Fresh osteochondral allografts possess the ability to restore a wide spectrum of articular and osteoarticular pathology, as a result, the clinical indications cover a broad range of pathology. As is true for other restorative procedures, in addition to evaluating the particular articular lesion, the careful assessment of the entire joint, as well as the individual, is important. Many proposed treatment algorithms suggest the use of allografts for large lesions (>2 or 3 cm) or for salvage in difficult reconstructive situations where bone loss is also present. In our experience, allografts can be considered as a primary treatment option for osteochondral lesions greater than 2 cm (approximately) in diameter, as is typically seen in osteochondritis dissecans (OCD) and osteonecrosis. Fresh allografts are also useful as a salvage procedure when other cartilage-restorative procedures, such as microfracture, osteoarticular transfer system (OATS), and autologous chondrocyte implantation, have been unsuccessful.

Additionally, allografts often are used for salvage reconstruction of post traumatic defects of the tibial plateau or the femoral condyle. Other indications for allografting in the knee include treatment of patellofemoral chondrosis or arthrosis and in very select cases of unicompartmental tibiofemoral arthrosis (Table 33-1).

Relative contraindications to the allografting procedure include uncorrected joint instability or uncorrected malalignment of the limb. An allograft may be considered in combination or as part of a staged procedure in these settings. Allografting should not be considered an alternative to prosthetic arthroplasty in an individual with symptoms and acceptable age and activity level for prosthetic replacement. In the younger individual, bipolar and multicompartmental allografting have been modestly successful. The presence of inflammatory disease or crystal-induced arthropathy is considered a relative contraindication, as well as is any unexplained synovitis. The use of fresh osteochondral allografts in individuals with altered bone metabolism, such as is seen in chronic steroid use, smoking, or even nonsteroidal anti-inflammatory agents, has not been studied extensively. Unlike other cartilage procedures, relative size of the lesion (large or small) is not considered a contraindication to allografting.

Common to all fresh allografting procedures is matching the donor with recipient. This is done on the basis of size. In the knee, an anteroposterior radiograph with a magnification marker is used, and a measurement
of the medial-lateral dimension of the tibia, just below the joint surface, is made (Fig. 33-1). This corrected measurement is used, and the tissue bank makes a direct measurement on the donor tibial plateau. Alternatively, a measurement of the affected condyle can be performed. A match is considered acceptable at ± 2 mm; however, it should be noted that there is a significant variability in anatomythat is not reflected in size measurements. In particular, in treating OCD, the pathologic condyle typically is larger, wider, and flatter; therefore, a larger donor generally should be used. When using allograft plugs or dowels, one is generally safe with a larger donor. Small donor condyles lead to problems with matching radius of curvature, particularly for grafts over 20 mm in diameter. Most femoral condyle lesions can be treated using dowel-type grafts. Commercially available instruments (Arthrex, Naples, FL) simplify the preparation, harvesting, and insertion of these grafts, which may be up to 35 mm in size (Fig. 33-2). Perhaps the most important step in preoperative planning is understanding that one is using human tissue and performing a transplantation. Respect for the donation process, understanding the recovery, processing, and safety issues are minimum requirements necessary for the surgeon wishing to use fresh allograft tissue.

For most femoral condyle lesions, allografting can be performed through a miniarthrotomy. In most situations, a diagnostic arthroscopy has been performed recently and is not a necessary component of the allografting procedure. However, if there are any unanswered questions regarding meniscal status, or the status of the other compartments, a diagnostic arthroscopy can be performed prior to the allografting procedure. Examination under anesthesia is done in the standard fashion, as is the diagnostic arthroscopy when the surgeon feels this is indicated. Only rarely do we perform arthroscopy, as adequate data have typically been collected prior to beginning the process of graft acquisition.