Factors Associated with Increased Allograft Failure Rate in Anterior Cruciate Ligament Reconstruction

Introduction

Allograft tissue is a common graft choice for anterior cruciate ligament reconstruction (ACLR). A 2013 survey conducted by the American Orthopaedic Society of Sports Medicine found that allograft was selected in 27% of those cases, with use trending higher in patients 40 years and older. Surgeons were more likely to use allograft for primary ACLR because of decreased donor site morbidity, decreased postoperative pain, improved cosmesis, and decreased surgical time. Concerns voiced regarding allograft use for primary ACLR included a younger patient, graft failure rates reported in the literature, patient intent to return to high anterior cruciate ligament (ACL)-demanding activity, graft incorporation rate, disease transmission, personal experience with graft failure, and cost.

Numerous studies, despite their small sample size, have suggested slower revascularization, inferior biologic properties, increased postoperative laxity, and decreased clinical outcome scores associated with the use of allograft tissue in ACLR when compared with autograft. The explanations for these findings have been multifactorial and remain incompletely understood, but are believed to be due to a combination of graft characteristics and patient attributes. Multiple studies from the Kaiser Permanente ACL Reconstruction Registry (KPACLRR) have provided descriptive and outcome data on ACLR from a large community-based sample. Of the 21,926 ACLRs in the KPACLRR registered between 2005 and 2013, 41% were performed with allograft. KPACLRR studies ranging from approximately 9800–16,200 patients have revealed that allografts have lower overall graft survival versus autografts, a 3.02 times higher risk of aseptic revision than bone–patellar tendon–bone (BPTB) autografts specifically, and are also a risk factor for nonrevision reoperations after ACLR. Most recently, in the largest such cohort ever, a 2015 KPACLRR study on 5968 allograft primary ACLR cases found that graft irradiation over 1.8 Mrad, BioCleanse graft processing, younger patients, male patients, and BPTB allograft are all associated with a higher risk of aseptic failure and subsequent revision surgery after primary allograft ACLR ( Fig. 117.1 ). This study will be discussed in further detail and serve as a benchmark comparison for additional research done on the topic.

Graft Processing

The goal of allograft processing remains to sterilize tissue to a minimum sterility assurance level of 10 ⁻³ , as mandated by the Food and Drug Administration for implanted biologic medical devices, without compromising mechanical properties or biologic potential. While oversight exists from the American Association of Tissue Banks, there remains no established gold standard for tissue processing, which can include a combination of hydrogen peroxide, high temperature, chemical washes, gamma irradiation, supercritical CO ₂ , antibiotics, fresh-frozen preservation, freeze-drying preservation, cryopreservation, proprietary techniques, and other methods, each with uncertain impact on the resultant biologic and mechanical properties of the tissue.