Cyclic loading comparison between biodegradable interference screw fixation and biodegradable double cross-pin fixation of human bone-patellar tendon-bone grafts.
OBJECTIVE
The aim of this study was to compare ultimate load, yield load, stiffness, and displacement after cyclic loading of a cross-pin technique and an interference screw technique for the fixation of bone-patellar tendon-bone (BPTB) grafts in anterior cruciate ligament (ACL) reconstruction.


METHODS
Biomechanical in vitro study.


METHODS
The devices tested were 2 2.7-mm biodegradable pins (RigidFix; Ethicon, Mitek Division, Norderstedt, Germany) and biodegradable interference screws (Absolute; Innovasive Devices, Marlborough, MA). Each device was used for the fixation of 10 8-mm, 9-mm, or 10-mm sized human BPTB grafts in tunnels drilled in bovine knees. Ultimate load, yield load, stiffness, and displacement after cyclic loading (1,000 cycles between 50 and 250 N) were then evaluated.


RESULTS
All 8-mm grafts that were fixed with cross-pins failed after a mean of 124 cycles of load. The 9-mm and 10-mm grafts survived the cyclic loading protocol. Yield load and maximum load of the 10-mm groups (cross-pin and interference screw) were significantly higher than that of the 9-mm groups. There was no significant difference in maximum load, yield load, and stiffness between the cross-pin and interference screw fixation technique for 1 graft size.


CONCLUSIONS
The biomechanical data suggest that femoral fixation of 9-mm and 10-mm BPTB grafts using 2.7-mm biodegradable cross-pins leads to primary stability that is comparable to that of biodegradable interference screws. Fixation of 8-mm BPTB grafts using 2.7-mm biodegradable cross-pins had poor results.


CONCLUSIONS
The diameter of the bone block is the limiting factor for the final fixation strength and the cyclical survival when using cross-pins. We strongly recommend not using this technique for bone blocks smaller than 9 mm in diameter.
Zantop
Thore
T
Department of Trauma, Hand, and Reconstructive Surgery, University Hospital Muenster , Muenster, Germany.
Ruemmler
Markus
M
Welbers
Barbara
B
Langer
Martin
M
Weimann
Andre
A
Petersen
Wolf
W
D020341:Absorbable Implants; D000818:Animals; D016118:Anterior Cruciate Ligament / Q000637:transplantation*; D001858:Bone Nails; D001863:Bone Screws; D002417:Cattle; D004868:Equipment Failure; D005269:Femur / Q000601:surgery / Q000637:transplantation*; D006801:Humans; D008422:Materials Testing; D017847:Patellar Ligament / Q000637:transplantation*; D013718:Tensile Strength; D013977:Tibia / Q000601:surgery / Q000637:transplantation*; D016474:Weight-Bearing