This is the follow up x-ray of a patient who underwent ACL reconstruction with a 4 bundle semi-tendinosus and gracilus 3 years previously. She presented for assessment of mild anterior knee pain after exercise. She had a full range of motion, the Lachman and pivot shift tests were negative, and the KT-1000 side to side difference was less than 2 mm. She had mild lateral subluxation of the patella in extension, and patella compression pain. The diagnosis at follow up was patellofemoral pain secondary to malalignment. She had routine x-ray done that showed the marked tunnel enlargement of 14 mm. The original graft diameter was 8 mm. The fixation was by tying the leader sutures over periosteal buttons. The appearance of the graft is exactly as appears on the x-ray. The femoral tunnel was the same, but it did not image as well.
Does anyone have any ideas about why this tunnel enlargement occurs?
Read the case and believe that this is due to free
tendon in the tunnel.
The reaction is different in different patients, being more marked where
there is tendon movement or a loose tendon fit. A study on femoral tunnel
enlargement that I performed in '93 showed that this did not occur where
bone was present in the tunnel. It also was more common with 9mm screws as
opposed to 7mm screws, I suspected (although this is just conjecture) that
this was due to the larger screw displacing the graft more in the tunnel
creating a greater propensity to "windshield wiper" effect. The tunnel
changes occured most between 6 months and one year, they where less
progressive after a year and non-progressive after two years. As you have
noted in this case there was no clinical effect from these tunnel changes,
but they are certainly of concern for possible revision situations and
possible fracture. The study was done on PT's, will hamstrings respond the
same?
I think it is important for us to keep looking for means of decreasing this
phenomena. Could this take the form of introducing some "bone meal" or
other osteoinductive agent into the tunnels during graft insertion? I know
there are surgeons working on this issue in the US. Are these changes an
indication to pursue an all-inside, blind socket technique as per Andreas
S. I haven't heard Andreas speak of these changes although he may not be
X-raying these patients.
I once remember a learned ACL surgeon from Ottawa responding " I don't
X-ray my ACL's" , when I asked him in '90 if he had noted any tunnel
changes in his patients.
Deak
Dr. R. Timothy Deakon
Sports Injury Clinic
250 Wyecroft Rd., Unit 18
Oakville, Ontario, CANADA
L6K 3T7
Ph 905 849 7220
Fax 905 849 7238
e-mail: kneedoc@wchat.on.ca
Is this the bungee effect?!
On revision of trans tibially placed BPTB grafts we often see that there
is no tendon-bone ingrowth in the juxta-articualar? area where the grafts
do move up and down...
Great case, supporting the anatomic Bioscrew hamstring fixation
technique.
Andreas Staehelin
Actually, tunnel enlargment(TE) seems to be the fashion argument among orthopedic
surgeon in this last part of the millennium. In the literature this phenomena has been
largely described with all types of grafts and different mechanical explanations have been
used to justify the presence of this large osteolysis, such as the bungee effect for the
hamstring grafts or the windshield wiper effect for the BPTB. I would like to make only
few considerations about this:
First we must learn the lesson from other orthopedic branches where
lesions, like the one described, have been studing from longer time. It
is possible to find an incredible number of paper about osteolitic
lesions after hip or knee replacement. It has been recently proposed
that an individual reaction or sensibility can explain this lesion. The
ipersensibility can be mediated by different citochines(TN-alpha or
IL-beta) which can lead to the osteolityic lesions. It is possible that
the same mechanism can act after a ligament reconstruction too.
Currently we don't know exactly why this lesion occurs but as suggested by different
authors, a combination of mechanical factors and biological response could explain this.
In the recent ISAKOS in Washington several authors presented papers with these hypothesis.
Do we have to find more stiffness system of fixation or more anatomical fixation in order
to reduce this effect? The answer is yes without doubts, but we must be aware that at the
moment no significative correlations have been demonstrated between TE and knee stability.
It is possible that we are only looking for the "rainbow pot". Long-term
observations will be necessary to determine the course of bone tunnel enlargment over time
and evaluate the clinical implications
Fabrizio Margheritini, MD
Laboratory of Arthroscopy and joint Surgery, Rome
E-mail: fab.mar@iol.it
Pier Paolo Mariani, MD
E-mail: ppm.las@iol.it
