Christopher C. Kaeding, M.D. “Bioabsorbable Versus Titanium ACL Interference Screws: Want Some Facts?”
What about metal screws vs. bioabsorbable screws?
The advantage of a metal interference screw is it can promote early integration of the bone graft into bone, it has higher initial fixation strength than other methods.
The cons of a metal interference screw are that it does produce an artifact on MR imaging, it can make revisions more difficult, it gets in the way, it can be difficult to remove. Once you remove it, it can leave a large bone void. If you’re not careful when you place your interference screw, you can advance your graft into your tunnel and loosen your graft. It’s also been reported these screws can cause graft laceration.
What about bioabsorbable interference screws? These are designed to absorb over time and be replaced by bone in two and three years. That’s in theory. It’s been widely reported that incomplete absorption and delayed ossification can exist beyond 5 years. These are composed typically of PGA [polyglycolic acid], PLA [polylactic acid], or most commonly a polymer hybrid of those two. More recently, bio-composites have been developed to increase bone incorporation with increased osteoconductive properties.
The pros of a bioabsorbable screw are easier revision and decreased artifact on MRI imaging. The cons are you have less fixation strength, it may break during insertion. Incomplete resorption or incorporation to the bone can lead to tunnel widening, a bony cyst, and migration.
What about usage? In an international survey in 2013, almost three times as many surgeons were using bioabsorbable screws as metal interference screws.
What about fixation? Nyland in 2015 showed different bioabsorbable screws showed similar fixation characteristics and metal screws had higher mean insertion torque and mean load to failure. Pena showed that both metal and screws had similar mechanisms of failure.
What about complications of metal vs. bio screws? Laxdal in 2006 showed that bio screws had significantly larger radiographic appearance of bone tunnels on the femoral and tibial sides at 6 and 24 months. Myers showed that bio screws had increased femoral tunnel width.
What about clinical outcomes? You see very little difference.
If you look at meta-analyses and the Cochrane reviews, you have to conclude there’s no difference between metal and bio screws in IKDC scores, Lysholm scores, KT arthrometry, pivot-shift testing, or Tegner activity scores.
In conclusion, metal and bio screws both provide good fixation. There’s some increase risk of complications in bio screws, implant failure from breakage, persistent knee effusion and tunnel widening, but no difference between metal or bio screws in patient-reported outcomes or functional outcomes.
Personally, I do use bio screws in the tibia. With careful technique, screw breakage has not been a problem for me. I avoid any intra-articular exposure of the screw. I don’t think these bio screws should be exposed any kind of synovial fluid. Hence, I do not use them for retrograde femoral fixation. I have had the rare subcutaneous cyst which is responded well with excision.
Moderator: What about for the revision ACL? Do you like to see plastic screws there or do you like metal screws there?
Dr. Keading: The plastic screw, if it’s not an absorbable screw, it’s got the same issues the metal screw does. In revision, the plastic screw can be more difficult to find and locate…
Moderator: Bioabsorbable or metal?
Dr. Keading: In hamstrings, I don’t use an interference screw, I use cortical suspension. In the tendons, in the tibia, I use a bioabsorbable screw.
Please visit https://orthosummit.com/ for more information on this year’s upcoming event on December 11-14, 2019 at the Bellagio in Las Vegas, Nevada.
