD) were used to evaluate JSW. Discrepancies were analyzed for various BPAs. Additionally, the reliability of measuring JSW using DAB, DPB, and AVD was evaluated in a proof-of-concept study on 100 knees using anteroposterior X-rays at three BPAs (neutral, 5° caudal, and 5° cephalic tilt).

RESULTS

In the simulation study, the AVD method had discrepancies below 1 mm from BPA 0° of 5°, 10° caudal tilt, and 5° cephalic tilt (P = 0.066, P = 0.120, and P < 0.001, respectively). However, the values of DAB and DPB showed significant discrepancies from BPA 0° (all over 1 mm and all P < 0.001) for various BPAs. The AVD measurement demonstrated the least discrepancy in JSW measurements based on BPA variations compared with DAB and DPB methods in the proof-of-concept study.

CONCLUSIONS

A simple method for accurately measuring joint space width, even when X-rays are taken at unintended angles can be applied in clinical practice.

CD39+CD55- Fb Subset Exhibits Myofibroblast-Like Phenotype and Is Associated with Pain in Osteoarthritis of the Knee

Recent studies utilizing single-cell analysis have unveiled the presence of various fibroblast (Fb) subsets within the synovium under inflammatory conditions in osteoarthritis (OA), distinguishing them from those in rheumatoid arthritis (RA). Moreover, it has been reported that pain in knee OA patients is linked to specific fibroblast subsets. Single-cell expression profiling methods offer an incredibly detailed view of the molecular states of individual cells. However, one limitation of these methods is that they require the destruction of cells during the analysis process, rendering it impossible to directly assess cell function. In our study, we employ flow cytometric analysis, utilizing cell surface markers CD39 and CD55, in an attempt to isolate fibroblast subsets and investigate their relationship with OA pathology. Synovial tissues were obtained from 25 knee OA (KOA) patients. Of these, six samples were analyzed by RNA-seq (n = 3) and LC/MS analysis (n = 3). All 25 samples were analyzed to estimate the proportion of Fb (CD45-CD31-CD90+) subset by flow cytometry. The proportion of Fb subsets (CD39+CD55- and CD39-CD55+) and their association with osteoarthritis pathology were evaluated. CD39+CD55- Fb highly expressed myogenic markers such as CNN1, IGFBP7, MYH11, and TPM1 compared to CD39-CD55+ Fb. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of upregulated differentially expressed genes (DEGs) in CD39+CD55- Fb identified the Apelin pathway and cGMP-PKC-signaling pathway as possibly contributing to pain. LC/MS analysis indicated that proteins encoded by myogenic marker genes, including CNN1, IGFBP7, and MYH11, were also significantly higher than in CD39-CD55+ Fb. CD39-CD55+ Fb highly expressed PRG4 genes and proteins. Upregulated DEGs were enriched for pathways associated with proinflammatory states ('RA', 'TNF signaling pathway', 'IL-17 signaling pathway'). The proportion of CD39+CD55- Fb in synovium significantly correlated with both resting and active pain levels in knee OA (KOA) patients (resting pain, ρ = 0.513, p = 0.009; active pain, ρ = 0.483, p = 0.015). There was no correlation between joint space width (JSW) and the proportion of CD39+CD55- Fb. In contrast, there was no correlation between the proportion of CD39-CD55+ Fb and resting pain, active pain, or JSW. In conclusion, CD39+CD55- cells exhibit a myofibroblast phenotype, and its proportion is associated with KOA pain. Our study sheds light on the potential significance of CD39+CD55- synovial fibroblasts in osteoarthritis, their myofibroblast-like phenotype, and their association with joint pain. These findings provide a foundation for further research into the mechanisms underlying fibrosis, the impact of altered gene expression on osteoarthritic joints, and potential therapeutic strategies.

A call for screening MRI as a tool for osteoarthritis clinical trials

Conventional radiography is the most commonly used imaging modality for the evaluation of osteoarthritis (OA) in clinical trials of disease-modifying OA drugs (DMOADs). Unfortunately, radiography has many shortcomings as an imaging technique to meaningfully assess the pathological features of OA. In this perspective paper, we will describe the reasons why radiography is not an ideal tool for structural OA assessment and why magnetic resonance imaging (MRI) should be preferred for such purposes. These shortcomings include a lack of reproducibility of radiographic joint space measurements (if conducted without using a standardized positioning frame), a lack of sensitivity and specificity, an insufficient definition of disease severity, a weak association of radiographic structural damage and pain, a lack of ability to depict many faces of OA, and incapability to depict diagnoses of exclusion. MRI offers solutions to these limitations of radiography. Several different phenotypes of OA have been recognized and it is important to recruit appropriate patients for specific therapeutic approaches in DMOAD trials. Radiography does not allow such phenotypical stratification. We will explain known hurdles for widespread deployment of MRI at eligibility screening and how they can be overcome by technological advances and the use of simplified image assessment.

Comparison of Six Different Methods for Measuring the Equine Hoof and Recording of its Three-Dimensional Conformation

Different measuring techniques have been used to objectify the classification of hoof shape. The MicroScribe is a novel tool that might prove useful for measuring hooves without prior reconstruction or compensation of projection artefacts. The aim of this study was to compare biometric data of the equine hoof collected by the MicroScribe tool and measurements collected directly from hooves, scaled photographs and radiographs, from photogrammetry models and computed tomography datasets. The suitability of MicroScribe generated data to differentiate individual hoof conformations was tested. A total of 62 measures were recorded from 16 forehooves. 21 linear and nine angular measures were collected by at least four methods each, and evaluated further by analysis of variance (ANOVA) and multivariate analysis of variance (MANOVA). Ratios and differences of these measures were calculated as suitable for the definition of hoof shapes and analysed as well. Absolute equivalency of methods was detected for five linear and none of the angular measurements. The precision of the tested measurement methods was comparable. In some cases, different methods measure different structures. Radiographs tended to overestimate, while computed tomography slides to underestimate distances. Photogrammetry and scaled photographs were less suitable for measuring hoof angles. The MicroScribe tool can readily be used for hoof measurements. Its values for linear measures showed good equivalency with other methods based on real hooves. For angular measurements, the uneven hoof surface might introduce imprecision. Not all hoof conformations could be detected based on measuring results alone. Diagnosis by a skilled veterinarian is still essential.