Future of Allografts in Sports Medicine

Disinfection protocol for human musculoskeletal allografts in tissue banking using hydrogen peroxide 30

Musculoskeletal allografts are used in reconstructive procedures, however, the risk of contamination with potential pathogens is possible, and safe transplantation requires multiple processing considerations. Hydrogen peroxide (H₂O₂) has commonly been used in bone washing because it can remove donor cells and eliminate antigens, pathogens, or cytotoxic agents from the matrix. The aim of this study was to evaluate the quantitative activity of H₂O₂ in a model of bone contamination with a high bacterial load to define the bioburden reduction. Twelve bone disc models were artificially contaminated with Staphylococcus aureus. The bones were treated with a washing process composed by antibiotics, 30% hydrogen peroxide, and 70% alcohol. Tryptic Soy Agar plates were directly inoculated with 100µL of each step of the washing process and colonies were counted in CFU/mL. Scanning electron microscopy was used for bone structural analysis before and after the washing process. After antibiotics, there was a drop of less than 1 log for cancellous bone and almost 1 log for cortical bone. However, after H₂O₂, there as a drop of 3 logs for cortical (p = 0.007), and 2 logs for cancellous bone (p = 0.063). The use of alcohol did not change the bioburden following H₂O₂ in cancellous and cortical bone. Despite the important drop of bacterial load, H₂O₂ was not enough to completely eradicate bacterial with this model of bioburden. H₂O₂ is useful in decontamination, but antibiotics have little activity, and alcohol is useless. The process is useful in decontamination up to 3 logs of bioburden.

Use of Allografts in Orthopaedic Surgery: Safety, Procurement, Storage, and Outcomes

The use of allografts has become a vital option for orthopaedic surgeons in the treatment of a variety of musculoskeletal lesions, ranging from osteochondral defects in the glenohumeral joint to meniscal deficiency in the young athlete. Nevertheless, barriers to treating a patient with an allograft-based procedure may arise from concerns over disease transmission, the navigation of tissue banks that supply allografts, the process of obtaining insurance approval, or optimal storage methods. This review serves to support orthopaedic surgeons in the incorporation of allografts into their practice by quelling these potential concerns. Fresh osteochondral allografts, fresh-frozen meniscal allografts, soft tissue allografts, and off-the-shelf cartilage products are the focus of this review amid broad overviews of allograft safety and tissue bank practices in the United States.

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.

Allograft replacement for absent native tissue

Context:

Structural instability due to poor soft tissue quality often requires augmentation. Allografts are important biological substitutes that are used for the symptomatic patient in the reconstruction of deficient ligaments, tendons, menisci, and osteochondral defects. Interest in the clinical application of allografts has arisen from the demand to obtain stable anatomy with restoration of function and protection against additional injury, particularly for high-demand patients who participate in sports. Traditionally, allografts were employed to reinforce weakened tissue. However, they can also be employed to substitute deficient or functionally absent tissue, particularly in the sports medicine setting.

Objective:

This article presents a series of 6 cases that utilized allografts to restore functionally deficient anatomic architecture, rather than just simply augmenting the degenerated or damaged native tissue. Detailed discussions are presented of the use of allografts as a successful treatment strategy to replace functionally weakened tissue, often after failed primary repairs.

Acellular flexor tendon allografts: a new horizon for tendon reconstruction

Flexor tendon injuries continue to pose a significant challenge to the hand surgeon. In particular, chronic tendon ruptures with adhesions of the tendons and sheath, damage or loss of the intrasynovial flexor tendons in zone II, and combined soft tissue and bone injuries present especially difficult problems for restoring satisfactory digital function. This challenge in flexor tendon reconstruction has motivated hand surgeons to explore and develop novel solutions for nearly a century. Recent advances and techniques in processing and decellularizing allograft human flexor tendon constructs may prove to be a new horizon for tendon reconstruction.

Reducing the radiation sterilization dose improves mechanical and biological quality while retaining sterility assurance levels of bone allografts

BACKGROUND

Bone allografts carry a risk of infection, so terminal sterilization by gamma irradiation at 25kGy is recommended; but is deleterious to bone quality. Contemporary bone banking significantly reduces initial allograft bioburden, questioning the need to sterilize at 25kGy.

METHODS

We inoculated allograft bone with Staphylococcus epidermidis and Bacillus pumilus, then exposed them to gamma irradiation at 0, 5, 10, 15, 20 and 25kGy. Mechanical and biological properties of allografts were also assessed. Our aim was to determine an optimal dose that achieves sterility assurance while minimizing deleterious effects on allograft tissue.

RESULTS

20-25kGy eliminated both organisms at concentrations from 10(1) to 10(3)CFU, while 10-15kGy sterilized bone samples to a bioburden concentration of 10(2)CFU. Irradiation did not generate pro-inflammatory bone surfaces, as evidenced by macrophage activation, nor did it affect attachment or proliferation of osteoblasts. At doses ≥10kGy, the toughness of cortical bone was reduced (P<0.05), and attachment and fusion of osteoclasts onto irradiated bone declined at 20 and 25kGy (P<0.05). There was no change in collagen cross-links, but a significant dose-response increase in denatured collagen (P<0.05).

CONCLUSIONS

Our mechanical and cell biological data converge on 15kGy as a threshold for radiation sterilization of bone allografts. Between 5 and 15kGy, bone banks can undertake validation that provides allografts with an acceptable sterility assurance level, improving their strength and biocompatibility significantly.

CLINICAL RELEVANCE

The application of radiation sterilization doses between 5 and 15kGy will improve bone allograft mechanical performance and promote integration, while retaining sterility assurance levels. Improved quality of allograft bone will promote superior clinical outcomes.

Revision anterior cruciate ligament reconstruction: an update

With the rising number of anterior cruciate ligament (ACL) reconstructions performed, revision ACL reconstruction is increasingly common nowadays. A broad variety of primary and revision ACL reconstruction techniques have been described in the literature. Recurrent instability after primary ACL surgery is often due to non-anatomical ACL graft reconstruction and altered biomechanics. Anatomical reconstruction must be the primary goal of this challenging revision procedure. Recently, revision ACL reconstruction has been described using double bundle hamstring graft. Successful revision ACL reconstruction requires an exact understanding of the causes of failure and technical or diagnostic errors. The purpose of this article is to review the causes of failure, preoperative evaluation, graft selection and types of fixation, tunnel placement, various types of surgical techniques and clinical outcome of revision ACL reconstruction.

Anterior cruciate ligament allograft surgery: underreporting of graft source, graft processing, and donor age

BACKGROUND

There has been much controversy regarding the effects of sterilization techniques and graft history on the structural integrity of allograft ligaments used in reconstruction of the anterior cruciate ligament. The purpose of this review was to comprehensively examine anterior cruciate ligament allograft studies published in the last decade to evaluate the extent to which tissue source, tissue processing techniques, and donor age are reported.

METHODS

The authors reviewed 202 articles published from 1999 through November 2009, of which 68 retrospective, prospective, biomechanical, and histology studies evaluating 4689 allografts were included.

RESULTS

The majority of studies do not accurately report key elements of graft history including tissue bank, processing or sterilization technique, or donor age. Underreporting was particularly prominent in clinical studies as compared with basic science studies. Limited reporting of allograft processing, allograft source, and donor age raises serious questions regarding the generalizability of published studies of allograft tissue for anterior cruciate ligament reconstruction. Conclusion/

CLINICAL RELEVANCE

Orthopaedic surgeons who use allograft tissue must understand the tissue treatments being used (ie, preservation methods, chemical and sterilization processes) to best inform their patients regarding the risks, benefits, and long-term outcomes when such tissues are used. A complete understanding of the implanted tissue, as well as surgeon and recipient demographics, is necessary to ensure appropriate and predictable long-term outcomes.

Validation of 11 kGy as a radiation sterilization dose for frozen bone allografts

A radiation sterilization dose (RSD) of 25 kGy is deleterious to bone allografts. This study aimed to establish a lower RSD for bone allografts using method 1 of International Standard Organisation 11137.2:2006. This provides a database to select an RSD corresponding to an allograft's bioburden, given that the bioburden's gamma resistance is equal to or less than the standard. This can be verified by irradiating 100 allografts at a dose selected to provide a sterility assurance level of 10(-2). The bioburden of our allografts was 0, which prescribed a verification dose of 1.3 kGy. After irradiating 100 allografts, sterility tests returned no positive cultures. We therefore validated an RSD of 11 kGy for allografts with that bioburden. According to the standard, this RSD provides a sterility assurance level of 10(-6) for bone allografts.