ACL Reconstruction Grafts

There are roughly 200,000 reported anterior cruciate ligament (ACL) injuries every year. Approximately 65% of reported injuries are surgically reconstructed. More specifically, the reconstructive surgery is known as a graft; a procedure that harvests healthy tissue and transplants it to the traumatized area. The ACL stabilizes the femur on the tibia from movement forwards and backwards, as well as restricting over rotation of the bones when the foot is planted. Reconstruction of the ACL involves the creation of two tunnels, one on the femur (thigh bone) and one on the tibia (shin bone).

The two major types of grafts for ACL injuries are autograft (your tissue) and allograft (cadaver tissue). Each type of graft has pros and cons. The type of graft used depends on a variety of factors; including but not limited to age and physical activity level. For example, a 17 year-old female varsity soccer player would get a different graft than a 38 year-old sedentary male.

Autografts are harvested from your own tissue. The most common are the quadriceps tendon, patellar tendon and inner hamstring (semitendinosus) tendon. 

More specifically, patellar tendon grafts are considered the gold standard as they harvest a piece of bone from the inferior pole (bottom) of the patella, a portion of the patellar tendon, a piece of bone from the tibial tuberosity (the bump on the shin). This is called a bone-tendon-bone (BTB) graft, and they help secure the bone tunnelling when they affix the reconstructed ACL in the femur and tibia bones within the joint. Used in young, athletic patients, BTB grafts promote early bone to bone healing around 6 weeks. It is common for patients with BTB grafts to experience quadriceps weakness, anterior knee pain/numbness with kneeling, as well as a higher probability to develop patellar tendonitis following the ACL reconstruction.

Next, hamstring tendon grafts are harvested from the semitendinosus muscle, where it is double or quadruple wrapped to be inserted into the ACL graft. Benefits of this surgery include a smaller incision in the back of the leg, less anterior knee pain, and greater integrity of the extensor mechanism as they dont impact the quadricep/patellar tendon, good tensile strength, lower incidence of reinjury, return to pre-operative condition. On the other hand, this particular graft yields a longer recovery time, potential damage of the saphenous nerve resulting in medial leg numbness, weakness in hamstring muscle from harvesting, longer time for graft integration (due to absence of bone plugs) as soft tissue healing to bone 8-12 weeks.

Quadriceps tendon harvesting is less common but becoming a very great option for their strength and resilience. Studies show that the quadriceps tendon has 20% more collagen fibrils per cross-sectional area than the patellar tendon. They can be used in adolescents with open growth plate as it would not violate the tibial tubercle apophysis. Benefits to use of this option include minimal acute postoperative pain, less kneeling pain following surgery, less graft site pain, and less of an effect on strength loss. The biggest flaw would include longer soft tissue healing and recovery time post operatively, and lack of long term follow up studies as it is a relatively new option.

Lastly, allografts are harvested from donor cadaver tissues and include ACL, hamstring, and patellar tendons as options. These are an excellent choice for people who need to return to work faster and don’t necessarily need higher level physical function like running, jumping and cutting. Some benefits include decreased muscle weakness, kneeling pain, risk of patellar fracture, and smaller incision sites. Significant disadvantages of allograft tissue are higher failure rates, increased time to incorporation, variability in mechanical strength due to secondary sterilization techniques, risk of disease transmission, immunogenic reaction, lack of long-term outcome data (especially for young patients under the age of 25), and higher cost.

In closing,

• There is an option for everyone 
• Picking the right graft depends on activity level and age. 
• Quadriceps tendon autograft has becoming more popular with surgeons and has a lower failure rate in young adults
• Allografts are a great option for those who need to return to usual function at a quicker time