Biomechanical comparison of three different surgical methods in the surgical treatment of distal tibial metaphyseal fractures. An animal model study

BACKGROUND: The aim of this study is to investigate mechanical properties of minimally invasive plate osteosynthesis (MIPO), supracutaneousplating (SP), and unilateral external fixators (UEF) which can be performed for open tibial fractures. METHODS: An unstable diaphysial tibia fracture was created in 60 fresh sheep tibia specimens by performing an osteotomy at the middle of bones. Specimens were divided into 3 groups. Specimens underwent fracture fixation with a standard MIPO technique, implanting the plate 15 mm from the bone for SP group. Unilateral uniplanar external fixators were achieved for UEF group. First, thirty specimens (10 specimen for each group) were loaded vertically along the tibial axis to 1800 N. Second, other 30 preperated bones were used for cyclical loading to avoid metal fatigue. For dynamic tests, a 350 N force was applied for 10,000 cycles. RESULTS: In compression testing (vertical loading up to 1800 N) of the three fixation instruments; construct stiffness was highest in MIPO group when compared with SP and UEF groups. While the stiffness of the MIPO group was similar to SP group, it was statistically higher than UEF group (P=0.08 and P=0.002, respectively). SP group was significantly stiffer than UEF group (P=0.0021). The mean peak load was highest in SP group and lowest in UEF group. The peak load in SP group was similar to the MIPO group, it was statistically higher than the UEF group (P=0.743 and P=0.002, respectively). CONCLUSION: Based on the biomechanical properties from this in vitro animal model study, SP technique was biomechanically stronger than UEF and has similar biomechanical properties with MIPO in terms of axial loading.