It has been debated for many years in the sports medicine field whether autograph or allografts are the better choice for an anterior cruciate ligament (ACL) tear. It has been fluctuating back and forth between the years, teetering between an autograft patellar tendon, an allograft hamstring tendon or patellar tendon, or an autograft hamstring tendon. There never seems to be any consistent or consensual basis on the topic. A study done on non-contact ACL injuries states that “An estimated 80,000 anterior cruciate ligament (ACL) tears occur annually in the United States” (Griffin et. al, 2000).
As the rise of ACL injuries continues to increase with each passing year, this question seems all the more relevant to many current and future athletes. Before we continue to delve into this question, let’s first define autografts and allografts.
An autograft is a graft transferred from one part of a patient’s body to another, such as one’s own patellar or hamstring tendon to replace their torn ACL (Taber’s Medical Dictionary).
An allograft is an organ or tissue transplanted from one member of a species to another genetically dissimilar member of the same species, such as a cadaver’s hamstring or patellar tendon to replace the athlete’s torn ACL (Taber’s Medical Dictionary).
One would assume that receiving a tissue from a cadaver would put them in a vulnerable position for tissue rejection. However, recipients of allografts take immunosuppressive drugs to prevent tissue rejection from occurring. The reconstruction of an ACL is crucial to the longevity of any given athlete due to it’s importance in maintaining the stability of the knee, particularly in activities involving cutting, pivoting or kicking. People with ruptured ACL’s have unstable knees that generally become more damaged over time. Therefore, surgical reconstruction is vital for the athlete in order to get back to regular sport activity. Now that we are familiar with the terminology, let’s see what the current research has to say about which is the better choice.
A study done on the rehabilitation after ACL reconstruction followed up with 68 patients two years after surgery to determine which method was the best. Thirty-four patients chose the patellar tendon graft, and 34 patients chose the hamstring tendon graft (Heijne & Werner, 2010). The patients were evaluated preoperatively for 3, 5, 7, and 9 months, and then 1 and 2 years after ACL reconstruction. The results from this study showed that the outcome regarding graft choice anterior knee laxity was in favor of the patellar tendon graft, and that the hamstring tendon graft led to larger laxity compared with the patellar graft. There was also a significant difference in rotational knee stability in favour of the patellar tendon graft. The patellar tendon graft resulted in higher activity level than hamstring graft. Another finding was that 2 years after ACL reconstruction, patients who chose the hamstring graft showed both significantly lower quadriceps and hamstrings strength ratio in comparison with patients operated on with patellar tendon graft as well as when compared with their own preoperative values (Heijne & Werner, 2010). The conclusion of this study shows that the patellar tendon graft leads to more stable knees with less anterior laxity and less pivot shift. Patients with hamstring ACL reconstruction need more hamstring strengthening exercises. Some of the study’s data indicated that patients operated on with hamstring grafts might need slower rehabilitation protocols, focusing more on hamstring strength than those with patellar tendon graft. Athletic patients with the patellar tendon ACL reconstruction returned to sports earlier and at a higher level than those operated on with hamstring tendon grafts (Heijne & Werner, 2010).
A second study on the patellar tendon versus the hamstring autograft for ACL ruptures in adults gathered 1597 young to middle-aged adults for this study. The results demonstrated that all of the movement tests they performed on the patients (instrumental, Lachman, pivot shift) for static stability consistently showed that patellar tendon reconstruction resulted in a more statically stable knee compared with hamstring tendon reconstruction (Dooley, Chan, Dainty, Mohtadi, and Whelan, 2006). Conversely, patients experienced more anterior knee problems, especially with kneeling, after patellar tendon reconstruction. Patellar tendon reconstructions resulted in a statistically significant loss of extension range of motion and a trend towards loss of knee extension strength. Hamstring tendon reconstructions demonstrated a trend towards loss of flexion range of motion and a statistically significant loss of knee flexion strength (Dooley, Chan, Dainty, Mohtadi, and Whelan, 2006). The conclusion of this study explains that while patellar tendon reconstructions are more likely to result in statically stable knees, they are also associated with more anterior knee problems (Dooley, Chan, Dainty, Mohtadi, and Whelan, 2006).
The third and final study did a meta-analysis comparing patellar tendon and hamstring tendon autografts. The researchers of this study gathered 1348 patients in the patellar tendon group, and 628 patients in the hamstring tendon group (Freedman, D’Amato, Nedeff, Kaz, and Bach, 2003). The results of this study showed that the rate of graft failure in the patellar tendon group was significantly lower, and a significantly higher proportion of patients in the patellar tendon group had a side-to-side difference of less than 3 mm on KT-1000 arthrometer testing than in the hamstring tendon group (Freedman, D’Amato, Nedeff, Kaz, and Bach, 2003). The KT-1000 knee arthrometer is an objective instrument to measure anterior tibial motion relative to the femur for anterior cruciate ligament reconstruction (Arneja & Leith, 2009). There was a higher rate of manipulation under anesthesia or lysis of adhesions and of anterior knee pain in the patellar tendon group. Patellar tendon autografts had a significantly lower rate of graft failure and resulted in better static knee stability and increased patient satisfaction compared with hamstring tendon autografts. However, patellar tendon autograft reconstructions resulted in an increased rate of anterior knee pain (Freedman, D’Amato, Nedeff, Kaz, and Bach, 2003).
The first study in this section talked about the comparison of auto and allograft hamstring tendon constructs for ACL reconstruction. The study gathered 84 patients total, with 37 choosing autografts and 47 choosing allografts (Edgar, Zimmer, Kakar, Jones, and Schepsis, 2008). The results of this study showed that at short to intermediate term follow-up, an allograft hamstring construct performs just as well as an autograft hamstring construct in all clinically monitored parameters (Edgar, Zimmer, Kakar, Jones, and Schepsis, 2008). Given some of the potential advantages of allograft constructs (no donor-site morbidity, shorter operative time, a potential graft tissue source for backup when harvested tissue is inadequate, and the ability to preoperatively select the appropriate length and diameter graft, thus adjusting to the size and weight of the patient), allograft constructs are becoming more widely used. The performance of the allograft counterpart of the typical autograft hamstring construct performs as well by all criteria at short to intermediate term followup (Edgar, Zimmer, Kakar, Jones, and Schepsis, 2008).
The second study looked at allografts versus autograft ACL reconstruction to see which method led to the least amount of complications. Their results showed that patient age and ACL graft type were significant predictors of graft failure for all study surgeons (Kaeding et.al, 2011). Patients in the age group of 10 to 19 years had the highest percentage of graft failures. The odds of graft rupture with an allograft reconstruction are 4 times higher than those of autograft reconstructions. For each 10 year decrease in age, the odds of graft rupture increase 2.3 times (Kaeding et.al, 2011). The conclusion formed from their data revealed that there is an increased risk of ACL graft rupture in patients who have undergone allograft reconstruction. Younger patients also have an increased risk of ACL graft failure (Kaeding et.al, 2011).
The final study in this section tested allograft ACL reconstruction in the young, active patient. Their results showed that high activity allograft patients had a 2.6 to 4.2 fold increase in the probability of graft failure compared with low activity bone-patellar tendon-bone allograft patients and low and high activity bone-patellar tendon-bone autograft patients (Barrett, Luber, Replogle, and Manley, 2010). Patients undergoing bone-patellar tendon-bone autograft reconstruction reported significantly fewer problems on a visual analog scale and scored significantly higher on the postoperative Tegner activity scale than patients undergoing allograft reconstruction (Barrett, Luber, Replogle, and Manley, 2010). The active allograft group is 2.6 to 4.2 times more likely to fail compared with low-activity allografts and low and high activity autografts. We conclude that fresh-frozen bone-patellar tendon-bone allografts should not be used in young patients who have a high Tegner activity score because of their higher risk of failure (Barrett, Luber, Replogle, and Manley, 2010).
Based on the three studies demonstrated above about allografts, the athlete should stay away from allografts due to the increased risk of ACL graft rupture and higher risk of failure. So this leaves the option of autografts. But which one? Well, based on the studies above, research shows that a patellar tendon autograft is the best way to go for the serious athlete. This is due to the patellar tendon autografts having a significantly lower rate of graft failure and resulting in better static knee stability and increased patient satisfaction compared with hamstring tendon autografts. All of the studies shown in the autograft section demonstrate that patellar tendon graft lead to more stable knees with less anterior laxity and less pivot shift. Patients that choose to go with the hamstring tendon autograft need more hamstring strengthening exercises, and slower rehabilitation protocols that needs to focus on hamstring strength than those that choose the patellar tendon autograft.
Furthermore, these studies show that athletic patients with patellar tendon autografts returned to their sport earlier and at a higher level than those operated on with hamstring tendon grafts. However there is a word of caution for the patellar tendon autograft, that all three studies agreed upon; and that is that the patellar tendon autograft reconstructions resulted in an increased rate of anterior knee pain, especially in a kneeling position. Besides the anterior knee problems, the patellar tendon reconstructions resulted in a statistically significant loss of extension range of motion and a trend towards loss of knee extension strength. Those that went with the hamstring tendon reconstructions demonstrated a trend towards loss of flexion range of motion and a statistically significant loss of knee flexion strength.
The big take home message here is that there will obviously be a handful of pros and cons between the choice of hamstring or patellar tendon autografts. Perhaps the biggest determiner in answering this question is what your sport is, what you really cannot afford to lose in terms of knee flexion/extension and knee pain, and weight out whether the pros and cons work for you on your field or court.
“A.” Taber’s Cyclopedic Medical Dictionary. Philadelphia: F.A. Davis, 2013. 123-24. Print.
Arneja, S., & Leith, J. (2009). Review article: Validity of the KT-1000 knee ligament arthrometer. Journal of Orthopaedic Surgery, 17(1).
Barrett, G. R., Luber, K., Replogle, W. H., & Manley, J. L. (2010). Allograft anterior cruciate ligament reconstruction in the young, active patient: Tegner activity level and failure rate. Arthroscopy: The Journal of Arthroscopic & Related Surgery, 26(12), 1593-1601.
Dooley, P. J., Chan, D. S., Dainty, K. N., Mohtadi, N. G., & Whelan, D. B. (2006). Patellar tendon versus hamstring autograft for anterior cruciate ligament rupture in adults. The Cochrane Library.
Edgar, C. M., Zimmer, S., Kakar, S., Jones, H., & Schepsis, A. A. (2008). Prospective comparison of auto and allograft hamstring tendon constructs for ACL reconstruction. Clinical orthopaedics and related research, 466(9), 2238-2246.
Freedman, K. B., D’Amato, M. J., Nedeff, D. D., Kaz, A., & Bach, B. R. (2003). Arthroscopic Anterior Cruciate Ligament Reconstruction A Metaanalysis Comparing Patellar Tendon and Hamstring Tendon Autografts. The American journal of sports medicine, 31(1), 2-11.
Griffin, L. Y., Agel, J., Albohm, M. J., Arendt, E. A., Dick, R. W., Garrett, W. E., … & Wojtys, E. M. (2000). Noncontact anterior cruciate ligament injuries: risk factors and prevention strategies. Journal of the American Academy of Orthopaedic Surgeons, 8(3), 141-150.
Heijne, A., & Werner, S. (2010). A 2-year follow-up of rehabilitation after ACL reconstruction using patellar tendon or hamstring tendon grafts: a prospective randomised outcome study. Knee Surgery, Sports Traumatology, Arthroscopy,18(6), 805-813.
Kaeding, C. C., Aros, B., Pedroza, A., Pifel, E., Amendola, A., Andrish, J. T., … & Spindler, K. P. (2011). Allograft versus autograft anterior cruciate ligament reconstruction predictors of failure from a MOON prospective longitudinal cohort. Sports Health: A Multidisciplinary Approach, 3(1), 73-81.