ACL Graft Options
What are the different available grafts for ACL reconstruction and what is the right choice for me?
There are 2 general categories of ACL grafts, those that come from a different part of a patient’s own body (autograft) and those that come from a donor (allograft). There are three main different types of autografts: bone-patellar tendon-bone autograft, hamstring autograft, and quadricep autograft. Graft selection for ACL reconstruction is largely based on the surgeon’s experience and preference, although certain patient-specific factors such as previous surgeries, other injuries, and patient size can impact the type of graft utilized. In general, allografts are appropriate options for those that are over 40 years old and engage in low demand physical activities. A study performed by Kaiser Permanente found that as patient age and Body Mass Index increased, there was a lower risk of needing a revision ACL reconstruction. The study also found that allografts and hamstring autograft were associated with higher risk of revision but that bone-patellar tendon-bone autografts were associated with a higher risk of needing an ACL reconstruction on the other leg. Below we describe some of the differences in autograft and allograft options.
Citation: Maletis GB, Inacio MC, Funahashi TT. Risk factors associated with revision and contralateral anterior cruciate ligament reconstructions in the Kaiser Permanente ACLR registry. Am J Sports Med. 2015 Mar;43(3):641-7. doi: 10.1177/0363546514561745. Epub 2014 Dec 29. PMID: 25548148.
Bone-Patellar Tendon-Bone Autograft
During your surgical procedure, an incision is made below the kneecap to expose the patellar tendon (See Picture). The central one-third of the patellar tendon is then measured and taken out with a bone plug on either side to be used as the new ACL. After harvesting the graft, the site where the graft was taken from is sutured closed and the gap is filled in with a bone autograft that comes from patient’s own body obtained during the creation of the ACL tunnels. The bone grafting helps with minimizing healing issues where the patellar tendon was taken from. The bone-patellar tendon-bone autograft has been considered the “gold standard” for many ACL reconstructions due to the ease of grafting, optimal outcomes, and faster incorporation into the knee (bone to bone healing) after surgery. This graft is popular especially for high performance or professional athletes as it allows for safer return to activity and high rates of return to sport. A potential drawback is that some patients complain of pain on the front of the knee as well as difficulty with kneeling due to the location of where the graft is taken.
The hamstrings, which makes up the group of muscles on the back of the thigh, can serve as another location for grafting. Hamstring autograft allows for a smaller incision to be made and a portion of the hamstring tendon is taken from the same leg the patient is having the ACL repaired (See Picture). Two muscles of the hamstrings, semitendinosus and gracilis, are used and can be prepared in either 2-stranded or 4-stranded for hamstring grafting and secured to the knee during surgery with different fixation devices including buttons or screws. Female athletes have been reported to have hamstring weakness and this graft type can be associated with re-tear of the ACL in this patient population. Patients may complain of weakness in the hamstring following surgery as well as possible numbness in the region where the graft was taken due to the location of sensory nerves. New studies also suggest that hamstrings can act to stabilize the knee as well and therefore “helping” the ACL in maintaining knee stability.
The quadriceps, which make up the thigh muscle, is another location where an ACL graft can be harvested (See Picture). Compared to the bone-patellar tendon-bone graft, the smaller incision and location of the graft is associated with less pain to the front of the knee after surgery. A potential advantage to the quadricep tendon is that it has a larger and more favorable area to harvest the graft. This graft can contain only soft tissue or can also include a bone block harvested from the patella together with the quadricep tendon. Recent data suggests that outcomes can be excellent with this graft although it seems to be inferior with a slightly higher re-rupture rate when compared to bone-patellar tendon-bone. In revision cases where bone-patellar tendon-bone was used during the first surgery, quadriceps tendon can be an appropriate option during the revision as it provides similar biomechanical strength to bone-patellar tendon-bone graft. Additionally, quadriceps tendon is another good option for kids who are skeletally immature and require an ACL reconstruction.
Allografts are tissue coming from a donor where the tissue has been frozen prior to being used for ACL reconstruction. The risk of disease transmission is less than 1 out of every 16,000,000 people. In comparison to the 3 autograft options described above, allografts do not require extra incisions and removal of tissue but are associated with longer time for incorporation into the patient’s knee. These grafts are also associated with a cost as they are not coming from the patient’s own body. According to previous studies, allografts may potentially be associated with increased risk of re-tear in young athletes <19 years old.