The 16-Year Evolution of Proximal Modular Stem Design – Eliminating Failure of Modular Junction
Background: The complexity of hip reconstruction has been and continues to be a perplexing problem with restoring leg length, femoral offset, joint stability and overall hip implant fixation. These were contributing factors that lead to the development of a novel proximal femoral component design “Apex Modular Stem” (Omni, Raynham, MA). The basic stem geometry features a straight stem with a metaphyseal fit and fill cone, a medial triangle and a modular neck junction that allows for version and offset adjustment.
In recent years, there has been great concern with the use of modularity in total hip arthroplasty. The goals of this study are (1) to identify complications with the use of a proximal modular design and (2) demonstrated factors that have eliminated those complications.
Methods: This is a retrospective study of a single surgeon series (Design A and Design B) of using the same cementless stem and proximal modular neck body (Apex Modular Stem and Omni Mod Hip Stem) from 2000 to 2016 totaling 2,125 stems. 483 stems were the Design A and 1,642 stems, were of the Design B style.
Results: Design A, 483 stems were implanted between 2000 and 2004. 31 alignment pins sheared resulting in a revision rate of 6.4%. Design B, 1,642 stems have been implanted between 2004 and 2016 all by the same surgeon, with no failures of the modular junction.
Conclusion: All implant devices entail a multitude of risks and benefits. The Apex Modular Stem (Design A), provided excellent fixation, minimal risk of modular junction corrosion, and simple control of anteversion and femoral offset. The limitation was found to be the risk of the alignment pin shearing (6.4%). The pin was enlarged to make it 225% stronger in torsional resistance, and in a subsequent series of over 1,600 femoral stems in a single surgeon series, there were no pin failures over a 12 year duration.
Cameron H.U. The Technique of Total Hip Arthroplasty. ISBN 0-8016-0825-2 1992 by Mosby-Year Book.
Tkach T, Low W, Cipolletti G.B., McTighe T. Target Restoration of Hip Mechanics in THA. AAOS Scientific Exhibit 2006, DOI: 10.13140/RG.2.1.1084.0167
Cameron H.U., Yung-Bok, J., Noiles, D.G., McTighe, T. Design Features and Early Clinical Results with a Modular Proximally Fixed Low Bending Stiffness Uncemented Total Hip Replacement. DOI: 10.13140/RG.2.1.4714.7040 Conference: AAOS 1988 Annual Meeting, Scientific Exhibit
Keppler, L., McTighe, T., The Role of Stem Modularity for THA in a Community Based Practice. Reconstructive Review Volume 2(Number 2): 16 · August 2012 DOI: 10.15438/rr.v2i2.10
Sales Training Slide Presentation by Omni (On file)
G. M. Kotzar, D. T. Davy, J. Berilla, and V. M. Goldberg. Torsional Loads in the Early Postoperative Period Following Total Hip Replacement. JBJS 13:945-955
T. W. Phillips, * L. T. Nguyen and S. D. Munro. Loosening of Cementless Femoral Stems: A Biomechanical Analysis of Immediate Fixation with Loading Vertical, Femur Horizontal. J. Biomechanics Vol. 24, No 1, pp. 37 48, 1991. 9,10
Keggii K, Keggi J, Kennon R, Tkach T, Low W, et al., Within Any Important Issue, There are Always Aspects No One Wishes to Discuss- Femoral Component Failure. Poster Exhibit ISTA, Oct. 2006
Jameel A, Majeed W, Razzaq A, Fatigue Analysis of Hip Prosthesis. Number 10, Vol 18, October 2012 Journal of Engineering p: 1100 to 1114.
Mierzejewska Z, Case Study and Failure Analysis of a Total Hip Stem Fracture. Advances In Materials Science, Vol. 15, No. 2 (44), June 2015 DOI: 10.1515/adms-2015-0007
T. McTighe, D. Brazil, W. Bruce. Metallic Alloys in Total Hip Arthroplasty. McTighe T, Brazil D, Bruce W. Metallic Alloys in Total Hip Arthroplasty. In: Cashman J, Goyal N, Parvizi J, eds. The Hip: Preservation, Replacement and Revision. Baltimore, MD: Data Trace Publishing Company; 2015:14-1–14-12
McTighe T, Brazil D, Clarke I, Keppler L, Keggi J, Tkach T, McPherson E. Metallic Modular Taper Junctions in Total Hip Arthroplasty. RR Vol 5, Number 2, July 2015 doi:10.15438/rr.5.2.108
White paper published by Omni 2004
Copyright (c) 2017 Thomas Tkach, Timothy McTighe
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.