S. Tepic et al., STRENGTH RECOVERY IN FRACTURED SHEEP TIBIA TREATED WITH A PLATE OR ANINTERNAL FIXATOR - AN EXPERIMENTAL-STUDY WITH A 2-YEAR FOLLOW-UP, Journal of orthopaedic trauma, 11(1), 1997, pp. 14-23
Objectives: Comparison of fracture healing with two different implants
: a conventional Dynamic Compression Plate (DCP) and a new internal Po
int Contact Fixator (PC-Fix). Design: Randomized prospective study in
experimental animals. Observation times: 12, 24, 48 and 96 weeks, with
six sheep per group. Setting: Following surgery, animals were kept wi
th unrestricted weight-bearing in individual stalls for 12 weeks, ther
eafter in groups. Animals: 56 adult Swiss mountain sheep. Intervention
: a standardized oblique fracture of the sheep tibia was reduced and c
ompressed by a lag screw and ''neutralized'' with one of the implants.
Main Outcome Measurements: Standard radiographs were used for callus
size measurements. After sacrifice the implant uas removed and both th
e treated bone and the contralateral bone were tested for static stren
gth in bending with the plate side under tension. Broken bones were pr
ocessed for histological evaluation. Results: In the DCP group all six
bones failed through the original fracture at 12 weeks. At 24 and 48
weeks two out of six, at 96 weeks one out of six bones failed through
the original fracture, others through one of the screw holes. In the P
C-Fix group there were no failures through the original fracture with
a single exception at 96 weeks. The strength values in the PC-Fix grou
ps of 12 and 96 weeks were significantly higher then in the correspond
ing DCP groups.Conclusions: Healing of simple diaphysial fractures tre
ated by PC-Fix was superior to that achieved by conventional plating.
The histological evaluation suggested that the observed differences ca
n be accounted for by the absence of implant-related cortical necrosis
and by the circumferentially uninterrupted (if smaller) callus in the
PC-Fix group.