Immune response to perforated and partially demineralized bone allografts

Decellularization of Massive Bone Allografts By Perfusion: A New Protocol for Tissue Engineering

In terms of large bone defect reconstructions, massive bone allografts may sometimes be the only solution. However, they are still burdened with a high postoperative complication rate. Our hypothesis is that the immunogenicity of residual cells in the graft is involved in this issue. Decellularization by perfusion might therefore be the answer to process and create more biologically effective massive bone allografts. Seventy-two porcine bones were used to characterize the efficiency of our sodium hydroxide-based decellularization protocol. A sequence of solvent perfusion through each nutrient artery was set up to ensure the complete decellularization of whole long bones. Qualitative (histology and immunohistochemistry [IHC]) and quantitative (fluoroscopic absorbance and enzyme-linked immunosorbent assay) evaluations were performed to assess the decellularization and the preservation of the extracellular matrix in the bone grafts. Cytotoxicity and compatibility were also tested. Comparatively to nontreated bones, our experiments showed a very high decellularization quality, demonstrating that perfusion is mandatory to achieve an entire decellularization. Moreover, results showed a good preservation of the bone composition and microarchitecture, Haversian systems and vascular network included. This protocol reduces the human leukocyte antigen antigenic load of the graft by >50%. The majority of measured growth factors is still present in the same amount in the decellularized bones compared to the nontreated bones. Histology and IHC show that the bones were cell compatible, noncytotoxic, and capable of inducing osteoblastic differentiation of mesenchymal stem cells. Our decellularization/perfusion protocol allowed to create decellularized long bone graft models, thanks to their inner vascular network, ready for in vivo implantation or to be further used as seeding matrices.

Three-Dimensional Scaffolds for Bone Tissue Engineering

Immobilization using external or internal splints is a standard and effective procedure to treat minor skeletal fractures. In the case of major skeletal defects caused by extreme trauma, infectious diseases or tumors, the surgical implantation of a bone graft from external sources is required for a complete cure. Practical disadvantages, such as the risk of immune rejection and infection at the implant site, are high in xenografts and allografts. Currently, an autograft from the iliac crest of a patient is considered the "gold standard" method for treating large-scale skeletal defects. However, this method is not an ideal solution due to its limited availability and significant reports of morbidity in the harvest site (30%) as well as the implanted site (5-35%). Tissue-engineered bone grafts aim to create a mechanically strong, biologically viable and degradable bone graft by combining a three-dimensional porous scaffold with osteoblast or progenitor cells. The materials used for such tissue-engineered bone grafts can be broadly divided into ceramic materials (calcium phosphates) and biocompatible/bioactive synthetic polymers. This review summarizes the types of materials used to make scaffolds for cryo-preservable tissue-engineered bone grafts as well as the distinct methods adopted to create the scaffolds, including traditional scaffold fabrication methods (solvent-casting, gas-foaming, electrospinning, thermally induced phase separation) and more recent fabrication methods (fused deposition molding, stereolithography, selective laser sintering, Inkjet 3D printing, laser-assisted bioprinting and 3D bioprinting). This is followed by a short summation of the current osteochondrogenic models along with the required scaffold mechanical properties for in vivo applications. We then present a few results of the effects of freezing and thawing on the structural and mechanical integrity of PLLA scaffolds prepared by the thermally induced phase separation method and conclude this review article by summarizing the current regulatory requirements for tissue-engineered products.

A Fresh Glimpse into Cartilage Immune Privilege

The increasing prevalence of degenerative cartilage disorders in young patients is a growing public concern worldwide. Cartilage's poor innate regenerative capacity has inspired the exploration and development of cartilage replacement treatments such as tissue-engineered cartilages and osteochondral implants as potential solutions to cartilage loss. The clinical application of tissue-engineered implants is hindered by the lack of long-term follow-up demonstrating efficacy, biocompatibility, and bio-integration. The historically reported immunological privilege of cartilage tissue was based on histomorphological observations pointing out the lack of vascularity and the presence of a tight extracellular matrix. However, clinical studies in humans and animals do not unequivocally support the immune-privilege theory. More in-depth studies on cartilage immunology are needed to make clinical advances such as tissue engineering more applicable. This review analyzes the literature that supports and opposes the concept that cartilage is an immune-privileged tissue and provides insight into mechanisms conferring various degrees of immune privilege to other, more in-depth studied tissues such as testis, eyes, brain, and cancer.

Association of Sex Mismatch Between Donor and Recipient With Graft Survivorship at 5 Years After Osteochondral Allograft Transplantation

BACKGROUND

Sex mismatch between donor and recipient has been considered a potential contributor to adverse outcomes after solid organ transplantation. However, the influence of sex mismatching in osteochondral allograft (OCA) transplantation has yet to be determined.

PURPOSE

To evaluate whether donor-recipient sex mismatching affects graft survival after OCA transplantation.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

In this review of prospectively collected data, patients who underwent OCA transplantation between November 2013 and November 2017 by a single surgeon were analyzed. Cumulative survival was assessed via the Kaplan-Meier method using log-rank tests to compare patients with similar donor groups. Multivariable Cox regression analysis adjusted for patient age, graft size, and body mass index was used to evaluate the influence of donor-recipient sex on graft survival.

RESULTS

A total of 154 patients were included: 102 (66.2%) who received OCAs from a same-sex donor and 52 (33.8%) who received OCAs from a different-sex donor. At 5-year follow-up, a significantly lower graft survival rate was observed for different-sex donor transplantation in comparison with same-sex donorship (63% vs 92%; P = .01). When correcting for age, graft size, and body mass index, donor-recipient sex-mismatch transplantation demonstrated a 2.9-times greater likelihood to fail at 5 years compared with donor-recipient same-sex transplantation (95% CI, 1.11-7.44; P = .03). A subgroup analysis showed no significant difference in graft survival between the female-to-female and female-to-male groups (91% and 84%, respectively). Conversely, male-to-male transplantation demonstrated a significantly higher cumulative 5-year survival (94%; P = .04), whereas lower survival was found with male-to-female donorship (64%; P = .04). Multivariable Cox regression indicated a 2.6-times higher likelihood of failure for the male-to-female group in comparison with the other groups (95% CI, 1.03-6.69; P = .04). Male-to-male transplantation had a tendency toward decreased likelihood of OCA failure (hazard ratio, 0.33), although without statistical significance (95% CI, 0.11-1.01; P = .052).

CONCLUSION

Mismatch between donor and recipient sex had a negative effect on OCA survival after transplantation, particularly in those cases when male donor tissue was transplanted into a female recipient.

Use of Platelet-Rich Fibrin in the Treatment of Grade 2 Furcation Defects: Systematic Review and Meta-Analysis

In periodontitis patients, furcation defects are crucial sites to regenerate due to their complex anatomy. Various modern surgical techniques and use of biomaterials have been suggested in the literature. Among all, platelet-rich fibrin (PRF) has potential in tissue regeneration thanks to its role in the release of growth factors. Therefore, the purpose of this study was to evaluate the beneficial effect of the addition of PRF to open flap debridement (OFD) or as an adjuvant to other biomaterials such as bone grafts in the treatment of grade 2 mandibular furcation defects. Systematic research was carried out on the databases Medline, Scopus, Embase, and Cochrane Library and registered on PROSPERO (CRD42020167662). According to the PICO guidelines by Cochrane, randomized trials and prospective non-randomized trials were evaluated, with a minimum follow-up period of 6 months. The inclusion criteria were the absence of systemic diseases, non-smoking patients, and a population aged from 18 to 65 years. Vertical pocket probing depth (PPD), vertical clinical attachment level (VCAL), and gingival recession (REC) were the primary outcomes. Vertical furcation depth (VFD), and the percentage of bone defect fill (%v-BDF) were considered as secondary outcomes. A meta-analysis of the primary and secondary outcomes was performed. Publication bias was assessed through a funnel plot. Eighty-four articles were initially extracted. Eight randomized clinical trials were analyzed according to the exclusion and inclusion criteria. The Quality assessment instrument (QAI) revealed four articles at low risk of bias, one at moderate, and three at high risk of bias. The metanalysis showed significant data regarding PPD, VCAL, VFD and %v-BDF in the comparison between PRF + OFD vs. OFD alone. The adjunct of PRF to a bone graft showed a significant difference for VCAL and a not statistically significant result for the other involved parameters. In conclusion, the adjunctive use of PRF to OFD seems to enhance the periodontal regeneration in the treatment of grade 2 furcation defects. The combination of PRF and bone graft did not show better clinical results, except for VCAL, although the amount of literature with low risk of bias is scarce. Further well-designed studies to evaluate the combination of these two materials are therefore needed.

Investigating the In Vitro Osteogenic Properties of the Inclusion Nanocarrier of Icariin with Beta-Cyclodextrin-Alginate

In this study, we created an inclusion nanocarrier of icariin (ICA) and β-cyclodextrin-alginate conjugate (ICA/β-CD-ALG) and determined its in vitro osteogenic ability on MC3T3-E1 cells. The morphological shape of the prepared β-CD-ALG with or without ICA was nano-sized and round. The use of β-CD-ALG achieved a sustained ICA release for up to 7 days. In vitro studies found that ICA/β-CD-ALG had a greater potential in osteogenesis on MC3T3-E1 cells compared to β-CD-ALG by exhibiting both higher alkaline phosphatase levels and the amount of calcium deposits. Moreover, ICA/β-CD-ALG greatly increased the levels of osteogenesis markers including osteocalcin (OCN) and osteopontin (OPN). Our results suggest that ICA/β-CD-ALG plays a significant role in cellular osteogenic activity.

Accelerated Osteogenic Differentiation of MC3T3-E1 Cells by Lactoferrin-Conjugated Nanodiamonds through Enhanced Anti-Oxidant and Anti-Inflammatory Effects

The purpose of this study was to investigate the effects of lactoferrin (LF)-conjugated nanodiamonds (NDs) in vitro on both anti-oxidant and anti-inflammation activity as well as osteogenic promotion. The application of LF-NDs resulted in sustained release of LF for up to 7 days. In vitro anti-oxidant analyses performed using Dichlorofluorescin diacetate (DCF-DA) assay and cell proliferation studies showed that LF (50 μg)-NDs effectively scavenged the reactive oxygen species (ROS) in MC3T3-E1 cells (osteoblast-like cells) after H₂O₂ treatment and increased proliferation of cells after H₂O₂ treatment. Treatment of lipopolysaccharide (LPS)-induced MC3T3-E1 cells with LF-NDs suppressed levels of pro-inflammatory cytokines, including interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). In addition, LF-NDs were associated with outstanding enhancement of osteogenic activity of MC3T3-E1 cells due to increased alkaline phosphatase (ALP) and calcium deposition. Our findings suggest that LF-NDs are an important substrate for alleviating ROS effects and inflammation, as well as promoting osteogenic differentiation of cells.

Structure–property relation of porous poly (l-lactic acid) scaffolds fabricated using organic solvent mixtures and controlled cooling rates and its bio-compatibility with human adipose stem cells

Thermally induced phase separation method was used to make porous three-dimensional poly (l-lactic acid) scaffolds. The effect of imposed thermal profile during freezing of the poly (l-lactic acid) in dioxane solution on the scaffold was characterized by their micro-structure, porosity (%), pore sizes’ distribution, and mechanical strength. The porosity (%) decreased considerably with increasing concentrations of poly (l-lactic acid) in the solution, while a decreasing trend was observed with increasing cooling rates. The mechanical strength increases with increase in poly (l-lactic acid) concentration and also with increase in the cooling rate for both types of solvents. Therefore, mechanical strength was increased by higher cooling rates while the porosity (%) remained relatively consistent. Scaffolds made using higher concentrations of poly (l-lactic acid; 7% and 10% w/v) in solvent showed better mechanical strength which improved relatively with increasing cooling rates (1°C–40°C/min). This phenomenon of enhanced structural integrity with increasing cooling rates was more prominent in scaffolds made from higher initial poly (l-lactic acid) concentrations. Human adipose–derived stem cells were cultured on these scaffold (7% and 10% w/v) prepared by thermally induced phase separation at all cooling rates to measure the cell proliferation efficiency as a function of their micro-structural properties. Mean pore sizes played a crucial role in cell proliferation than percent porosity since all scaffolds were >88% porous. The viability percent of human adipose tissue–derived adult stem cells increased consistently with longer periods of culture. Thus, poly (l-lactic acid) scaffolds prepared by thermally controlled thermally induced phase separation method could be a prime candidate for making ex vivo tissue-engineered grafts for surgical implantation.

Outcomes of Latarjet Versus Distal Tibia Allograft for Anterior Shoulder Instability Repair: A Matched Cohort Analysis

BACKGROUND

Anterior glenoid reconstruction with fresh distal tibia allograft (DTA) has been described for management of recurrent shoulder instability, with encouraging early outcomes; however, no comparative data with the Latarjet procedure are available.

PURPOSE

The purpose of this study was to compare the clinical outcomes between patients undergoing DTA and a matched cohort of patients undergoing Latarjet.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A review was conducted of prospectively collected data for patients with a minimum 15% anterior glenoid bone loss who underwent shoulder stabilization via either the DTA or Latarjet procedure and had a minimum follow-up of 2 years. Consecutive patients undergoing DTA were matched in a 1-to-1 format to patients undergoing Latarjet by age, body mass index, history of contact sports, and number of previous shoulder operations. Patients were evaluated pre- and postoperatively with a physical examination and the following outcome assessments: Simple Shoulder Test, visual analog scale, American Shoulder and Elbow Surgeons, Western Ontario Shoulder Instability Index, and Single Assessment Numeric Evaluation. Complications, reoperations, and episodes of recurrent instability were analyzed. Statistical analysis was performed with Student t tests, with P < .05 considered significant.

RESULTS

A total of 100 patients (50 Latarjet, 50 DTA) with a mean ± SD age of 25.6 ± 6.1 years were analyzed at 45 ± 20 months (range, 24-111) after surgery. Thirty-two patients (64%) in each group underwent prior ipsilateral shoulder surgery (range, 1-3). Patients undergoing DTA had significantly greater glenoid bone loss defects when compared with patients undergoing Latarjet (28.6% ± 7.4% vs 22.4% ± 10.3%, P = .001). Patients in both groups experienced significant improvements in all outcome scores after surgery ( P < .05 for all). No significant differences were found in postoperative scores between the Latarjet and DTA groups: visual analog scale (0.67 ± 0.97 vs 1.83 ± 2.31), American Shoulder and Elbow Surgeons (91.06 ± 8.78 vs 89.74 ± 12.66), Western Ontario Shoulder Instability Index (74.30 ± 21.84 vs 89.69 ± 5.50), or Single Assessment Numeric Evaluation (80.68 ± 7.21 vs 90.08 ± 13.39) ( P > .05 for all). However, patients in the Latarjet group had superior Simple Shoulder Test outcomes ( P = .011). There were 10 complications (10%) for the entire cohort, including 5 in the Latarjet group (3 of which required reoperation) and 5 in the DTA group (3 of which required reoperation). The overall recurrent instability rate was 1% (1 patient).

CONCLUSION

Fresh DTA reconstruction for recurrent anterior shoulder instability results in a clinically stable joint with similar clinical outcomes as the Latarjet procedure. Longer-term studies are needed to determine if these results are maintained over time.

Harnessing macrophage-mediated degradation of gelatin microspheres for spatiotemporal control of BMP2 release

Biomaterials-based approaches to harnessing the immune and inflammatory responses to potentiate wound healing hold important promise. Bone fracture healing is characterized by an acute inflammatory phase, followed by a transition to a regenerative and repair phase. In this study, we developed genipin-crosslinked gelatin microspheres designed to be preferentially degraded by inflammatory (M1) macrophages. Highly crosslinked (>90%) microspheres allowed efficient incorporation of bioactive bone morphogenetic protein 2 (BMP2), a potent stimulator of osteogenesis in progenitor cells, via electrostatic interactions. Release of BMP2 was directly correlated with degradation of the gelatin matrix. Exposure of microspheres to polarized murine macrophages showed that degradation was significantly higher in the presence of M1 macrophages, relative to alternatively activated (M2) macrophages and unpolarized controls. Microsphere degradation in the presence of non-inflammatory cells resulted in very low degradation rates. The expression of matrix metalloproteinases (MMPs) and tissue inhibitors of MMP (TIMPs) by macrophages were consistent with the observed phenotype-dependent degradation rates. Indirect co-culture of BMP2-loaded microspheres and macrophages with isolated adipose-derived mesenchymal stem cells (MSC) showed that M1 macrophages produced the strongest osteogenic response, comparable to direct supplementation of the culture medium with BMP2. Controlled release systems that are synchronized with the inflammatory response have the potential to provide better spatiotemporal control of growth factor delivery and therefore may improve the outcomes of recalcitrant wounds.

Mesenchymal Stromal Cells from the Maternal Segment of Human Umbilical Cord is Ideal for Bone Regeneration in Allogenic Setting

Umbilical cord (UC) is a discarded product from the operating theatre and a ready source of mesenchymal stromal cells (MSCs). MSCs from UC express both embryonic and adult mesenchymal stem cell markers and are known to be hypoimmunogenic and non-tumorigenic and thus suitable for allogeneic cell transplantation. Our study aimed to determine the degree of immunotolerance and bone-forming capacity of osteodifferentiated human Wharton's jelly-derived mesenchymal stromal cells (hWJ-MSCs) from different segments of UC in an allogenic setting. UCs were obtained from healthy donors delivering a full-term infant by elective Caesarean section. hWJ-MSCs were isolated from 3 cm length segment from the maternal and foetal ends of UCs. Three-dimensional fibrin constructs were formed and implanted intramuscularly into immunocompetent mice. The mice were implanted with 1) fibrin construct with maternal hWJ-MSCs, 2) fibrin construct with foetal hWJ-MSCs, or 3) fibrin without cells; the control group received sham surgery. After 1 month, the lymphoid organs were analysed to determine the degree of immune rejection and bone constructs were analysed to determine the amount of bone formed. A pronounced immune reaction was noted in the fibrin group. The maternal segment constructs demonstrated greater osteogenesis than the foetal segment constructs. Both maternal and foetal segment constructs caused minimal immune reaction and thus appear to be safe for allogeneic bone transplant. The suppression of inflammation may be a result of increased anti-inflammatory cytokine production mediated by the hWJ-MSC. In summary, this study demonstrates the feasibility of using bone constructs derived from hWJ-MSCs in an allogenic setting.

Enhancing Cell Proliferation and Osteogenic Differentiation of MC3T3-E1 Pre-osteoblasts by BMP-2 Delivery in Graphene Oxide-Incorporated PLGA/HA Biodegradable Microcarriers

Lack of bioactivity has seriously restricted the development of biodegradable implants for bone tissue engineering. Therefore, surface modification of the composite is crucial to improve the osteointegration for bone regeneration. Bone morphogenetic protein-2 (BMP-2), a key factor in inducing osteogenesis and promoting bone regeneration, has been widely used in various clinical therapeutic trials. In this study, BMP-2 was successfully immobilized on graphene oxide-incorporated PLGA/HA (GO-PLGA/HA) biodegradable microcarriers. Our study demonstrated that the graphene oxide (GO) facilitated the simple and highly efficient immobilization of peptides on PLGA/HA microcarriers within 120 min. To further test in vitro, MC3T3-E1 cells were cultured on different microcarriers to observe various cellular activities. It was found that GO and HA significantly enhanced cell adhesion and proliferation. More importantly, the immobilization of BMP-2 onto the GO-PLGA/HA microcarriers resulted in significantly greater osteogenic differentiation of cells in vitro, as indicated by the alkaline phosphate activity test, quantitative real-time polymerase chain reaction analysis, immunofluorescence staining and mineralization on the deposited substrates. Findings from this study revealed that the method to use GO-PLGA/HA microcarriers for immobilizing BMP-2 has a great potential for the enhancement of the osseointegration of bone implants.

Effectiveness of Lavage Techniques in Removing Immunogenic Elements from Osteochondral Allografts

Objective This study aimed to compare standard saline lavage to combination saline and high-pressure carbon dioxide (CO₂) lavage in removing marrow elements from osteochondral allografts. Design Six fresh hemicondyles were obtained. Three osteochondral allograft plugs (15-mm diameter, 6-mm depth) were harvested from each hemicondyle and randomized to 1 of 3 treatment arms: A, no lavage; B, 1 L standard saline lavage; C, simultaneous saline (1 L) and 1-minute high-pressure CO₂ lavage. After hematoxylin and eosin staining, a "percentage fill" of remaining marrow elements was calculated for each overall sample and then repeated in 3 distinct compartments for each sample based on depth from surface: 1, deepest third; 2, middle third; and 3, most superficial third. Trial arms B and C were compared with 1-tailed Student t tests. Results Group A had an overall percentage fill of 51.2% ± 8.8%. While both lavage techniques decreased overall remaining marrow elements, group B yielded significantly higher percentages of remaining marrow elements than group C (28.6% ± 16.5%, 14.6% ± 8.7%, P = 0.045). On depth analysis, group A exhibited homogenous filling of trabecular space (63.0% ± 15.5%, 67.6% ± 13.7%, and 55.2% ± 10.1% in zones 1, 2, and 3, respectively). Both lavage arms equally removed marrow elements from superficial zone 3 (B, 17.4% ± 9.2%; C, 15.6% ± 12.4%, P = 0.41) and middle zone 2 (B, 30.2% ± 17.7%; C, 21.4% ± 15.5%, P = 0.18). However, group C lavage removed significantly more marrow elements in deep zone 1 than group B (29.7% ± 10.9%, 58.5% ± 25.2%, P = 0.01). Conclusion Combination saline and high-pressure CO₂ lavage more effectively clears marrow elements from osteochondral allografts than saline alone.

Pulsed lavage cleansing of osteochondral grafts depends on lavage duration, flow intensity, and graft storage condition

Introduction

Osteochondral allograft (OCA) transplantation is generally effective for treating large cartilage lesions. Cleansing OCA subchondral bone to remove donor marrow elements is typically performed with pulsed lavage. However, the effects of clinical and experimental parameters on OCA marrow removal by pulsed lavage are unknown. The aim of the current study was to determine the effects on marrow cleansing in human osteochondral cores (OCs) of (1) lavage duration, (2) lavage flow intensity, and (3) OC sample type and storage condition.

Methods

OCs were harvested from human femoral condyles and prepared to a clinical geometry (cylinder, diameter = 20 mm). The OCs were from discarded remnants of Allograft tissues (OCA) or osteoarthritis patients undergoing Total Knee Replacement (OCT). The experimental groups subjected to standard flow lavage for 45 seconds (430 mL of fluid) and 120 seconds (1,150 mL) were (1) OCT/FROZEN (stored at -80°C), (2) OCT/FRESH (stored at 4°C), and (3) OCA/FRESH. The OCA/FRESH group was subsequently lavaged at high flow for 45 seconds (660 mL) and 120 seconds (1,750 mL). Marrow cleansing was assessed grossly and by micro-computed tomography (μCT).

Results

Gross and μCT images indicated that marrow cleansing progressed from the OC base toward the cartilage. Empty marrow volume fraction (EMa.V/Ma.V) increased between 0, 45, and 120 seconds of standard flow lavage, and varied between groups, being higher after FROZEN storage (86–92% after 45–120 seconds) than FRESH storage of either OCT or OCA samples (36% and 55% after 45 and 120 seconds, respectively). With a subsequent 120 seconds of high flow lavage, EMa.V/Ma.V of OCA/FRESH samples increased from 61% to 78%.

Conclusions

The spatial and temporal pattern of marrow space clearance was consistent with gradual fluid-induced extrusion of marrow components. Pulsed lavage of OCAs with consistent time and flow intensity will help standardize marrow cleansing and may improve clinical outcomes.

Distal Tibia Allograft Glenoid Reconstruction in Recurrent Anterior Shoulder Instability: Clinical and Radiographic Outcomes

PURPOSE

To assess the clinical and radiographic outcomes of patients with recurrent anterior shoulder instability treated with fresh distal tibia allograft (DTA) glenoid reconstruction.

METHODS

Consecutive patients with a minimum 15% anterior glenoid bone loss associated with recurrent anterior instability who underwent stabilization with DTA glenoid reconstruction were retrospectively reviewed. Patients were evaluated with the American Shoulder and Elbow Society score, Western Ontario shoulder instability index, and single numerical assessment evaluation score at a minimum 2 years after surgery. All patients also underwent postoperative imaging evaluation with computed tomography where graft incorporation and allograft angle were measured. Statistical analysis was performed with paired t-tests, with P < .05 considered significant.

RESULTS

A total of 27 patients (100% male) with an average age of 31 ± 5 years and an average follow-up of 45 months (range, 30-66) were included. There were significant improvements in preoperative to postoperative American Shoulder and Elbow Society score (63-91, P < .01), Western Ontario shoulder instability index (46% to 11% of normal, P < .01), and single numerical assessment evaluation score (50-90.5, P < .01) outcomes. Analysis of computed tomography data at an average 1.4 years postoperatively (available for 25 patients) showed an allograft healing rate of 89% (range, 80% to 100%), average allograft angle of 14.9° (range, 6.6° to 29.3°), and average allograft lysis of 3% (range, 0% to 25%). Grafts with lesser allograft angles (<15°) were better opposed to the anterior glenoid, showing superior healing and graft incorporation. There were no cases of recurrent instability.

CONCLUSIONS

At an average follow-up of 45 months, fresh DTA reconstruction for recurrent anterior shoulder instability results in a clinically stable joint with excellent clinical outcomes and minimal graft resorption. Optimal allograft placement resulted in superior bony incorporation with the native glenoid.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Glenoid Reconstruction With Distal Tibia Allograft for Recurrent Anterior Shoulder Instability

Anterior glenoid bone loss is present in nearly all cases of recurrent anterior glenohumeral instability. Treating glenoid bone loss in the setting of recurrent instability is challenging, and often, soft tissue stabilization procedures in isolation are inadequate. The nonanatomic, incongruous joint resulting from most bony augmentation procedures has motivated investigators to find an alternative solution. Recently, the use of fresh distal tibia allograft has been reported as an anatomic, osteoarticular reconstructive option for restoring the glenoid arc and maintaining glenohumeral congruency. This article describes the surgical technique for glenoid reconstruction with distal tibia allograft for recurrent anterior shoulder instability. [Orthopedics. 2017; 40(1):e199-e205.].

Biomaterials with Antibacterial and Osteoinductive Properties to Repair Infected Bone Defects

The repair of infected bone defects is still challenging in the fields of orthopedics, oral implantology and maxillofacial surgery. In these cases, the self-healing capacity of bone tissue can be significantly compromised by the large size of bone defects and the potential/active bacterial activity. Infected bone defects are conventionally treated by a systemic/local administration of antibiotics to control infection and a subsequent implantation of bone grafts, such as autografts and allografts. However, these treatment options are time-consuming and usually yield less optimal efficacy. To approach these problems, novel biomaterials with both antibacterial and osteoinductive properties have been developed. The antibacterial property can be conferred by antibiotics and other novel antibacterial biomaterials, such as silver nanoparticles. Bone morphogenetic proteins are used to functionalize the biomaterials with a potent osteoinductive property. By manipulating the carrying modes and release kinetics, these biomaterials are optimized to maximize their antibacterial and osteoinductive functions with minimized cytotoxicity. The findings, in the past decade, have shown a very promising application potential of the novel biomaterials with the dual functions in treating infected bone defects. In this review, we will summarize the current knowledge of novel biomaterials with both antibacterial and osteoinductive properties.

Effect of lactoferrin-impregnated porous poly(lactide-co-glycolide) (PLGA) microspheres on osteogenic differentiation of rabbit adipose-derived stem cells (rADSCs)

The aim of this study was to develop lactoferrin (LF)-impregnated porous poly(lactide-co-glycolide) (PLGA) microspheres (PMs) to induce osteogenic differentiation of rabbit adipose-derived stem cells (rADSCs). Porous PLGA PMs were fabricated by a fluidic device and their surfaces were modified with heparin-dopamine (Hep-DOPA). Then, LF (100μg, 500μg, and 1000μg) was impregnated on the surface of heparinized PMs (Hep-PMs) via electrostatic interactions to yield LF-impregnated PMs. PMs and modified PMs were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Osteogenic differentiation of rADSCs on PMs and modified PMs was demonstrated by alkaline phosphatase (ALP) activity, calcium deposition, and mRNA expression of osteocalcin and osteopontin. Successful immobilization of Hep-DOPA and LF on the surface of PMs was confirmed by XPS analysis. LF-impregnated PMs generated significantly greater ALP activity, calcium deposition, and mRNA expression of osteocalcin and osteopontin compared with PMs. These results suggested that LF-impregnated PMs effectively induced osteogenic differentiation of rADSCs.

Enhanced differentiation of human embryonic stem cells on extracellular matrix-containing osteomimetic scaffolds for bone tissue engineering

Current methods of treating critical size bone defects include autografts and allografts, however, both present major limitations including donor-site morbidity, risk of disease transmission, and immune rejection. Tissue engineering provides a promising alternative to circumvent these shortcomings through the use of autologous cells, three-dimensional scaffolds, and growth factors. We investigated the development of a scaffold with native bone extracellular matrix (ECM) components for directing the osteogenic differentiation of human embryonic stem cells (hESCs). Toward this goal, a microsphere-sintering technique was used to fabricate poly(lactic-co-glycolic acid) (PLGA) scaffolds with optimum mechanical and structural properties. Human osteoblasts (hOBs) were seeded on these scaffolds to deposit bone ECM for 14 days. This was followed by a decellularization step leaving the mineralized matrix intact. Characterization of the decellularized PLGA scaffolds confirmed the deposition of calcium, collagen II, and alkaline phosphatase by osteoblasts. hESCs were seeded on the osteomimetic substrates in the presence of osteogenic growth medium, and osteogenicity was determined according to calcium content, osteocalcin expression, and bone marker gene regulation. Cell proliferation studies showed a constant increase in number for hESCs seeded on both PLGA and ECM-coated PLGA scaffolds. Calcium deposition by hESCs was significantly higher on the osteomimetic scaffolds compared with the control groups. Consistently, immunofluorescence staining demonstrated an increased expression of osteocalcin in hESCs seeded on ECM-coated osteomimetic PLGA scaffolds. Gene expression analysis of RUNX2 and osteocalcin further confirmed osteogenic differentiation of hESCs at the highest expression level on osteomimetic PLGA. These results together demonstrate the potential of PLGA scaffolds with native bone ECM components to direct osteogenic differentiation of hESCs and induce bone formation.

The role of immunologic response in fresh osteochondral allografting of the knee

BACKGROUND

Osteochondral allografting, a restorative treatment option for articular cartilage lesions in the knee, involves transplantation of fresh osteochondral tissue with no tissue matching. Although retrieval studies have not consistently shown evidence of immunologic response, development of anti-human leukocyte antigen class I cytotoxic antibodies has been observed in allograft recipients.

HYPOTHESIS

Postallograft antibody formation is related to graft size and may affect clinical outcome.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

This study retrospectively compared 42 antibody-positive postallograft patients with 42 antibody-negative patients. Groups were matched for age, sex, and body mass index but not intra-articular disease severity. Seventeen patients (20%) were lost to follow-up. Of the remaining 67 patients (33 antibody-positive and 34 antibody-negative), average follow-up time was 50.3 months (range, 24-165 months). Mean age was 38.1 years (range, 15-68 years) with 58% being male. Graft area was categorized as small (<5 cm2), medium (5-10 cm2), or large (>10 cm2). Graft survival and Knee Society function scores were used to measure clinical outcome.

RESULTS

Of the 84 patients, 80 had graft area data. Of 27 patients with large graft area, 19 (70%) had positive postoperative antibody screens, compared with 1 of 16 (6%) with small graft area (P < .001). Graft survival rates in the antibody-positive and antibody-negative groups were 64% and 79%, respectively (P = .152). Mean postoperative Knee Society function scores in surviving antibody-positive and antibody-negative groups were 88.3 and 84.6 points, respectively (P = .482).

CONCLUSION

Antibody development after fresh, non-tissue-matched osteochondral allograft transplants in the knee appears related to graft size. No difference was observed in clinical outcome between groups. Graft survival is multifactorial, and the effect that the immunologic response has on clinical outcome merits further investigation.

VEGF-incorporated biomimetic poly(lactide-co-glycolide) sintered microsphere scaffolds for bone tissue engineering

Regenerative engineering approaches utilizing biomimetic synthetic scaffolds provide alternative strategies to repair and restore damaged bone. The efficacy of the scaffolds for functional bone regeneration critically depends on their ability to induce and support vascular infiltration. In the present study, three-dimensional (3D) biomimetic poly(lactide-co-glycolide) (PLAGA) sintered microsphere scaffolds were developed by sintering together PLAGA microspheres followed by nucleation of minerals in a simulated body fluid. Further, the angiogenic potential of vascular endothelial growth factor (VEGF)-incorporated mineralized PLAGA scaffolds were examined by monitoring the growth and phenotypic expression of endothelial cells on scaffolds. Scanning electron microscopy micrographs confirmed the growth of bone-like mineral layers on the surface of microspheres. The mineralized PLAGA scaffolds possessed interconnectivity and a compressive modulus of 402 ± 61 MPa and compressive strength of 14.6 ± 2.9 MPa. Mineralized scaffolds supported the attachment and growth and normal phenotypic expression of endothelial cells. Further, precipitation of apatite layer on PLAGA scaffolds resulted in an enhanced VEGF adsorption and prolonged release compared to nonmineralized PLAGA and, thus, a significant increase in endothelial cell proliferation. Together, these results demonstrated the potential of VEGF-incorporated biomimetic PLAGA sintered microsphere scaffolds for bone tissue engineering as they possess the combined effects of osteointegrativity and angiogenesis.

The effect of a slow mode of BMP-2 delivery on the inflammatory response provoked by bone-defect-filling polymeric scaffolds

We investigated the inflammatory response to, and the osteoinductive efficacies of, four polymers (collagen, Ethisorb, PLGA and Polyactive) that bore either an adsorbed (fast-release kinetics) or a calcium-phosphate-coating-incorporated (slow-release kinetics) depot of BMP-2. Titanium-plate-supported discs of each polymer (n = 6 per group) were implanted at an ectopic (subcutaneous) ossification site in rats (n = 48). Five weeks later, they were retrieved for a histomorphometric analysis of the volumes of ectopic bone and foreign-body giant cells (a gauge of inflammatory reactivity), and the degree of polymer degradation. For each polymer, the osteoinductive efficacy of BMP-2 was higher when it was incorporated into a coating than when it was directly adsorbed onto the material. This mode of BMP-2 carriage was consistently associated with an attenuation of the inflammatory response. For coated materials, the volume density of foreign-body giant cells was inversely correlated with the volume density of bone (r(2) = 0.96), and the volume density of bone was directly proportional to the surface-area density of the polymer (r(2) = 0.97). Following coating degradation, other competitive factors, such as the biocompatibility and the biodegradability of the polymer itself, came into play.

Biomimetic coatings for bone tissue engineering of critical-sized defects

The repair of critical-sized bone defects is still challenging in the fields of implantology, maxillofacial surgery and orthopaedics. Current therapies such as autografts and allografts are associated with various limitations. Cytokine-based bone tissue engineering has been attracting increasing attention. Bone-inducing agents have been locally injected to stimulate the native bone-formation activity, but without much success. The reason is that these drugs must be delivered slowly and at a low concentration to be effective. This then mimics the natural method of cytokine release. For this purpose, a suitable vehicle was developed, the so-called biomimetic coating, which can be deposited on metal implants as well as on biomaterials. Materials that are currently used to fill bony defects cannot by themselves trigger bone formation. Therefore, biological functionalization of such materials by the biomimetic method resulted in a novel biomimetic coating onto different biomaterials. Bone morphogenetic protein 2 (BMP-2)-incorporated biomimetic coating can be a solution for a large bone defect repair in the fields of dental implantology, maxillofacial surgery and orthopaedics. Here, we review the performance of the biomimetic coating both in vitro and in vivo.

A novel biomimetic polymer scaffold design enhances bone ingrowth

There has been recent interest in treating large bone defects with polymer scaffolds because current modalities such as autographs and allographs have limitations. Additionally, polymer scaffolds are utilized in tissue engineering applications to implant and anchor tissues in place, promoting integration with surrounding native tissue. In both applications, rapid and increased bone growth is crucial to the success of the implant. Recent studies have shown that mimicking native bone tissue morphology leads to increased osteoblastic phenotype and more rapid mineralization. The purpose of this study was to compare bone ingrowth into polymer scaffolds created with a biomimetic porous architecture to those with a simple porous design. The biomimetic architecture was designed from the inverse structure of native trabecular bone and manufactured using solid free form fabrication. Histology and muCT analysis demonstrated a 500-600% increase in bone growth into and adjacent to the biomimetic scaffold at five months post-op. This is in agreement with previous studies in which biomimetic approaches accelerated bone formation. It also supports the applicability of polymer scaffolds for the treatment of large tissue defects when implanting tissue-engineering constructs. (c) 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009.

Osteochondral allografts: state of the art

The use of osteochondral allografts to treat focal osteochondral lesions continues to gain popularity, supported by long-term results. Clinicians must be knowledgeable concerning the possible risks of disease transmission, graft rejection, infection, and graft failure to advise the patient and obtain an informed consent. With advancing scientific and clinical research, future operative indications will likely continue to expand. A significant amount of literature regarding storage methods has recently been published; it is hoped that continued research will lead to techniques for prolonged graft storage to prevent availability concerns.

Review: Mineralization of Synthetic Polymer Scaffolds for Bone Tissue Engineering

It has repeatedly been shown that demineralization improves the ability of bone auto- and allografts to regenerate natural bone tissue. Conversely, much work in the field of bone tissue engineering has used composite materials consisting of a mineralized phase or materials designed to mineralize rapidly in situ. In this review, we seek to examine these disparate roles of mineralization and the underlying factors that cause this discordance and to examine methods and principles of the mineralization of synthetic polymer scaffolds. Biomimetic approaches to mineralization and phosphorus-containing materials are highlighted, and a brief section focusing on drug-delivery strategies using mineralized scaffolds is included.

Anterior spinal arthrodesis with structural cortical allografts and instrumentation for spine tumor surgery

STUDY DESIGN

The authors report on anterior vertebral reconstruction following tumor resection with use of fresh-frozen, cortical, long-segment allografts prepared from diaphyseal sections of long bones. A retrospective analysis of clinical outcomes is presented.

OBJECTIVE

To analyze the results following the use of cortical allografts in the treatment of spine tumors.

SUMMARY OF BACKGROUND DATA

Metastatic disease and primary spinal bone tumors may result in progressive vertebral collapse, instability, deformity, pain, and neurologic deficit. Controversy as to the appropriate type of anterior reconstruction and/or graft material persists.

METHODS

From 1995 until 2001, 30 patients with primary spinal bone tumors or metastases to the spine were treated by anterior vertebral reconstruction with fresh-frozen cortical bone allografts. Grafts were used in combination with anterior and posterior instrumentation.

RESULTS

The median survival was 14 months. Ninety-three percent of all allografts were radiographically incorporated as early as 6 months after surgery in spite of adjuvant chemotherapy and radiation therapy. Fourteen patients (46%) had intraoperative or postoperative complications. Two patients underwent revision surgery for local recurrence. There were no allograft infections, fractures, or collapse.

CONCLUSION

Anterior column reconstruction with structural cortical allografts proved to be a reliable technique in patients with spine tumors. Postoperative complications can often be successfully managed.

Estudo histológico dos enxertos ósseos homólogos humanos

Devido ao crescente uso dos enxertos homólogos humanos (aloenxertos) nas cirurgias ortopédicas reconstrutivas, há a necessidade do completo conhecimento de suas características biomecânicas e histológicas. Este estudo compara, quanto às características histológicas, os enxertos de cadáver colhidos de côndilo femoral a fresco, aos criopreservados a menos 80° C por trinta dias. São comparados vinte espécimes em cada grupo, quanto aos seguintes parâmetros histológicos: viabilidade celular, presença de vascularização, necrose, manutenção da matriz óssea, processo inflamatório, remodelação óssea e fibrose. Após análise estatística utilizando o método de Fisher (p<0,05), o estudo conclui que apenas a viabilidade celular apresenta mudança significativa após a criopreservação. Os enxertos ósseos não necessitam de células viáveis para sua utilização. Logo, o processo de criopreservação é um método útil para o armazenamento dos aloenxertos em bancos de tecidos não inviabilizando seu emprego futuro nas cirurgias ortopédicas.