Graft Choice for ACL Reconstruction
Assistant Professor Orthopedic Surgery
Director Sports Medicine Clinic
Ottawa On, Canada
Ph 613 520-3510
Fax 613 520-3974
The type of graft that the surgeon chooses for ACL reconstruction has
evolved over the past few decades. Erickson popularized the patellar tendon
graft autograft that Jones had originally described in 1960. This became the
popular graft choice in the late 70's.
In the light of harvest site morbidity and post op
stiffness associated with the patellar tendon graft, many surgeons began to
look at other choices, semi- tendinosis, allograft, and synthetics. Fowler and
then Rosenberg popularized the use of the semi-tendinosus. However even Fowler
was not convinced of strength of the graft as he developed the LAD (ligament
augmentation device) to supplement the semitendinosus. Gore-Tex, Leeds-Keio and
Dacron were choices as an alternative synthetic graft. The initial experience
was usually satisfactory. However, with the longer follow up, the results
Allograft was another choice that avoided the problem
of harvest site morbidity. The initial allograft that was sterilized with
ethylene oxide had very poor results. The freeze dried, fresh frozen and
cryopreserved are the most popular methods of preservation of allografts today.
This has become a popular alternative to the autograft to reduce the harvest
site morbidity, as well as the operative time.
The aggressive post-op rehab program advocated by
Shelbourne in the 90's greatly diminished the problems associated with the
patellar tendon graft. Prior to this change you had to be an athlete just to
survive the rehab program.
There was renewed interest in the semi-tendinosis
during the mid 90's. Biomechanical testing on the multiple bundle
semitendinosus and gracilus grafts demonstrated it to be stronger and stiffer.
This knowledge combined with improved fixation with devices such as the
endo-button gave surgeons more confidence with no bone soft tissue grafts. The
endo button made the procedure endoscopic, and eliminated the need for the
Fulkerson and others popularized the use of the
quadriceps tendon graft. This again reduced the harvest morbidity, especially
when only the tendon portion was harvested.
Shelbourne has described the use of the patellar tendon
autograft from the opposite knee. With both the patellar tendon and the
semitendinosus added to the list of graft choices, the need for the use of an
allograft is minimized.
The latest twist in fixation is to use an interference
fit screw to fixate the graft at the tunnel entrance. This produces a graft
construct that is strong, short, and stiff. It means that now the surgeon just
has to learn one technique for drilling the tunnels and he can chose whatever
graft he wishes, hamstring, patellar tendon, quadriceps tendon or allograft.
Successful anterior cruciate ligament reconstruction is
dependent on a number of factors including: patient selection, surgical
technique, postoperative rehabilitation, and associated secondary restraint
ligamentous instability. Errors in graft selection, tunnel placement,
tensioning, or fixation methods chosen may also lead to graft failure. The
comparison studies in the literature show that the outcome is almost the same
irregardless of the graft choice. The most important aspect of the operation is
to place the tunnels in the correct position. The choice of graft is really
Table 1: The evolution in graft choice at the Sports Medicine Clinic.
The patellar tendon graft was
originally described as the gold standard graft. It is still the most widely
used ACL replacement graft, but is not without it's problems.
Shelbourne has pushed the envelope further with the
patellar tendon graft. He has recently reported on the use of the patellar
tendon graft from the opposite knee, with an average return to play of 4 months
The advantages of the patellar tendon graft are early
bone to bone healing at 6 weeks, consistent size and shape of the graft and
ease of harvest.
The disadvantages are the harvest site morbidity of
patellar tendonitis and anterior knee pain, patellofemoral joint tightness with
late chondromalacia, late patella fracture, late patellar tendon rupture, loss
of range of motion, injury to the infra-patellar branch of the saphenous nerve.
As you can see in the reference list, most of the complications are due to the
harvest of the patellar tendon. This is still the main drawback to the use of
With the improvement in the technique
of the preparation of the multiple bundle graft, this graft choice has become
The advantages of the multiple bundle graft is that the
it now is stronger and stiffer,
Grafts courtesy Dr. Steve Howell.
The disadvantages of the graft are the various methods
use to fix the graft to bone, staples, endo-button, interference fit screws,
the graft harvest can be difficult, the tendons can be cut off short, and there
is a longer time for graft healing to bone, approximately 10-12 weeks.
Issues in Hamstring Grafts
There are several issues with hamstring
grafts that have to be dealt with, such as the graft strength, fixation to
bone, donor site morbidity and length of time to heal to the bone tunnel.
Noyes originally reported that one
strand is only 70% of the strength of the ACL. Sepaga subsequently reported
that the semi-t and gracilis composite graft is equal to an 11 mm patellar
tendon graft. Marder and Larson felt that the 4 bundle composite graft that is
tensioned equally is 250% the strength of the normal ACL. Howell demonstrated
that 4 bundles of composite graft has 4,300 N to failure compared to1750 N to
failure for the native ACL.
Brown has shown that a 4 bundle semi-t
and gracilis composite graft is 2X the patellar tendon stiffness and 3X normal
The fixation has evolved from staples
to endobutton to interference screws and ultimately to cross pins. Both the
Endo button and tying sutures over periosteal buttons may be too weak and
elastic, producing the bungee effect in the graft. This leads to a layer of
fibrous tissue around the graft giving the tunnel enlargement appearance. This
is a weak fixation. Isabashi and Fu showed that moving the fixation closer to
the tunnel entrance shortened the graft and improved the results. Pinczewski
showed no difference in outcome with interference screw fixation in semi-t and
patellar tendon, except for harvest site morbidity (difficulty in kneeling)
Pull out strength studies by several authors, Caborn, Weiler, Paulos, showed
adequate pullout strength for the interference screw soft tissue fixation. (all
above 400 N )
Semitendinosus takes 10-12 weeks to
heal to bone. During this period of time the graft has to be protected if the
fixation is not strong.
Donor site Morbidity
In follow up the semitendinosus
reconstruction has 3-21% of anterior knee pain compared to 12-40% for the
patellar tendon reconstruction. Lipsome found there was no demonstrable
weakness of knee flexion after hamstring harvest. Injury to the saphenous nerve
is an uncommon complication of the tendon stripping.
Early aggressive rehabilitation
Aligetti and Marder showed there was no
difference in outcome with early aggressive rehab. Therefore, the
semitendinosus graft has been shown to withstand aggressive rehab, and early
return to sports. Howell has also reported early return to sports without a
brace at 6 months using cross pin femoral fixation.
The main allure of the allograft is the
absence of harvest site morbidity. However, the allograft did not initially
have good reviews due to the ethylene oxide sterilization process. This caused
the graft to be weak and fail easily. With the advent of the freeze dried and
cryopreserved process there is minimal risk of disease transmission or graft
The advantages of the allograft are no harvest site
morbidity, are available off the shelf.
The disadvantages of the allograft are the risk of
disease transmission, a weak graft, if radiated or from an older patient, a
longer time to incorporate into the bone tunnels, the graft is not universally
available, and is expensive.
The quadriceps tendon has gained
popularity in the late 90's due to the ease of harvest and the large cross
sectional size. Fulkerson has popularized this graft source. Day, Morgan and
others have advocated the use of the graft harvested without a bone block from
the patella. This further reduces the morbidity of the harvest.
The advantages of the quads tendon graft is less
harvest site morbidity, and a larger cross sectional area of graft.
The disadvantages are harvest site morbidity, and the
graft has a bone block on only one end of graft.
The initial allure of the synthetic was
as an alternative to the patellar tendon graft harvest problems. However, with
long term follow up the failures became unacceptable.
The advantages of synthetic grafts are no harvest site
morbidity, no disease transmission.
The disadvantages are a higher rate of late graft
failure, an increased risk of late infection, and they are expensive.
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