Original ArticleFemoral Nailing Through the Trochanter: The Reamer Pathway Indicates a Helical Nail ShapeEhmke, Larry W MS; Polzin, Britton M I MD; Madey, Stephen M MD; Bottlang, Michael PhD Author Information Accepted for publication September 13, 2006. From the *Legacy Biomechanics Laboratory, Portland, Oregon; and †Oregon Health and Sciences University, Portland, Oregon. This research has been supported in part by a research grant from Synthes (USA). This article does not include devices that are the subject to FDA approval. Reprints: Michael Bottlang, PhD, Legacy Biomechanics Laboratory, 1225 NE 2nd Ave, Portland, OR 97232 (e-mail: [email protected]). Journal of Orthopaedic Trauma: November 2006 - Volume 20 - Issue 10 - p 668-674 doi: 10.1097/01.bot.0000247073.79430.87 Buy Metrics Abstract Objectives: This biomechanical study captured the reamer pathway in human femurs reamed through a greater trochanteric entry portal. The spatial pathway of the reamed intramedullary canal was analyzed to determine how closely a helix can match the dimensions of this canal. Methods: Twenty-one human cadaveric femurs were reamed through a trochanteric entry portal 12 mm lateral to the superior trochanteric border. The pathway of the reamer canal was measured with a 3-dimensional motion tracking sensor. The magnitude and direction of curvature along the reamed canal was calculated and an average canal pathway was determined. Finally, a best-fit helix was derived by comparing the average canal pathway with 90 different computer-generated helix pathways. Results: The reamed canal exhibited a medially directed curvature of 1.97 ± 0.30 m−1 magnitude proximally and an anteriorly directed curvature of 1.21 ± 0.27 m−1 magnitude in the midsection. This multiplanar curvature could best be approximated by a helix with 1000 mm radius and 0.6 degree/mm pitch. This helix coincided within ± 1 mm with the reamed canal over 59% of the canal length. It deviated 4 mm medial and 7 mm posterior at the entry portal and 7 mm medial and 3 mm posterior at the distal end of the reamed canal. Conclusion: These results provide a scientific rationale for the design of helically shaped intramedullary nails. Helical nails introduced through a trochanteric entry site may offer reduced bone stresses, ease insertion, and facilitate removal. This in turn may reduce the likelihood of iatrogenic intraoperative fracture. Copyright © 2006 Wolters Kluwer Health, Inc. All rights reserved.