Medial Cortex Strain Distribution During Noncemented Total Hip Arthroplasty.Elias, John J. PhD; Nagao, Masato MD; Chu, Yung-Hua MS; Carbone, John J. MD; Lennox, Dennis W. MD; Chao, Edmund Y.S. PhDAuthor Information From the Orthopaedic Biomechanics Laboratory, Johns Hopkins University, Baltimore, MD. Supported by Good Samaritan Hospital, Baltimore, MD. The prostheses and implantation equipment were provided by Osteonics, Allendale, NJ. Reprint requests to Edmund Y.S. Chao, PhD, Johns Hopkins Biomechanics Laboratory, Good Samaritan Hospital, 4th Floor, 5601 Loch Raven Boulevard, Baltimore, MD 21239. Received: October 19, 1998. Revised: February 18, 1998; April 23, 1999. Accepted: May 10, 1999. Clinical Orthopaedics and Related Research (1976-2007): January 2000 - Volume 370 - Issue - pp 250-258 Buy Abstract Intraoperative proximal femur fractures are a significant concern during noncemented total hip arthroplasty. The current study was performed to investigate the hypothesis that broaching the femur and inserting the stem without using mallet applied impact loads will reduce the risk of intraoperative fracture. Rosette strain gauges were applied to the medial and anteromedial cortex of six human anatomic specimen femurs to compare the strain distribution for broaching and stem insertion. Eight additional femurs were used to compare the strain distribution for stem insertion using impact loading and constant rate stem insertion. For the impact loading stem insertions, the soft tissues surrounding the femur were modeled. Constant rate stem insertions were performed using a mechanical testing machine. The largest strains measured at the medial and anteromedial sites primarily were aligned with the femur hoop axis. The largest strain magnitude, orientation, and sign (tensile or compressive) varied widely among femurs. The stem insertion strains were significantly larger than the broaching strains (two-way analysis of variance with replication). The impact stem insertion strains were not significantly different from the constant rate stem insertion strains. The results indicate that the femur geometry and material properties have a greater influence on the strain distribution than does the implantation technique. © 2000 Lippincott Williams & Wilkins, Inc.