Greater revision rate seen with ACL graft placement central to the femoral footprint

Issue: July 2014

Placement of the ACL graft in a more central femoral footprint position during reconstruction led to a 3.3 times greater revision rate than graft placement in a high femoral anteromedial position, according to research presented at the Magellan Society Annual Meeting.

Perspective from Scott F. Dye, MD

Some surgeons have changed their surgical technique for ACL reconstruction from a transtibial approach with high anteromedial femoral tunnel placement to a transportal technique, in which the femoral tunnel position is more central in the footprint, according to Mark Clatworthy, MBChB, FRACS, of Middlemore Hospital in Auckland, New Zealand.

Clatworthy conducted a prospective database study of one surgeon’s experience with the two techniques. “One technique was a transtibial technique where the femoral ACL tunnel is placed in a high anteromedial position,” Clatworthy told Orthopedics Today. “The other technique (transportal technique) was an anteromedial portal technique where the femoral ACL tunnel is placed in a more distal and posterior position.”

Failure was classified as return to the same surgeon for revision, which Clatworthy noted may underestimate the revision rate. From 2000 to 2009, 1,003 patients underwent transtibial ACL reconstructions and were followed for 4 years to 13 years. In 2009, the surgeon changed his technique to a more central femoral footprint transportal technique and followed 478 patients who underwent surgery with this technique for 1 year to 4 years.

Revision and failure rates

Of the 1,003 ACL grafts placed using the transtibial technique, Clatworthy reported 47 revisions — a revision rate of 4.7%. Twenty-five of the 478 grafts placed with the transportal technique were revised for a revision rate of 5.2%.

Because the ACL grafts placed with the transportal technique had a shorter follow-up period (1 year to 4 years vs. 4 years to 13 years with the transtibial technique), Clatworthy determined the revision rate per 100 graft years to replicate the accepted arthroplasty revision rate. The revision rate for the transtibial technique was 0.57 per 100 graft years vs. 1.90 per 100 graft years with the transportal technique — a 3.3 times higher revision rate.

In addition, 40% of the transtibial ACL graft failures occurred during the first year after surgery compared with 76% of the transportal ACL graft failures.

Change in femoral tunnel position

“I have changed my femoral tunnel position due to the higher failure rate,” Clatworthy said. “I still use a transportal technique, but place the graft in the anteromedial position — farther back (proximally) and higher (anteriorly).”

Clatworthy noted that the higher graft strains from placing the graft in a central femoral footprint position may explain the higher failure rate. – by Tina DiMarcantonio

References:

Clatworthy M. Central Anatomic ACL Reconstruction Has a Higher Revision Rate Than High AM ACL Reconstruction. Presented at: Magellan Society Annual Meeting; April 10-13, 2014; Kobe, Japan.

For more information:

Mark Clatworthy, MBChB, FRACS, can be reached at Auckland Bone & Joint Surgery, Ascot Hospital, Level 1, 90 Greenlane Rd. East, Remuera, Auckland, New Zealand; 09 520 9632; email: markc@abjs.co.nz.
Disclosure: Clatworthy has no relevant financial disclosures.

Perspective

Scott F. Dye, MD

One might think that by this time in history, orthopedic sports medicine would have solved the problem of how best to surgically address the ACL-injured knee. The prodigious work of Dr. Freddie Fu of the University of Pittsburgh defined and encouraged a more “anatomic” ACL reconstruction (ACLR) technique, for which he appropriately won the American Academy of Orthopaedic Surgeon’s highest academic honor: the 2014 Kappa Delta Award. This appeared to offer a definitive answer to the problem. However, in the hands of some other surgeons, it has not worked out that way.

Dr. Clatworthy’s study confirms the anecdotal observations of some surgeons that in attempting to re-create a more anatomic footprint of the ACL on the femur (by drilling the tunnel through a separate anterior-medial arthroscopic portal rather than through a more traditional transtibial portal), his rates of early graft failure were substantially (3.3 times) greater. This led him to revert to drilling the older, more familiar, “high AM” position on the femur compared to the more central position in the more “anatomic” technique, but with less graft failures.

How is the practicing orthopedic surgeon to interpret this information? First off, one should realize there are many factors that play a role in the outcome of this type of surgery beyond the placement of the femoral tunnel, including: selection of graft type, the aggressiveness of the postoperative rehab and the ultimate level of activity to which that joint will be exposed.

What is the real ‘bottom line’ for the patient? Is it not a knee that functions pain-free for decades without the early onset of osteoarthritis? The knee is resilient, metabolically, if its unique biological characteristics are respected. Dr. Clatworthy has shown that in his patients’ knees, the exact placement of the graft on the femur is not the determinant factor in how well they do clinically. In other words, the living knee is capable of adapting to this “less-than-anatomic” position without early graft failure. How they will do long term is another question. It is well to remember that many ACL-injured knees do well without any surgery — the so-called “copers,” as Dr. Frank Noyes taught us.

Perhaps the problem with the early failures and the more “anatomic” ACL reconstruction is a combination of factors, including: the angle the graft takes entering the femoral tunnel and the high internal loads the posterolateral component is exposed to in full extension, in addition to the graft type and postoperative rehab.

I am a proponent of the concept of slowing down on the postoperative rehab to allow the newly (iatrogenically) injured joint (the knee does not know the difference between major surgery and an “axe attack”) to fully recover metabolically — to come to full joint homeostasis. This process is rate-limited and can easily take up to 18 months or longer. Tim Hewett, PhD, a highly respected researcher in sports medicine from Ohio State University, is now even advocating protecting the knee for 24 months.

There may be nothing inherent in the more “anatomic” ACLR technique that cannot be corrected by the use of a bone-tendon-bone graft and slowing down on the postoperative rehab, but that has yet to be proven. Further research will likely result in a safer, more reliable anatomic technique given time.

Dr. Clatworthy’s study should, however, take the pressure off orthopedic surgeons who have felt they must learn and perform the more “anatomic” technique to be current and to get the “latest and best” outcomes. On the other hand, those surgeons who have made the switch to the more “anatomic” technique and who are achieving excellent clinical results should feel no compunction to change back. There are many paths to the mountain top.

In the end, it is not exactly where one places the graft on the femur, to the exact millimeter, it is how one respects (and gets patients and their physical therapists, athletic trainers, etc. to respect) the biology of the living knee.

I believe the achievement and maintenance of joint homeostasis (manifested most readily by a functional, pain-free, nonarthritic knee for decades) is more important than any single structural characteristic.

Scott F. Dye, MD

Associate clinical professor orthopaedic surgery

University of California

San Francisco

Disclosures: Dye has no relevant financial disclosures.