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Yuji Uchio, MD et al ABSTRACT The success of an ACL
reconstruction is dependent upon the surgical technique, the graft used,
and the rehab post-operatively. Animal
studies have shown the origination of fibers perpendicular to the graft,
similar to Sharpey’s fibers, in as early as 12 weeks. Most of the animal studies have indicated that in patellar
tendon and hamstring grafts, there is incorporation of the graft into bone
between 24-52 weeks. However,
there are no studies in humans that tell us when the graft becomes
biologically fixed in the bone tunnel. This study involved 64 patients who
received quadruple looped semitendinosis hamstring grafts using femoral
fixation via the endobutton and tibial fixation via staples.
Rehab protocol included bracing in 20-30 degrees flexion for the
first few days, and avoiding extension via a soft brace for 3 months.
Lysholm scores were obtained, along with KT-2000 scores at
3,6,9,12, 18, and 24 months respectively.
MRI was performed at the same times as the KT-2000 tests, and
second look arthroscopy was performed at a mean of 24 months to remove the
staples. During this second
look, it was determined if there was complete synovium covering over the
end of the femoral tunnel where the graft entered the bone.
Also, at this time, a contrast medium was injected into the bony
tunnel and then scanned to determine if there was detection in the tunnel. Scores for the KT-2000 were
considered poor if greater than 3mm for side-to-side difference.
Poor scores were given if there was incomplete synovium covering
and/or contrast medium leakage. There
was a correlation between the MRI results showing increased signal
intensity in the tunnel, and the poor scores seen with the contrast medium
and probing to find gapping in the tunnel. The data suggests that there are
basically 4 groups seen: The
first has complete synovium covering, extremely stiff graft at 120% and no
side to side difference in the KT-2000.
A second group had a stable knee but with a gap, the third group
had an unstable knee with no gap, while the fourth and worst group had an
unstable knee with a gap. It appears that either MR imaging
or mechanical testing of the graft at 3 months should be performed to
determine exactly how that patient is proceeding with his/her bony tunnel.
Those who are not completely healing on time should have their
rehab program eased off until there is either higher stiffness of the
graft, or lower signal intensity. COMMENTS The article is the first to assess
bony tunnel ingrowth after ACL reconstruction in humans, but uses a
technique that is effective but not common any more (the endobutton),
along with what sounds like a very outdated protocol.
There is always the likelihood that, according to Wolff’s Law,
that the increased controlled stresses used by more modern protocols, may
actually facilitate bony tunnel anchoring. The study does not address some
of the newer techniques used, such as the bony mulch screw, which may have
a faster bony anchoring time due to the bone product that is packed into
the tunnel.
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