INTERNAL-FIXATION STRENGTH OF SUTURE ANCHORS - UPDATE 1997

Two new areas of anchor development are biodegradable anchors and ''mi ni'' anchors. The group of biodegradable anchors tested include the Bi o-Anchor, LactoSorb, Biofix, Bio-Statak, Mini Screw suture anchor, DeP uy 4.5 molded, DePuy 4.5 machined, DePuy 3.5 machined, TAG Wedge 4, TA G Rod 2, TAG Wedge 3, TAG Wedge 2, and Stealth. ''Mini anchors'' have drill holes or minor diameters of <2.2 mm. Those tested include the Mi ni Revo and Bio-Anchor, miniHarpoon, mini Mitek and Fast in 3, Statak 1.5 and 2.5, SB 2 and PeBA. 3, Corkscrew 5, Corkscrew 3.5, and Fastak A2, Ogden 2.5, TAG Wedge 2, ROC 1.9, and Questus 2.5. Additional ancho rs tested that fit neither category include the Anspach, Questus 3.5 a nd 5.0, SE 3 and PeBA-C, Ogden 3.5, Fast in 4, Ultrafix, and the ROC 3 .5, ROC 2.8, ROC 2.3, and ROC XS. An anchor comparison, using an estab lished protocol in fresh porcine femurs, recorded failure strength, fa ilure mode, eyelet size, minor and major diameters, and drill hole siz es. Except for the Bio-Anchor and TAG Wedge 2, biodegradable anchors t end to be larger to compensate for their lower strength relative to me tal. Biodegradable screw anchors' predominant failure mode was eyelet cutout, whereas biodegradable nonscrew anchors failed predominantly by anchor pullout. From an initial mechanical perspective, these biodegr adable anchors perform acceptably. Both biodegradable and ''mini'' anc hors include screw and nonscrew designs. As expected, screw designs pe rform well and generally fail at higher loads than nonscrew anchors. A lthough biodegradable anchors, as a group, are not as strong as metal anchors, they are stronger than the sutures for which they are designe d. The move to smaller (''mini'') and biodegradable anchors is support ed by these data. Whether an anchor fails at twice the suture breaking strength or 10 times the suture breaking strength should make no diff erence.