Table 2.
Experimental studies considering the effects of inter-fragmentary shear on fracture healing.
| Author | Subjects (n) | Method | Outcome |
|---|---|---|---|
| Schell et al. (29) | Sheep (40) | Mid-diaphyseal tibial osteotomy was performed and fixed with a gap of 3.0 mm. Two fixators were used, a rigid fixator and a fixator with high axial rigidity and no resistance to shear motion | The group with free shear movement had significantly reduced torsional strength and stiffness at every time point. Three animals in this group presented hypertrophic non-unions after 6 months |
| Vetter et al. (9) | Sheep (64) | Mid-diaphyseal tibial osteotomy was performed and fixed with a gap of 3.0 mm. The animals were divided into two groups, one with rigid fixation, and the other with a fixator, which allowed greater shear movement | Histological slices where categorized as belonging to one of six different healing stages based on topological features present. Rigid fixation resulted in a faster progression in healing, this could also be seen in the ratio of bone area to total are which was higher for rigid fixation |
| Bishop et al. (27) | Sheep (18) | Mid-diaphyseal tibial osteotomy was performed and fixed with a gap of 2.4 mm. Three groups one with rigid fixation, one with torsional shear, and one with IFC. Movement was stimulated to cause 25% principal strain | The group with torsional shear motion had a greater callus area and similar stiffness when compared to the group with no motion, while IFC produced small callus, less advanced with little bridging |
| Schell et al. (18) | Sheep (64) | Mid-diaphyseal femoral osteotomy was performed and fixed with a gap of 3.0 mm. Two different fixators were used of different stiffness. This resulted in greater IFS within the less stable group | Throughout the healing significantly more cartilage formed with the less rigid fixation group. The rigid group had a larger callus formation. At 9 weeks, there was no significant difference between the two groups |
| Park et al. (28) | Rabbit (56) | Two cohorts with oblique and transverse tibial fractures each consisting of a rigid fixation and a sliding fixation group. The sliding fixator allowed IFC while the transverse group and IFS in the oblique group | The oblique IFS group showed accelerated healing compared to the other three groups, the torsional strength by 4 weeks exceeded that of intact bone |
| Klein et al. (30) | Sheep (12) | Mid-diaphyseal femoral osteotomy was performed and fixed with a gap of 3.0 mm. One group of animals was fixed through un-reamed medullary nailing allowing torsional rotation of 10°, the other with a rigid frame fixator. The IFMs were measured throughout | The nailed group showed significantly inferior healing compared to the rigidly fixed group, when comparing mechanical properties and histological sections of the callus after 9 weeks |
| Lienau et al. (31) | Sheep (64) | Mid-diaphyseal tibial osteotomy gap of 3.0 mm stabilized with a frame fixator. Test group received a fixator, which allowed increased IFS compared to control | Group with higher IFS initially showed a lower blood supply, the healing stage for this group lagged behind, presenting lower stiffness at 6 weeks, this was compensated after 9 weeks. However, the rigid group appeared to have entered the remodeling phase, whereas, the IFS group had not |
| Epari et al. (32) | Sheep (64) | Mid-diaphyseal tibial osteotomy gap of 3.0 mm, stabilized with a frame fixator. Test group a fixator, which allowed increased IFS compared to control | IFS induced a larger amount of cartilage formation compared control, while also have a more compliant callus. The remodeling process was initiated earlier for rigidly fixed fractures |