Background: Large interfragmentary movements may delay bone-healing.
The hypothesis of the present study was that a reduction of interfragmentary
movements, especially of torsional rotation and bending angles, would support
the healing process and lead to improved healing following unreamed tibial
nailing. The objective of this study was to investigate healing of an unstable
tibial osteotomy site following stabilization with unreamed nailing with a
modified tibial device that had angle stable holes for the locking bolts. We
compared those findings with healing after stabilization of such sites with
standard unreamed tibial nailing. The duration of the study period was nine
Methods: The site of a standardized displaced osteotomy (3-mm gap)
in twelve ovine tibiae was stabilized with unreamed tibial nailing: six
animals were treated with a modified nail that had angle stable holes for the
locking bolts, and six were treated with standard unreamed tibial nailing. In
vivo gait analysis with optical measurements of interfragmentary movements and
simultaneous measurements of ground reaction parameters were performed three
days after the operation and once weekly afterward. After the animals were
killed at nine weeks, the treated and contralateral tibiae were explanted, the
implants were removed, and radiographs were made and evaluated for bridged
cortices. Each pair of tibiae was also mechanically tested until torsional
failure, after which the whole callus region was subjected to histological and
Results: Throughout the examination period, the interfragmentary
movements in all directions were significantly smaller in the group treated
with the angle stable tibial nail than they were in the group treated with
standard unreamed tibial nailing. The limbs treated with the angle stable
tibial nails returned to almost full weight-bearing during the period of the
investigation, whereas those treated with standard nailing did not.
Histomorphometric analysis, radiographic data, and mechanical testing showed
superior bone-healing following treatment with the angle stable tibial
Conclusions: Use of an angle stable tibial nail may help to reduce
interfragmentary movements in vivo and thus lead to superior bone-healing
compared with that following standard unreamed tibial nailing.
Clinical Relevance: The reduction of the interfragmentary movements
by unreamed nailing seems to combine the advantages of favorable biological
conditions with the mechanical advantages of systems with a higher
biomechanical stiffness. The general concept of "optimizing"
interfragmentary movements by using unreamed nailing with angle stable bolts
needs to be confirmed in a prospective randomized clinical investigation.