Background <p>Diaphyseal fractures of both forearm bones (both-bone forearm fractures) are common pediatric injuries. When surgical treatment is indicated, elastic stable intramedullary nailing is widely used due to its minimally invasive nature and favorable outcomes. Nail design may vary – straight, pre-contoured, or a combination of both – however, the influence of these configurations on fracture reduction has not been clearly explored. The aim of this study was to investigate postoperative radiological outcomes after stabilization of both-bone forearm fractures with either two non-contoured nails, two contoured nails, or one non-contoured and one contoured nail in human cadaveric bones.</p> Methods <p>Twelve human cadaveric forearms from 6 adult donors were used and standardized AO PCCF22-D/4.1 transverse diaphyseal fractures of the radius and ulna were created. Titanium elastic nails (TENs) were inserted retrograde in the radius and anterograde in the ulna creating 3 groups with either 2 straight TENs (Group 1), 1 straight and 1 curved TEN (Group 2), or 2 curved TENs (Group 3). Anteroposterior and lateral radiographs of each intact and instrumented specimen were taken in supination. Parameters of interest included total bone length, maximal radial bow (MRB), and location of the maximal radial bow (LMRB).</p> Results <p>Both total bone lengths remained nearly unchanged after ETN instrumentation across the groups (<i>p</i> ≥ 0.608). After instrumentation MRB decreased significantly in Group 1 and increased significantly in Group 2 (<i>p</i> ≤ 0.003), however, it was without a significant change in Group 3 (<i>p</i> = 0.113). In addition, MRB in instrumented state was significantly lower in Group 1 versus both Group 2 and Group 3 (<i>p</i> ≤ 0.005), and significantly different between Group 2 and Group 3 (<i>p</i> = 0.040). LMRB did not change significantly after instrumentation in each separate group and remained comparable across the groups (<i>p</i> ≥ 0.213).</p> Conclusions <p>The use of two pre-contoured titanium elastic nails resulted in the smallest deviation from the natural anatomical alignment after reduction of diaphyseal both-bone forearm fractures. Fixation of these fractures with one non-contoured and one pre-contoured nail leads to overcorrection of the radial bow whereas utilization of two non-contoured nails leads to the most inferior results, with reduction of the radial bow, which may potentially affect forearm range of motion and therefore requires clinical correlation to confirm its functional relevance.</p>