title: The effect of interference screw diameter on soft tissue graft fixation.
abstract: Tibial fixation of soft-tissue grafts is a weak link in anterior cruciate ligament reconstruction. Previous studies have examined varying interference screw lengths, screw types and tunnel sizes as means to improve graft fixation. We hypothesized that increasing interference screw diameter would significantly increase the maximum load to failure of the graft and decrease the graft's initial slippage. Seventy tibialis anterior and tibialis posterior tendons were divided, looped, trimmed, and sutured to simulate 4-strand hamstring grafts. These grafts were then inserted into composite bone blocks having pre-drilled 8 mm holes and fixed with 8 mm, 9 mm, 10 mm, 11 mm, or 12 mm interference screws. Fourteen grafts were tested for each screw size. The graft was first cyclically loaded from 50 N to 250 N at 0.3 Hz for 100 cycles to measure graft slippage. The graft was then tested to failure at 0.5 mm/sec to determine the maximum load to failure and mode of failure. Graft slippage was not affected by screw diameter. Maximum load to failure increased with increasing screw diameter up to 11 mm; 11 mm screw fixation was 20% stronger than 8 mm screw fixation. In this model, no increase in graft fixation was seen in by increasing interference screw diameter beyond 3 mm of the tunnel diameter.
authors.affiliation: NYU-Hospital for Joint Diseases Department of Orthopaedic Surgery, 15th Floor, 301 East 17th Street, New York, New York 10003, USA.
authors.forename: Suk
authors.initials: S
authors.lastname: Namkoong
authors.forename: Christian S
authors.initials: CS
authors.lastname: Heywood
authors.forename: Jonathan T
authors.initials: JT
authors.lastname: Bravman
authors.forename: Kazuho
authors.initials: K
authors.lastname: Ieyasa
authors.forename: Frederick J
authors.initials: FJ
authors.lastname: Kummer
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Meislin
mesh_terms: D000328:Adult; D016118:Anterior Cruciate Ligament / Q000637:transplantation*; D001696:Biomechanical Phenomena; D001863:Bone Screws; D050376:Bone-Patellar Tendon-Bone Grafting / Q000295:instrumentation* / Q000379:methods; D004868:Equipment Failure; D006801:Humans; D008422:Materials Testing; D008875:Middle Aged; D016119:Posterior Cruciate Ligament / Q000637:transplantation*; D013977:Tibia