The rate of reoperation and graft failure following anterior cruciate ligament (ACL) reconstruction with the use of allograft is not only higher than that for autograft but considerably higher in younger patients, according to a study presented at the annual meeting of the Arthroscopy Association of North America.

In light of these findings, the authors of the study, which was presented by Lutul D. Farrow, MD, of the Cleveland Clinic, recommend against using allografts for ACL repair in patients younger than age 25.

Hypothesis undone
Although previous reports had indicated higher failure and reoperation rates for allograft reconstruction versus autograft, Dr. Farrow said his colleagues had not noted such a discrepancy in their own clinical practices. But, when they undertook this retrospective review of patients who had undergone ACL reconstruction during an 8-year period, they found higher rates of failure in the allograft group and markedly higher rates in allograft patients younger than 25.

Among the patients who had undergone ACL surgery during the study period, the authors were able to reach 123 (67 male, 56 female) for telephone follow-up. The average age at surgery was 29 years, with a mean follow-up of 50.3 months (range 11 to 111 months). A total of 99 patients had received allograft and 24 patients had autograft ACL reconstruction.

Among patients who received allografts, 17 percent (17 of 99) required additional surgery (such as mensical repair, hardware removal, revision ACL surgery, or cartilage trimming) following ACL reconstruction. The rate of reoperations for patients younger than age 25 was 30.8 percent.

The rate of ACL-revision surgery was 10.1 percent in the allograft group and 4.2 percent in the autograft group. Patients younger than age 25 who received allografts had a revision rate of 20.5 percent, versus 0 percent for those with autograft.

Despite the higher rates of reoperations and revision surgeries, 93 percent of those who received allografts were “happy” they had surgery and 88 percent said that they would have the surgery again. Patient satisfaction was even higher among autograft patients (100 percent on both counts).

Patients in the allograft group who had additional surgeries reported lower Tegner Lysholm (average: 59) and International Knee Documentation Committee (IKDC) (average: 54) scores compared with Tegner Lysholm and IKDC scores of 83 and 79, respectively, for those who did not have additional surgeries (P = 0.0025 and 0.006, respectively).

Tegner Lysholm and IKDC scores were similar between those patients older than 25 (81.8 and 77.5, respectively) and younger than age 25 (81.8 and 78). However, Tegner Lysholm activity scores were higher in those patients younger than age 25 both before and after ACL reconstruction (7.5 and 6.0, respectively) compared with those older than age 25 (6.1 and 5.3).

Within the patient cohort, researchers were able to identify a subset of 19 primary ACL reconstructions (13 allograft, 6 autograft) performed on Division I athletes from the University of Arizona. All of those patients were younger than age 25. The rate of reoperation was 69 percent in the allograft group and 50 percent in the autograft group. There were eight ACL failures (62 percent) in the allograft group and none in the autograft group. Not all of the patients who experienced a failure opted for revision surgery.

The choice
Dr. Farrow noted that the ideal graft choice for ACL reconstruction is still a subject of intense debate. Proposed advantages that support the use of allografts include less morbidity and/or pain from a less invasive procedure, faster recovery, increased sizing options and shorter surgical times, and the associated lower cost. Yet, this study, one of the largest to date performed with a comparison group, appears to confirm that using allograft results in markedly higher failure rates in younger patients, especially in high-activity patients and in patients younger than age 25.

The results, said Dr. Farrow, were “somewhat surprising and practice changing for us.” Although he had not been using allograft in most patients, this study led him and his colleagues “to counsel heavily against allograft reconstruction” in younger patients.

Causes for failure
“I think we are still learning why allograft failure occurs,” Dr. Farrow said. “Some authors suggest there is an immune response to the graft. Also, the ideal allograft preparation is fresh, unfrozen, and not irradiated. Unfortunately, allografts have to be frozen so as to be available for everyone and they have to go through some sort of sterilization to make them aseptic. I don’t think we can get past that.

“Still, we’ve gotten better about not irradiating too much,” he continued, “and have gotten away from chemical preparations that are detrimental to the graft, so that has become less of an issue over the past decade.”

In young athletic patients, especially elite athletes such as the Division I players in the study, “patients want to get back on the field or to the court as quickly as possible after ACL reconstruction,” he said. “Accelerated rehabilitation may outpace both the rate at which graft is incorporated into the bone at the attachment points and rate of ligamentization. Allowing an athlete to return to play at 5 months may be too soon, especially because ligamentization happens much more slowly in the allograft tendon.”

Whether the autograft is from the patellar tendon, quadriceps tendon, or hamstring (Figs. 1, 2), Dr. Farrow said he counsels patients aged 25 to 50 years to receive an autograft, unless they have strong objections. “What we take from your body is the best thing we can put into your body. Some of the advantages of allograft—less pain, improved motion—go away after the early, 6-week postoperative period.”

He is “more likely to counsel patients older than age 50 to receive an allograft, because the graft we get out of the freezer may be better than their own tissue. It may be unnecessary to add the morbidity of the autograft procedure when the patient just wants to get back to day-to-day activities or low-level athletic activities.” The potential difficulty of obtaining an autograft makes allograft better suited for the active obese patient who needs a stable knee, after conservative management has failed.

Continued research is needed to further refine the decision-making process for graft use in ACL reconstruction, Dr. Farrow said. “The answer as to when to use allograft in ACL reconstruction will continue to be better defined as the basic science of graft healing and incorporation into bony tunnels is elucidated and postoperative rehabilitation protocols and return to play are modified.”

A large prospective, randomized study would provide more reliable information to guide surgeons. Investigators in the Multicenter Orthopaedic Outcomes Network (MOON), which has been following ACL reconstruction patients since 2002, have found a 20 percent allograft failure rate in 18-year-old athletes—and that research is affecting how young injured athletes are treated. (See “Large ACL Study Yields Clinical Insights for Treatment,” AAOS Now, March 2012.) Dr. Farrow also said that an investigation of synovial fluid in the joint space, evaluating for a low-level inflammatory reaction to allografts, would be helpful.

Co-authors with Dr. Farrow (Mitek, Musculoskeletal Transplantation Foundation) of “Long Term Outcomes Following Allograft Anterior Cruciate Ligament Reconstruction” are Eric A. Lenehan , MD (no conflicts); W. Barrett Payne, MD (no conflicts); Brad Askam, MD (DePuy), and William A. Grana, MD, MPH (American Journal of Orthopedics, American Orthopaedic Society for Sports Medicine).

Terry Stanton is senior science writer for AAOS Now. He can be reached at tstanton@aaos.now

Bottom Line

• Recent reports have indicated higher rates of reoperation and failure for ACL reconstruction using allograft.
• In this study, the revision rate for allograft patients was 10.1 percent versus 4.2 percent for autograft; among patients younger than age 25, it was 20.5 percent for allograft and 0 percent for autograft.
• Factors contributing to allograft failure may include delayed graft incorporation, effects of sterilization, and overaggressive rehabilitation protocols, as well as a possible auto-immune reaction.
• The authors strongly recommend against the use of allograft for ACL reconstruction in patients younger than age 25 and generally recommend autograft for patients aged 25 to 50 years.