[Animal experiment studies of "biological" plate osteosynthesis of multi-fragment fractures of the femur].

In three groups (A, B, C) of 12 sheep each, defined, reproducible comminuted subtrochanteric fractures were produced in three steps without devascularization of the bone: (1) longitudinal biocortical osteotomies limited by bore holes as breakpoints, (2) an external fixator producing a static lateral bending load of 0.20 kN, (3) sudden three-point antero-posterior compression. Sheep in group A were treated with direct reduction and anatomical reconstruction of each fracture according to the principles of the AO/ASIF group and with an angle blade plate. In group B the same plate was used, but no attempt was made to reduce fragments anatomically. Length and alignment were restored with indirect reduction techniques (distraction via external fixator and articulating tension device) only. The treatment applied in group C incorporated the same reduction modes as that in group B, but an experimental plate with point bone contact and unicortical, fixed screws were used. After 4, 8 and 12 weeks of full weight-bearing, the femurs were harvested for radiographic analysis and biomechanical testing. Subjective evaluation of fracture healing by 20 independent orthopaedic trauma surgeons resulted in significantly higher ratings for groups B and C than for group A after 8 (p = 0.07) and 12 weeks (p = 0.09). Density scan measurements showed little change in bone density as a percentage of that on the intact side over 12 weeks (108.1, 105.7, 104.4) in group A, but revealed marked changes in groups B and C (95.7, 117.5, 133.6 and 104.2, 125.6, 120.6), reflecting higher masses of callus.(ABSTRACT TRUNCATED AT 250 WORDS)