Quantification of cephalomedullary nail fit in the femur using 3D computer modelling: a comparison between 1.0 and 1.5m bow designs

Abstract

BackgroundThe radius of curvature (ROC) misfit of cephalomedullary nails during anterograde nailing can lead to complications such as distal anterior cortical encroachment. This study quantified the anatomical fit of a new nail with 1.0-m ROC (TFN-ADVANCED™ Proximal Femoral Nailing System [TFNA]) compared with a nail with 1.5-m ROC (Gamma3 Long Nail R1.5 [Gamma3]).MethodsWe generated 63 three-dimensional models (48 female, 45 right femur) representing the cortical surfaces of the femora (31 Caucasian, 28 Japanese, and 4 Thai). The mean age of the specimens was 77 years (±8.1), and the mean height was 158.5 cm (±9.6). Utilizing a customized software tool, nail fit was determined from the total surface area of nail protrusion from the inner cortex surface and maximum distance of nail protrusion in the axial plane; the position of the distal nail tip within the canal was also determined.ResultsOverall, TFNA had both a significantly smaller mean total surface area of nail protrusion (915.8 vs. 1181.6 mm2; P < 0.05) and a mean maximum distance of nail protrusion in the axial plane (1.9 vs. 2.1 mm; P = 0.007) when compared with Gamma3. The mean total surface area of nail protrusion was significantly smaller with TFNA versus Gamma3 in both the Caucasian (P = 0.0009) and Asian (Japanese and Thai) samples (P = 0.000002); the mean maximum distance of TFNA protrusion was significantly smaller in Asians (P = 0.04), but not in Caucasians (P = 0.08). Most tip positions for both nail types were anterior, but TFNA had a higher number of center positions than Gamma3 (13 vs. 7) and a shift from the far anterior cortex to the center of the medullary canal (overall and in Caucasians). In Asians, the most prominent position was far anterior for both nails.ConclusionsThe 1.0-m ROC TFNA nail resulted in better fit than the 1.5-m ROC Gamma3 nail. Clinical trials and case studies should be conducted in the future to verify if these findings would also result in clinical improvements.

Proximal femur anatomy-implant geometry discrepancies

“…While this study cannot confirm the ethnicity of its sample group, the cohort was from an African population not previously included in femur canal curvature studies. The results echo Schmutz's concern for anatomy-implant mismatch and should alert a surgeon to identify curvature mismatch preoperatively and use CMNs with a smaller radius of curvature or a short CMN [30]. Parameter mismatch may be due to intentional design philosophy, and for instance, the decreased CMN radius of curvature design may be a response to limit the effect of nail rotation by the surgeon to match native anteversion.…”

Femoral antecurvation—A 3D CT Analysis of 1232 adult femurs

“…Despite the extensive research, the results vary over a relatively large range, from 885 to 1446 mm [ 2 , 4 , 5 , 13 , 14 ]. Due to the small number of patients [ 3 , 5 ] and lack of data [ 4 , 13 ], no reliable conclusion may be drawn on differences in antecurvation between Asian and Western populations.…”

<p>Risk Factors for Anterior Cortical Impingement of Short Cephalomedullary Nail in Chinese Elderly Patients with Intertrochanteric Fracture</p>

“…Anterior cortical impingement is a common phenomenon after intramedullary fixation in Asian patients with intertrochanteric fractures. 12,13,18,20,21 Chang et al 13 reviewed 158 Chinese patients and found that the incidence of anterior femoral cortical impingement was 34.8%. In this study, we found that anterior cortical impingement is popular in Chinese elderly patients with intertrochanteric fracture stabilized with an intramedullary nail.…”