Primary stability of interference screw fixation. Influence of screw diameter and insertion torque.
Interference screw fixation is frequently used in anterior cruciate ligament reconstruction with the bone-patellar tendon-bone graft. There have been no data available about the influence of screw diameter and insertion torque on primary stability. We designed a cadaveric study using paired knees to analyze the comparative effectiveness of 20-mm long screws of different diameters (9 mm versus 7 mm) and the significance of torque during screw insertion. Testing to failure was performed in a tensiometer with a crosshead speed of 200 mm/min. After slippage of a bone peg in the 7-mm screw specimens, the experiment was repeated in each specimen with a 9-mm screw fixation. Maximum tensile force was greater at the femoral insertion than at the tibial site. Results of refixations with 9-mm screws were only slightly inferior to the original 9-mm screw fixation specimens. Our results further showed that the torque can be used as a predictor of the stability of the bone block but cannot be used as an indicator for the strength of the reconstruction. The 7-mm screws are not recommended for tibial fixation. Failed 7-mm screw fixations can be replaced by 9-mm screws and refixations were successful in our study model.
Orthopaedic Hospital, Hannover Medical School, Germany.
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Kohn
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Rose
D000328:Adult; D001863:Bone Screws; D016025:Bone Transplantation / Q000295:instrumentation* / Q000473:pathology / Q000502:physiology; D004867:Equipment Design; D004868:Equipment Failure; D005260:Female; D005269:Femur / Q000601:surgery; D005544:Forecasting; D006801:Humans; D008297:Male; D008875:Middle Aged; D017847:Patellar Ligament / Q000473:pathology / Q000503:physiopathology / Q000637:transplantation*; D012399:Rotation; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D013977:Tibia / Q000601:surgery