MRI-based analysis of patellofemoral cartilage contact, thickness, and alignment in extension, and during moderate and deep flexion

Magnetic resonance imaging for assessment of the quadriceps tendon cross-sectional area as an adjunctive diagnostic parameter in patients with patellofemoral pain syndrome

OBJECTIVES

In this study, we aimed to provide a more valuable diagnostic parameter and more equivocal assessment of the diagnostic potential of patellofemoral pain syndrome (PFPS) by comparing the quadriceps tendon cross-sectional area (QTCSA) with the quadriceps tendon thickness (QTT), a traditional measure of quadriceps tendon hypertrophy.

PATIENTS AND METHODS

Between March 2014 and August 2020, a total of 30 patients with PFPS (16 males, 14 females; mean age, 30.4±11.2 years; range, 16 to 49 years) and 30 healthy individuals (19 males, 11 females; mean age: 30.8±13.8 years; range, 17 to 62 years) who underwent knee magnetic resonance imaging (MRI) were retrospectively analyzed. T1-weighted turbo spin-echo transverse MRI scans were obtained. The QTCSA was measured on the axial angled phases of the images by drawing outlines, and the QTT was measured at the most hypertrophied quadriceps tendon.

RESULTS

The mean QTT and QTCSA in the patients with PFPS (6.33±0.80 mm and 155.77±36.60 mm2, respectively) were significantly higher than those in the control group (5.77±0.36 mm and 111.90±24.10 mm2, respectively; p<0.001, for both). The receiver operating characteristic curve was used to confirm the sensitivities and specificities for both the QTT and QTCSA as predictors of PFPS. The optimal diagnostic cut-off value for QTT was 5.98 mm, with a sensitivity of 66.7%, a specificity of 70.0%, and an area under the curve (AUC) of 0.75 (range, 0.62 to 0.88). The optimal diagnostic cut-off value for QTCSA was 121.04 mm2, with a sensitivity of 73.3%, a specificity of 70.0%, and an AUC of 0.83 (range, 0.74 to 0.93).

CONCLUSION

Based on our study results, the QTCSA seems to be a more reliable diagnostic indicator for PFPS than QTT.

Patella-Posterior Turning Point of the Distal Femur Distance Is a Potential Indicator for Diagnosing Patella Alta in Recurrent Patellar Dislocation Population

PURPOSE

To introduce a simple patellar height measurement method (patella-posterior turning point of the distal femur [P-PTP] Distance) independent of patellar anatomy with standardized patient position, and tested the reliability, validity, and diagnostic accuracy compared with commonly used ratios in knee extension.

METHODS

We retrospectively reviewed 418 computed tomography (CT) images of the knee joint in a group of patients who were diagnosed recurrent patellar dislocation (RPD). With the three-dimensional (3D) CT reconstructed knee, patellar height was qualitatively assessed by the patellar engagement with the femoral trochlea in terminal knee extension to divide RPD population into case (patella alta) and control group. With digitally reconstructed lateral radiographs, patellar height was measured with P-PTP distance (perpendicular distances between the distal edge of patella articular surface and posterior turning point of distal femur), and four commonly used ratios: Caton-Deschamps index, Modified Insall-Salvati index, Blackburne-Peel index, and Insall-Salvati index. An unpaired t-test was conducted to determine significant differences between groups. Correlation coefficient, intra- and inter-observer reliability, receiver operating characteristic (ROC) curves and the area under the ROC curve (AUC) were also calculated.

RESULTS

198 knee images (198 patients) were included for final evaluation. Patella alta was present in 72 knees (36.3%) with RPD. The effect size was relatively large between the case and control group for P-PTP distance (d = -1.619; 95% CI, -1.948 to -1.286). P-PTP distance correlated moderately to strongly with four commonly used ratios (P < .001). Intraobserver and interobserver reliability was good for P-PTP distance. The AUC of the ROC curve was categorized as excellent for P-PTP distance, better than other measurements (P < .001), and the cutoff value was 4.2 mm with the highest sensitivity (86.11%) and specificity (84.92%).

CONCLUSIONS

The measurement method, P-PTP distance, showed good intra-observer and inter-observer reliability, well correlated with commonly used ratios, and presented best diagnostic accuracy among commonly used ratios for predicting RPD. P-PTP distance might be a potential indicator for identifying patella alta in RPD patients when supine and knee extended.

CLINICAL RELEVANCE

The measurement reported in this study may help in advancing clinical evaluation of patella alta, providing an alternative and simple method to measure patellar height. Standing or weight-bearing plain lateral radiographs obtained from the routine practice should be further assessed in the next step to further validate the method.

Variation in the Thickness of Knee Cartilage. The Use of a Novel Machine Learning Algorithm for Cartilage Segmentation of Magnetic Resonance Images

BACKGROUND

The variation in articular cartilage thickness (ACT) in healthy knees is difficult to quantify and therefore poorly documented. Our aims are to (1) define how machine learning (ML) algorithms can automate the segmentation and measurement of ACT on magnetic resonance imaging (MRI) (2) use ML to provide reference data on ACT in healthy knees, and (3) identify whether demographic variables impact these results.

METHODS

Patients recruited into the Osteoarthritis Initiative with a radiographic Kellgren-Lawrence grade of 0 or 1 with 3D double-echo steady-state MRIs were included and their gender, age, and body mass index were collected. Using a validated ML algorithm, 2 orthogonal points on each femoral condyle were identified (distal and posterior) and ACT was measured on each MRI. Site-specific ACT was compared using paired t-tests, and multivariate regression was used to investigate the risk-adjusted effect of each demographic variable on ACT.

RESULTS

A total of 3910 MRI were included. The average femoral ACT was 2.34 mm (standard deviation, 0.71; 95% confidence interval, 0.95-3.73). In multivariate analysis, distal-medial (-0.17 mm) and distal-lateral cartilage (-0.32 mm) were found to be thinner than posterior-lateral cartilage, while posterior-medial cartilage was found to be thicker (0.21 mm). In addition, female sex was found to negatively impact cartilage thickness (OR, -0.36; all values: P < .001).

CONCLUSION

ML was effectively used to automate the segmentation and measurement of cartilage thickness on a large number of MRIs of healthy knees to provide normative data on the variation in ACT in this population. We further report patient variables that can influence ACT. Further validation will determine whether this technique represents a powerful new tool for tracking the impact of medical intervention on the progression of articular cartilage degeneration.

Biomaterials to Mimic and Heal Connective Tissues

Connective tissue is one of the four major types of animal tissue and plays essential roles throughout the human body. Genetic factors, aging, and trauma all contribute to connective tissue dysfunction and motivate the need for strategies to promote healing and regeneration. The goal here is to link a fundamental understanding of connective tissues and their multiscale properties to better inform the design and translation of novel biomaterials to promote their regeneration. Major clinical problems in adipose tissue, cartilage, dermis, and tendon are discussed that inspire the need to replace native connective tissue with biomaterials. Then, multiscale structure-function relationships in native soft connective tissues that may be used to guide material design are detailed. Several biomaterials strategies to improve healing of these tissues that incorporate biologics and are biologic-free are reviewed. Finally, important guidance documents and standards (ASTM, FDA, and EMA) that are important to consider for translating new biomaterials into clinical practice are highligted.

Distalization and Medialization of Tibial Tuberosity for the Treatment of Potential Patellar Instability with Patella Alta

Purpose  The aim of the study was to test the distalization and medialization of the tibial tuberosity (DMTT) for the treatment of patellar instability associated with patella alta, focusing on residual instability and pain. Methods  Twenty-four consecutive patients (26 knees) suffering from patellofemoral instability and patella alta were treated by DMTT. Two groups were identified, which differed for documented history of frank patella dislocation. The groups were named objective patellar instability (OPI) (history of dislocation) and potential patella instability (PPI) (no dislocation). Outcome was measured with visual analogue scale (VAS), Kujala score, and Tegner score. Comparison between groups was performed using Student's t -test, Wilcoxon rank score, and Fisher's exact test (significance at p  < 0.05). Results  At 50 ± 18 and 41 ± 18 months of follow-up, respectively, both PPI and OPI groups obtained a significant pain reduction and functional improvement. The PPI group showed a significant decrease of the subjective instability. No procedure-related complications were reported. Conclusion  This study suggests that DMTT is a viable option for PPI patients with patella alta. The outcome was comparable between PPI and OPI cases; however, decrease in subjective instability was significantly greater in PPI patients. Level of Evidence  Level III, retrospective comparative study.

[Research progress of rehabilitation after autologous chondrocyte implantation on knee]

Objective

To summarize the research progress of rehabilitation after autologous chondrocyte implantation (ACI).

Methods

The literature related to basic science and clinical practice about rehabilitation after ACI in recent years was searched, selected, and analyzed.

Results

Based on the included literature, the progress of the graft maturation consists of proliferation phase (0-6 weeks), transition phase (6-12 weeks), remodeling phase (12-26 weeks), and maturation phase (26 weeks-2 years). To achieve early protection, stimulate the maturation, and promote the graft-bone integrity, rehabilitation protocol ought to be based on the biomechanical properties at different phases. Weight-bearing program, range of motion (ROM), and options or facilities of exercise are importance when considering a rehabilitation program.

Conclusion

It has been proved that the patients need a program with an increasingly progressive weight-bearing and ROM in principles of rehabilitation after ACI. Specific facilities can be taken at a certain phase. Evidences extracted in the present work are rather low and the high-quality and controlled trials still need to improve the rehabilitation protocol.