Silicone and Pyrocarbon Artificial Finger Joints

Positive impact of pyrocarbon and mechanical loading on cartilage-like tissue synthesis in a scaffold-free process

Aiming to build a tissue analogue engineered cartilage from differentiated chondrocytes, we investigated the potential of a pyrocarbon (PyC)-based and scaffold-free process, under mechanical stimulation. PyC biomaterial has shown promise in arthroplasty and implant strategies, and mechanical stimulation is recognized as an improvement in regeneration strategies. The objective was to maintain the cell phenotype to produce constructs with cartilage-like matrix composition and mechanical properties. Primary murine chondrocytes were deposited in drop form between two biomaterial surfaces expanded to 500 μm and a uniaxial cyclic compression was applied thanks to a handmade tribo-bioreactor (0.5 Hz, 100 μm of amplitude, 17 days). Histology and immunohistochemistry analysis showed that PyC biomaterial promoted expression of cartilage-like matrix components (glycosaminoglycans, type II collagen, aggrecan). Importantly, constructs obtained in dynamic conditions were denser and showed a cohesive and compact shape. The most promising condition was the combined use of PyC and dynamic stimulation, resulting in constructs of low elasticity and high viscosity, thus with an increased damping factor. We verified that no calcium deposits were detectable and that type X collagen was not expressed, suggesting that the cells had not undergone hypertrophic maturation. While most studies focus on the comparison of different biomaterials or on the effect of different mechanical stimuli separately, we demonstrated the value of combining the two approaches to get as close as possible to the biological and mechanical qualities of natural hyaline articular cartilage.

Medical exposure to micro(nano)plastics: An exposure pathway with potentially significant harm to human health that should not be overlooked

Micro(nano)plastics (MNPs) are an emerging type of contaminants that are widely present in the environments that people live in. MNPs can enter the human body in a variety of pathways, but the three main ones are through dietary intake, air inhalation, and skin contact. However, it has been discovered that medical plastics used in medical activities also pose potential risks to MNPs exposure as exposure pathways are continuously refined and clarified. Unfortunately, there is currently insufficient study on the exposure of medical plastics and MNPs, and exposure risks and potential health problems are frequently overlooked. This study aimed to close this research gap by searching the databases of China National Knowledge Infrastructure (CNKI), PubMed, and Web of Science for relevant literature. It then filtered out publications that contained information relevant to keywords such as micro(nano)plastics, medical plastics, exposure pathways, and human health in order to do analysis and summary. We discovered that medical plastics are a high-risk source of direct MNPs exposure to the human body, and this exposure could pose a potential harm to human health. Because of the potential harm to human health, this work presents the medical exposure of MNPs for the first time and calls for more research and attention on this vital area.

Management of Index Finger Metacarpophalangeal Joint Arthritis

Metacarpophalangeal joint arthritis of the index finger is a debilitating disease often caused by osteoarthritis or inflammatory arthritides such as rheumatoid arthritis. Treatment options include nonsurgical management with nonsteroidal anti-inflammatory drugs, splinting, occupational therapy, corticosteroid injections, and disease-modifying antirheumatic drugs. Operative management options include arthrodesis and arthroplasty, which can be further broken down into silicone implants and 2 component resurfacing implants. The article summarizes the current literature for each of the treatment options for metacarpophalangeal joint arthritis of the index finger.

Development of novel hybrid 3D-printed degradable artificial joints incorporating electrospun pharmaceutical- and growth factor-loaded nanofibers for small joint reconstruction

Small joint reconstruction remains challenging and can lead to prosthesis-related complications, mainly due to the suboptimal performance of the silicone materials used and adverse host reactions. In this study, we developed hybrid artificial joints using three-dimensional printing (3D printing) for polycaprolactone (PCL) and incorporated electrospun nanofibers loaded with drugs and biomolecules for small joint reconstruction. We evaluated the mechanical properties of the degradable joints and the drug discharge patterns of the nanofibers. Empirical data revealed that the 3D-printed PCL joints exhibited good mechanical and fatigue properties. The drug-eluting nanofibers sustainedly released teicoplanin, ceftazidime, and ketorolac in vitro for over 30, 19, and 30 days, respectively. Furthermore, the nanofibers released high levels of bone morphogenetic protein-2 and connective tissue growth factors for over 30 days. An in vivo animal test demonstrated that nanofiber-loaded joints released high concentrations of antibiotics and analgesics in a rabbit model for 28 days. The animals in the drug-loaded degradable joint group showed greater activity counts than those in the surgery-only group. The experimental data suggest that degradable joints with sustained release of drugs and biomolecules may be utilized in small joint arthroplasty.

Biomechanical comparative finite element analysis between a conventional proximal interphalangeal joint flexible hinge implant and a novel implant design using a rolling contact joint mechanism

BACKGROUND

The rolling contact joint (RCJ) mechanism is a system of constraint that allows two circular bodies connected with flexible straps to roll relative to one another without slipping. This study aims to compare the biomechanical characteristics between the conventional proximal interphalangeal joint (PIPJ) flexible hinge (FH) implant and the novel PIPJ implant adopting a RCJ mechanism during PIPJ range of motion using finite element (FE) analysis.

METHODS

The three-dimensional (3D) surface shape of a conventional PIPJ FH implant was obtained using a 3D laser surface scanning system. The configuration and parameters of the novel PIPJ implant were adapted from a previous study. The two implants were assumed to have the same material characteristics and each implant was composed of a hyperelastic material, silicone elastomers. The configuration data for both implants were imported to a computer-aided design program to generate 3D geometrical surface and hyperelastic models of both implants. The hyperelastic models of both implants were imported into a structural engineering software to produce the FE mesh and to perform FE analysis. The FE analysis modeled the changes of mechanics during flexion-extension motion between 0° and 90° of two PIPJ implants. The mean and maximum values of von-Mises stress and strain as well as the total moment reaction based on the range of motion of the PIPJs were calculated. The mean values within the PIPJ's functional range of motion of the mean and maxinum von-Mises stress and strain and the total moment reaction were also determined.

RESULTS

The maximum values for the von-Mises stress, and strain, as well as the total moment reactions of the conventional PIPJ FH and novel PIPJ implants were all at 90° of PIPJ flexion. The maximum value of each biomechanical property for the novel PIPJ implant was considerably lower compared with that of the conventional PIPJ FH implant. The mean values within the PIPJ's functional range of motion of the maximum von-Mises stress and strain for the novel PIPJ implant was approximately 6.43- and 6.46-fold lower compared with that of the conventional PIPJ FH implant, respectively. The mean value within a PIPJ's functional range of motion of the total moment reaction of the novel PIPJ implant was approximately 49.6-fold lower compared with that of the conventional PIPJ FH implant.

CONCLUSIONS

The novel PIPJ implant with an RCJ mechanism may offer improved biomechanical performance compared with conventional PIPJ FH implant.

Shifting the paradigm: ankylosis arthroplasty for the proximal interphalangeal joint with a novel collateral ligament reconstruction

Silicone arthroplasty for proximal interphalangeal joint ankylosis is rarely performed, partly due to the potential for lateral joint instability. We present our experience performing proximal interphalangeal joint arthroplasty for joint ankylosis, using a novel reinforcement/reconstruction technique for the proper collateral ligament. Cases were prospectively followed-up (median 13.5 months, range 9-24) and collected data included range of motion, intraoperative collateral ligament status and postoperative clinical joint stability; a seven-item Likert scale (1-5) patient-reported outcomes questionnaire was also completed. Twenty-one ankylosed proximal interphalangeal joints were treated with silicone arthroplasty, and 42 collateral ligament reinforcements undertaken in 12 patients. There was improvement in range of motion from 0° in all joints to a mean of 73° (SD 12.3); lateral joint stability was achieved in 40 out of 42 of collateral ligaments. High median patient satisfaction scores (5/5) suggest that silicone arthroplasty with collateral ligament reinforcement/reconstruction should be considered as a treatment option in selected patients with proximal interphalangeal joint ankylosis.Level of evidence: IV.