7.3-mm cannulated-shaft screws show no difference in compression or load to failure compared to 7.0-mm variable-pitch screws for bovine capital physeal fracture repair

Abstract Objective To compare compression and load to failure of 7.3-mm threaded-shaft screws (7.3 TSSs) and 7.0-mm variable-pitch (7.0 VP) fully threaded compression screws for bovine capital physeal fracture fixation. We hypothesized that the 7.3 TSSs would provide significantly more compression and higher load to failure than the 7.0 VP screws and that reconstructed specimens would not fail when subjected to simulated walking load. Methods Compression was measured utilizing wooden fracture simulators that were randomly assigned to be repaired with either 7.3 TSSs or 7.0 VP screws (n = 8), and compression was recorded with a FlexiForce sensor. Cadaveric bovine femurs with induced capital physeal fractures were repaired with either 7.3 TSSs (n = 5) or 7.0 VP screws (n = 5) before being placed through 1,400 cycles under cyclic loading and single load to failure in a load press. Results The median compression for the 7.3 TSSs (70.2 N; range, 44.7 to 76.3) was not significantly different compared to 7.0 VP screws (33.4 N; range, 25.55 to 40.45). No constructs failed during cyclic loading. There was no significant difference between the mean force at the time of failure of the 7.3 TSSs (6.67 ± 1.62 kN) and 7.0 VP screws (10.4 ± 3.73 kN). Conclusions 7.3 TSSs and 7.0 VP screws demonstrated no significant difference in compression or load to failure. Clinical Relevance The present study supports the use of 7.3 TSSs and 7.0 VP screws to repair bovine capital physeal fractures. Further in vivo investigation to evaluate the impact of soft tissues and additional cycling is needed prior to implementing 7.0 VP screws in clinical cases.