Graft selection in ACL reconstructive surgery: past, present, and future Ahmad Oryan, Ali Moshiri and Abdolhamid Meimandi-Parizi ABSTRACT Anterior cruciate ligament (ACL) tear is a frequent orthopaedic injury. ACL reconstruction, both in humans and animals, is more developed than in past decades. Many experimental and clinical trial studies have been performed, using various grafts with several different techniques, aiming to improve ACL reconstruc- tion. However, there is still a large gap between the present treatment modalities and the final outcome in patients who have had ACL reconstructive surgery. The autograft bone- patellar tendon-bone complex and hamstring tendon grafts are the gold standard graft types for ACL reconstruction. This review introduces graft options and discusses advantages, disadvan- tages, and outcomes. Bone tunnel healing, strategies to enhance the bone tunnel healing, and the future of ACL reconstruction also are briefly described. Key Words anterior cruciate ligament, patellar tendon, hamstring tendon, bone tunnel healing, graft selection INTRODUCTION O ver the past 10 years, anterior cruciate ligament (ACL) reconstructive surgery has improved. 1--4 The procedure usually is carried out arthroscopically using different types of grafts. 1,5,6 Despite the popularity of the procedure, the preferred graft remains controversial. Ideally, the graft should have similar characteristics as the native ACL, be incorporated in the tibial and femoral tunnels with proper fixation characteristics, heal fast and maintain its viscoelastic characteristics for a long time with minimal adverse effects on the extensor mechanism, without pain or osteoarthrosis. 7--9 This paper discusses different types of grafts, their characteristics, and their outcomes in human ACL recon- structive surgery. Because of insufficient healing potential in the bone tunnel or abrasion of the graft at the tunnel exit, all types of ACL reconstruction have a proportion of graft failure. Therefore, bone tunnel healing and strategies to improve healing potential are discussed in this paper. The new areas of research in ACL reconstructive surgery also have been suggested for those who are engaged in reconstructive surgical research. GRAFT SELECTION IN ACL RECONSTRUCTION Different types of grafts have been used to reconstruct the torn ACL. Generally, these can be divided into autogenous, allogenous, and xenogenous grafts based on the species of the donor. Tissue-engineered grafts are the fourth new type that can be made up of any of the previously mentioned grafts, from synthetic products or their combinations. 9,10 Tissue- engineered grafts overlap with the xenografts but possess more options and can be divided into three categories, including biologic, synthetic, or hybrid grafts, based on the origin of their material. 10 The advantages and disadvantages of each graft type are briefly highlighted in Table 1. AUTOGRAFTS Intraarticular reconstruction of the ACL can be done using many types of autogenus grafts, such as combined semiten- dinosus gracilis hamstring tendon, bone-patellar tendon-bone composites, or quadriceps tendon. 27 However, most surgeons prefer the central third of the patellar ligament; others use one or two strands of hamstring tendon. 11 Recently, four strands were found to be superior to two strands. 2 The advantages of autografts compared with allografts have been demonstrated. 11 For example, they are not involved in transmission of diseases, do not initiate host’s immune reaction, and are inexpensive. 11 However, serious limitations have been suggested for autografts, such as limited availability, increased operative time, and adverse functional changes, including muscle weakness at the donor site and graft site morbidity, which may have a detrimental effect on the final outcome of the surgical reconstruction. 12 ALLOGRAFTS The clinical data of both humans and animals have suggested that, as with autograft tissues, the allograft tissue revascularizes and becomes viable after implantation. 12,13,22 However, the rate of graft incorporation and remodeling are slower for allograft than for autograft. 12 Clinical studies with 5-year and 7-year follow-up have demonstrated that the outcomes of early ACL allograft reconstructions are similar to those of the autografts. 10,28 The incidence of chronic knee effusion after allograft reconstruction diminishes. This is perhaps because of the improved allograft procurement and School of Veterinary Medicine, Shiraz University, Shiraz, Iran Financial Disclosure: The authors report no conflicts of interest. Correspondence to Ali Moshiri, DVM, DVSc, Division of Surgery and Radiology, Department of Clinical Sciences, School of Veterinary Medicine, Shiraz University, Shiraz, Fars, Iran Tel: þ 989123409835; þ 982188002991; fax: þ 987116138662; e-mail: dr.ali.moshiri@gmail.com 1940-7041 r 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins REVIEW ARTICLE Volume 24  Number 3  May/June 2013 Current Orthopaedic Practice 321