Mechanical and structural characteristics of the new BONE-LOK cortical-cancellous internal fixation device

Abstract 

The purpose of this study was to evaluate the structural and mechanical characteristics of a new and unique titanium cortical-cancellous helical compression anchor with BONE-LOK (Triage Medical, Inc., Irvine, CA) technology for compressive internal fixation of fractures and osteotomies. This device provides fixation through the use of a distal helical anchor and a proximal retentive collar that are united by an axially movable pin (U.S. and international patents issued and pending). The helical compression anchor (2.7-mm diameter) was compared with 3.0-mm diameter titanium cancellous screws (Synthes, Paoli, PA) for pullout strength and compression in 7# and 12# synthetic rigid polyurethane foam (simulated bone matrix), and for 3-point bending stiffness. The following results (mean ± standard deviation) were obtained: foam block pullout strength in 12# foam: 2.7-mm helical compression anchor 70 ± 2.0 N and 3.0-mm titanium cancellous screws 37 ± 11 N; in 7# foam: 2.7-mm helical compression anchor 33 ± 3 N and 3.0-mm titanium cancellous screws 31 ± 12 N. Three-point bending stiffness, 2.7-mm helical compression anchor 988 ± 68 N/mm and 3.0-mm titanium cancellous screws 845 ± 88 N/mm. Compression strength testing in 12# foam: 2.7-mm helical compression anchor 70.8 ± 4.8 N and 3.0-mm titanium cancellous screws 23.0 ± 3.1 N, in 7# foam: 2.7-mm helical compression anchor 42.6 ± 3.2 N and 3.0-mm titanium cancellous screws 10.4 ± 0.9 N. Results showed greater pullout strength, 3-point bending stiffness, and compression strength for the 2.7-mm helical compression anchor as compared with the 3.0-mm titanium cancellous screws in these testing models. This difference represents a distinct advantage in the new device that warrants further in vivo testing. (The Journal of Foot & Ankle Surgery 42(1):15–20, 2003)

Keywords:  BONE-LOK, internal fixation, compression, cancellous screw, osteotomy, fracture