jot_v19_pp693-697

jot_v19_pp693-697 - ORIGINAL ARTICLE Mechanical Study of...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
O RIGINAL A RTICLE Mechanical Study of the Safe Distance Between Distal Femoral Fracture Site and Distal Locking Screws in Antegrade Intramedullary Nailing Shannon B. Antekeier, MD, Robert L. Burden, Jr., MEng, Michael J. Voor, PhD, and Craig S. Roberts, MD Objective: To determine the safe distance for distal femoral fractures relative to the distal locking screws in antegrade intra- medullary femoral nailing using a currently available titanium alloy nail design. Design: Cyclic (fatigue) mechanical testing study. Setting: Biomechanics laboratory. Intervention: Intramedullary nailing of left synthetic Fberglass composite femora with type 32/33-C fractures at 1, 2, 3, and 4 cm from the more proximal of the distal locking screws. Main Outcome Measurement: The number of loading cycles to failure of the nail. Results: A load level of 700 N through the femoral mechanical axis was validated as adequate to cause fatigue failure within 200,000 cycles in slotted stainless- steel nails. In the nonslotted titanium alloy nails, this load level caused failure in only 1 of 3 nails with a fracture at 2 cm from the more proximal of the 2 distal locking screws and in 2 of 3 nails with a fracture at 1 cm from the more proximal of the 2 distal locking screws. All of the other nails did not fail . 1 million cycles. Conclusions: Under laboratory conditions, it is safe to assume that an antegrade titanium alloy nail will survive 1 million compres- sion/bending cycles when the fracture is $ 3 cm from the more proximal of the 2 distal locking screws. Key Words: intramedullary nailing, fatigue, femur, fracture, screw hole, mechanical study ( J Orthop Trauma 2005;19:693–697) A ntegrade intramedullary Fxation of distal femoral frac- tures is limited by the proximity of the fracture site to the more proximal of the 2 distal locking screws. 1 Based on analysis of clinical failures and Fnite element analysis of early slotted and locked stainless- steel nails, Bucholz et al 2 in a 1987 article recommended a minimum distance of 5 cm to prevent fatigue fracture of the nail. However, newer nail designs are no longer slotted and are made from stronger materials, such as titanium alloy, 3 thus increasing their fatigue strength. Several studies indicate that fractures can be successfully treated when the fracture is closer to the distal screws than the previously recommended 5 cm. 1,4–8 We hypothesized that current nail designs allow closer spacing between the fracture site and the more proximal of the distal locking screws than the 5-cm recommendation. The Frst objective of this study was to reproduce the conditions of the study by Bucholz et al 2 using the same Grosse-Kempf TM nail design (Howmedica, Mahwah, NJ) that was reported on in their clinical series and used in their Fnite element analysis to establish the 5-cm recommendation. The second objective was to apply these conditions to currently available titanium alloy nails (TriGen TM , Smith & Nephew, Memphis, TN) to evaluate the validity of the 5-cm recom- mendation in modern nail designs.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 07/30/2011 for the course ME 492 taught by Professor Hojinahn during the Spring '11 term at Yeditepe Üniversitesi.

Page1 / 5

jot_v19_pp693-697 - ORIGINAL ARTICLE Mechanical Study of...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online