Don't know much biology: redux

Editorial Commentary: Fill It up: The Fate of "Absorbable" Implants

Surgeons make conscious decisions daily regarding implants. But do they really know what happens in the body to "absorbable anchors?" How long does it take to resorb, and what fills the space left behind? Absorbable materials can be very different, and well-done studies are important to help us understand the process and to guide our decisions.

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

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.

Tibial tunnel widening after bioresorbable poly-lactide calcium carbonate interference screw usage in ACL reconstruction

Developing bio-absorbable interference screws for anterior cruciate ligament (ACL) reconstruction has proven to be a challenging task. The aim of this study was to investigate the osteogenetic response of poly-lactide carbonate (PLC) interference screws in ACL reconstruction in humans. Ten patients (median age, 28 years) underwent arthroscopic ACL reconstruction with semitendinosus/gracilis tendon graft and a PLC interference screw. The patients were scanned with a multi-slice CT scanner 2 weeks and 1 year postoperatively. Fourteen days postoperatively a mean tunnel widening of 78% [52%; 110%] was observed. At 1-year follow-up, the mean tunnel widening was 128% [84%; 180%]. No sign of bone replacement or bone ingrowth was observed. Factors such as accelerated rehabilitation, micro-motions, and early screw degradation might be responsible for this large tunnel widening. Our results demonstrate the difficulty in translation of preclinical data. This study illustrates the need for extensive preclinical investigation of new materials for clinical purposes.