Radiation sterilization of tissue allografts: A review

Sequential irradiation does not improve fatigue crack propagation resistance of human cortical bone at 15 kGy

Sequential irradiation has been advocated for mitigating the reduction in fatigue properties of tendon compared to a single dose. However, to our knowledge, its capability of mitigating fatigue losses in bone is unknown. Recently, we reported that sequential irradiation did not mitigate losses in high-cycle S-N fatigue life of cortical bone at 15 kGy; however, it is unclear if sequential irradiation provides a benefit to fatigue crack propagation resistance. Our previous study also showed that radiation-induced collagen chain fragmentation and crosslinking increased from 0 to 15 kGy, suggesting that both likely contribute to the reduction in high-cycle S-N fatigue life within this dose range. Our objectives were: 1) to evaluate the fatigue crack propagation resistance of cortical bone and the effect of radiation on fracture plane damage zone thickness (DZT) at the crack tip in the dose range of 0-15 kGy, and 2) to evaluate whether sequential irradiation at 15 kGy mitigates the loss of fatigue crack propagation resistance of cortical bone compared to a single irradiation dose. Compact tension specimens from four male donor femoral pairs (ages 21-61 years old) were divided into 5 treatment groups (0 kGy, 5 kGy, 10 kGy, 15 kGy, and a 15 kGy sequential irradiation dose of 5 kGy sequentially irradiated with 10 kGy) and subjected to fatigue crack propagation testing (n = 3-4 specimens per group) where fatigue crack growth rate da/dN and cyclic stress intensity factor ΔK were determined. Following testing, specimens were bulk stained in basic fuchsin, embedded in poly(methylmethacrylate), sectioned, and mounted on acrylic slides to evaluate fracture plane DZT at known crack lengths. Sections were then imaged with a fluorescence microscope, and fracture plane DZT was measured using ImageJ (n = 3-4 specimens per group) and analyzed as a function of ΔK. We observed a decrease in fatigue crack propagation resistance at 15 kGy compared to doses of 10 kGy or lower (p ≤ 0.013). Fracture plane DZT decreased overall with increasing radiation dose from 0 to 15 kGy. Sequential irradiation offered no improvement in fatigue crack propagation resistance (p = 0.98). Radiation-induced collagen chain fragmentation and crosslinking in this dose range likely contribute to a decrease in energy dissipation capability with increasing radiation dose. Other alternative radiation sterilization methods besides sequential irradiation may be warranted to mitigate radiation-induced tissue damage and extend the functional lifetime of structural cortical bone allografts.

The influence of radiation-induced collagen chain fragmentation, crosslinking, and sequential irradiation on the high-cycle fatigue life of human cortical bone

Both high-cycle fatigue life and fatigue crack propagation resistance of human cortical bone allograft are radiation dose-dependent between 0 and 25 kGy such that higher doses exhibit progressively shorter lifetimes. Recently, we have shown that collagen chain fragmentation and stable crosslink accumulation may contribute to the radiation dose-dependent loss in fatigue crack propagation resistance of human cortical bone. To our knowledge, the influence of these mechanisms on high-cycle fatigue life of cortical bone have not been established. Sequential irradiation has also been shown to mitigate the loss of fatigue life of tendons, however, whether this mitigates losses in fatigue life of cortical bone has not been explored. Our objectives were to evaluate the influence of radiation-induced collagen chain fragmentation and crosslinking on the high-cycle fatigue life of cortical bone in the dose range of 0-15 kGy, and to evaluate the capability of sequential irradiation at 15 kGy to mitigate the loss of high-cycle fatigue life and radiation-induced collagen damage. High-cycle fatigue life specimens from four male donor femoral pairs were divided into 5 treatment groups (0 kGy, 5 kGy, 10 kGy, 15 kGy, and 15 kGy sequentially irradiated) and subjected to high-cycle fatigue life testing with a custom rotating-bending apparatus at a cyclic stress of 35 MPa. Following fatigue testing, collagen was isolated from fatigue specimens, and collagen chain fragmentation and crosslink accumulation were quantified using SDS-PAGE and a fluorometric assay, respectively. Both collagen chain fragmentation (p = 0.006) and non-enzymatic crosslinking (p < 0.001) influenced high-cycle fatigue life, which decreased with increasing radiation dose from 0 to 15 kGy (p = 0.016). Sequential irradiation at 15 kGy did not offer any mitigation in high-cycle fatigue life (p = 0.93), collagen chain fragmentation (p = 0.99), or non-enzymatic crosslinking (p ≥ 0.10) compared to a single radiation dose of 15 kGy. Taken together with our previous findings on the influence of collagen damage on fatigue crack propagation resistance, collagen chain fragmentation and crosslink accumulation both contribute to radiation-induced losses in notched and unnotched fatigue life of cortical bone. To maximize the functional lifetime of radiation sterilized structural cortical bone allografts, pathways other than sequential radiation should be explored to mitigate collagen matrix damage.

New chamber stapes prosthesis: Effect of ionizing radiation on material and functional properties

New chamber stapes prosthesis (ChSP) is a middle-ear prosthesis intended for use in ear surgery for restoring the patient's middle ear function. As the prosthesis is an implantable medical device, it must be sterilized before use. However, possible alterations in the material and the functional properties following the sterilization process can influence the safety aspects while using the prosthesis. The purpose of this paper was to determine the effects of ionizing radiation (IR) on the physicochemical and biological properties of the new chamber prosthesis by utilizing EPR spectroscopy, mechanical testing, and cytotoxicity studies. Our research shows that the radiation treatment increases the hardness and the elastic modulus of the polymer, decreases the stiffness of the prosthesis membrane, and does not cause chemical changes in the polymers that may result in cytotoxicity. Furthermore, new ChSPs were successfully tested in preclinical in vitro tests. The test results justify the undertaking of further work, including in vivo biocompatibility tests and clinical trials, which would eventually lead to the increased use of the prosthesis in clinical practice.

The Relationship Between Exogenous Testosterone Use and Risk for Primary Anterior Cruciate Ligament Rupture

Background

In the United States, testosterone therapy has markedly increased in recent years. Currently, there is a paucity of evidence evaluating the risk of ligamentous injuries in patients taking testosterone replacement therapy (TRT).

Purpose/Hypothesis

The purpose of this study was to quantify the association between TRT and the incidence of anterior cruciate ligament (ACL) injuries and the subsequent risk of ACL reconstruction (ACLR) failure. It was hypothesized that individuals receiving TRT would demonstrate an increased risk for index ACL injury and ACL rerupture.

Study Design

Cohort study; Level of evidence, 3.

Methods

This is a retrospective cohort study utilizing the PearlDiver database. Records were queried between 2011 and 2020 for patients aged 18 to 59 years who filled a testosterone prescription. A matched control group based on age, sex, Charlson Comorbidity Index, tobacco use, diabetes, and hypothyroidism consisted of patients aged 18 to 59 years who had never filled a prescription for exogenous testosterone. International Classification of Diseases, 9th and 10th Revisions and Current Procedural Terminology (CPT) codes were utilized to identify patients with ACL injuries and those undergoing reconstruction. Multivariable logistic regression was used to compare rates of ACL injury at 6 months, 1 year, and 2 years after initiating TRT. ACLR failure was also examined at 1-year intervals for 5 years for individuals filling a TRT prescription.

Results

A total of 851,816 patients were enrolled, with 425,908 patients in the TRT and control groups, respectively. The TRT cohort was significantly more likely to experience an ACL tear during 6-month (OR, 2.66; 95% CI, 2.17-3.26), 1-year (OR, 2.46; 95% CI, 2.11-2.86), and 2-year (OR, 2.22; 95% CI, 1.98-2.48) periods. The rate of reconstruction failure did not differ between the 2 cohorts at up to 5 years of follow-up (P > .05).

Conclusion

Patients receiving TRT were significantly more likely to sustain a primary ACL rupture but were not at a statistically significant increased risk of reconstruction failure.

Composites of Polylactic Acid with Diatomaceous Earth for 3D-Printing Biocompatible Scaffolds: A Systematic Study of Their Mechanical, Thermal, and Biocompatibility Properties

This study explores the development of biocompatible scaffolds for bone regeneration, utilizing polylactic acid (PLA) combined with calcium phosphate as a pH buffer and diatomaceous earth as a biocompatibilizer. These materials were extruded and 3D-printed to enhance cell adhesion and biodegradability after enough cell growth. The biocompatibility of the resulting composites, with different proportions of the components and sterilization methods, was tested according to the ISO 10993 protocol. The optimal performance, with nearly zero cytotoxicity, was observed with 20 PLA/1 CP/1 DE mass ratios and gamma sterilization. Tension analysis and scanning electron microscopy (SEM) were applied to the 3D-printed composites, which were also analyzed by differential scanning calorimetry (DSC) to understand the origin of the tension properties better, which were comparable to those of cancellous bone. Degradation tests under physiological conditions for 13 weeks showed no significant mass loss. Furthermore, it was observed that cell adhesion, viability, proliferation, and osteoconduction are possible in the scaffolds studied, opening opportunities for future studies to substantiate the use of 3D-printed silica-filled composites as an alternative to homologous implants for various bone regeneration applications.

An injectable subcutaneous colon-specific immune niche for the treatment of ulcerative colitis

As a chronic autoinflammatory condition, ulcerative colitis is often managed via systemic immunosuppressants. Here we show, in three mouse models of established ulcerative colitis, that a subcutaneously injected colon-specific immunosuppressive niche consisting of colon epithelial cells, decellularized colon extracellular matrix and nanofibres functionalized with programmed death-ligand 1, CD86, a peptide mimic of transforming growth factor-beta 1, and the immunosuppressive small-molecule leflunomide, induced intestinal immunotolerance and reduced inflammation in the animals' lower gastrointestinal tract. The bioengineered colon-specific niche triggered autoreactive T cell anergy and polarized pro-inflammatory macrophages via multiple immunosuppressive pathways, and prevented the infiltration of immune cells into the colon's lamina propria, promoting the recovery of epithelial damage. The bioengineered niche also prevented colitis-associated colorectal cancer and eliminated immune-related colitis triggered by kinase inhibitors and immune checkpoint blockade.

Pericardium decellularization in a one-day, two-step protocol

Scaffolds used in tissue engineering can be obtained from synthetic or natural materials, always focusing the effort on mimicking the extracellular matrix of human native tissue. In this study, a decellularization process is used to obtain an acellular, biocompatible non-cytotoxic human pericardium graft as a bio-substitute. An enzymatic and hypertonic method was used to decellularize the pericardium. Histological analyses were performed to determine the absence of cells and ensure the integrity of the extracellular matrix (ECM). In order to measure the effect of the decellularization process on the tissue's biological and mechanical properties, residual genetic content and ECM biomolecules (collagen, elastin, and glycosaminoglycan) were quantified and the tissue's tensile strength was tested. Preservation of the biomolecules, a residual genetic content below 50 ng/mg dry tissue, and maintenance of the histological structure provided evidence for the efficacy of the decellularization process, while preserving the ECM. Moreover, the acellular tissue retains its mechanical properties, as shown by the biomechanical tests. Our group has shown that the acellular pericardial matrix obtained through the super-fast decellularization protocol developed recently retains the desired biomechanical and structural properties, suggesting that it is suitable for a broad range of clinical indications.

Dose-dependent effects of gamma radiation sterilization on the collagen matrix of human cortical bone allograft and its influence on fatigue crack propagation resistance

Fatigue crack propagation resistance and high-cycle S-N fatigue life of cortical bone allograft tissue are both negatively impacted in a radiation dose-dependent manner from 0 to 25 kGy. The standard radiation sterilization dose of 25-35 kGy has been shown to induce cleavage of collagen molecules into smaller peptides and accumulation of stable crosslinks within the collagen matrix, suggesting that these mechanisms may influence radiation-induced losses in cyclic fracture resistance. The objective of this study was to determine the radiation dose-dependency of collagen chain fragmentation and crosslink accumulation within the dose range of 0-25 kGy. Previously, cortical bone compact tension specimens from two donor femoral pairs were divided into four treatment groups (0 kGy, 10 kGy, 17.5 kGy, and 25 kGy) and underwent cyclic loading fatigue crack propagation testing. Following fatigue testing, collagen was isolated from one compact tension specimen in each treatment group from both donors. Radiation-induced collagen chain fragmentation was assessed using SDS-PAGE (n = 5), and accumulation of pentosidine, pyridinoline, and non-specific advanced glycation end products were assessed using a fluorometric assay (n = 4). Collagen chain fragmentation increased progressively in a dose-dependent manner (p < 0.001). Crosslink accumulation at all radiation dose levels increased relative to the 0 kGy control but did not demonstrate dose-dependency (p < 0.001). Taken together with our previous findings on fatigue crack propagation behavior, these data suggest that while collagen crosslink accumulation may contribute to reduced notched fatigue behavior with irradiation, dose-dependent losses in fatigue crack propagation resistance are mainly influenced by radiation-induced chain fragmentation.

Freezing does not influence the microarchitectural parameters of the microstructure of the freshly harvested femoral head bone

The femoral head is one of the most commonly used bones for allografts and biomechanical studies. However, there are few reports on the trabecular bone microarchitectural parameters of freshly harvested trabecular bones. To our knowledge, this is the first study to characterize the microstructure of femoral heads tested immediately after surgery and compare it with the microstructure obtained with conventional freezing. This study aims to investigate whether freezing at -80 °C for 6 weeks affects the trabecular microstructure of freshly harvested bone tissue. This study was divided into two groups: one with freshly harvested human femoral heads and the other with the same human femoral heads frozen at -80 °C for 6 weeks. Each femoral head was scanned using an X-ray microcomputed tomography scanner (µCT) to obtain the microarchitectural parameters, including the bone volume fraction (BV/TV), the mean trabecular thickness (Tb.th), the trabecular separation (Tb.sp), the degree of anisotropy (DA), and the connectivity density (Conn.D). There was no statistically significant difference between the fresh and the frozen groups for any of the parameters measured. This study shows that freezing at -80 °C for 6 weeks does not alter bone microstructure compared with freshly harvested femoral heads tested immediately after surgery.

A Histological and Biomechanical Analysis of Human Acellular Dermis (HAD) Created Using a Novel Processing and Preservation Technique

Background

Large and complex defects requiring reconstruction are challenging for orthopaedic surgeons. The use of human acellular dermal (HAD) matrices to augment large soft tissue defects such as those seen in massive rotator cuff tears, knee extensor mechanism failures and neglected Tendo-Achilles tears has proven to be a valuable tool in surgeons reconstructive armamentarium. Different methods for allograft decellularization and preservation alter the native properties of the scaffold. Traditional processing and preservation methods have shown to have drawbacks that preclude its widespread use. Some of the common issues include inferior biomechanical properties, the risk of rejection, limited customization, difficulty in storing and transporting, the requirement of pre-operative preparation, and last but not the least increased cost.

Methods

We describe a novel processing and preservation method utilizing a two-step non-denaturing decellularization method coupled with preservation using a water-sequestering agent (glycerol) to remove immunogenic components while retaining biomechanical properties. The efficiency of this novel process was compared with the traditional freeze-drying method and verified by histological evaluation and biomechanical strength analysis.

Results

The absence of cellular components and matrix integrity in hematoxylin and eosin-stained glycerol-preserved HAD (gly-HAD) samples compared to freeze-dried HAD (FD-HAD) demonstrated effective yet gentle decellularization. Biomechanical strength analysis revealed that gly-HADs are stronger with an ultimate tensile load to the failure strength of 210 N compared to FD-HAD (124N). The gly-HADs were found to have an optimal suture-retention strength of 126 N. Finally, sterility testing of the resultant grafts was checked to ensure a sterility assurance level of 10-6 to establish implantability.

Conclusion

The novel processing and preservation technique is described in this paper to create a Human Acellular Dermis with higher biomechanical strength and superior histological characteristics. The processing and preservation technique ensured high sterility assurance levels to establish implantability.

Effect of gamma and Ultraviolet-C sterilization on BMP-7 level of indigenously prepared demineralized freeze-dried bone allograft

The presence of bone morphogenetic proteins in demineralized freeze-dried bone allograft (DFDBA) are responsible for developing hard tissues in intraosseous defects. The most common mode of sterilization of bone allografts, i.e., Gamma rays, have dramatic effects on the structural and biological properties of DFDBA, leading to loss of BMPs. Ultraviolet-C radiation is a newer approach to sterilize biodegradable scaffolds, which is simple to use and ensures efficient sterilization. However, UV-C radiation has not yet been effectively studied to sterilize bone allografts. This study aimed to compare and evaluate the effectiveness of Gamma and Ultraviolet-C rays in sterilizing indigenously prepared DFDBA and assess their effect on the quantity of BMP-7 present in the allograft. DFDBA samples from non-irradiated, gamma irradiated, and UV-C irradiated groups were tested for BMP-7 level and samples sterilized with gamma and UV-C rays were analysed for sterility testing. The estimated mean BMP-7 level was highest in non-irradiated DFDBA samples, followed by UV-C irradiated, and the lowest in gamma irradiated samples. Our study concluded that UV-C rays effectively sterilized DFDBA as indicated by negative sterility test and comprised lesser degradation of BMP-7 than gamma irradiation.

Use of allograft bone matrix in clinical orthopedics

Clinical orthopedics continuously aims to improve methods for bone formation. Clinical applications where bone formation is necessary include critical long bone defects in orthopedic trauma or tumor patients. Though some biomaterials combined with autologous stem cells significantly improve bone repair, critical-size damages are still challenged with the suitable implantation of biomaterials and donor cell survival. Extracellular matrix (ECM) is the fundamental structure in tissues that can nest and nourish resident cells as well as support specific functions of the tissue type. ECM also plays a role in cell signaling to promote bone growth, healing and turnover. In the last decade, the use of bone-derived ECMs or ECM-similar biomaterials have been widely investigated, including decellularized and demineralized bone ECM. In this article, we reviewed the current productions and applications of decellularized and demineralized bone matrices. We also introduce the current study of whole limb decellularization and recellularization.

Decellularized Human Dermis for Orthoplastic Extremity Reconstruction

The reconstruction of patients who possess multi morbid medical histories remains a challenge. With the ever-increasing number of patients with diabetes, infections, and trauma, there is a consistent need for promotion of soft tissue healing and a reliable substrate to assist with every aspect of soft tissue reconstruction, as well as the loss of fascial domain. Several proprietary products filled some of these needs but have failed to fulfill the needs of the clinician when faced with reconstructing multiple soft tissue systems, such as the integument and the musculoskeletal system. In this paper we discuss the use of decellularized human dermis (DermaPure®, Tissue Regenix, Universal City, TX, USA) through which a unique human tissue processing technique (dCELL® technology, Tissue Regenix, Universal City, TX, USA) and the creation of multiple product forms have proven to exhibit versatility in a wide range of clinical needs for successful soft tissue reconstruction. The background of human tissue processing, basic science, and early clinical studies are detailed, which has translated to the rationale for the success of this unique soft tissue substrate in orthoplastic reconstruction, which is also provided here in detail.

Bone morphogenetic protein-2 loaded triple helix recombinant collagen-based hydrogels for enhancing bone defect healing

The development of efficacious bone substitute biomaterials remains a major challenge for research and clinical surgical. Herein, we constructed triple helix recombinant collagen (THRC) -based hydrogels loading bone morphogenetic protein-2 (BMP-2) to stimulate bone regeneration in cranial defects. A series of in situ forming hydrogels, denoted as THRC-oxidized carboxymethylcellulose (OCMC)-N-succinyl-chitosan (NSC) hydrogels, was synthesized via a Schiff base reaction involving OCMC, THRC and NSC. The hydrogels underwent rapid formation under physiological pH and temperature conditions. The composite hydrogel exhibits a network structure characterized by uniform pores, the dimensions of which can be tuned by varying THRC concentrations. The THRC-OCMC-NSC and THRC-OCMC-NSC-BMP2 hydrogels display heightened mechanical strength, substantial biodegradability, and lower swelling properties. The THRC-OCMC-NSC hydrogels show exceptional biocompatibility and bioactivity, accelerating cell proliferation, adhesion, and differentiation. Magnetic resonance imaging, computed tomography and histological analysis of rat cranial defects models revealed that the THRC-OCMC-NSC-BMP2 hydrogels substantially promote new bone formation and expedite bone regeneration. The novel THRC-OCMC-NSC-BMP2 hydrogels emerge as promising candidates for bone substitutes, demonstrating substantial potential in bone repair and regeneration applications.

Cellular Bone Matrix in Spine Surgery - Are They Worth the Risk: A Systematic Review

STUDY DESIGN

Systematic Review.

OBJECTIVE

To review the literature for complications and outcomes after the implantation of cellular bone matrix (CBM) during spine fusion.

METHODS

The PubMed database was queried from inception to January 31, 2023 for any articles that discussed the role of and identified a specific CBM in spinal fusion procedures. Adverse events, reoperations, methods, and fusion rates were collected from all studies and reported.

RESULTS

Six hundred articles were identified, of which 19 were included that reported outcomes of 7 different CBM products. Seven studies evaluated lumbar fusion, 11 evaluated cervical fusion, and 1 study reported adverse events of a single CBM product. Only 4 studies were comparative studies while others were limited to case series. Fusion rates ranged from 68% to 98.7% in the lumbar spine and 87% to 100% in the cervical spine, although criteria for radiographic fusion was variable. While 7 studies reported no adverse events, there was no strict consensus on what constituted a complication. One study reported catastrophic disseminated tuberculosis from donor contaminated CBM. The authors of 14 studies had conflicts of interest with either the manufacturer or distributor for their analyzed CBM.

CONCLUSIONS

Current evidence regarding the use of cellular bone matrix as an osteobiologic during spine surgery is weak and limited to low-grade non-comparative studies subject to industry funding. While reported fusion rates are high, the risk of severe complications should not be overlooked. Further large clinical trials are required to elucidate whether the CBMs offer any benefits that outweigh the risks.

A Day in the Life of a Surgical Instrument: The Cycle of Sterilization

Surgeons must be confident that the instruments they use do not pose risk of infection to patients due to bioburden or contamination. Despite this importance, surgeons are not necessarily aware of the steps required to ensure that an instrument has been properly sterilized, processed, and prepared for the next operation. At the end of an operation, instruments must be transported to the sterile processing unit. There, instruments are decontaminated before being sterilized by heat, chemical, or radiation-based methods. Following this, they are stored before being brought back into use. This review highlights the intricacies of the processing of surgical instruments at the conclusion of an operation so that they are ready for the next one.

The effect of sterilization and storage on the viscoelastic properties of human tendon allografts - Continued: Storage for 0 to 4 months

The role of donor-derived tendons, also known as allografts, in anterior cruciate ligament replacement surgeries is steadily increasing. Before surgery, temporary storage and, in most cases, sterilization are essential. It is, thus, crucial to determine how these procedures alter the grafts' biomechanical properties. The purpose of this research was to analyze the effect of different sterilization methods (native, frozen, frozen + 21 kGy gamma irradiation, frozen + 21 kGy electron beam irradiation) and storage durations (0 to 4 months) on the deformation and creep of two tendon types (tibialis anterior, peroneus longus). 80 tibialis anterior and 83 peroneus longus tendons from 51 human cadavers were included. The samples were removed, placed in a radio-cryoprotectant solution, then slowly cooled, sterilized and stored at -80 °C. All groups were subject to 60 s static creep test with 250 N load. Deformation during the loading phase, creep during static loading, and the ratio of these two were evaluated. Deformation at the end of the loading phase and creep consistently exhibited significantly smaller values in the tibialis anterior compared to the peroneus longus type, as well as in electron beam-sterilized grafts as opposed to gamma beam-sterilized ones. Prolonged storage periods (within 0 to 4 months) resulted in a notable increase in these values, particularly in deformation. Based on the experimental data, the tibialis anterior tendon type and sterilization by gamma beam irradiation are better choices for anterior cruciate ligament reconstruction than the peroneus longus and sterilization by electron beam. Increased storage time affects negatively the evaluated mechanical properties.

Impact of irradiation on load-to-failure in bone-patellar tendon-bone allografts: A systematic review and meta-analysis

Introduction

To evaluate the impact various levels of irradiation have on bone-patellar tendon-bone (BTB) allograft load-to-failure.

Materials and methods

Pubmed, Google Scholar and Embase were searched for studies reporting load-to-failure measurements of BTB allografts following gamma or eBeam irradiation. All systematic reviews, editorials, as well as studies that utilized animal models and/or other graft sources (achilles, hamstring, quadriceps) were excluded. Meta-analysis was performed to compare the impact of low dose (19 ≤ kGy), intermediate (20-49 kGy) and high dose (>50 kGy) gamma and eBeam radiation on load-to-failure.

Results

Twelve studies, containing a total of 429 BTB allografts (159 controls, 270 irradiated), were identified. Load-to-failure of BTB allograft was significantly decreased at intermediate (20-49 kGy) doses of radiation, while low (≤19 kGy) and high (>50 kGy) doses did not significantly change load-to-failure.

Conclusions

Intermediate doses of radiation may negatively impact the biomechanical integrity of BTB allograft in vitro. Future studies are required to examine clinical outcomes at varying irradiation levels.

Determination of the Sterilization Dose of Gamma-Ray Irradiation for Polyvinyl Alcohol-Collagen-Chitosan Composite Membrane as a Material for Periodontal Regenerative Surgery

OBJECTIVE

 Membrane sterility is very necessary considering its function as an implant material. Therefore, this research aims to determine the dose of gamma-ray irradiation for the sterilization of polyvinyl alcohol (PVA)-collagen-chitosan composite membranes used as regenerative surgery materials.

MATERIALS AND METHODS

 A total of 100 pieces of the composite membranes were prepared in a size of 2.0 × 1.5 cm by mixing 7.5% PVA, 3% collagen, and 2% chitosan using the film casting method in three batches. Furthermore, the bioburden test was performed to determine the initial microbial count in the sample by following ISO 11737-1. The results were used to ascertain the dose of gamma-ray irradiation on the sample according to ISO 11137-2. The dose verification test was then performed at the sterility assurance level 10-6.

RESULTS

 The average result of the bioburden test from three batches was 6.6 colony forming unit; hence, the verification dose was 4.8 kGy. In the verification dose test, since there was only one contaminated sample, the sterility dose test was continued.

CONCLUSION

 The sterile gamma-ray irradiation dose for PVA-collagen-chitosan composite membrane was 17.1 kGy.

Updates on Recent Clinical Assessment of Commercial Chronic Wound Care Products

Impaired wound healing after trauma, disorders, and surgeries impact millions of people globally every year. Dysregulation in orchestrated healing mechanisms and underlying medical complications make chronic wound management extremely challenging. Besides standard-of-care treatments including broad spectrum antibiotics and wound-debridement, novel adjuvant therapies are clinically tested and commercialized. These include topical agents, skin substitutes, growth factor delivery, and stem cell therapies. With a goal to overcome factors playing pivotal role in delayed wound healing, researchers are exploring novel approaches to elicit desirable healing outcomes in chronic wounds. Although recent innovations in wound care products, therapies, and devices are extensively reviewed in past, a comprehensive review summarizing their clinical outcomes is surprisingly lacking. Herein, this work reviews the commercially available wound care products and their performance in clinical trials to provide a statistically comprehensive understanding of their safety and efficacy. The performance and suitability of various commercial wound care platforms, including xenogeneic and allogenic products, wound care devices, and novel biomaterials, are discussed for chronic wounds. The current clinical evaluation will provide a comprehensive understanding of the benefits and drawbacks of the most-recent approaches and will enable researchers and healthcare providers to develop next-generation technologies for chronic wound management.

The Influence of Combined Sterilization Factors on the Structural and Functional Characteristics of Bone Implants

The results of a comprehensive study of the patterns of structural and functional changes in bone tissue samples after combined (ozone + radiation) sterilization are presented. The study used a different approach to the sterilization process with selective ozone or radiation exposure and an integral, combined one, based on a combined ozone-oxygen treatment of bone samples at the first stage and radiation at the second. The methods of IR spectroscopy, scanning electron microscopy with a prefix for elemental analysis, atomic force microscopy, and mechanical analysis with determination of elastic-plastic properties (Vickers microhardness index) were used in the work. It is shown that the ozone exposure used at the first stage of the combined sterilization process of bone implants does not lead to negative consequences with respect to their properties and characteristics. The results obtained serve as a scientific and methodological basis for the further improvement and optimization of sterilization technologies (including combined). They also offer a comprehensive justification of the parameters of sterilization regimes to ensure the safety of using bone implants during reconstructive operations, minimizing structural and functional changes in bone matter, and creating effective health-saving technologies and the possibility of using them for various biomedical applications.

Case report: Tuberculosis recall on bone graft patient

Background

Bone grafting is commonly used in spine surgery to supplement or replace the need for autografts. This is harvested, prepared, and utilized predominantly for osteoconductive properties. Anterior cervical discectomy and fusion, a procedure to decompress and fuse the spine which treats herniated discs and compressed nerves, commonly uses Polyetheretherketone (PEEK) interbody filled with allograft bone matrices to reconstruct the disc space after a discectomy is performed.

Case Description

The presented case is one of a 57-year-old male patient who underwent an uneventful cervical 5-6 and cervical 6-7 discectomy and fusion using a PEEK interbody and bone allograft. The allograft had been prepared using cancellous bone particles with preserved living cells and demineralized cortical bone fibers to facilitate bone repair and healing, which is a common technique. The allograft was aseptically processed to preserve native factors that can support bone repair and prevent contamination and cross-contamination of the product. Additionally, the product was sterilized using gamma irradiation to further prevent contamination.

Outcome

Unfortunately, with the presented case, the State's Department of Health and The Center for Diseases Control and Prevention identified that the graft was from a source contaminated with tuberculosis. The patient being reported went on to develop disseminated tuberculosis, including lung abscesses and osteomyelitis.

Conclusions

The current case highlights that there was contamination of the donor bone sources. Tuberculosis was not screened in the tissue donor even though he had risk factors, symptoms, and signs consistent with tuberculosis. Although there are methods to screen potential organ donors for tuberculosis, there is currently no approved standard laboratory tuberculosis screening tool for bone grafts. Thus, this emphasizes the importance of proper screening among individual institutions for even the most uncommon diseases in all donated bone grafts.

The cell-assembled extracellular matrix: A focus on the storage stability and terminal sterilization of this human "bio" material

The Cell-Assembled extracellular Matrix (CAM) is an attractive biomaterial because it provided the backbone of vascular grafts that were successfully implanted in patients, and because it can now be assembled in "human textiles". For future clinical development, it is important to consider key manufacturing questions. In this study, the impact of various storage conditions and sterilization methods were evaluated. After 1 year of dry frozen storage, no change in mechanical nor physicochemical properties were detected. However, storage at 4 °C and room temperature resulted in some mechanical changes, especially for dry CAM, but physicochemical changes were minor. Sterilization modified CAM mechanical and physicochemical properties marginally except for hydrated gamma treatment. All sterilized CAM supported cell proliferation. CAM ribbons were implanted subcutaneously in immunodeficient rats to assess the impact of sterilization on the innate immune response. Sterilization accelerated strength loss but no significant difference could be shown at 10 months. Very mild and transient inflammatory responses were observed. Supercritical CO2 sterilization had the least effect. In conclusion, the CAM is a promising biomaterial since it is unaffected by long-term storage in conditions available in hospitals (hydrated at 4 °C), and can be sterilized terminally (scCO2) without compromising in vitro nor in vivo performance. STATEMENT OF SIGNIFICANCE: In the field of tissue engineering, the use of extracellular matrix (ECM) proteins as a scaffolding biomaterial has become very popular. Recently, many investigators have focused on ECM produced by cells in vitro to produce unprocessed biological scaffolds. As this new kind of "biomaterial" becomes more and more relevant, it is critical to consider key manufacturing questions to facilitate future transition to the clinic. This article presents an extensive evaluation of long-term storage stability and terminal sterilization effects on an extracellular matrix assembled by cells in vitro. We believe that this article will be of great interest to help tissue engineers involved in so-called scaffold-free approaches to better prepare the translation from benchtop to bedside.

Sourcing and development of tissue for transplantation in reconstructive surgery: A narrative review

The wealth of allogeneic and xenogeneic tissue products available to plastic and reconstructive surgeons has allowed for the development of novel surgical solutions to challenging clinical problems, often obviating the need to inflict donor site morbidity. Allogeneic tissue used for reconstructive surgery enters the tissue industry through whole body donation or reproductive tissue donation and has been regulated by the FDA as human cells, tissues, and cellular and tissue-based products (HCT/Ps) since 1997. Tissue banks offering allogeneic tissue can also undergo voluntary regulation by the American Association of Tissue Banks (AATB). Tissue prepared for transplantation is sterilized and can be processed into soft tissue or bone allografts for use in surgical reconstruction, whereas non-transplant tissue is prepared for clinical training and drug, medical device, and translational research. Xenogeneic tissue, which is most often derived from porcine or bovine sources, is also commercially available and is subject to strict regulations for animal breeding and screening for infectious diseases. Although xenogeneic products have historically been decellularized for use as non-immunogenic tissue products, recent advances in gene editing have opened the door to xenograft organ transplants into human patients. Herein, we describe an overview of the modern sourcing, regulation, processing, and applications of tissue products relevant to the field of plastic and reconstructive surgery.

Evaluation of decellularization process for developing osteogenic bovine cancellous bone scaffolds in-vitro

Current immunological issues in bone grafting regarding the transfer of xenogeneic donor bone cells into the recipient are challenging the industry to produce safer acellular natural matrices for bone regeneration. The aim of this study was to investigate the efficacy of a novel decellularization technique for producing bovine cancellous bone scaffold and compare its physicochemical, mechanical, and biological characteristics with demineralized cancellous bone scaffold in an in-vitro study. Cancellous bone blocks were harvested from a bovine femoral head (18-24 months old) subjected to physical cleansing and chemical defatting, and further processed in two ways. Group I was subjected to demineralization, while Group II underwent decellularization through physical, chemical, and enzymatic treatments. Both were then freeze-dried, and gamma radiated, finally producing a demineralized bovine cancellous bone (DMB) scaffold and decellularized bovine cancellous bone (DCC) scaffold. Both DMB and DCC scaffolds were subjected to histological evaluation, scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS), fourier-transform infrared spectroscopy (FTIR), quantification of lipid, collagen, and residual nucleic acid content, and mechanical testing. The osteogenic potential was investigated through the recellularization of scaffolds with human osteoblast cell seeding and examined for cell attachment, proliferation, and mineralization by Alizarin staining and gene expression. DCC produced a complete acellular extracellular matrix (ECM) with the absence of nucleic acid content, wider pores with extensive interconnectivity and partially retaining collagen fibrils. DCC demonstrated a higher cell proliferation rate, upregulation of osteogenic differentiation markers, and substantial mineralized nodules production. Our findings suggest that the decellularization technique produced an acellular DCC scaffold with minimal damage to ECM and possesses osteogenic potential through the mechanisms of osteoconduction, osteoinduction, and osteogenesis in-vitro.

Fatigue crack propagation and fracture toughness of cortical bone are radiation dose-dependent

Cortical bone allograft sterilized with a standard γ-radiation dose of 25-35kGy has demonstrated reduced static and cyclic fracture resistance compared with unirradiated bone. To mitigate radiation damage, we recently observed a dose-dependent response of high-cycle fatigue behavior of human cortical bone from 0 to 25 kGy, with lower doses exhibiting logarithmically longer fatigue lives. The objectives of this study were as follows: (1) to determine whether fracture toughness, work-to-fracture, and fatigue crack propagation resistance of human cortical bone are also radiation dose-dependent, and (2) to determine the associations of radiation dose and a Raman biomarker for collagen disorder with fracture properties. Compact tension specimens were machined from two donor femoral pairs and allocated to four treatment groups: 0 (unirradiated control), 10, 17.5, and 25 kGy. Fracture toughness specimens were monotonically loaded to failure and the critical stress intensity factor (KC ) was determined. Work-to-fracture was calculated from the load versus displacement integral up to fracture. Fatigue crack propagation specimens were cyclically loaded under constant room-temperature irrigation and fatigue crack growth rate (da/dN) and cyclic stress intensity (∆K) were calculated. Fracture toughness, work-to-fracture, and fatigue crack propagation resistance decreased 18%, 33%, and 15-fold from 0 to 25 kGy, respectively (p < 0.05). Radiation dose was more predictive of fracture properties than collagen disorder. These findings support that quasi-static and fatigue fracture properties of cortical bone are radiation dose-dependent within this dose range. The structural alterations arising from irradiation that cause these losses in fracture resistance remain to be elucidated.

Management and outcomes of surgical site tuberculosis infection due to infected bone graft in spine surgery: a single-institution experience and 1-year postoperative follow-up

OBJECTIVE

In 2021, several patients across the United States received bone allograft contaminated with Mycobacterium tuberculosis (TB). TB is typically a pulmonary infection with many possible extrapulmonary manifestations, including skeletal tuberculosis. However, TB is a rare causative organism of postoperative surgical site infection. Iatrogenic skeletal TB infections are not widely reported in the medical literature; therefore, treatment and associated outcomes are relatively unknown. In this series, the authors report 6 cases of patients who received a mesenchymal stem cell-enhanced bone graft infected with TB at their institution, including the clinical courses, imaging findings, management plans, and outcomes at 1 year postoperatively.

METHODS

A retrospective review was performed of 6 consecutive patients who underwent spinal fusion surgery at the authors' institution and received bone graft from a lot contaminated with TB. Collected data included patient demographic characteristics, indications for surgery, surgical procedures performed, timing of contamination discovery, medical treatment, and follow-up information including reoperation, healing progress, and imaging findings.

RESULTS

Five of 6 patients (83.3%) eventually tested positive for TB via interferon-gamma release assay or wound culture. They experienced significant complications, including surgical site infections with neck swelling, pain, dysphagia, and wound dehiscence. Extensive soft-tissue infection was common; however, significant bony involvement was not observed. Surgical wound debridement was required in 4 patients, and all patients received medical management with standard RIPE (rifampin, isoniazid pyrazinamide, pyridoxine, and ethambutol) therapy for 8 weeks with extension of rifampin and isoniazid for scheduled 12 months. All patients (excluding 1 patient who died of COVID-19) showed signs of improvement with adequately healing wounds at the most recent follow-up at a median (range) of 12 (6-13) months postoperatively. To date, no patients have developed pulmonary TB.

CONCLUSIONS

Direct inoculation with TB via contaminated bone grafts resulted in a high rate of severe soft-tissue infection, although extensive skeletal and pulmonary involvement has not been observed at 1 year postoperatively; this review includes the longest reported follow-up period for this TB outbreak. Medical management remains the mainstay of therapy for these patients, with most patients showing recovery with oral antibiotic therapy. The severity of these infections arising from mesenchymal stem cell-containing bone allografts that undergo an alternative sterilization process than standard allografts raises concerns regarding the added risks of infection, which should be weighed against the expected benefits of these grafts.

[Autologous bone implant for reconstructive surgery after decompressive craniectomy in children]

The concept of post-traumatic skull defect closure is based on restoration of anatomical relationships for the maximum possible recovery of brain function, i.e. it is considered as a stage of surgical rehabilitation. The choice of implants in pediatric patients is limited. In this regard, the «gold standard» is still autologous bone implant.

MATERIAL AND METHODS

We propose a method for storage and sterilization of autologous bone implant. The last one implies keeping at a temperature of -80 ˚C with sterilization in a vacuum chamber filled with hydrogen peroxide vapors of biocidal plasma medium. Sterilization is provided by 45-minute cycle immediately before surgery. We report skull defect closure using autologous bone implants in 79 patients. Evaluation of effectiveness of storage and sterilization of autologous bone implant included analysis of mechanical properties of bone after sterilization, intra-operative microbiological monitoring, incidence of infections in early postoperative period, follow-up with assessment of resorption.

RESULTS

Early infectious complications occurred in 2 patients (2.5%). Complete resorption with redo surgery occurred in 6 (10.1%) cases. Sterilization in low-temperature plasma of hydrogen peroxide changes mechanical properties of the bone, increases durability under compressive stresses and decreases durability under tensile conditions. This does not affect functional tasks of autologous bone. The proposed method of storage and sterilization is accompanied by low risk of infections and resorption. Storage of autologous bone implant at a temperature of -80 ˚C with subsequent sterilization in low-temperature plasma of hydrogen peroxide can be considered as a safe and effective method for skull defect closure in children after decompressive surgery.

Risk Factors for Complications Following Staged Alveolar Ridge Augmentation and Dental Implantation: A Retrospective Evaluation of 151 Cases with Allogeneic and 70 Cases with Autogenous Bone Blocks

Purpose: the aim of this study was to identify potential risk factors favoring complications by assessing the number and types of complications associated with allogeneic or autogenous bone blocks applied as onlay grafts for alveolar ridge augmentation prior to implantation. Methods: A retrospective chart review on the success of 151 allogeneic and 70 autogenous bone blocks in a cohort of 164 consecutive patients, who were treated over a period of 6 years by the same surgeon, was conducted. Statistical conclusions were based on ROC curves and multiple logistic regression models. Results: Complications were observed more frequently with autogenous bone blocks (14 out of 70 cases; 20%) compared to allogeneic bone blocks (12 out of 151 cases; 7.9%; p = 0.013). However, these complications were minor and did not impact the successful dental rehabilitation. In a multiple logistic regression model, the risk of a complication was increased by the use of an autogenous bone block (OR = 3.2; p = 0.027), smoking (OR = 4.8; p = 0.007), vertical augmentation above a threshold of 2.55 mm (OR = 5.0; p = 0.002), and over-contouring (OR = 15.3; p < 0.001). Conclusions: Overall, the complication rate of ridge augmentations carried out with autogenous or allogeneic bone blocks was low. Despite previous recommendations, over-contouring and a vertical augmentation above a threshold of 2.55 mm should be avoided.

Chitosan-Based Membranes for Skin Wound Repair in a Dorsal Fold Chamber Rat Model

Frequently, deep partial and full-thickness skin wounds do not spontaneously regenerate. To restore the normal function of skin, epidermal and dermal components have to be supplied to the wound bed by grafting various substrates. Available options are limited and frequently costly. Herein, authors present a possible approach using 3D skin scaffolds capable of mimicking structure and biological functions of the extracellular matrix, providing, in parallel, a good environment for cell attachment, proliferation and differentiation. Low-molecular weight chitosan-based membranes were prepared by freeze-drying and ionizing radiation techniques to be used as skin scaffolds. Poly (vinyl alcohol), PVA, vinyl pyrrolidone, VP, and gelatin from cold water fish were incorporated. Information regarding membranes' physical-chemical properties from SEM analysis, swelling and weight loss, together with biological response through in vitro assays (using Human Caucasian Fetal Foreskin Fibroblast) allowed the selection of an optimized batch of membranes that was used as skin scaffold in a dorsal rat model wound. The in vivo implantation assays (in Wistar rats) resulted in very promising results: (i) healing process faster than control; (ii) good vascularization; (iii) viable new tissues morphologically functional.

Sterilization of Polymeric Implants: Challenges and Opportunities

Degradable and environmentally responsive polymers have been actively developed for drug delivery and regenerative medicine applications, yet inadequate consideration of their compatibility with terminal sterilization presents notable barriers to clinical translation. This Review discusses industry-established terminal sterilization methods and aseptic processing and contrasts them with innovative approaches aimed at preserving the integrity of polymeric implants. Regulatory guidelines, fiscal considerations, and potential pitfalls are discussed to encourage early integration of sterility regulatory considerations in material designs.