Hemiarthroplasty implants should have very low stiffness to optimize cartilage contact stress

Decoding the "Fingerprint" of Implant Materials: Insights into the Foreign Body Reaction

Foreign body reaction (FBR) is a prevalent yet often overlooked pathological phenomenon, particularly within the field of biomedical implantation. The presence of FBR poses a heavy burden on both the medical and socioeconomic systems. This review seeks to elucidate the protein "fingerprint" of implant materials, which is generated by the physiochemical properties of the implant materials themselves. In this review, the activity of macrophages, the formation of foreign body giant cells (FBGCs), and the development of fibrosis capsules in the context of FBR are introduced. Additionally, the relationship between various implant materials and FBR is elucidated in detail, as is an overview of the existing approaches and technologies employed to alleviate FBR. Finally, the significance of implant components (metallic materials and non-metallic materials), surface CHEMISTRY (charge and wettability), and physical characteristics (topography, roughness, and stiffness) in establishing the protein "fingerprint" of implant materials is also well documented. In conclusion, this review aims to emphasize the importance of FBR on implant materials and provides the current perspectives and approaches in developing implant materials with anti-FBR properties.

Elbow hemiarthroplasty and total elbow arthroplasty provided a similar functional outcome for unreconstructable distal humeral fractures in patients aged 60 years or older: a multicenter randomized controlled trial

BACKGROUND

Semiconstrained total elbow arthroplasty (TEA) is an established treatment for elderly patients with distal humeral fractures not amenable to stable internal fixation (unreconstructable). In recent years, there has been increasing interest in elbow hemiarthroplasty (EHA), a treatment option which does not entail restrictions on weight-bearing as opposed to TEA. These 2 treatments have not been compared in a randomized controlled trial (RCT). The aim of this study was to compare the functional outcome of EHA and TEA for the treatment of unreconstructable distal humeral fractures in elderly patients.

MATERIAL AND METHODS

This was a multicenter randomized controlled trial (RCT). Patients were included between January 2011 and November 2019 at one of 3 participating hospitals. The inclusion criteria were an unreconstructable distal humeral fracture, age ≥60 years and independent living. The final follow-up took place after ≥2 years. The primary outcome measure was the Disabilities of the Arm, Shoulder, and Hand (DASH) score. Secondary outcome measures were the Mayo Elbow Performance Score (MEPS), the EQ-5D index, range of motion (flexion, extension, pronation, and supination) and grip strength.

RESULTS

Forty patients were randomized to TEA (n = 20) and EHA (n = 20). Five patients died before completing the final follow-up, leaving 18 EHA and 17 TEA patients for analysis. There were 31 women. The mean age was 74.0 (SD, 8.5) years in the EHA group and 76.9 (SD, 7.6) in the TEA group (P = .30). The mean DASH score was 21.6 points in the EHA group and 27.2 in the TEA group (P = .39), a difference of -5.6 points (95% CI: -18.6 to 7.5). There were no differences between treatment with EHA and TEA for the mean values of the MEPS (85.0 vs. 88.2, P = .59), EQ-5D index (0.92 vs. 0.86, P = .13), extension (29° vs. 29°, P = .98), flexion (126° vs. 136°, P = .05), arc of flexion-extension (97° vs. 107°, P = .25), supination (81° vs. 75°, P = .13), pronation (78° vs. 74°, P = .16) or grip strength (17.5 kg vs. 17.2 kg, P = .89). There were 6 adverse events in each treatment group.

CONCLUSION

In this RCT, both elbow hemiarthroplasty (EHA) and total elbow arthroplasty (TEA) resulted in a good and similar functional outcome for unreconstructable distal humeral fractures in elderly patients at a minimum of 2 years of follow-up.

In Vivo Biocompatibility of an Innovative Elastomer for Heart Assist Devices

Cardiac surgical approaches require the development of new materials regardless of the polyurethanes used for pulsatile blood pumps; therefore, an innovative biomaterial, a copolymer of poly(ethylene terephthalate) and dimer fatty acid (dilinoleic acid) modified with D-glucitol, hereafter referred to as PET/DLA, has been developed, showing non-hemolytic and atrombogenic properties and resistance to biodegradation. The aim of this work was to evaluate in vivo inflammatory responses to intramuscular implantation of PET/DLA biomaterials of different compositions (hard to soft segments). Two copolymers containing 70 and 65 wt.% of hard segments, as in poly(ethylene terephthalate) and dilinoleic acid in soft segments modified with D-glucitol, were used for implantation tests to monitor tissue response. Medical grade polyurethanes Bionate II 90A and Bionate II 55 were used as reference materials. After euthanasia of animals (New Zealand White rabbits, n = 49), internal organs and tissues that contacted the material were collected for histopathological examination. The following parameters were determined: peripheral blood count, blood smear with May Grunwald–Giemsa staining, and serum C-reactive protein (CRPP). The healing process observed at the implantation site of the new materials after 12 weeks indicated normal progressive collagenization of the scar, with an indication of the inflammatory–resorptive process. The analysis of the chemical structure of explants 12 weeks after implantation showed good stability of the tested copolymers in contact with living tissues. Overall, the obtained results indicate great potential for PET/DLA in medical applications; however, final verification of its applicability as a structural material in prostheses is needed.

The effect of hemiarthroplasty implant modulus on contact mechanics: an experimental investigation

BACKGROUND

Hemiarthroplasties cause damage to the cartilage that they articulate against, which is a major limitation to their use. This study investigated the use of lower-stiffness materials to determine whether they improve hemiarthroplasty contact mechanics and thus reduce the risk of cartilage damage.

METHODS

Eleven fresh-frozen cadaveric upper extremities were disarticulated and fixed in a custom-built jig that applied a static load of 50 N to the radiocapitellar joint. Flexion angles of 0°, 45°, 90°, and 135° were tested with radial head implants made of cobalt-chrome (CoCr) and ultrahigh-molecular-weight polyethylene (UHMWPE) compared with the native radial head. A Tekscan thin-film sensor was used to measure the contact area and contact pressure between the radius and capitellum.

RESULTS

UHMWPE and CoCr were too stiff in the application of hemiarthroplasty, resulting in lower contact areas and higher contact pressures relative to the native joint. The native contact area was, on average, 42 ± 20 mm² larger than that of UHMWPE (P < .001) and 55 ± 24 mm² larger than that of CoCr (P < .001). UHMWPE had a contact area 13 ± 10 mm² greater than that of CoCr (P = .014).

DISCUSSION AND CONCLUSION

This study shows that even though UHMWPE has a stiffness several times lower than CoCr, the use of this material in hemiarthroplasty led to only a minor improvement in contact mechanics. Neither implant restored contact similar to the native articulation. Investigations into new materials to improve the contact mechanics of hemiarthroplasty should focus on materials with a lower stiffness than UHMWPE.

Three-dimensional-printed custom-made patellar endoprosthesis for recurrent giant cell tumor of the patella: A case report and review of the literature

BACKGROUND

Giant cell tumor (GCT) is a benign lesion and rarely involves the patella. This disease is characterized by a relatively high recurrence rate after primary treatment. En bloc resection has been a predominant option for recurrent GCT. However, total patellectomy can lead to disruption of the knee. Therefore, exploration of functional reconstruction of the extensor mechanism is worthwhile.

CASE SUMMARY

A 54-year-old woman presented with right knee pain and swelling, and was diagnosed as having a GCT in the patella following curettage and autograft. Medical imaging revealed a lytic and expanded lesion involving the whole patella with focal cortical breaches and pathological fracture. Based on the combination of histological, radiological, and clinical features, a diagnosis of recurrent GCT in the patella was made (Campanacci grade III). After a multidisciplinary team discussion, three-dimensional (3D)-printed custom-made patellar endoprosthesis was performed following en bloc resection for reconstructing the extensor mechanism. The patient was followed for 35 mo postoperatively. No evidence of local recurrence, pulmonary metastasis, or osteoarthritis of the right knee was observed. The active flexion arc was 0°-120°, and no extension lag was detected. A favorable patellar tracking and height (Insall-Salvati ratio 0.93) were detected by radiography.

CONCLUSION

We depict a case of a GCT at the right patella, which was successfully treated by patellectomy and 3D-printed custom-made endoprosthetic replacement. The patella normal reconstruction, the precise-fit articular design, and gastrocnemius flap augmentation could lead to satisfactory knee function and a low rate of complications in the short-term follow-up.

Studying and simulation of ellipsoidal contact models for application in AFM nano manipulation

Four contact models including Hertz, Jamari, Jeng-Wang and Weng-Tang-Zhou-Zhu were considered. To verify the results of contact mechanics, the indentation depth has been compared with spherical geometry. According to the obtained results, by comparing the spherical and elliptical geometries, the indentation depth for spherical geometry is higher than for the ellipsoidal geometry, due to the existence of eccentricity in elliptical contact models which does not exist in spherical geometry. Among the models, the Jeng-Wang and Weng-Tang-Zhou-Zhu are models that are based on the contact of a particle with the substrate. Based on the existing experimental work, Jeng-Wang is the most suitable model for being applied in particle-substrate contact point. The Hertz model has been developed from crowned cylinder equations in order to be implemented for ellipsoidal geometry, moreover the Jamari model investigates two ellipses in contact with each other. By comparing Jeng-Wang and Weng-Tang-Zhou-Zhu models it is obvious that Jeng-Wang has the highest indentation depth while for the Weng-Tang-Zhou-Zhu model it is the lowest. These trends happen for two contact points. Also four materials are compared, among which graphite and chromium have the highest and the lowest indentation depths, respectively. Finally based on the obtained results Jeng-Wang and Jamari are the most suitable contact models that can be implemented in the manipulation of ellipsoidal nanoparticles.