Allograft is most commonly used in lower demand patients, or patients who are undergoing revision ACL surgery (when an ACL reconstruction fails). Biomechanical studies show that allograft (donor tissue from a cadaver) is not as strong as a patient's own tissue (autograft). For many patients, however, the strength of the reconstructed ACL using an allograft is sufficient for their demands. Therefore this may be an excellent option for patients not planning to participate in high-demand sports (e.g. soccer, basketball, etc.).
- Advantages: Performing the surgery using allograft allows for decreased operative time, no need to remove other tissue to use for the graft, smaller incisions, and less post-operative pain. Furthermore, if the graft were to fail, revision surgery could be performed using either the patellar tendon or hamstring grafts.
- Disadvantages: Historically, these grafts were of poor quality and carried a significant risk of disease transmission. More recently, techniques of allograft preparation have improved dramatically, and these problems have greatly improved. However, the process of graft preparation (freeze-drying), kills the living cells, and decreases the strength of the tissue. There is also the concern of disease transmission. While sterilization and graft preparation minimizes this risk, it does not eliminate it entirely. The risk of complication from other factors unrelated to allograft tissue is much higher than the risk of disease transmission, but it is still there.
Summary
Many surgeons have a preferred technique for different reasons. The strength of patellar tendon and hamstring grafts is essentially equal. There is no right answer as to which is best, at least not one that has been proven in orthopedic studies. The strength of allograft tissue is less than the other grafts, but the strength of both the patellar tendon and hamstring tendon grafts exceed the strength of a normal ACL. The bottom line is 85% to 95% of patients will have clinically stable knees following ACL reconstructive surgery.
