Allograft Use In primary ACL Surgery: Who Is The Ideal Candidate?

During the past 5 years, the controversy surround graft selection in ACL surgery has clarified a bit. Multiple peer review articles from respected ACL surgeons have documented an increased failure rate in “young” patients using allograft tissue. However, there is much more to the story.

When looking at ACL surgery results and graft selection, one has to compare apples to apples. This is difficult to do in a single study when you have so many different variables that potentially affect outcome. In the ideal world, every ACL study would include the Marx activity level of the patient. How often and intense does the patient “test” the knee, i.e., attempt ACL-dependent activities? This is critically important in that the ACL may not be so important in the majority of activities the average person does. However, it is entirely different if they participate in level 1 sports every day. Most ACL studies include both groups of patients, active and not so active. One would also compare only males to males, females to females, and the exact same “allograft” to form a cohort group. I am unaware of an ideal study that has done such.

Outcomes

ACL surgeons have attempted to answer this question by looking at outcomes based on age, i.e., the younger patient, the more active the patient is and, most importantly, the more non-compliant the patient is. The reasoning is this patient group really tests results. If you look at the literature for the past 5 years, multiple studies have documented increased failure rate using allograft in this ideal study population. However, it is not the end of the chapter. Not all “allografts” are the same, which is critically important to understand.

Once a surgeon decides to use allograft tissue, the surgeon is the patient’s tissue banker. You select the exact allograft, tissue processing, preparation and mode of placement and fixation. It is up to the surgeon to be current on tissue banking protocols and outcomes using that specific tissue bank and specific type of allograft.

Are all surgeons investing time and energy in learning about “allograft” tissue processing? Each company that sells allografts may have their own proprietary method of tissue processing. Has it been tested in animals? Has it been tested in clinical trials? The surgeon must ask these important questions. What do we know about the biological incorporation of the allograft? There seems to be a consensus of basic science physicians that allograft tissue incorporates much slower than autograft tissue. Why do we have the same therapy protocols for both if biology is delayed in allograft? Why do we allow allograft patients to return to sport at the same time as autografts if the biology is delayed and the ultimate strength of the graft is delayed? These questions remain a mystery to me.

Unanswered questions

Placing allograft tissue in a non-compliant 16-year-old high school athlete simply may be a bad decision because the patient is non-compliant and returns to ACL activities too soon to match the biologic incorporation of the allograft tissue. The exact same sequence in a 40-year-old compliant professional who waits 1 year to return to level 1 sports may do perfect. These are currently unanswered questions.

In my own knee ligament practice of about 200 ACL reconstructions per year, I am biased toward autograft tissue in primary ACL surgery. I do a few revisions for failed allografts in young patients. I reserve the use of allografts for revision cases where autograft tissue is not available in the same extremity.

What are your thoughts on the use of allografts in primary ACL surgery? Who is the ideal candidate? Do you change your postoperative therapy protocol to account for delayed biological incorporation of the allograft? Do you delay return to level 1 sports for 9 months to 12 months because of delayed biological response?