title: Biomechanical evaluation of a new cross-pin technique for the fixation of different sized bone-patellar tendon-bone grafts.
abstract: To overcome the disadvantages of interference-screw fixation of bone-patellar tendon-bone (BPTB) grafts, new fixation techniques for anterior cruciate ligament (ACL) grafts using biodegradable pins have been developed. The hypothesis of the present study was that cross-pin fixation techniques provide a primary stability that is comparable to that of interference screws. A biomechanical in vitro study was discussed. Human BPTB grafts of 8, 9 and 10 mm diameter were fixed in bovine knees with biodegradable cross pins (diameter: 2.0, 2.7 or 3.2 mm) or biodegradable interference screws. Stiffness and ultimate load were evaluated. For 9 and 10 mm BPTB grafts, no statistically significant difference in maximum load and stiffness was found between the four fixation techniques tested. For 8 mm bone blocks the maximum load of the 3.2 mm pins (274.2 N) was significantly lower than for the 2.0 mm pins (479.8 N) and the interference screws (504.0 N). Predominant failure mode in this group was bone-block fracture. Thicker grafts (9 and 10 mm) fixed with the 2.0 mm pins predominantly failed by implant fracture. Femoral fixation of 8, 9 and 10 mm BPTB grafts using cross pins leads to biomechanical properties that are comparable to biodegradable interference screws when tested by a single-cycle load to failure. Cross pins provide a rigid fixation for 9 and 10 mm BPTB grafts.
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, 3471 Fifth Avenue, Kaufmann Building, Suite 1011, Pittsburgh, PA 15213, USA.
authors.forename: Thore
authors.initials: T
authors.lastname: Zantop
authors.forename: Barbara
authors.initials: B
authors.lastname: Welbers
authors.forename: Andre
authors.initials: A
authors.lastname: Weimann
authors.forename: Markus
authors.initials: M
authors.lastname: Rümmler
authors.forename: Jürgen
authors.initials: J
authors.lastname: Hedderich
authors.forename: Volker
authors.initials: V
authors.lastname: Musahl
authors.forename: Wolf
authors.initials: W
authors.lastname: Petersen
mesh_terms: D020341:Absorbable Implants; D000704:Analysis of Variance; D000818:Animals; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D001696:Biomechanical Phenomena; D001858:Bone Nails; D002417:Cattle; D004867:Equipment Design; D006801:Humans; D066298:In Vitro Techniques; D010329:Patella / Q000601:surgery*; D013710:Tendons / Q000502:physiology / Q000637:transplantation*; D013718:Tensile Strength