Compaction versus extraction drilling for fixation of the hamstring tendon graft in anterior cruciate ligament reconstruction

Initial strength of quadrupled hamstring tendon grafts fixed with titanium interference screws was assessed in 30 pairs of porcine tibiae. Bone tunnels were drilled with either compaction drilling (stepped routers) or conventional extraction drilling (cannulated drill bits). Fifteen pairs of specimens were subjected to a single-cycle load-to-failure test, while the rest underwent a cyclic-loading test to further assess the quality of the fixation. No significant difference between the two drilling techniques was found with regard to yield load, displacement at yield load, stiffness, or mode of failure. Porcine trabecular bone mineral density was determined using peripheral quantitative computed tomography and compared with that of young women and men at a site corresponding to that of the tibial bone drill hole of an anterior cruciate ligament reconstruction. There was a significant difference between the two species (210 +/- 45 mg/cm(3) in porcine tibial bone versus 129 +/- 30 mg/cm(3) in women and 134 +/- 34 mg/cm(3) in men), suggesting that porcine knee specimens may have limitations in studies of graft fixation in anterior cruciate ligament reconstruction. We found no difference between extraction and compaction drilling in initial fixation strength of a hamstring tendon graft for anterior cruciate ligament reconstruction using a porcine model.