Arthroscopic International Cartilage Repair Society Classification System Has Only Moderate Reliability in a Porcine Cartilage Repair Model

A biocompatible pea protein isolate-derived bioink for 3D bioprinting and tissue engineering

Three-dimensional bioprinting is a potent biofabrication technique in tissue engineering but is limited by inadequate bioink availability. Plant-derived proteins are increasingly recognized as highly promising yet underutilized materials for biomedical product development and hold potential for use in bioink formulations. Herein, we report the development of a biocompatible plant protein bioink from pea protein isolate. Through pH shifting, ethanol precipitation, and lyophilization, the pea protein isolate (PPI) transformed from an insoluble to a soluble form. Next, it was modified with glycidyl methacrylate to obtain methacrylate-modified PPI (PPIGMA), which is photocurable and was used as the precursor of bioink. The mechanical and microstructural studies of the hydrogel containing 16% PPIGMA revealed a suitable compress modulus and a porous network with a pore size over 100 μm, which can facilitate nutrient and waste transportation. The PPIGMA bioink exhibited good 3D bioprinting performance in creating complex patterns and good biocompatibility as plenty of viable cells were observed in the printed samples after 3 days of incubation in the cell culture medium. No immunogenicity of the PPIGMA bioink was identified as no inflammation was observed for 4 weeks after implantation in Sprague Dawley rats. Compared with methacrylate-modified gelatin, the PPIGMA bioink significantly enhanced cartilage regeneration in vitro and in vivo, suggesting that it can be used in tissue engineering applications. In summary, the PPIGMA bioink can be potentially used for tissue engineering applications.

Decreased Elastic Modulus of Knee Articular Cartilage Based on New Macroscopic Methods Accurately Represents Early Histological Findings of Degeneration

OBJECTIVE

Ex vivo nanoindentation measurement has reported that elastic modulus decreases as cartilage degenerates, but no method has been established to macroscopically evaluate mechanical properties in vivo. The objective of this study was to evaluate the elastic modulus of knee joint cartilage based on macroscopic methods and to compare it with gross and histological findings of degeneration.

DESIGN

Osteochondral sections were taken from 50 knees with osteoarthritis (average age, 75 years) undergoing total knee arthroplasty. The elastic modulus of the cartilage was measured with a specialized elasticity tester. Gross findings were recorded as International Cartilage Repair Society (ICRS) grade. Histological findings were graded as Mankin score and microscopic cartilage thickness measurement.

RESULTS

In ICRS grades 0 to 2 knees with normal to moderate cartilage abnormalities, the elastic modulus of cartilage decreased significantly as cartilage degeneration progressed. The elastic modulus of cartilage was 12.2 ± 3.8 N/mm for ICRS grade 0, 6.3 ± 2.6 N/mm for ICRS grade 1, and 3.8 ± 2.4 N/mm for ICRS grade 2. Similarly, elastic modulus was correlated with Mankin score (r = -0.51, P < 0.001). Multiple regression analyses showed that increased Mankin score is the most relevant factor associated with decreased elastic modulus of the cartilage (t-value, -4.53; P < 0.001), followed by increased histological thickness of the cartilage (t-value, -3.15; P = 0.002).

CONCLUSIONS

Mechanical properties of damaged knee cartilage assessed with new macroscopic methods are strongly correlated with histological findings. The method has potential to become a nondestructive diagnostic modality for early cartilage damage in the clinical setting.

Preoperative Medial Tightness and Narrow Medial Joint Space Are Predictive Factors for Lower Extremity Alignment Change Toward Varus After Opening-Wedge High Tibial Osteotomy

Background:

Time-dependent changes in lower extremity alignment after an opening-wedge high tibial osteotomy (OWHTO) have been poorly investigated. Moreover, few studies have investigated risk factors of postoperative alignment change.

Purposes:

To investigate time-dependent alignment changes and identify predictive factors for postoperative alignment change after OWHTO.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

This study included patients who underwent OWHTO between March 2010 and September 2018. A total of 142 knees with a mean follow-up of 42 months were included and classified as the change group when the amount of hip-knee-ankle (HKA) angle change was >1°; if otherwise, then as the no-change group. HKA angle was obtained at 6 time points: preoperatively and at 3 months, 6 months, 1 year, 2 years, and final follow-up postoperatively. Multiple regression analysis was performed to identify the factors that were correlated with the changes in the HKA angle from 3 months to the final follow-up.

Results:

Among the 142 knees, 59 (42%) were included in the change group. The overall postoperative HKA angles progressed serially toward varus after OWHTO. The mean angles of the 6 time points were 8.5°, –3.7°, –3.6°, –3.3°, –3.1°, and –2.7°, respectively. The mean HKA angles of the change and no-change groups were 9.1°, –4.3°, –3.4°, –2.8°, –2.0°, and –1.4° and 8.1°, –3.3°, –3.8°, –3.6°, –3.8°, and –3.7°, respectively. Greater change in the HKA angle was predicted by preoperatively greater valgus stress joint line convergence angles and less medial joint space width.

Conclusion:

Of the cases of OWHTO, 42% showed correction loss of >1° at a mean follow-up of 42 months. The overall postoperative HKA angles progressed serially to varus angles after OWHTO. Preoperative greater valgus stress joint line convergence angles and less medial joint space width were predictive factors for greater change in alignment toward varus after OWHTO.

Recent strategies of collagen-based biomaterials for cartilage repair: from structure cognition to function endowment

Collagen, characteristic in biomimetic composition and hierarchical structure, boasts a huge potential in repairing cartilage defect due to its extraordinary bioactivities and regulated physicochemical properties, such as low immunogenicity, biocompatibility and controllable degradation, which promotes the cell adhesion, migration and proliferation. Therefore, collagen-based biomaterial has been explored as porous scaffolds or functional coatings in cell-free scaffold and tissue engineering strategy for cartilage repairing. Among those forming technologies, freeze-dry is frequently used with special modifications while 3D-printing and electrospinning serve as the structure-controller in a more precise way. Besides, appropriate cross-linking treatment and incorporation with bioactive substance generally help the collagen-based biomaterials to meet the physicochemical requirement in the defect site and strengthen the repairing performance. Furthermore, comprehensive evaluations on the repair effects of biomaterials are sorted out in terms of in vitro, in vivo and clinical assessments, focusing on the morphology observation, characteristic production and critical gene expression. Finally, the challenge of biomaterial-based therapy for cartilage defect repairing was summarized, which is, the adaption to the highly complex structure and functional difference of cartilage.

Graphical abstract

Comparison Between Arthroscopic and Histological International Cartilage Repair Society Scoring Systems in Porcine Cartilage Repair Model

OBJECTIVE

The arthroscopic and histological International Cartilage Repair Society (ICRS) scores are designed to evaluate cartilage repair quality. Arthroscopic ICRS score can give a maximum score of 12 and the histological score can give values between 0% and 100% for each of its 14 subscores. This study compares these methods in an animal cartilage repair model. This study hypothesizes that there is a significant correlation between these methods.

DESIGN

A chondral defect was made in the medial femoral condyle of 18 pigs. Five weeks later, 9 pigs were treated with a novel recombinant human type III collagen/polylactide scaffold and 9 were left untreated to heal spontaneously. After 4 months, the medial condyles were evaluated with a simulated arthroscopy using the ICRS scoring system followed by a histological ICRS scoring.

RESULTS

This porcine cartilage repair model produced repaired cartilage tissue ranging from good to poor repair tissue quality. The mean arthroscopic ICRS total score was 6.8 (SD = 2.2). Histological ICRS overall assessment subscore was 38.2 (SD = 31.1) and histological ICRS average points were 60.5 (SD = 19.5). Arthroscopic ICRS compared with histological ICRS average points or its overall assessment subscore showed moderate correlation (r = 0.49 and r = 0.50, respectively). The interrater reliability with the intraclass correlation coefficients for arthroscopic ICRS total scores, histological ICRS overall assessment subscore, and ICRS average points showed moderate to excellent reliability.

CONCLUSIONS

Arthroscopic and histological ICRS scoring methods for repaired articular cartilage show a moderate correlation in the animal cartilage repair model.