Gamma irradiation: effects on biomechanical properties of human bone-patellar tendon-bone allografts

Myths and Facts About Allograft Use in Anterior Cruciate Ligament Reconstruction: A Detailed Review of the Literature

» Patient-Specific Graft Selection: Graft selection for anterior cruciate ligament reconstruction (ACLR) requires a nuanced approach that considers various patient-specific factors, such as age, activity level, comorbidities, and surgical goals. Generally, allografts are preferred for older patients with less active lifestyles, whereas autografts are more suitable for younger, active patients because of autografts' lower retear rates.» Impact of Sterilization Techniques: Sterilization and processing techniques significantly affect the biomechanical properties and outcomes of allografts. While high-dose irradiation reduces allograft strength and compromises healing, low-dose irradiation or nonirradiated grafts offer superior biomechanical and clinical outcomes. However, standardized sterilization protocols are yet to be established.» Comparative Outcomes of Allografts and Autografts: Evaluating the literature on allografts vs. autografts in ACLR remains challenging because of the significant variability in patient characteristics, outcome measures, graft strength testing, and sterilization techniques across studies.

Comparison of clinical outcomes between hamstring tendon autografts and hybrid grafts in ACL reconstruction: a systematic review and meta-analysis

BACKGROUND

Hamstring tendon (HT) autografts have become a popular choice for anterior cruciate ligament (ACL) reconstruction. However, small-diameter grafts are inevitably encountered during surgery, which have poor biomechanical properties. Hybrid grafts (HGs) using an allograft combined with small diameter HT are gaining interest from surgeons.

HYPOTHESIS

There would be no difference between the HT autograft and HG in terms of failure, knee stability, and patient-reported outcomes.

STUDY DESIGN

Systematic review and meta-analysis; Level of evidence, 4.

METHODS

The PubMed, Embase, web of science and Cochrane databases were systematically searched from their inception until July 1, 2022. Clinical trials that compared HG and HT autografts were included. The quality of the included studies was assessed with the Cochrane Collaboration's risk of bias tool and the modified Newcastle-Ottawa Scale. Extracted data were pooled with fixed or random effects depending on the detected heterogeneity.

RESULTS

A total of 14 eligible studies involving 1411 patients (HT: 863; HG: 548) were included in the quantitative meta-analysis. The mean age of the patients involved ranged from 14.6 to 40.4 years. Compared to patients who received HT autografts, patients receiving HGs had similar postoperative failure rate (OR, 0.99; P = 0.97; I2 = 41%), side-to-side difference (MD, -0.16; P = 0.13; I2 = 41%), Subjective IKDC (MD, 0.51; P = 0.58; I2 = 69%), Lysholm (MD, 2.79; P = 0.1; I2 = 79%), Tegner (MD, -0.88; P = 0.56; I2 = 0%). When the available data for failure rate were analyzed by the dose of irradiation, patient age, and mean diameter of the HT, the results of subgroup analyses did not change substantially.

CONCLUSION

This review found no significant differences in failure rates, knee stability, or patient-reported outcomes between autologous HT and HG in ACLR. Surgeons should prioritize autografts of adequate size through optimized techniques and consider hybrid grafts as a last resort, considering the risks associated with allografts.

Diagnosis and treatment of anterior cruciate ligament injuries: Consensus of Chinese experts part II: Graft selection and clinical outcome evaluation

Background

In the recent decade, there has been substantial progress in the technologies and philosophies associated with diagnosing and treating anterior cruciate ligament (ACL) injuries in China. The therapeutic efficacy of ACL reconstruction in re-establishing the stability of the knee joint has garnered widespread acknowledgment. However, the path toward standardizing diagnostic and treatment protocols remains to be further developed and refined.

Objective

In this context, the Chinese Association of Orthopaedic Surgeons (CAOS) and the Chinese Society of Sports Medicine (CSSM) collaboratively developed an expert consensus on diagnosing and treating ACL injury, aiming to enhance medical quality through refining professional standards.

Methods

The consensus drafting team invited experts across the Greater China region, including the mainland, Hong Kong, Macau, and Taiwan, to formulate and review the consensus using a modified Delphi method as a standardization approach. As members of the CSSM Lower Limb Study Group and the CAOS Arthroscopy and Sports Medicine Study Group, invited experts concentrated on two pivotal issues: "Graft Selection" and "Clinical Outcome Evaluation" during the second part of the consensus development.

Results

This focused discussion ultimately led to a strong consensus on nine specific consensus terms.

Conclusion

The consensus clearly states that ACL reconstruction has no definitive "gold standard" graft choice. Autografts have advantages in healing capability but are limited in availability and have potential donor site morbidities; allografts reduce surgical trauma but incur additional costs, and there are concerns about slow healing, quality control issues, and a higher failure rate in young athletes; synthetic ligaments allow for early rehabilitation and fast return to sport, but the surgery is technically demanding and incurs additional costs. When choosing a graft, one should comprehensively consider the graft's characteristics, the doctor's technical ability, and the patient's needs. When evaluating clinical outcomes, it is essential to ensure an adequate sample size and follow-up rate, and the research should include patient subjective scoring, joint function and stability, complications, surgical failure, and the return to sport results. Medium and long-term follow-ups should not overlook the assessment of knee osteoarthritis.

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.

Comparison of failure rates and functional outcomes between hamstring autografts and hybrid grafts in anterior cruciate ligament reconstruction: A systematic review and meta-analysis

BACKGROUND

The viability of augmenting small-diameter hamstring autografts with allografts remains unclear. Recent studies have reported different clinical results after allograft augmentation. Hence, we sought to determine whether hamstring autografts and hybrid grafts differed in terms of failure rates and functional outcomes after anterior cruciate ligament (ACL) reconstruction. We also evaluated whether the results of the comparisons differed based on allograft sterilization methods.

PATIENTS AND METHODS

This systematic review and meta-analysis were performed by searching the PubMed, Cochrane Library, and EMBASE databases to identify prospective or retrospective studies (evidence levels 1, 2, or 3) that compared the failure rates and functional outcomes of ACL reconstruction using autografts and hybrid grafts.

RESULTS

We identified 15 relevant studies, including 1,521 patients, with 798 and 723 treated using autografts and hybrid grafts, respectively. Fourteen studies were retrospective comparative studies, and one was a prospective randomized controlled trial. Of these, three studies used non-irradiated allografts. In the analysis of all participants, no significant differences in failure rates and subjective International Knee Documentation Committee (IKDC) scores were observed between the autograft and hybrid graft groups. Comparing the autograft and hybrid graft groups that used non-irradiated allografts, no differences in the failure rates and subjective IKDC scores were also noted. Meanwhile, in the groups that used irradiated allograft, the autograft group demonstrated higher Lysholm knee scores and reduced anterior laxity than the hybrid graft group.

DISCUSSION

Overall, ACL reconstruction using hybrid grafts may not reduce failure rates compared to reconstructions using hamstring autografts, although hybrid grafts with irradiation may decrease functional outcomes.

LEVEL OF EVIDENCE

III; systematic review of level II and III studies.

Current trends in graft choice for anterior cruciate ligament reconstruction - part I: anatomy, biomechanics, graft incorporation and fixation

Graft selection in anterior cruciate ligament (ACL) reconstruction is critical, as it remains one of the most easily adjustable factors affecting graft rupture and reoperation rates. Commonly used autografts, including hamstring tendon, quadriceps tendon and bone-patellar-tendon-bone, are reported to be biomechanically equivalent or superior compared to the native ACL. Despite this, such grafts are unable to perfectly replicate the complex anatomical and histological characteristics of the native ACL. While there remains inconclusive evidence as to the superiority of one autograft in terms of graft incorporation and maturity, allografts appear to demonstrate slower incorporation and maturity compared to autografts. Graft fixation also affects graft properties and subsequent outcomes, with each technique having unique advantages and disadvantages that should be carefully considered during graft selection.

Allografts: expanding the surgeon's armamentarium

In Germany, bone allografts are widely used and their application in clinics has increased over the years. Successful use of allografts depends on many factors such as the procurement, processing, sterilization and the surgeon's surgical experience. Tissue banks have provided safe and sterile allografts for decades ranging from hard to soft tissue. Allografts are obtained from various tissues such as bone, tendon, amniotic membrane, meniscus and skin. An advantage of allografts is their wide applicability that has never been limited by indication restrictions thus providing a huge benefit for surgeon's. The use of the correct allograft in different indications is extremely important. Thereby surgeons have access to various allograft forms such as mineralized, demineralized, freeze-dried, paste, powder, chips strips and putty. The vast options of allografts allow surgeon's to use allografts in indications they deem fit. Currently, the application of allografts is at the discretion of the expert surgeon. However, regulations are often changed locally or internationally and may impact/limit allograft use to certain indications. Here, we report the different indications where our peracetic acid (PAA) sterilised bone allografts were used as well as general literature on bone allograft use in other indications.

Effects of Chemical Sterilization and Gamma Irradiation on the Biochemical and Biomechanical Properties of Human Tendon Allografts In Vitro Study

Objective

Pre‐implantation sterilization procedures for tendons are important measures to reduce the risk of disease transmission, however these procedures may compromise tendon microarchitecture and biomechanical properties to varying degrees. We explore the effects of different sterilization procedures on the micro‐histology, biomechanical strength and biochemical properties of human tendon allografts in vitro study.

Methods

The tendon allografts were harvested from cadaveric donors after the donors were serologically screened by antibody or nucleic acid testing of infectious agents. All samples were divided into five groups, which were fresh‐frozen group (control group), 15 kGy gamma irradiation group, 25 kGy gamma irradiation group, 70% ethanol group, and peracetic acid‐ethanol group. Each group included 10 tendons for testing. Histological staining and transmission electron microscopy were applied to observe the internal structure and arrangement of tendon collagen fibers, while the machine learning classifier was trained to distinguish the darker cross‐sections of collagen fibers and brighter backgrounds of the electron micrograph to detect the distribution of diameters of tendon collagen fibers. The viscoelasticity, mechanical properties and material properties of tendon allografts were examined to detect the influence of different intervention factors on the biomechanical properties of tendons.

Results

Histological staining and transmission electron microscopy showed that the structure of fresh‐frozen tendons was similar to the structures of other experimental groups, and no obvious fiber disorder or delamination was observed. In the uniaxial cyclic test, the cyclic creep of 25 kGy irradiation group (1.5%) and peracetic acid‐ethanol group (1.5%) were significantly lower than that of the control group (3.6%, F = 1.52, P = 0.039) while in the load‐to‐failure test, the maximum elongation and maximum strain of the peracetic acid‐ethanol group were significantly higher than those of the control group (F = 4.60, P = 0.010), and there was no significant difference in other biomechanical indicators. According to the experimental results of denatured collagen, it could be seen that no matter which disinfection procedure was used, the denaturation of the tendon sample would be promoted (F = 1.97, P = 0.186), and high‐dose irradiation seemed to cause more damage to collagen fibers than the other two disinfection procedures (296.2 vs 171.1 vs 212.9 μg/g).

Conclusion

Biomechanical experiments and collagen denaturation tests showed that 15 kGy gamma irradiation and 70% ethanol can preserve the biomechanical strength and biochemical properties of tendons to the greatest extent, and these two sterilization methods are worthy of further promotion.

Comparison of clinical outcomes of using the nonirradiated and irradiated allograft for anterior cruciate ligament (ACL) reconstruction: A systematic review update and meta-analysis

BACKGROUND

This study was a systematic review comparing the clinical outcomes of using the nonirradiated and irradiated allograft for anterior cruciate ligament (ACL) reconstruction.

METHODS

A comprehensive literature search was conducted using multiple databases, including Medline, Embase, and Cochrane. All databases were searched from the earliest records through August 2019 using the following Boolean operators: irradiated AND nonirradiated AND ACL AND allograft. All prospective and retrospective controlled trials were retrieved that directly compared physical examination and knee function scores and patient-rated outcomes between the nonirradiated and irradiated allograft for ACL reconstruction.

RESULTS

Three prospective and 2 retrospective articles were identified by the search, and the findings suggested that the nonirradiated allografts were superior to the irradiated allografts based on improved knee joint functional scores and decreased failure rate, even though there was no significantly difference with respect to overall IKDC, range of motion, vertical jump test, and one-leg hop test.

CONCLUSIONS

Irradiated allograft should be limited to be used in ACL surgery and further research into new alternative sterilization techniques are needed to avoiding the disease transmission without interference with the biomechanical properties of the grafts.

Biocomponentes à base de hidroxiapatita: Influência da esterilização na resistência mecânica

Objetivo O objetivo deste estudo foi avaliar a influência da esterilização na resistência mecânica à compressão e flexão de biocomponentes à base de hidroxiapatita obtida a partir de osso bovino liofilizado e sua associação com quitosana.

Métodos O osso bovino liofilizado foi processado em partículas de 100 μm e misturado à quitosana em proporção de 50% de seu peso. A mistura foi acondicionada em moldes metálicos para preparo dos espécimes e esterilizada a 127°C em autoclave para posterior experimentação. Os espécimes foram submetidos a ensaios de compressão e flexão seguindo a norma 5833 da International Organization for Standardization (ISO); os espécimes eram blocos cilíndricos de 6 × 12 mm (para ensaios de compressão) e placas de 75 × 10 × 3,3 mm (para ensaios de flexão). As amostras foram divididas em quatro grupos de 20 espécimes cada, sendo 10 para ensaios de compressão e 10 para ensaios de flexão. Três grupos foram esterilizados (por autoclavagem, raios gama e óxido de etileno), enquanto o quarto grupo (controle) não foi. Os testes mecânicos obtidos nos diferentes processos de esterilização foram comparados por análise de variância (ANOVA, p < 0,05) seguido pelo teste de comparação múltipla de médias de Tukey, com intervalo de confiança de 95%.

Resultados Os espécimes apresentaram resistências médias à compressão de 10,25 MPa para o grupo de controle e 3,67 MPa, 9,65 MPa e 9,16 MPa após esterilização com óxido de etileno, raios gama e autoclavagem, respectivamente. Os resultados do teste de flexão mostraram uma resistência média de 0,40 MPa no grupo de controle, e 0,15 MPa, 0,17 MPa e 0,30 MPa após esterilização com óxido de etileno, raios gama e autoclavagem, respectivamente. A compressão máxima observada no grupo esterilizado com óxido de etileno foi estatisticamente diferente à obtida no grupo de controle (p = 0,0002), esterilizado com raios gama (p = 0,0003) e autoclavado (p = 0,0006). A flexão máxima dos espécimes esterilizados com raios gama foi estatisticamente diferente à observada no grupo de controle (p = 0,0245). No entanto, a resistência à flexão foi baixa em todos os espécimes.

Conclusão A esterilização em autoclave não foi associada a diferenças estatisticamente significativas nos testes de compressão ou flexão. Assim, a autoclave foi a melhor opção de esterilização para os biocomponentes à base de hidroxiapatita neste estudo.

Peracetic Acid-Ethanol Processed Human Tendon Allograft: A Morphological, Biochemical, and Biomechanical Study In Vitro

OBJECTIVE

To clarify the morphological, biochemical, and biomechanical effects of peracetic acid-ethanol sterilization processing to human hamstring tendon allografts for different time periods.

METHODS

Thirty-two fresh-frozen human hamstring tendon allografts obtained from an allograft supplier were prepared and incubated in peracetic acid-ethanol solution (PES) containing 1% v/v peracetic acid and 24% v/v ethanol. Specimens were randomly classified into four groups according to the PES processing time (untreated as the control group, 30 min as the PES30 group, 120 min as the PES120 group, and 240 min as the PES240group). Light microscopy with hematoxylin-eosin and toluidine blue were performed, along with transmission electron microscopy (TEM) to measure the collagen fibril diameters and their distributions, from which the collagen fibril index (CFI) and mass average diameter (MAD) were calculated. The thermal stability and collagen denaturation were analyzed by differential scanning calorimetry (DSC) and collagen denaturation test by α-chymotrypsin. Cyclic loading and failure testing were applied on five tendons from each group, from which the cyclic creep strain, elastic modulus, maximum stress, maximum strain, and strain energy density were calculated.

RESULTS

Tendons in the control, PES30, PES120 groups showed similar regularly aligned collagen fibers in light microscopy images, while the images from the PES240 group revealed relatively disordered and heterogeneous collagen bundles with larger interfiber spaces. TEM analysis showed that the mean diameter (F = 3.09, P = 0.04) was lower in the PES120 group (87.15 ± 4.76 nm) than it was in the control group (99.39 ± 9.19 nm) but not statistically (P = 0.05). Moreover, the CFI value in the PES30 group (65.37 ± 4.14%) was the lowest among groups (all P ≤ 0.01), while no variance existed in density and MAD among groups (F = 2.09, P = 0.13, and F = 0.27, P = 0.85, respectively). The onset temperature (H = 8.74, P = 0.03) and peak temperature (H = 9.97, P = 0.02) were decreased in the PES30 group compared to the control group (P = 0.02 and P = 0.01, respectively), but there were no differences in enthalpy of denaturation among groups (F = 2.20, P = 0.17). The collagen denaturation test revealed lower hydroxyproline concentrations in PES-treated specimens with no statistical differences among groups (H = 8.86, P = 0.07). The maximum stress showed variance (F = 10.52, P < 0.01) that it was higher in PES30 group (68.29 ± 10.86 MPa) compared to the PES120 and the PES240 group, while it was lower in the PES120 group (19.40 ± 4.94 MPa) compared to the control and the PES30 group (all P < 0.05). The strain energy density (F = 7.34, P < 0.01) was over 4 times higher in the PES30 group (7.39 ± 2.51 MPa) than it was in the PES120 group (1.56 ± 0.64 MPa, P < 0.01).

CONCLUSION

PES treatment for 30 min has no adverse effect on the properties of human hamstring tendon allografts, longer processing time could not promise better properties preservation.

Influence of peracetic acid-ethanol sterilisation on the biomechanical properties of human meniscus transplants

Purpose

Meniscus allograft transplantation (MAT) is a possible treatment for patients suffering with pain after meniscectomy. Here, peracetic acid (PAA) sterilised meniscus transplants were investigated on whether they would provide an adequate alternative to fresh-frozen transplants in their viscoelastic and mechanical properties.

Methods

In this analysis, 31 menisci donors (26 male and 5 female) were included. The average donor age was 49.87 years, ranging from 32 to 65 years. Menisci of matched pairs of knees underwent chemical sterilisation while counterparts were left fresh-frozen. Stiffness and load to failure were determined via suture retention. Further menisci were analysed while attached to the tibial bone block using a novel test device to mimic physiological load distribution. Meniscus relaxation, stiffness and failure loads were determined. Histology and biphasic properties of the menisci were examined and results were analysed using paired t-tests.

Results

A novel custom built test device allowed the application of physiological loads for suture retention testing and revealed no significant differences between PAA sterilised (14.85 ± 4.46 N/mm, 50.49 ± 17.01 N) and fresh-frozen (18.26 ± 4.46 N/mm, 59.49 ± 21.07 N) regarding stiffness and failure load, respectively. Furthermore, initial 200 N loading showed significantly higher strain in sterilised menisci (18.87 ± 1.56) compared to fresh frozen (13.81 ± 1.04). Load relaxation experiments demonstrated significantly lower relaxation for sterilised menisci (77.71 ± 1.62) compared to fresh-frozen (89.11 ± 1.00, p-value < 0.0001).

Conclusion

Peracetic acid sterilised human menisci performed equally to fresh-frozen counterparts in a suture retention test and in physiological failure testing providing an adequate alternative. However, meniscus relaxation, biphasic properties and strain were shown to be significantly different between the groups. A common problem of MAT is graft extrusion or shrinkage, therefore the parameters measured here should be considered and may influence meniscus extrusion after transplantation.

Level of evidence

n/a (experimental study)

The Influence of Radiation on Bone and Bone Cells-Differential Effects on Osteoclasts and Osteoblasts

The bone is a complex organ that is dependent on a tight regulation between bone formation by osteoblasts (OBs) and bone resorption by osteoclasts (OCs). These processes can be influenced by environmental factors such as ionizing radiation (IR). In cancer therapy, IR is applied in high doses, leading to detrimental effects on bone, whereas radiation therapy with low doses of IR is applied for chronic degenerative and inflammatory diseases, with a positive impact especially on bone homeostasis. Moreover, the effects of IR are of particular interest in space travel, as astronauts suffer from bone loss due to space radiation and microgravity. This review summarizes the current state of knowledge on the effects of IR on bone with a special focus on the influence on OCs and OBs, as these cells are essential in bone remodeling. In addition, the influence of IR on the bone microenvironment is discussed. In summary, the effects of IR on bone and bone remodeling cells strongly depend on the applied radiation dose, as differential results are provided from in vivo as well as in vitro studies with varying doses of IR. Furthermore, the isolated effects of IR on a single cell type are difficult to determine, as the bone cells and bone microenvironment are building a tightly regulated network, influencing on one another. Therefore, future research is necessary in order to elucidate the influence of different bone cells on the overall radiation-induced effects on bone.

Comparing Hamstring Autograft With Hybrid Graft for Anterior Cruciate Ligament Reconstruction: A Systematic Review

PURPOSE

To systematically review the literature in an effort to compare the demographics and clinical outcomes of patients undergoing anterior cruciate ligament reconstruction (ACLR) with a hamstring tendon autograft (HT) versus an irradiated or nonirradiated hybrid autograft-allograft.

METHODS

A systematic review of the PubMed, Cochrane Library, and Embase databases was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. All English-language literature that reported general demographics and compared the clinical outcomes of patients undergoing primary ACLR with autograft versus hybrid graft (HG) with a minimum 2-year follow-up was reviewed by 2 independent reviewers. Search terms used were "anterior cruciate ligament" and "hybrid graft." Patients were assessed based on graft failure, anteroposterior laxity, and patient-reported outcomes (Knee Injury and Osteoarthritis Outcome Score, visual analog scale, Subjective International Knee Documentation Committee score, Lysholm, and Tegner scores). Study quality was evaluated with the Modified Coleman Methodology Score and ROBINS-I risk of bias tool.

RESULTS

Twelve studies (1 level II, 11 level III) met inclusion criteria (follow-up, 2.0-8.9 years), including 471 patients undergoing ACLR with an irradiated hybrid graft (IH), 89 patients with a nonirradiated hybrid graft, and 829 patients with HT. Graft diameter ranged from 7.5 to 10.0 mm and from 6.5 to 10.0 mm in HG and HT patients, respectively. Overall, graft failure ranged from 0% to 30.0% and from 0% to 28.3% in HG and HT patients, respectively (I² = 35.9%; 95% confidence interval 0%-74.8%). Among HG patients, graft failure ranged from 0%-30.0% and from 2.4%-4.2% in IH and nonirradiated hybrid graft groups, respectively (I² = 33.6%; 95% confidence interval, 0%-71.8%). Results for postoperative anteroposterior laxity and patient-reported outcomes were also inconsistent.

CONCLUSIONS

Patients undergoing ACLR with HT demonstrate inconsistent differences in clinical outcomes at midterm follow-up compared with IH patients.

LEVEL OF EVIDENCE

III, systematic review of level II and III studies.

Effects of SCCO2, Gamma Irradiation, and Sodium Dodecyl Sulfate Treatments on the Initial Properties of Tendon Allografts

Sterile and decellularized allograft tendons are viable biomaterials used in reconstructive surgeries for dense connective tissue injuries. Established allograft processing techniques including gamma irradiation and sodium dodecyl sulfate (SDS) can affect tissue integrity. Supercritical carbon dioxide (SCCO₂) represents a novel alternative that has the potential to decellularize and sterilize tendons with minimized exposure to denaturants, shortened treatment time, lack of toxic residues, and superior tissue penetration, and thus efficacy. This study attempted to develop a single-step hybrid decellularization and sterilization protocol for tendons that involved SCCO₂ treatment with various chemical additives. The processed tendons were evaluated with mechanical testing, histology, scanning electron microscopy (SEM), and Fourier-transform infrared (FTIR) spectroscopy. Uniaxial mechanical testing showed that tendons treated with SCCO₂ and additive NovaKill^TM Gen2 and 0.1% SDS had significantly higher (p < 0.05) ultimate tensile stress (UTS) and Young's modulus compared to gamma-irradiated and standard-SDS-treated tendons. This was corroborated by the ultrastructural intactness of SCCO₂-treated tendons as examined by SEM and FTIR spectroscopy, which was not preserved in gamma-irradiated and standard SDS-treated tendons. However, complete decellularization was not achieved by the experimented SCCO₂-SDS protocols used in this study. The present study therefore serves as a concrete starting point for development of an SCCO₂-based combined sterilization and decellularization protocol for allograft tendons, where additive choice is to be optimized.

Regeneration of skeletal system with genipin crosslinked biomaterials

Natural biomaterials, such as collagen, gelatin, and chitosan, are considered as promising candidates for use in tissue regeneration treatment, given their similarity to natural tissues regarding components and structure. Nevertheless, only receiving a crosslinking process can these biomaterials exhibit sufficient strength to bear high tensile loads for use in skeletal system regeneration. Recently, genipin, a natural chemical compound extracted from gardenia fruits, has shown great potential as a reliable crosslinking reagent, which can reconcile the crosslinking effect and biosafety profile simultaneously. In this review, we briefly summarize the genipin extraction process, biosafety, and crosslinking mechanism. Subsequently, the applications of genipin regarding aiding skeletal system regeneration are discussed in detail, including the advances and technological strategies for reconstructing cartilage, bone, intervertebral disc, tendon, and skeletal muscle tissues. Finally, based on the specific pharmacological functions of genipin, its potential applications, such as its use in bioprinting and serving as an antioxidant and anti-tumor agent, and the challenges of genipin in the clinical applications in skeletal system regeneration are also presented.

Verwendung von Allografts

Humanes Spendergewebe stellt einen integralen Bestandteil der Versorgung von muskuloskeletalen Erkrankungen des Menschen dar, wie beispielsweise die Rekonstruktion von Bandverletzungen, ausgedehnten osteochondralen Defekten oder ossären Defektaufbauten. Hierbei kommen verschiedene Gewebearten, Knochen, Sehnen, Bänder, Knorpel in zellfreier und vitaler zellbasierter Darreichungsform zur Anwendung. In vielen Ländern der Welt haben sich diese Verfahren als Standardtherapie in der rekonstruktiven arthroskopischen Chirurgie etabliert. In deutschsprachigen europäischen Ländern ist deren Anwendung jedoch limitiert, da hier Rechtsvorschriften existieren, die der Sicherheit des Patienten dienen, den Einsatz dieser Gewebe allerdings teilweise erschweren. Dieser Beitrag soll einen Überblick über die aktuellen Anforderungen und Voraussetzungen in Österreich, Deutschland und der Schweiz geben sowie dem Kliniker eine Anleitung für die aktuellen Möglichkeiten der rechtskonformen Nutzung von humanem Spendergewebe zu therapeutischen Zwecken bieten.

[Progress of sterilization and preservation methods for allografts in anterior cruciate ligament reconstruction]

OBJECTIVE

To review the current status and progress of sterilization and preservation for allograft in anterior cruciate ligament reconstruction.

METHODS

The related literature about the sterilization and preservation of allografts in anterior cruciate ligament reconstruction was extensively reviewed and summarized.

RESULTS

There are many sterilization methods for allografts, the most commonly used method is γ-ray irradiation, but the optimal irradiation dose is still unclear. Electron beam irradiation is also available, but excessive dose is harmful to graft shaping. A combined sterilization method combining physics and chemistry methods is still being explored. Cryopreservation is the most commonly used method of preservation. In order to reduce the influence of crystals, the principle of "slow cooling and rapid rewarming" should be adhered to as far as possible.

CONCLUSION

The processing methods of allograft can affect the effectiveness of anterior cruciate ligament reconstruction. The clinical doctors should consider the sterilization and preservation methods in practice.

Allograft for knee ligament surgery: an American perspective

PURPOSE

Allografts are frequently use for ligamentous reconstruction at the knee. In the United States, tissue donation and distribution are highly regulated processes with thorough oversight from private and government entities. Allograft is widely available in the United States and allograft procurement is a large industry with varying procurement, sterilization, processing, and distribution procedures. It is important to understand allograft regulation and processing which may affect graft mechanical properties and biological graft integration.

METHODS

English-language literature, United States government and regulatory agency statues pertaining to allograft procurement, distribution, and usage were reviewed and the findings summarized.

RESULTS

During the processing of allograft, multiple factors including sterilization procedures, irradiation, storage conditions, and graft type all affect the biomechanical properties of the allograft tissue. Biological incorporation and ligamentization of allograft does occur, but at a slower rate compared with autograft. For ligamentous reconstruction around the knee, allograft offers shorter operative time, no donor-site morbidity, but has shown an increased risk for graft failure compared to autograft.

CONCLUSION

This article reviews the regulations on graft tissue within the United States, factors affecting the biomechanics of allograft tissue, differences in allograft tissue choices, and the use of allograft for anterior cruciate ligament reconstruction and multiligamentous knee injury reconstruction.

LEVEL OF EVIDENCE

V.

The use of allograft tendons in primary ACL reconstruction

PURPOSE

Graft choice in primary anterior cruciate ligament (ACL) reconstruction remains controversial. The use of allograft has risen exponentially in recent years with the attraction of absent donor site morbidity, reduced surgical time and reliable graft size. However, the published evidence examining their clinical effectiveness over autograft tendons has been unclear. The aim of this paper is to provide a current review of the clinical evidence available to help guide surgeons through the decision-making process for the use of allografts in primary ACL reconstruction.

METHODS

The literature in relation to allograft healing, storage, sterilisation, differences in surgical technique and rehabilitation have been reviewed in addition to recent comparative studies and all clinical systematic reviews and meta-analyses.

RESULTS

Early reviews have indicated a higher risk of failure with allografts due to association with irradiation for sterilisation and where rehabilitation programs and post-operative loading may ignore the slower incorporation of allografts. More recent analysis indicates a similar low failure rate for allograft and autograft methods of reconstruction when using non-irradiated allografts that have not undergone chemically processing and where rehabilitation has been slower. However, inferior outcomes with allografts have been reported in young (< 25 years) highly active patients, and also when irradiated or chemically processed grafts are used.

CONCLUSION

When considering use of allografts in primary ACL reconstruction, use of irradiation, chemical processing and rehabilitation programs suited to autograft are important negative factors. Allografts, when used for primary ACL reconstruction, should be fresh frozen and non-irradiated. Quantification of the risk of use of allograft in the young requires further evaluation.

LEVELS OF EVIDENCE

III.

Irradiation sterilization used for allogenetic tendon: a literature review of current concept

Tendon injury is a very common type of sports trauma, and its incidence has increased over the past decades. Surgical reconstruction with tendon allograft has been increasingly used to restore the motor function and stability of the injured site. However, the risk of disease transmission caused by allogeneic tendon transplantation has been a major problem for tissue bank researchers and clinicians. In order to eliminate the risk of disease transmission, a process of terminal sterilization is necessary. Ionizing irradiation, including gamma irradiation and electron beam irradiation is the most commonly used method for the terminal sterilization, which has been widely proved to be able to effectively inactivate the contained pathogens. Nevertheless, some accompanying damage to the mechanical and histological properties of collagen fibers in tendons will be caused. Therefore, more and more studies have begun to pay attention to the protective effect of radiation protection agents, including the radical scavengers and cross-linking agents, in the irradiation sterilization of allogeneic tendons.

Autograft or Allograft? Irradiated or Not? A Contrast Between Autograft and Allograft in Anterior Cruciate Ligament Reconstruction: A Meta-analysis

PURPOSE

To compare the clinical outcomes and adverse events associated with irradiated and nonirradiated allografts in anterior cruciate ligament (ACL) reconstruction.

METHODS

PubMed, Web of Science, and EMBASE were searched for randomized controlled trials from January 1990 to March 2018 to compare autograft with allograft in ACL reconstruction. Both objective and subjective outcomes of the function and adverse events were meta-analyzed. Two comparisons were summarized: (1) autograft and nonirradiated allograft and (2) autograft and irradiated allograft. The bias risk was based on the Cochrane Handbook for Systematic Reviews of Interventions. The overall risk ratio or weighted mean difference was calculated using a fixed- or random-effects model. Heterogeneity between studies was evaluated by the Q and the I² statistics.

RESULTS

Eleven trials were included in this review for meta-analysis. A total of 1,172 patients were involved (465 autograft and 461 nonirradiated allograft; 141 autograft and 138 irradiated allograft patients). The average follow-up varied from 2 to >10 years. The mean patient age varied from 22 to 32.8 years. The total failure rate was 2.5%. Our analyses demonstrated better clinical outcomes in autograft than irradiated allograft, which could be observed clearly through the International Knee Documentation Committee score (3.84; 95% confidence interval [CI], 1.93-5.76; P < .0001; I² = 0%), Lysholm score (2.94; 95% CI, 0.66-5.22; P = .01; I² = 0%), and Tegner score (0.14; 95% CI, -0.08 to 0.36; P = .22; I² = 0%) with fewer adverse events 0.20 (95% CI, 0.11-0.39; P < .00001; I² = 0%). There were no significant differences in autograft and nonirradiated allograft groups (P = .47, P = .27, P = .24, and P = .24, respectively).

CONCLUSIONS

Autograft offered greater advantages in functional outcomes and adverse events than irradiated allograft in ACL reconstruction; however, there were no significant differences between autograft and nonirradiated allograft in ACL reconstruction.

LEVEL OF EVIDENCE

Level II, meta-analysis of Level I and Level II studies.

Effect of x-rays and gamma radiations on the bone mechanical properties: literature review

The bone auto grafting, isografting, allografting and xenografting are used for defective bone replacement or treatment in almost all living species. The X-ray and Gamma (electromagnetic radiation) sterilization performed on the donor bone graft to prevent toxicity or migration of virus/bacterial infections from donors to reciver. Conversely, X-ray and Gamma radiation deteriorates the bone mechanical properties and bone become more susceptible to fracture. Fracture toughness as well as other mechanical properties of bone change with these radiations. In this literature review the effect of the X-rays and Gamma radiation on bone mechanical properties are discussed. All relevant literature was reviewed. After reviewing the literature only the research relating to the effect of X-rays and Gamma radiations on bone mechanical properties are included. Literature studies showed significant effect of the X-rays and Gamma radiations on the mechanical properties of the bones. In some studies the differences exists on the doses of radiations which were discussed in this study. The high energetic electromagnetic radiation (X-rays and Gamma radiations) changed/modify the collagen network of the bone, which reduced the mechanical properties of bone; however these changes depend on the radiation dose.

A Single Bundle Anterior Cruciate Ligament Reconstruction (ACL-R) Using Hamstring Tendon Autograft and Tibialis Anterior Tendon Allograft: A Comparative Study

The main purpose of this study was to compare the clinical outcomes of patients undergoing a single bundle anterior cruciate ligament reconstruction (ACL-R) of using quadrupled hamstring (4HT) autografts and two-strand tibialis anterior (2TA) allografts, and to find out the rate of graft failure and possible causes. We hypothesized that there would be no difference in the clinical outcome, and graft failure would be associated with the use of small sized allograft in young active males with high demand of sports activities. We retrospectively evaluated 222 patients (male, n=167, female, n=55) undergoing ACL-R between January 2010 and July 2014. Of 222 patients, 115 were included in the 4HT autograft group and 107 patients in the 2TA allograft group. Inclusion criteria were primary unilateral ACL-R with a minor MCL (<grade II) injury with or without meniscus tear and had at least 2.5 years of follow-up. Subjective evaluation was performed using Tegner-Lysholm score, modified Cincinnati knee score, and IKDC knee form. Anteroposterior laxity was assessed using ADT and Lachman test whereas rotational laxity was assessed using pivot shift test. Similarly, functional assessment was performed using range of motion (ROM), Daniel's one-leg hop test, and overall IKDC score. Clinical outcomes were satisfactory and comparable in both groups with no statistically significant difference in all the respective parameters. No statistically significant difference was observed in graft re-rupture rate. However, most graft failures occurred in young active males with high demand of sports activities, graft size smaller than 8 mm, and use of allograft. An autograft with at least 8 mm diameter should be considered in a young active male with high demand of sports activities to avoid graft failure.

Limited field radiation therapy results in decreased bone fracture toughness in a murine model

Fragility fractures are a well-known complication following oncologic radiotherapy, and it is suspected that radiation-induced embrittlement of bone within the treatment field may contribute to fracture risk. To explore this phenomenon, a mouse model (BALB/cJ) of fractionated, limited field, bilateral hindlimb irradiation (4x5 Gy) was used. The effects of radiation on femoral (cortical) bone fracture toughness, morphology, and biochemistry-including advanced glycation end products (AGEs)-were quantified and compared to Sham group samples prior to irradiation and at 0, 4, 8, and 12 weeks post-irradiation. Additionally, alterations to bone fracture toughness mediated directly by radiation (independent of cellular mechanisms) were determined using devitalized mouse cadaver femurs. Finally, the contribution of AGEs to reduced fracture toughness was examined by artificially ribosylating mouse femurs ex vivo. These data demonstrate that in vivo irradiation results in an immediate (-42% at 0 weeks, p < 0.001) and sustained (-28% at 12 weeks, p < 0.001) decrease in fracture toughness with small changes in morphology (-5% in cortical area at 12 weeks), and minimal changes in bone composition (tissue mineral density, mineral:matrix ratio, and AGE content). Irradiation of devitalized femurs also reduced fracture toughness (-29%, p < 0.001), but to a lesser extent than was seen in vivo. While artificial ribosylation decreased fracture toughness with time, the extent of glycation needed to induce this effect exceeded the AGE accumulation that occurred in vivo. Overall, hindlimb irradiation induced a substantial and sustained decrease in bone fracture toughness. Approximately half of this decrease in fracture toughness is due to direct radiation damage, independent of cellular remodeling. Collagen glycation in vivo was not substantially altered, suggesting other matrix changes may contribute to post-radiotherapy bone embrittlement.

Effect of 3 Preservation Methods (Freezing, Cryopreservation, and Freezing + Irradiation) on Human Menisci Ultrastructure: An Ex Vivo Comparative Study With Fresh Tissue as a Gold Standard

BACKGROUND

Three main meniscus preservation methods have been advocated: freezing (-80°C), freezing with gamma irradiation (-80°C + 25 kGy), and cryopreservation (-140°C).

HYPOTHESIS

All preservation methods will result in structural and architectural properties similar to those of fresh meniscus, defined as the gold standard.

STUDY DESIGN

Controlled laboratory study.

METHODS

Five human intact menisci were collected from 5 patients undergoing total knee arthroplasty. The inclusion criteria were patients <70 years old with primary unilateral (medial) femorotibial knee osteoarthritis and without surgical or traumatic history on the operated knee. Four cubes (9 mm³) were cut inside of the white, or avascular, area of each specimen's middle horn and divided into 4 groups: "fresh" control, frozen (-80°C), cryopreserved (-140°C), and frozen + irradiated (-80°C + 25 kGy). Specimens of the control group were evaluated at day 1, and specimens from the frozen, cryopreserved, and frozen + irradiated groups were evaluated after 1 month of storage. Evaluation was performed with electron microscopy according a validated protocol to analyze (1) mean diameters of the collagen fibers in longitudinal and transverse sections in 5 points per section and (2) validated architectural scores.

RESULTS

No significant difference was found between the control and cryopreserved groups regarding mean transverse and longitudinal diameters (transverse: 95.39 ± 15.87 nm vs 99.62 ± 19.23 nm, P = .1; longitudinal: 96.31 ± 13.96 nm vs 94.57 ± 16.42 nm, P = .1). Significant differences were found between the control and frozen groups (transverse: 95.39 ± 15.87 nm vs 70.20 ± 13.94 nm, P < .001; longitudinal: 96.31 ± 13.96 nm vs 71.28 ± 10.64 nm, P < .001) and the control and frozen + irradiated groups (transverse: 95.39 ± 15.87 nm vs 63.1 ± 15.57 nm, P < .001; longitudinal: 96.31 ± 13.96 nm vs 60.9 ± 14.8 nm, P < .001). Regarding architectural score calculation, there were significant differences between the control and frozen groups (4.5 ± 1.3 vs 2.3 ± 1.4, P = .02) and the control and frozen + irradiated groups (4.5 ± 1.3 vs 1.4 ± 0.9, P = .02).

CONCLUSION

Cryopreservation is the only method that preserves fresh meniscus architectural specificities. Freezing and freezing + irradiation methods modify histologic properties of meniscal allograft. Irradiation deeply alters diameters and the organization of collagen fibers, and this method should be used with caution to preserve and sterilize meniscus tissue.

CLINICAL RELEVANCE

The results of our study exhibited detrimental effects of simple freezing and freezing + irradiation on the collagen network of sample meniscus. If those effects occur in menisci prepared for allograft procedures, important differences could appear on the basis of the preservation procedure in terms of the graft's mechanical properties and, thus, the patient's outcomes.

Comparison of clinical outcomes after anterior cruciate ligament reconstruction with hamstring tendon autograft versus soft-tissue allograft: A meta-analysis of randomised controlled trials

BACKGROUND

Hamstring tendon autografts and soft-tissue allograft are commonly used for anterior cruciate ligament (ACL) reconstruction. However, the clinical outcomes between these two grafts are controversial. This meta-analysis was performed to compare clinical outcomes of primary ACL reconstruction with hamstring tendon autografts versus soft-tissue allografts.

MATERIALS AND METHODS

PubMed, Embase, and the Cochrane Library were searched through 8 September 2017 to identify randomized controlled studies that compared hamstring tendon autografts with soft-tissue allografts for primary ACL reconstruction. Two authors independently graded the methodological quality of each eligible study using the Cochrane Collaboration tool and extracted relevant data. Statistical heterogeneity among the trials was evaluated with chi-square and I-square tests. A sensitivity analysis was conducted to explore sources of heterogeneity. Subgroup analysis was performed to identify potential differences according to type of reconstruction technique (single-bundle or double-bundle).

RESULTS

Eight studies with 785 combined patients (396 hamstring tendon autografts and 389 soft-tissue allografts) were included. Two studies had a high risk of bias. The other six studies had unclear risk of bias. There were significant differences between the groups in subjective International Knee Documentation Committee (IKDC) score (mean difference [MD], 2.43; 95%CI, 0.69-4.18; p = 0.006), Tegner score (MD, 0.24; 95%CI, 0.03-0.45; p = 0.03), and side-to-side difference (MD, -1.37; 95%CI, -2.44 to -0.30; p = 0.01). There was no significant difference between the groups in Lysholm score, complications, pivot shift test, anterior drawer test, Lachman test, overall IKDC score, or range of motion. Subgroup analysis demonstrated that for primary ACL reconstruction using the single-bundle technique, soft-tissue allografts were inferior to hamstring tendon autografts in subjective IKDC score, anterior drawer test, and side-to-side difference.

CONCLUSION

Soft-tissue allografts are inferior to hamstring tendon autografts with respect to subjective patient evaluation and knee stability but superior in the complication of hypoesthesia for patients undergoing primary ACL reconstruction.

Effects of graft preconditioning on γ-irradiated deep frozen tendon allografts used in anterior cruciate ligament reconstruction

Preconditioning of the grafts prior to implantation into the knee is considered to reduce the loss of tension caused by graft viscoelasticity after anterior cruciate ligament reconstruction. The present study analyzed the impacts of different preconditioning forces on the biomechanical properties of the γ-irradiated deep frozen tendon allografts. A total of 36 tendon grafts were randomly divided into three groups and were preconditioned at 80 N (group 1), 160 N (group 2) and 320 N (group 3) for 10 min. Subsequently, the grafts were gradually completely relaxed for 1 min and subsequently received 25 cyclic loads of 0–80 N. Afterwards, the grafts were loaded to 80 N, which was maintained for 30 min. Finally, load was gradually increased until ultimate failure at maximum load (UFML) was obtained. There were significant differences in the stiffness and UFML values between the 3 groups (all P<0.05). The graft stiffness in group 3 significantly increased compared with the other 2 groups, and the stiffness of group 2 grafts increased compared with group 1. The UFML in group 3 was significantly lower compared with groups 1 and 2, while there was no significant difference between groups 1 and 2. In the present study, the results suggested that increasing the initial tension could effectively reduce the loss of stiffness due to viscoelasticity for the γ-irradiated deep frozen allogeneic tendon grafts. However, overloaded initial tension decreased the tensile strength.

Comparison of Clinical Outcomes After Anterior Cruciate Ligament Reconstruction Using a Hybrid Graft Versus a Hamstring Autograft

PURPOSE

This study aimed to compare the clinical outcomes of patients who underwent anterior cruciate ligament (ACL) reconstruction with a hybrid graft versus an autograft after 3 years of follow-up.

METHODS

Among 57 patients with an ACL injury who underwent ACL reconstruction, 28 patients received a hybrid graft (gracilis and semitendinosus tendon autograft plus a soft tissue allograft) and 29 patients received an autograft (gracilis and semitendinosus tendon autograft). The 2 groups were compared after a minimum 3-year follow-up regarding International Knee Documentation Committee (IKDC) assessment of knee function and stability, pivot-shift test, Lachman test, and KT-1000 side-to-side differences. The patient-reported Tegner activity score, Lysholm score, and subjective IKDC score were also compared. Graft failures were identified by patient-reported outcomes, physical examinations, or magnetic resonance imaging, and were confirmed on second-look arthroscopy; failure rate was compared between groups.

RESULTS

At final follow-up, the 2 groups significantly differed in pivot-shift test result (P = .013) and Lachman test result (P = .027). The failure rate tended to be greater in the hybrid graft group (14.3%) than in the autograft group (3.4%) (P = .148). All 5 patients with failed graft reconstruction were revised after second-look arthroscopy. The KT-1000 side-to-side differences at final follow-up were significantly inferior in the hybrid graft group (3.5 ± 2.0) compared with the autograft group (2.5 ± 1.0, P = .024). The hybrid graft group also had a lower mean Lysholm score (P = .000) and subjective IKDC score (P = .006) than the autograft group. The mean Tegner activity score was 6.8 ± 0.8 in the hybrid graft group and 6.9 ± 0.6 in the autograft group (P = .436).

CONCLUSIONS

The knee stability and patient-reported scores in the autograft-irradiated allograft hybrid graft ACL reconstruction group were significantly inferior compared with those in the autograft ACL reconstruction group.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Does Donor Age of Nonirradiated Achilles Tendon Allograft Influence Mid-Term Results of Revision ACL Reconstruction?

Purpose  The purpose of the present study was to investigate if the donor age of nonirradiated Achilles tendon allograft could influence the clinical results of revision anterior cruciate ligament (ACL) reconstruction.

Methods  All patients that underwent ACL revision between 2004 and 2008 with at least 4 years of follow-up were included. For all the patients that met the inclusion criteria, the age of the graft donor was obtained from the tissue bank. Lysholm score was administered to patients that met inclusion criteria. In addition, patients were divided in two groups based on the donor age (<45 years vs. ≥45 years), and the baseline characteristics and outcomes were compared.

Results  Fifty-two patients were evaluated at a mean 4.8 ± 0.8 years follow-up with Lysholm score. The Lysholm significantly improved from 62.3 ± 6.6 at preoperative status to 84.4 ± 12.3 at final follow-up. The mean donor age was 48.7 ± 8.4 years; a significant difference in Lysholm score was noted between patients that received an allograft with a donor age <45 years (14 patients; 27%) and those receiving an allograft with a donor age ≥45 years (38; 73%) (89.5 ± 3.2 vs. 80.1 ± 11.1, respectively; p  = 0.0469). The multiple regression model showed the donor age, the final follow-up, and the preoperative Lysholm score as significant predictors of postoperative Lysholm score ( p  < 0.0002).

Conclusion  Donor age of nonirradiated Achilles tendon allograft influenced the mid-term results of revision ACL reconstruction, thus advising the use of grafts from young donors.

Level of Evidence  Level III, retrospective comparative study.

What Factors Influence the Biomechanical Properties of Allograft Tissue for ACL Reconstruction? A Systematic Review

BACKGROUND

Allograft tissue is used in 22% to 42% of anterior cruciate ligament (ACL) reconstructions. Clinical outcomes have been inconsistent with allograft tissue, with some series reporting no differences in outcomes and others reporting increased risk of failure. There are numerous variations in processing and preparation that may influence the eventual performance of allograft tissue in ACL reconstruction. We sought to perform a systematic review to summarize the factors that affect the biomechanical properties of allograft tissue for use in ACL reconstruction. Many factors might impact the biomechanical properties of allograft tissue, and these should be understood when considering using allograft tissue or when reporting outcomes from allograft reconstruction.

QUESTIONS/PURPOSES

What factors affect the biomechanical properties of allograft tissue used for ACL reconstruction?

METHODS

We performed a systematic review to identify studies on factors that influence the biomechanical properties of allograft tissue through PubMed and SCOPUS databases. We included cadaveric and animal studies that reported on results of biomechanical testing, whereas studies on fixation, histologic evaluation, and clinical outcomes were excluded. There were 319 unique publications identified through the search with 48 identified as relevant to answering the study question. For each study, we recorded the type of tissue tested, parameters investigated, and the effects on biomechanical behavior, including load to failure and stiffness. Primary factors identified to influence allograft tissue properties were graft tissue type, sterilization methods (irradiation and chemical processing), graft preparation, donor parameters, and biologic adjuncts.

RESULTS

Load to failure and graft stiffness varied across different tissue types, with nonlooped tibialis grafts exhibiting the lowest values. Studies on low-dose irradiation showed variable effects, whereas high-dose irradiation consistently produced decreased load to failure and stiffness values. Various chemical sterilization measures were also associated with negative effects on biomechanical properties. Prolonged freezing decreased load to failure, ultimate stress, and ultimate strain. Up to eight freeze-thaw cycles did not lead to differences in biomechanical properties of cadaveric grafts. Regional differences were noted in patellar tendon grafts, with the central third showing the highest load to failure and stiffness. Graft diameter strongly contributed to load-to-failure measurements. Age older than 40 years, and especially older than 65 years, negatively impacted biomechanical properties, whereas gender had minimal effect on the properties of allograft tissue. Biologic adjuncts show potential for improving in vivo properties of allograft tissue.

CONCLUSIONS

Future clinical studies on allograft ACL reconstruction should investigate in vivo graft performance with standardized allograft processing and preparation methods that limit the negative effects on the biomechanical properties of tissue. Additionally, biologic adjuncts may improve the biomechanical properties of allograft tissue, although future preclinical and clinical studies are necessary to clarify the role of these treatments.

CLINICAL RELEVANCE

Based on the findings of this systematic review that emphasize biomechanical properties of ACL allografts, surgeons should favor the use of central third patellar tendon or looped soft tissue grafts, maximize graft cross-sectional area, and favor grafts from donors younger than 40 years of age while avoiding grafts subjected to radiation doses > 20 kGy, chemical processing, or greater than eight freeze-thaw cycles.

Is Dual Semitendinosus Allograft Stronger Than Turndown for Achilles Tendon Reconstruction? An In Vitro Analysis

BACKGROUND

Large Achilles tendon defects pose a treatment challenge. The standard treatment with a turndown flap requires a large extensile incision, puts the sural nerve at risk, and demands slow, careful rehabilitation. Dual allograft semitendinosus reconstruction is a new clinical alternative that has the theoretical advantages of a smaller incision, less dissection, and a stronger construct that may allow for faster rehabilitation.

QUESTIONS/PURPOSES

In a cadaver biomechanical model, we compared the dual allograft semitendinosus reconstruction with the myofascial turndown in terms of (1) mechanical strength and resistance to deformation and (2) failure mechanisms in reconstruction of large segmental Achilles defects.

METHODS

An 8-cm segmental Achilles defect was created in 18 cadaveric lower extremities, nine matched pairs without defect or previous surgery (mean age, 78.4 years; range, 60-97 years; three female and six male pairs). Femoral neck densitometry to determine bone mineral density found that all specimens except two were osteopenic or osteoporotic. Specimens in each pair were assigned to allograft or turndown reconstruction. The constructs were mounted on a load frame and differential variable reluctance transducers were applied to measure deformation. Specimens were preconditioned and then loaded axially. Tensile force and proximal and distal construct deformation were measured at clinical failure, defined as 10 mm of displacement, and at ultimate failure, defined as failure of the reconstruction. Failure mechanism was recorded.

RESULTS

Tensile strength at time zero was higher in the allograft versus the turndown construct at clinical failure (156.9 ± 29.7 N versus 107.2 ± 20.0 N, respectively; mean difference, -49.7 N; 95% CI, -66.3 to -33.0 N; p < 0.001) and at ultimate failure (290.9 ± 83.2 N versus 140.7 ± 43.5 N, respectively; mean difference, -150.2 N; 95% CI, -202.9 to -97.6 N; p < 0.001). Distal construct deformation was lower in the turndown versus the allograft construct at clinical failure (1.6 ± 1.0 mm versus 4.7 ± 0.7 mm medially and 2.2 ± 1.0 mm versus 4.8 ± 1.1 mm laterally; p < 0.001). Semitendinosus allograft failure occurred via calcaneal bone bridge fracture in eight of nine specimens. All myofascial turndowns failed via suture pullout through the fascial tissue at its insertion.

CONCLUSION

In this comparative biomechanical study, dual semitendinosus allograft reconstruction showed greater tensile strength and construct deformation compared with myofascial turndown in a cadaveric model of large Achilles tendon defects.

CLINICAL RELEVANCE

Further study of dual semitendinosus allograft for treatment of severe Achilles tendon defects with cyclic loading and investigation of clinical results will better elucidate the clinical utility and indications for this technique.

Increased Risk of Revision After Anterior Cruciate Ligament Reconstruction With Bone-Patellar Tendon-Bone Allografts Compared With Autografts

BACKGROUND

The use of allograft tissue for anterior cruciate ligament reconstruction (ACLR) remains controversial.

PURPOSE

To compare the risk of aseptic revision between bone-patellar tendon-bone (BPTB) autografts and BPTB allografts.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

A retrospective cohort study of prospectively collected data was conducted using the Kaiser Permanente ACLR Registry. A cohort of patients who underwent primary unilateral ACLR with BPTB autografts and BPTB allografts was identified. Aseptic revision was the endpoint. The type of graft and allograft processing method (nonprocessed, <1.8-Mrad, and ≥1.8-Mrad irradiation) were the exposures of interest evaluated. Age (≤21 and ≥22 years) was evaluated as an effect modifier. Analyses were adjusted for age, sex, and race. Kaplan-Meier curves and Cox proportional hazards models were employed. Hazard ratios (HRs) and 95% CIs are provided.

RESULTS

The BPTB cohort consisted of 5586 patients: 3783 (67.7%) were male, 2359 (42.2%) were white, 1029 (18.4%) had allografts (nonprocessed: 155; <1.8 Mrad: 525; ≥1.8 Mrad: 288), and 4557 (81.6%) had autografts. The median age was 34.9 years (interquartile range [IQR], 25.4-44.0) for allograft cases and 22.0 years (IQR, 17.6-30.0) for autograft cases. The estimated cumulative revision rate at 2 years was 4.1% (95% CI, 2.9%-5.9%) for allografts and 1.7% (95% CI, 1.3%-2.2%) for autografts. BPTB allografts had a significantly higher adjusted risk of revision than BPTB autografts (HR, 4.54; 95% CI, 3.03-6.79; P < .001). This higher risk of revision was consistent with all allograft processing methods when compared with autografts and was also consistently higher in patients with allografts regardless of age.

CONCLUSION

When BPTB allograft tissue was used for ACLR, an overall 4.54 times adjusted higher risk of revision was observed compared with surgery performed with a BPTB autograft. Whether the tissue was irradiated with either high- or low-dose radiation, chemically processed, or not processed at all made little difference in the risk of revision. The differences in the revision risk were also consistent in younger and older patients. Surgeons and patients should be aware of the increased risk of revision when a BPTB allograft is used for ACLR.

Supercritical Carbon Dioxide–Based Sterilization of Decellularized Heart Valves

•

Sterilization of a decellularized aortic valve was investigated.

•

Various sterilization techniques including EOW, gamma radiation, ETPA, LHD, and scCO₂ were applied.

•

Brown and Brenn staining, Periodic acid-Schiff staining, and aerobic broth culturing were used to characterize sterility.

•

Differential scanning calorimetry was used to determine tissue matrix cross-linking.

•

Scanning electron microscopy was used to characterize tissue matrix damage, at the structural level.

•

EOW sterilization, which is done with electrolyzed water, could not sterilize efficiently.

•

Gamma sterilization damaged the tissue matrix.

•

Ethanol and peracetic acid–treated samples were cross-linked.

•

Hydrogen peroxide sterilization damaged the tissue matrix.

•

Supercritical carbon dioxide sterilization method was found efficient to provide 100% sterility of the sample. It neither damages nor cross-links the tissue.

Sterilization of grafts is essential. Supercritical carbon dioxide, electrolyzed water, gamma radiation, ethanol-peracetic acid, and hydrogen peroxide techniques were compared for impact on sterility and mechanical integrity of porcine decellularized aortic valves. Ethanol-peracetic acid– and supercritical carbon dioxide–treated valves were found to be sterile using histology, microbe culture, and electron microscopy assays. The cusp tensile properties of supercritical carbon dioxide–treated valves were higher compared with valves treated with other techniques. Superior sterility and integrity was found in the decellularized valves treated with supercritical carbon dioxide sterilization. This sterilization technique may hold promise for other decellularized soft tissues.

Arthroscopic anatomic double-bundle ACL reconstruction using irradiated versus non-irradiated hamstring tendon allograft

PURPOSE

To analyse the clinical outcome of anatomic double-bundle anterior cruciate ligament (ACL) reconstruction with irradiated versus non-irradiated hamstring allograft.

METHODS

One hundred and twelve patients who met the inclusion and exclusion criteria of the study were prospectively randomized consecutively into irradiated hamstring tendon allograft (Ir-Allo) group and non-irradiated allograft (Non-ir-Allo) group. All surgeries were done by the same senior surgeon with double-bundle reconstruction technique. Before surgery and at follow-up points, patients were evaluated by the same observer according to clinical evaluations.

RESULTS

Eighty-three patients (Non-ir-Allo, 44; Ir-Allo, 39) fulfilled complete follow-up and got full clinical evaluations. The mean follow-up period was 5.7 years (ranging from 5.0 to 6.5 years). At the final follow-up, significant differences were found when comparing the results of the two groups according to Lachman test, ADT, pivot shift test and KT-2000 arthrometer testing (P < 0.05). According to KT-2000, 86.4 % of patients in the Non-ir-Auto group and 35.9 % in the Ir-Allo group had a side-to-side difference of <3 mm. According to the overall IKDC, functional, subjective evaluations and activity level testing, no significant differences were found between the two groups. Regarding the arthritic progression, there was significant difference between the two groups (Ir-Allo group: 30.8 %, Non-ir-Allo group: 11.4 %, P < 0.05).

CONCLUSION

A significant increase in anterior and rotational laxity in patients of the Ir-Allo group was found according to evaluations. No significant differences in activity level and functional scores were found between the two groups. We do not advocate the irradiated hamstring tendon allograft for ACL reconstruction.

LEVEL OF EVIDENCE

I.

Use of polyvinylpyrrolidone-iodine solution for sterilisation and preservation improves mechanical properties and osteogenesis of allografts

Allografts eliminate the disadvantages associated with autografts and synthetic scaffolds but are associated with a disease-transmission risk. Therefore, allograft sterilisation is crucial. We aimed to determine whether polyvinylpyrrolidone-iodine (PVP-I) can be used for sterilisation and as a new wet-preservation method. PVP-I-sterilised and preserved allografts demonstrated improved mechanical property, osteogenesis, and excellent microbial inhibition. A thigh muscle pouch model of nude mice showed that PVP-I-preserved allografts demonstrated better ectopic formation than Co₆₀-sterilised allografts (control) in vivo (P < 0.05). Furthermore, the PVP-I-preserved group showed no difference between 24 h and 12 weeks of allograft preservation (P > 0.05). PVP-I-preserved allografts showed more hydrophilic surfaces and PVP-I-sterilised tendons showed higher mechanical strength than Co₆₀-sterilised tendons (P < 0.05). The level of residual PVP-I was higher without washing and with prolonged preservation (P < 0.05). In vitro cellular tests showed that appropriate PVP-I concentration was nontoxic to preosteoblast cells, and cellular differentiation measured by alkaline phosphatase activity and osteogenic gene markers was enhanced (P < 0.05). Therefore, the improved biological performance of implanted allografts may be attributable to better surface properties and residual PVP-I, and PVP-I immersion can be a simple, easy method for allograft sterilisation and preservation.

Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction With a Hamstring Tendon Autograft and Fresh-Frozen Allograft: A Prospective, Randomized, and Controlled Study

PURPOSE

To compare the clinical outcome of anatomic double-bundle (DB) anterior cruciate ligament (ACL) reconstruction with a hamstring tendon autograft versus fresh-frozen allograft.

METHODS

Between January 2010 and December 2011, in a prospective randomized study, we included 157 patients who were planned to receive anatomic DB ACL reconstruction with a hamstring tendon autograft or fresh-frozen allograft. All surgeries were performed by the same senior surgeon with the DB reconstruction technique. The fixation of femoral side grafts was by means of an EndoButton, and the tibial side grafts were fixed with a bioabsorble interference screw augmented with a staple. The same rehabilitation protocol was applied to all the patients. Patients were evaluated preoperatively and at the follow-up points. Evaluations included detailed history, physical examination, radiograph, functional knee ligament testing, KT-2000 arthrometer testing, Harner's vertical jump and Daniel's one-leg hop tests, Lysholm score, Tegner score, the International Knee Documentation Committee (IKDC) standard evaluation form, and Cincinnati knee score.

RESULTS

One hundred and twenty-one patients (Auto, 62; Allo, 59) fulfilled complete follow-up and got full clinical evaluations. The mean follow-up was 4.6 years (4.0 to 5.5 years) for both groups. No significant differences were found between the 2 groups according to the evaluations aforementioned except that patients in the Allo group had shorter operation time compared with the Auto group (P = .001). Fifty-three (85.5%) patients in the Auto group and 50 (84.7%) patients in the Allo group had a side-to-side difference of less than 3 mm. Four (6.5%) patients in the Auto group and 4 (6.8%) patients in the Allo group had a side-to-side difference of more than 5 mm. Fifty-nine (95.8%) patients in the Auto group and 55 (93.2%) patients in the Allo group were normal or nearly normal according to the overall IKDC. According to the subjective IKDC, the average scores were 90 and 89 points, respectively, for the Auto and Allo groups. The mean Lysholm and Tegner scores were 90 points and 7.9 points for the Auto group, respectively, and 89 points and 7.8 points for the Allo group, respectively. For the Cincinnati knee score, the average scores were 91 and 90 points, respectively, for the Auto and Allo groups. A total of 11.3% (7 of 62) of patients in the Auto group and 11.9% (7 of 59) of patients in the Allo group had an arthritic progression. There was no statistical difference between the 2 groups at the final follow-up.

CONCLUSIONS

With the anatomic DB ACL reconstruction technique, comparable objective and subjective clinical results can be achieved with the use of a fresh-frozen hamstring tendon allograft compared with an autograft.

LEVEL OF EVIDENCE

Level II, prospective randomized clinical trial.

Do Processing Methods Make a Difference in Acellular Dermal Matrix Properties?

BACKGROUND

The use of acellular dermal matrices (ADMs) has become the standard of practice in many reconstructive and aesthetic surgical applications. Different methods used to prepare the allograft tissue for surgical use can alter the ADMs natural properties. Aseptic processing has been shown to retain the natural properties of ADMs more favorably than terminally sterilized ADMs. Terminal sterilization has been historically linked to alteration of biological materials. In vitro work was conducted to compare ADM processing methods.

OBJECTIVES

Characterize aseptically processed ADMs and compare cell-matrix interaction characteristics to terminally sterilized ADMs.

METHODS

Two aseptically processed ADMs, FlexHD Pliable and BellaDerm, were characterized via histological evaluation, biomechanical integrity, enzymatic degradation, and in vitro cell studies. FlexHD Pliable was compared to Alloderm Ready-to-Use (RTU).

RESULTS

Histological evaluation revealed that FlexHD Pliable had a uniform, open structure compared to BellaDerm. Mechanical characterization demonstrated that BellaDerm had higher strength and stiffness compared to FlexHD Pliable, which maintained higher elasticity. Immunohistochemical analysis verified that key matrix proteins remained intact after aseptic processing. Cell studies found that fibroblasts attached more readily, and proliferated faster on FlexHD Pliable compared to BellaDerm. Additionally, fibroblasts infiltrated into FlexHD Pliable from both sides and on the dermal side in BellaDerm and produced an abundance of multi-layered matrix proteins (collagen, fibronectin) when compared to AlloDerm RTU which was sparse.

CONCLUSIONS

Aseptically processed FlexHD Pliable and BellaDerm provide a suitable, biocompatible option for tissue repair and regeneration in aesthetic and reconstructive surgical applications.

Maximum load to failure of high dose versus low dose gamma irradiation of anterior cruciate ligament allografts: A meta-analysis

BACKGROUND

The objective of this study was to systematically evaluate the existing literature to compare the biomechanical effects of low dose and high dose gamma irradiation on commonly used ACL allografts.

METHODS

A systematic search was performed in PubMed, Cumulative Index for Nursing and Allied Health Literature (CINAHL), Cochrane Reviews, SCOPUS, and SportDiscus. Nine studies were identified that met the following inclusion criteria: 1) controlled laboratory study, 2) investigation of standard allografts for anterior cruciate ligament reconstruction (ACLR), 3) gamma irradiation (dose reported) and a negative control group, and 4) mechanical loading (results reported).

RESULTS

Nine studies met all inclusion and exclusion criteria. There was a dose-dependent relationship between radiation and decreased mechanical tendon integrity. Low dose radiation (<2.5Mrad [Mrad]) showed graft weakening with an average of 4.3% decrease in load to failure (standardized mean difference [SMD], 0.23; 95% CI 0.216, 0.68; p=0.31), whereas high-dose radiation showed a significantly larger (32.4% average) decrease in load to failure (SMD, 1.79; 95% CI 1.194, 2.38; p<0.001).

CONCLUSIONS

Gamma irradiation has a negative effect on tendon allograft strength that is dose-dependent, with particularly large effects noted at irradiation doses of ≥2.5Mrad.

Irradiated Hamstring Tendon Allograft Versus Autograft for Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction: Midterm Clinical Outcomes

BACKGROUND

Most studies on grafts for anterior cruciate ligament (ACL) reconstruction (ACLR) have been of autografts or nonirradiated allografts with a single-bundle (SB) technique. Outcome reports evaluating anatomic double-bundle (DB) ACLR with a hamstring tendon autograft versus irradiated allograft are rare.

PURPOSE

To compare the clinical outcomes of arthroscopic anatomic DB ACLR with a hamstring tendon autograft versus irradiated allograft.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 2.

METHODS

Between 2008 and 2009, a total of 107 patients undergoing arthroscopic DB ACLR were prospectively randomized consecutively into 1 of 2 groups (autograft [Auto] group and irradiated allograft [Ir-Allo] group). All the surgical procedures were performed by the same senior surgeon using the DB reconstruction technique. All irradiated hamstring tendon allografts were sterilized with 2.5 Mrad of irradiation before distribution and were obtained from a single certified tissue bank. Graft fixation on the femoral side was by an Endobutton, and on the tibial side by a bioabsorbable interference screw augmented with a staple. The same rehabilitation protocol was applied to all patients. Before surgery and at a mean of 6.9 years of follow-up, patients were evaluated by the same observer according to objective and subjective clinical evaluations including detailed history, physical examination, radiography, functional knee ligament testing, KT-2000 arthrometer testing, Harner vertical jump and Daniel 1-legged hop tests, Lysholm score, Tegner score, International Knee Documentation Committee (IKDC) standard evaluation form, and Cincinnati knee score.

RESULTS

A total of 83 patients (Auto: n = 40 [mean age, 29.2 ± 6.9 years]; Ir-Allo: n = 43 [mean age, 28.6 ± 7.2 years]) fulfilled follow-up and clinical evaluations. No significant differences were found between the 2 groups according to the overall IKDC functional and subjective evaluations as well as testing of activity levels. Significant between-group differences were found when comparing the results at final follow-up according to the Lachman test, anterior drawer test, pivot-shift test, and KT-2000 arthrometer measurements (P < .001). Most importantly, 87.5% of patients in the Auto group and 34.9% in the Ir-Allo group had a side-to-side difference <3 mm. The rate of laxity (side-to-side difference >5 mm) with an irradiated allograft (30.2%) was higher than that with an autograft (7.5%) (P < .001). The failure rate in the Ir-Allo group (30.2%) was higher than that in the Auto group (7.5%) (P < .001). Anterior and rotational stability decreased significantly in the Ir-Allo group; patients in the Ir-Allo group also had a shorter operation time. There were 10.0% (4/40) of patients in the Auto group and 32.6% (19/43) of patients in the Ir-Allo group who had arthritic progression (P < .05).

CONCLUSION

There were no significant differences in postoperative activity levels and functional outcomes between the Auto and Ir-Allo groups. However, a significant increase in anterior and rotational laxity in the Ir-Allo group was found according to evaluations. We do not advocate an irradiated hamstring tendon allograft for DB ACLR.

TRIAL REGISTRATION

Clinical Trial Register System of The Affiliated Hospital of Qingdao University (qdfy-ky2008-12).

Effects of gamma irradiation on the biomechanical properties of peroneus tendons

Purpose

This study was designed to investigate the biomechanical properties of nonirradiated (NI) and irradiated (IR) peroneus tendons to determine if they would be suitable allografts, in regards to biomechanical properties, for anterior cruciate ligament reconstruction after a dose of 1.5–2.5 Mrad.

Methods

Seven pairs of peroneus longus (PL) and ten pairs of peroneus brevis (PB) tendons were procured from human cadavers. The diameter of each allograft was measured. The left side of each allograft was IR at 1.5–2.5 Mrad, whereas the right side was kept aseptic and NI. The allografts were thawed, kept wet with saline, and attached in a single-strand fashion to custom freeze grips using liquid nitrogen. A preload of 10 N was then applied and, after it had reached steady state, the allografts were pulled at 4 cm/sec. The parameters recorded were the displacement and force.

Results

The elongation at the peak load was 10.3±2.3 mm for the PB NI side and 13.5±3.3 mm for the PB IR side. The elongation at the peak load was 17.4±5.3 mm for the PL NI side and 16.3±2.0 mm for the PL IR side. For PL, the ultimate load was 2,091.6±148.7 N for NI and 2,122.8±380.0 N for IR. The ultimate load for the PB tendons was 1,485.7±209.3 N for NI and 1,318.4±296.9 N for the IR group. The ultimate stress calculations for PL were 90.3±11.3 MPa for NI and 94.8±21.0 MPa for IR. For the PB, the ultimate stress was 82.4±19.0 MPa for NI and 72.5±16.6 MPa for the IR group. The structural stiffness was 216.1±59.0 N/mm for the NI PL and 195.7±51.4 N/mm for the IR side. None of these measures were significantly different between the NI and IR groups. The structural stiffness was 232.1±45.7 N/mm for the NI PB and 161.9±74.0 N/mm for the IR side, and this was the only statistically significant difference found in this study (P=0.034).

Conclusion

Our statistical comparisons found no significant differences in terms of elongation, ultimate load, or ultimate stress between IR and NI PB and PL tendons. Only the PB structural stiffness was affected by irradiation. Thus, sterilizing allografts at 1.5–2.5 Mrad of gamma irradiation does not cause major alterations in the tendons’ biomechanical properties while still providing a suitable amount of sterilization for anterior cruciate ligament reconstruction.

Autograft versus allograft in anterior cruciate ligament reconstruction: A meta-analysis with trial sequential analysis

BACKGROUND

Anterior cruciate ligament (ACL) reconstruction is considered as the standard surgical procedure for the treatment of ACL tear. However, there is a crucial controversy in terms of whether to use autograft or allograft in ACL reconstruction. The purpose of this meta-analysis is to compare autograft with allograft for patients undergoing ACL reconstruction.

METHODS

PubMed, EMBASE, and the Cochrane Library were searched for randomized controlled trials that compared autograft with allograft in ACL reconstruction up to January 31, 2016. The relative risk or mean difference with 95% confidence interval was calculated using either a fixed- or random-effects model. The risk of bias for individual studies according to the Cochrane Handbook. The trial sequential analysis was used to test the robustness of our findings and get more conservative estimates.

RESULTS

Thirteen trials were included, involving 1636 participants. The results of this meta-analysis indicated that autograft brought about lower clinical failure, better overall International Knee Documentation Committee (IKDC) level, better pivot-shift test, better Lachman test, greater Tegner score, and better instrumented laxity test (P < 0.05) than allograft. Autograft was not statistically different from allograft in Lysholm score, subjective IKDC score, and Daniel 1-leg hop test (P > 0.05). Subgroup analyses demonstrated that autograft was superior to irradiated allograft for patients undergoing ACL reconstruction in clinical failure, Lysholm score, pivot-shift test, Lachman test, Tegner score, instrumented laxity test, and subjective IKDC score (P < 0.05). Moreover, there were no significant differences between autograft and nonirradiated allograft.

CONCLUSIONS

Autograft is superior to irradiated allograft for patients undergoing ACL reconstruction concerning knee function and laxity, but there are no significant differences between autograft and nonirradiated allograft. However, our results should be interpreted with caution, because the blinding methods were not well used.

Anterior Cruciate Ligament Reconstruction Using a Combination of Autograft and Allograft Tendon: A MOON Cohort Study

Background:

Anterior cruciate ligament (ACL) reconstruction with hamstring autografts less than 8.5 mm in diameter is associated with worse patient-reported outcome scores and increased risk of revision surgery compared with reconstructions performed with larger grafts. One proposed solution to small autograft harvest is to create a hybrid graft by augmenting autografts with allograft tissue to increase graft diameter.

Purpose:

To compare hybrid autograft/allograft ACL reconstruction to autograft ACL reconstruction, specifically analyzing the patient-reported outcome scores and the risk of revision surgery at 2 years postoperative.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

From the years 2002 to 2009, a total of 34 patients were identified from a prospectively collected database as having undergone hybrid ACL reconstruction. Twenty-seven of 34 (79.4%) patients had a 2-year follow-up. These 27 patients were matched by age (within 1 year) and sex to 27 patients who underwent hamstring autograft ACL reconstruction during the same period. At the 2-year mark, revision surgery risk and patient-reported outcome scores were compared between the 2 groups.

Results:

The mean age for the hybrid and matched groups (±SD) was 20.9 ± 7.0 years. Both the hybrid and control groups had 17 males and 10 females. There was no significant difference in preoperative patient-reported outcome scores, meniscus tears, or cartilage lesions between the 2 groups. Graft size was larger in the hybrid group (9.5 ± 0.6 mm) than in the autograft group (8.4 ± 0.9 mm) (P < .001). At 2 years postoperative, patient-reported outcome scores were similar between the hybrid and autograft groups. Revision surgery was required in 5 (18.5%) patients who underwent hybrid reconstruction compared with 2 (7.4%) of those who underwent autograft reconstruction (P = .26).

Conclusion:

Patients who undergo ACL reconstruction with hybrid hamstring grafts and hamstring autografts report similar patient-reported outcome scores at 2 years postoperative but may be at increased risk for revision ACL reconstruction.

In vitro effects of 0 to 120 Grays of irradiation on bone viability and release of growth factors

BACKGROUND

High dose radiation therapy is commonly used in maxillofacial surgeries to treat a number of head and neck tumors. Despite its widespread use, little information is available regarding the effects of irradiation on bone cell viability and release of growth factors following dose-dependent irradiation.

METHODS

Bone samples were collected from porcine mandibular cortical bone and irradiated at doses of 0, 7.5, 15, 30, 60 and 120 Grays. Thereafter, cell viability was quantified, and the release of growth factors including TGFβ1, BMP2, VEGF, IL1β and RANKL were investigated over time.

RESULTS

It was observed that at only 7.5Gy of irradiation, over 85 % of cells were non-vital and by 60 Gy, all cells underwent apoptosis. Furthermore, over a 7-fold decrease in VEGF and a 2-fold decrease in TGFβ1 were observed following irradiation at all tested doses. Little change was observed for BMP2 and IL1β whereas RANKL was significantly increased for all irradiated samples.

CONCLUSIONS

These results demonstrate the pronounced effects of irradiation on bone-cell vitality and subsequent release of growth factors. Interestingly, the largest observed change in gene expression was the 7-fold decrease in VEGF protein following irradiation. Future research aimed at improving our understanding of bone following irradiation is necessary to further improve future clinical treatments.