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A NEW APPROACH TO NECK SPARING THA STEM



Abstract

Introduction: Architectural changes in the proximal femur after THA continue to be a problem. In an attempted, to reduce these changes some surgeon designers have advocated the concept of neck sparing stem designs.

To-date neck-sparing stems have been disappointing in their ability to maintain the calcar. A new approach was undertaken to improve load transfer and to create a tissue-sparing stem that would be simple in design, reproducible in technique and provide for fine-tuning joint mechanics while maintaining compressive loads to the calcar.

Methods: Review of previous published work was evaluated along with FEA modeling in creating a new approach to neck sparing stems for THA. The MSA Stem is a simple curved stem with a unique lateral T-back designed for torsional stability, ease of preparation and insertion. The proximal design has a novel proximal conical shape designed to transfer compressive forces to the calcar.

A modular neck provides for fine-tuning joint mechanics.

Results: FEA modeling will be reviewed. Strain patterns for the MSA stem demonstrated better patterns vs. long stems or the short Biodynamic stem.

Discussion: In theory neck retaining devices provide or:

  • Bone and Tissue sparring

  • Restoration of joint mechanics

  • Minimal blood loss

  • Potential reduction in rehabilitation

  • Ease of revision

  • Simple surgical technique

  • Options for bearing surface

  • Selection of femoral head diameter

  • Standard surgical approach to the hip

We are encouraged and believe there are advantages in the concept of neck sparing stems. Clinical/surgical evaluation is now underway and will be reported on in the future.

Correspondence should be addressed to ISTA Secretariat, PO Box 6564, Auburn, CA 95604, USA. Tel: 1-916-454-9884, Fax: 1-916-454-9882, Email: ista@pacbell.net