Differences in biomechanical stability of femur fracture fixation when using titanium nails of increasing diameter

Abstract

Purpose The purpose of this study was to compare the biomechanical stability generated when utilizing increasing sizes of titanium (Ti) flexible nails for fixation of simulated comminuted femur fractures. Methods Five synthetic adolescent-sized femur models were reamed to create a 9-mm canal. A 2-cm section was removed in the mid-diaphysis to simulate comminution. Each femur was first stabilized with bilateral, retrograde 3.0-mm titanium elastic nails. Femurs were tested in axial rotation and axial compression. The constructs were removed, and femurs were re-nailed with 3.5-mm nails. Identical testing was conducted. These nails were then removed, and femurs were re-nailed with 4.0-mm nails. This provided data on ''canal fill'' representing 67, 78 and 89% of the reamed canal diameter. Data for axial rotation (degrees) and failure load (N) required to produce 5 mm of fracture shortening were analyzed with a one-way ANOVA (P \ 0.05) and a Tukey's post-hoc test for multiple comparisons. Results For axial rotation, there were statistically significant improvements in rotational control for each increase in nail size. For axial stability, each increase in nail size resulted in increased axial failure loads to 5 mm, although these data were not statistically different. A specific comparison between 3.0-and 3.5-mm nails for compressive stability found significantly greater stability afforded by using 3.5-mm nails. Conclusions Data from this study demonstrate that increasing the amount of canal fill provides significant improvements in rotational control. The largest improvement was seen when increasing from 3.0-to 3.5-mm nails. While increasing the nail size from 3.5 to 4.0 mm again provided greater stability, larger nails may be more difficult to insert. Thus, increasing the nail size for femoral fracture fixation should be considered after measuring the diameter of the canal and evaluating the potential difficulty of insertion as well as specific demands of the fracture pattern.

Fraturas instáveis do fêmur em crianças tratadas com hastes intramedulares elásticas de titânio

“…They present an excellent consolidation rate, as demonstrated in our study, and rates of 97 to 100% can be found in the literature (14,20) . The length of hospital stay is short.…”

“…Surgical treatment enables early mobilization and has become an alternative of interest, especially for children presenting multiple trauma, cranial-encephalic trauma, floating knee, multiple fractures and vascular injuries (3,5,15,19,20) , which occur mainly in cases of high-energy trauma.…”

“…The commonest of these are pain at the nail insertion site, nail protrusion and nail migration or exit. Most of these complications are due to technical failures: for example, the technical guidelines state that the nail should be a maximum of 1 cm outside of the bone and should not be angled, so as to avoid protrusion and consequent local irritation (13,14,15,20) . Many complications are difficult to assess because of retrospective study designs and incomplete data in the medical files.…”

“…Anterograde insertion presents a low risk of osteonecrosis of the femoral head or injury to the proximal growth plate of the femur, while retrograde insertion avoids these two sequelae. Therefore, in our clinic, we firstly indicate retrograde insertion and then, exceptionally, anterograde insertion (20) . Several studies have shown that overgrowth may occur after a femoral diaphysis fracture during childhood, and that this may create a discrepancy in the lower limbs that persists until adolescence and young adulthood (5,12) .…”

Results of Surgical Treatment of Paediatric Diaphyseal Fractures of Long Bones Using Intramedullary Elastic Nail

“…4,5 This produces the following four properties that are essential for acheiving optimal results: flexural, axial, translational and rotational stability.⁴ The intramedullary nail also has the advantage of immediate stability which permits early mobilization and faster return to normal activities with low complication rate. 6,7 …”