ACL Graft Options
Broadly speaking the various options for ACL reconstruction are:
  • Autograft: tissue from the patient’s own body
    • Hamstring tendon
    • Patella tendon
    • Quadriceps tendon
  • Allograft: donor tissue from a cadaver’s body
    • Achilles tendon
    • Tibialis anterior tendon
  • Synthetic: industrial made 
Hamstring and patella tendon grafts are the most commonly and widespread used grafts. They have the best and most reliable results short and long term. 
Hamstring tendon
  • Can be taken from the same injured leg (ipsilateral) or the other knee (contralateral) if the hamstrings have already been taken (e.g. revision operation) or there is a medial sided injury in addition to the ACL injury
  • Hamstrings are a group of muscles at the back of the thigh
  • Two of these are taken to make the ACL graft:
    • Gracillis
    • Semitendinosus
  • They are then doubled over to obtain adequate thickness for the new ACL graft
  • If necessary can be tripled over if doubling was of insufficient thickness for the ACL graft

Advantages
  • No risk of anterior knee pain (pain at the front of the knee) or patella fracture as caused by a patella tendon graft
  • Smaller incision (wound) to harvest them
  • Less pain in the early and later phases
  • Easily available
  • Hamstring graft is at least twice as strong as native ACL and when tripled even stronger

Disadvantages
  • Common to have patch of numbness around the wound
  • Graft healing of soft tissue to bone takes slightly longer than the bone to bone healing that occurs in a patella tendon graft
Verdict: The preferred graft of choice.
Patella tendon graft
  • The middle third of the patella tendon is taken (the tissue that connects the patella to the tibia)
  • Along with the tendon, bone blocks on either side are taken i.e. from the patella and the tibia 
  • That’s why the graft is called medically bone-patella tendon-bone graft

Advantages
  • A reliably good graft that used to be the gold standard for ACL reconstruction in the past
  • Due to the bone blocks on either side it has more rapid bond to the femur and tibia than a hamstring graft (soft tissue to bone healing is slower)
  • This means that patients feel their knee more stable in the first 6-8 weeks compared to hamstrings but later they balance out and feel equally stable
  • It is 1.5 times stronger than the native ACL graft

Disadvantages
  • More painful (short and long term) than hamstrings as bone blocks are taken from patella and tibia
  • Increased risk of ongoing anterior knee pain 
  • Difficulty with kneeling long term
  • As a result it is not recommended in patients with pre-existing anterior knee pain or those who kneel a lot
  • Increased risk of graft rupture if patient had pre-existing patella tendinopathy
  • Longer wound
  • Risk of patella fracture: 
    • Rare but a bad complication to happen
    • Will require further surgery to fix the patella
Verdict: Reserved for revision ACL reconstruction or upon patient’s request.
Allografts
  • Allograft tendons can be: 
    • Soft tissue: 
      • Hamstrings
      • Tibialis posterior
      • Tibialis anterior
    • Bone-tendon:
      • Bone-patella-tendon-bone
      • Achilles tendon
      • Quadriceps tendon

Advantages
  • No donor site complications from taking an autograft
  • No damage to hamstrings or patella tendon
  • Less postoperative pain 
  • Fewer and/or smaller wounds leading to better cosmesis
  • Reduced operative time
  • Useful in revision ACL and multiligament reconstructions when may have reduced options for autograft use

Disadvantages
  • Sterilisation and processing methods can impact quality of the allograft:
    • Radiation in particular that was used to sterilise the grafts, has been shown to significantly reduce strength of the graft and increase rate of subsequent rupture
    • Allografts should be fresh frozen and non-irradiated and from donors who are less than 40 years old
  • Worse outcomes than autografts overall but especially in high demand athletes
  • Caution when used in younger athletes (<20 year) as have about 5x higher graft rupture rates
  • Slower onset and rate of incorporation of allograft versus autograft
  • Concern for disease transmission:
    • HIV, hepatitis
    • Risk reported to be 1 in 1.6 million
    • However, no reported case yet for HIV transmission following allograft ACL reconstruction
  • Expensive
  • Not as readily available
Verdict: Can be considered for recreational athlete upon request. Useful in revision and multiligament reconstructions.
Synthetic grafts
  • Numerous synthetic grafts have been tried since the 1970s 
  • The original grafts had an unacceptably high failure rate
  • When they did fail they caused excessive synovitis reaction and articular cartilage damage
  • They have since been abandoned but newer synthetic grafts have come out since the 1990s
  • The newer grafts still have greatly inferior outcomes to autografts and are not as widely used

Advantages
  • Quick and easy to use
  • Very strong

Disadvantages
  • Expensive
  • Worse results compared to autografts
  • When they fail are more difficult to revise:
    • When they rupture they cause excessive inflammatory reaction within the knee and abrasion to the cartilage
Verdict: Not used for ACL reconstruction.