A Biomechanical Advantage of the Lengthening with an External Fixator Over an Intramedullary Nail: An Experimental Study in Saw Bones and Cadeveric Bones

PURPOSE: To know biomechanical differences in methods of limb lengthening between using monolateral external fixator and using external fixator over an intramedullary nail. MATERIALS AND METHODS: In acryl rods, saw-bone, and cadeveric bone, we created two lengthening models of using monolateral external fixator and using external fixator over an intramedullary nail. The axial compression test was done on the site of osteotomy for lengthening. To fix the models, half pins of 5 mm in diameter and nails of 9 mm in diameter were used. Using MTS (Material Test System) machine, we evaluated the differences of axial stiffness according to the presence of an intramedullary nail or the numbers of half-pins which were fixed at each side of osteotomy. RESULTS: Lengthening over an intramedullary nail, comparing to monolateral external fixator only, increased the axial stiffness by 1.1~1.2 times in acryl rods, 1.2~1.6 times in saw bones, and 15.6~15.9 times in cadeveric bones when the same numbers of half-pins were used. In saw bone and cadaveric bone, the group of two half pins in lengthening over an intramedullary nail was stiffer than the group of three pins in lengthening with monolateral external fixator. CONCLUSION: In the distraction of the limb, the addition of an intramedullary nail may increase the axial stiffness of the frame of monolateral external fixator. In lengthening over an intramedullary nail, it is enough to distract the bone with fixing two half pins at each sides of osteotomy.

Internal Bone Transport in the Management of Tibial Bone Defects

PURPOSE: To retrospectively review the results of internal bone transport in the management of tibial bone defect using ilizarov fixator. MATERIALS AND METHODS: We treated 39 cases of tibial bone defect (16 of traumatic bone loss, 23 after treatment of osteomyelitis). The mean age of index procedure was 33.8 years (range, 13~66 years), and all of them had follow-up study for a mean of 3.5 years (range, 1.6~8 years). The mean transported amount was 6.3 cm (range, 2.7~20 cm), and the external fixator was removed after 345 days (range, 120~700 days). The mean external fixation index was 60.3 days/cm (range, 13.1~121.3 days/cm). RESULTS: Primary union of distraction and docking site was achieved in all, but two patients had failure in union of docking site. Functional results showed 6 excellent, 19 good, 10 fair, and 4 fair. The patients under age 20 showed better functional outcomes than the others. Among 73 complications (incidence, 1.87 cases/ patient), 27 of major complications with residual sequelae occurred in 20 patients. The residual sequelae were more common in the patients who had the concomitant injuries in the same leg. CONCLUSION: Internal bone transport can solve the large amount of tibial bone defect. However, the complications are not uncommon, which might be related to the concomitant injures in the same leg.