Prospective analysis of
failure rate and predictors of failure after anatomic anterior cruciate
ligament reconstruction with allograft

Van Eck CF, Schkrohowsky JG,
Working ZM, Irrgang JJ, Fu FH. Am J Sports Med. 2012 Apr 03.

Re-injury rates after ACL
reconstruction (ACLR) are shockingly high, with up to 25% of patients suffering
a re-injury.  Surgical advancements
abound in attempting to decrease re-injury rates and the development of
osteoarthritis after ACL injury, but highly structured prospective analysis of
re-injury rates for each type of ACLR are not currently available.  Therefore, the purpose of this investigation
was to systematically analyze the re-injury rate of patients undergoing an
anatomic ACLR with allograft tissue, as well as to identify predictors of
re-injury. Patients undergoing ACLR at the University of Pittsburgh Medical
Center were prospectively enrolled in a registry and followed for up to 4
years. The outcomes of interest in this study were operational definitions of
failure – 1) subjective complaints of instability, 2) > 5mm difference in
arthrometry between limbs, 3) abnormal pivot-shift, or 4) re-rupture diagnosed
on MRI or arthroscopy. Return to sport clearance was not granted until around 9
months post-operatively. A re-injury rate of 13% (13% double bundle ACLR vs.
11% in single bundle ACLR) was observed in this cohort. Age (younger than 19)
and earlier return to sport (222 days vs. 267 days or 7m v 9m) were associated
with graft failure.

For all of the talk about the
potential for anatomic ACLR or double-bundle ACLR to improve outcomes after
injury, these results put newer methods right on par with previously
established methods.  The authors propose
(and the numbers support) that timing of return to sport may need to be
adjusted with an anatomic allograft ACLR to prevent re-injury (and hopefully
restore normal biomechanics). Without graft source morbidity (anterior knee
pain with patellar tendon graphs; hamstring weakness with hamstring grafts),
which invariably delays rehabilitation, patients with an allograft may simply
feel too good and do too much, too soon. 
However, with long term deficits in strength that can result from
autograft harvest, an allograft has many advantages.  The one thing that is frequently overlooked
in the re-injury literature is the measured functional capability of patients
returning to sport after ACL reconstruction (Barber-Westin, Phys
Sportsmed 2011
).  Leading European
researchers have recommended extremely high levels of measured functional test symmetry
before returning to sport (Thomee,
KSSTA 2011
), but we do not see any mention of objective testing in this
cohort of patients. The authors mention that many athletes return to sport
without express clearance of their surgeon, which is clearly a concern for
patients returning to sport before they are ready.  But another question is how many patients are
cleared for sport before they are physically ready? Ligamentization does not
occur for nearly a year, but we see many players return to sport before one
year without any issues – what makes them different than those who re-injure?
And more importantly, can we identify them without sophisticated and
cost-prohibitive biomechanical analysis? 
Do you have a separate protocol for patients who have had an ACLR with
an allograft or an anatomic ACLR? Or do you treat them the same and allow them
to return when the numbers show they are performing symmetrically? What are the
red flags that you look for in a patient after ACLR?

Written by: Andrew Lynch
Reviewed by:  Stephen Thomas

Related Posts:

van Eck CF, Schkrohowsky JG, Working ZM, Irrgang JJ, & Fu FH (2012). Prospective analysis of failure rate and predictors of failure after anatomic anterior cruciate ligament reconstruction with allograft. The American Journal of Sports Medicine, 40 (4), 800-7 PMID: 22238055