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Editorial Commentary: The Acrid Bioscrew in Anterior Cruciate Ligament Reconstruction of the Knee

      Abstract

      Bioresorbable screws have been widely adopted for graft fixation in knee anterior cruciate ligament (ACL) reconstruction on the promise of screw resorbtion and replacement by bone. When considering the value of bioresorbable screws, it is imperative to understand that the “A” in PGA and PLA, the base ingredient of all bioscrews, is for Acid. All resorb by a process of hydrolysis; the speed and extent of resorbtion is determined by both the acidity of the screw and the environment in which it is placed. Regrettably, the promise of reliable, predictable screw resorbtion and replacement by bone remains elusive, despite the addition of “osteoconductive” materials. For the most part, bioresorbables are associated with good clinical outcomes for ACL reconstruction; they are not “dangerous,” just disappointing with respect to bony replacement. We propose that nonresorbing inert plastics such as PEEK (polyether ether ketone) may be better suited for the purpose of graft fixation devices for ACL reconstruction.
      I read with interest the article “Radiographic Tibial Tunnel Assessment After Anterior Cruciate Ligament Reconstruction Using Hamstring Tendon Autografts and Biocomposite Screws: A Prospective Study With Five-Year Follow-up” by Karikis, Ejerhed, Sernert, Rostgård-Christensen, and Kartus.
      • Karikis I.
      • Ejerhed L.
      • Sernert N.
      • Rostgård-Christensen L.
      • Kartus J.
      Radiographic tibial tunnel assessment after anterior cruciate ligament reconstruction using hamstring tendon autografts and biocomposite screws: A prospective study with five-year follow-up.
      The authors examined the radiological appearance of tibial tunnels 5 years after knee anterior cruciate ligament (ACL) reconstruction with a biocomposite screw, and concluded that no tunnel widening had occurred over time.
      This leads me to opine regarding the value of “biocomposite,” “osteoconductive,” and “resorbable” materials for fixation in current ACL reconstruction techniques and ligament repair to bone. Why do we have these bioscrews?
      The advantages and disadvantages of metal screws are well described and understood by surgeons. “Bioscrews” were designed with the goal of creating a screw that is radiologically friendly, able to provide strong fixation until the graft incorporates, and then fully undergo resorbtion to be replaced by bone. Although most studies have shown that “bioscrews” are associated with good clinical outcomes, which may be equivalent to metal screws,
      • Kaeding C.
      • Farr J.
      • Kavanaugh T.
      • Pedroza A.
      A prospective randomized comparison of bioabsorbable and titanium anterior cruciate ligament interference screws.
      • Kousa P.
      • Jarvinen T.L.N.
      • Kannus P.
      • Jarvinen M.
      Initial fixation strength of bioabsorbable and titanium interference screws in anterior cruciate ligament reconstruction.
      • Caborn D.
      • Coen M.
      • Neef R.
      • Hamilton D.
      • Nyland J.
      • Johnson D.
      Quadrupled semitendinosus-gracilis autograft fixation in the femoral tunnel: A comparison between a metal and a bioabsorbable interference screw.
      • Abate J.
      • Fadale P.
      • Hulstyn M.
      • Walsh W.
      Initial fixation strength of polylactic acid interference screws in anterior cruciate ligament reconstruction.
      • Weiler A.
      • Windhagen H.
      • Raschke M.
      • Laumeyer A.
      • Hoffmann R.
      Biodegradable interference screw fixation exhibits pull-out force and stiffness similar to titanium screws.
      • Barber F.A.
      Poly-D,L-lactide interference screws for anterior cruciate ligament reconstruction.
      • Zantop T.
      • Weimann A.
      • Schmidtko R.
      • Herbort M.
      • Raschke M.J.
      • Petersen W.
      Graft laceration and pullout strength of soft-tissue anterior cruciate ligament reconstruction: In vitro study comparing titanium, poly-D,L-lactide, and poly-D,L-lactide tricalcium phosphate screws.
      • Laxdal G.
      • Kartus J.
      • Eriksson B.I.
      • Faxen E.
      • Sernert N.
      • Karlsson J.
      Biodegradable and metallic interference screws in anterior cruciate ligament reconstruction surgery using hamstring tendon grafts: Prospective randomized study of radiographic results and clinical outcome.
      • Shen C.
      • Jiang S.-D.
      • Jiang L.-S.
      • Dai L.-Y.
      Bioabsorbable versus metallic interference screw fixation in anterior cruciate ligament reconstruction: A meta-analysis of randomized controlled trials.
      • Myers P.
      • Logan M.
      • Stokes A.
      • Boyd K.
      • Watts M.
      Bioabsorbable versus titanium interference screws with hamstring autograft in anterior cruciate ligament reconstruction: A prospective randomized trial with 2-year follow-up.
      • Drogset J.O.
      • Straume L.G.
      • Bjørkmo I.
      • Myhr G.
      A prospective randomized study of ACL-reconstructions using bone-patellar tendon-bone grafts fixed with bioabsorbable or metal interference screws.
      there is also evidence that these screws are not readily absorbed by the body, nor replaced with bone.
      • Kaeding C.
      • Farr J.
      • Kavanaugh T.
      • Pedroza A.
      A prospective randomized comparison of bioabsorbable and titanium anterior cruciate ligament interference screws.
      • Warden W.H.
      • Friedman R.
      • Teresi L.M.
      • Jackson D.W.
      Magnetic resonance imaging of bioabsorbable polylactic acid interference screws during the first 2 years after anterior cruciate ligament reconstruction.
      • McGuire D.A.
      • Barber F.A.
      • Elrod B.F.
      • Paulos L.E.
      Bioabsorbable interference screws for graft fixation in anterior cruciate ligament reconstruction.
      • Ma C.B.
      • Francis K.
      • Towers J.
      • Irrgang J.
      • Fu F.H.
      • Harner C.H.
      Hamstring anterior cruciate ligament reconstruction: A comparison of bioabsorbable interference screw and endobutton-post fixation.
      • Warden W.H.
      • Chooljian D.
      • Jackson D.W.
      Ten-year magnetic resonance imaging follow-up of bioabsorbable poly-L-lactic acid interference screws after anterior cruciate ligament reconstruction.
      The literature is scattered with reported complications and adverse events, including cyst formation, sterile abscess formation, inflammatory reaction, breakage, intra-articular migration, transcutaneous migration, tunnel widening, and osteolysis.
      • Laxdal G.
      • Kartus J.
      • Eriksson B.I.
      • Faxen E.
      • Sernert N.
      • Karlsson J.
      Biodegradable and metallic interference screws in anterior cruciate ligament reconstruction surgery using hamstring tendon grafts: Prospective randomized study of radiographic results and clinical outcome.
      • Kiekara T.
      • Paakkala A.
      • Suomalainen P.
      • Huhtala H.
      • Järvelä T.
      Femoral and tibial tunnel diameter and bioabsorbable screw findings after double-bundle ACL reconstruction in 5-year clinical and MRI follow-up.
      • Konan S.
      • Haddad F.
      A clinical review of bioabsorbable interference screws and their adverse effects in anterior cruciate ligament reconstruction surgery.
      • Bostman O.M.
      • Pihlajamaki H.K.
      Adverse tissue reactions to bioabsorbable fixation devices.
      One of the early “osteoconductive bioscrews” was recalled from the market by the manufacturer after unpredicted inflammatory reactions in the first year after implantation, which gave the then editors of Arthroscopy cause to consider “we don't know as much biology as we thought.”
      • Lubowitz J.H.
      • Poehling G.G.
      Don't know much biology: Redux.
      It is far more enlightening to examine the chemistry of polyglycolic acid (PGA)- and polylactic acid (PLA)-based bioscrews than biology. It is imperative to understand that the “A” in PGA and PLA, the base ingredient of all bioscrews, is for Acid. These are solid acids that resorb by “hydrolysis,” that is, dissolve in water forming liquid acid. In areas of good blood supply, the acid is well buffered and then metabolized (such as resorbable sutures). However, in areas of poor blood supply such as bone, the pH can be so low that acidic tissue damage occurs, resulting in bone destruction. For this reason, and because of it, manufacturers have added buffers to increase pH, as well as osteoconductive materials such as hydroxyapatite and tricalcium phosphate to stimulate bone formation. Despite various screw formulations, bone formation is only observed late in the reabsorption process, and only then in bioscrews with a composition that are slowly resorbed in excess of 5 years.
      • Warden W.H.
      • Chooljian D.
      • Jackson D.W.
      Ten-year magnetic resonance imaging follow-up of bioabsorbable poly-L-lactic acid interference screws after anterior cruciate ligament reconstruction.
      • Arama Y.
      • Salmon L.J.
      • Sri-Ram K.
      • Linklater J.
      • Roe J.P.
      • Pinczewski L.A.
      Bioabsorbable versus titanium screws in anterior cruciate ligament reconstruction using hamstring autograft: A prospective, blinded, randomized controlled trial with 5-year follow-up.
      The composition of ingredients, size of the acidic crystals, and method of manufacture (annealing the surface slows hydrolysis) will determine how the material will behave in a given location. Thus, not all “bioscrews” are equal, nor behave in the same way.
      Tunnel widening was not found by Karikis et al. with a poly-levo dextro-lactide (PLDLA) and b-tricalcium phosphate composite screw,
      • Karikis I.
      • Ejerhed L.
      • Sernert N.
      • Rostgård-Christensen L.
      • Kartus J.
      Radiographic tibial tunnel assessment after anterior cruciate ligament reconstruction using hamstring tendon autografts and biocomposite screws: A prospective study with five-year follow-up.
      but has certainly been reported in other series.
      • Laxdal G.
      • Kartus J.
      • Eriksson B.I.
      • Faxen E.
      • Sernert N.
      • Karlsson J.
      Biodegradable and metallic interference screws in anterior cruciate ligament reconstruction surgery using hamstring tendon grafts: Prospective randomized study of radiographic results and clinical outcome.
      • Shen C.
      • Jiang S.-D.
      • Jiang L.-S.
      • Dai L.-Y.
      Bioabsorbable versus metallic interference screw fixation in anterior cruciate ligament reconstruction: A meta-analysis of randomized controlled trials.
      Magnetic resonance imaging and computed tomography were not available in this study so the extent of ossification or screw degradation could not be determined. Furthermore, the study examined only the tibial tunnel, and we should remember that a screw made of the same material may behave differently in the femoral tunnel.
      • Arama Y.
      • Salmon L.J.
      • Sri-Ram K.
      • Linklater J.
      • Roe J.P.
      • Pinczewski L.A.
      Bioabsorbable versus titanium screws in anterior cruciate ligament reconstruction using hamstring autograft: A prospective, blinded, randomized controlled trial with 5-year follow-up.
      Surgeons should consider each screw on its own merits. To my mind, tunnel widening may not occur as seen in the study by Karikis et al., but if the screw is also still present after 5 years, this may be a moot point to the surgeon.
      It is worthwhile re-examining the reasoning for bioscrews.
      • Easier revision, no need to remove an osteointegrated titanium device.
      • The implied promise of bone tunnel reformation.
      In my experience the majority of revision ACL surgery occurs within the first 5 years.
      • Bourke H.
      • Salmon L.J.
      • Waller A.
      • Patterson V.
      • Pinczewski L.A.
      The survival of the anterior cruciate ligament graft and the contralateral ACL at a minimum of 15 years.
      • Morgan M.D.
      • Salmon L.J.
      • Waller A.
      • Roe J.P.
      • Pinczewski L.A.
      Fifteen-year survival of endoscopic anterior cruciate ligament reconstruction in patients aged 18 years and younger.
      • Thompson S.
      • Salmon L.
      • Waller A.
      • Linklater J.
      • Roe J.
      • Pinczewski L.
      Twenty-year outcomes of a longitudinal prospective evaluation of isolated endoscopic anterior cruciate ligament reconstruction with patellar tendon autografts.
      In bioscrew fixation cases, the surgeon does not encounter healthy bone, rather a partially decomposed bioscrew in soft bone, which is definitely not an advantage in revision surgery.
      The material properties of “bioscrews” may change and evolve subtly, but for the most part resorption of “bioscrews” is, at best, unreliable and replacement by bone is rare. As the promise of reliable screw resorption and bone formation remains elusive with “bioscrews,” my personal preference is now to use a nonresorbing inert plastic interference screw for fixation of ACL grafts. This offers the same advantages as a resorbable bioscrew, but without the risk of unpredictable biologic reactions, and easier revision surgery.
      The goal of bioscrews was lofty, the animal science was encouraging, the manufacturers were heralding the “age of biologics,” and we adopted bioscrews with gusto, myself included. Sadly, the experience has disappointed. Perhaps a simpler design of a nonreactive plastic such as PEEK (polyether ether ketone) is a better base for screw production.

      Supplementary Data

      References

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        Bioabsorbable versus titanium screws in anterior cruciate ligament reconstruction using hamstring autograft: A prospective, blinded, randomized controlled trial with 5-year follow-up.
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