Elsevier

The Journal of Arthroplasty

Volume 17, Issue 6, September 2002, Pages 773-778
The Journal of Arthroplasty

Original Articles
Morse-type tapers: Factors that may influence taper strength during total hip arthroplasty*,**

https://doi.org/10.1054/arth.2002.33565Get rights and content

Abstract

We studied the effect of varying impaction force, repeated impactions, and fluid contamination on the disassembly strength of Morse-type tapers in 4 commercially available, modular femoral total hip components. The effect of varying techniques of taper assembly on the distraction force was studied. Our results show a reproducible and linear relationship between the taper impaction force and the disassembly force. The force necessary to separate the taper for a given impaction force varied, however, among manufacturers. Repeated impactions added little strength, and we found that when multiple impactions of varying force are used, the strength is roughly equivalent to the expected strength from the single strongest blow. Fluid contamination at the taper interface had unpredictable effects on taper strength. Copyright 2002, Elsevier Science (USA). All rights reserved.

Section snippets

Taper description

Typically, Morse tapers are described by the angle that the taper surface makes with respect to the longitudinal axis of the stem component. In this study, 4 commercial brands of modular THA implants were tested (Prosthesis A, Zimmer, Inc., Warsaw, IN; Prosthesis B, Smith & Nephew Richards, Memphis, TN; Prosthesis C, Wright Medical Technology, Arlington, TN; Prosthesis D, Johnson & Johnson–DePuy, Warsaw, IN). All of the prostheses consisted of titanium alloy stems and cobalt-chrome alloy heads

Force of impaction

The force imparted by the weight on the femoral head impactor was determined at a variety of drop heights. A linear relationship existed between the drop height and the force of impaction (Fig. 1).

. Experimental drop heights and their corresponding impaction forces.

For each prosthesis tested, linear regression techniques were used to calculate the proportionality constants between the distraction and the impaction forces. A drop height effect was observed illustrating that an increased impaction

Discussion

Many variables affect the disassembly strength of Morse-type tapers. As we showed in a previous report, the design of these tapers varies considerably among manufacturers [4]. These design features, such as taper angle, taper mismatch, and surface roughness, play a large role in determining the strength of the taper when impacted with a standardized force [4]. There are many variables, however, that affect the mechanical strength of the taper that are under the surgeon's control, including the

Conclusion

We can provide surgeons with some guidelines for the optimal use of modular femoral prostheses that employ a Morse-type taper. First, because the disassembly strength of the taper is a linear function of the impaction force, the greatest possible impact should be delivered to the taper when it is assembled. Although this hypothesis was not tested formally, the implication is that the axis of impaction should be in-line with the axis of the taper. Off-axis blows reduce the vector component of

References (14)

  • N Shareef et al.

    Effect of manufacturing tolerances on the micromotion and the Morse taper interface in modular hip implants using the finite element technique

    Biomaterials

    (1996)
  • JP Collier et al.

    The tradeoffs associated with modular hip prostheses

    Clin Orthop

    (1995)
  • JC McCarthy et al.

    Custom and modular components in primary total hip replacement

    Clin Orthop

    (1997)
  • JP Collier et al.

    Corrosion at the interface of cobalt-alloy heads on titanium-alloy stems

    Clin Orthop

    (1991)
  • AH Schmidt et al.

    Assessing Morse taper function: The relationship between impaction force, disassembly force, and design variables

  • DA Loch et al.

    Axial pull-off strength of dry and wet taper head connections on a modular shoulder prosthesis

  • JP Collier et al.

    Corrosion between the components of modular hip prostheses

    J Bone Joint Surg Br

    (1992)
There are more references available in the full text version of this article.

Cited by (115)

  • Diagnosis and management of METS-Stanmore Morse taper failure

    2023, Orthopaedics and Traumatology: Surgery and Research
  • Diagnosis and management of METS-Stanmore Morse taper failure

    2023, Revue de Chirurgie Orthopedique et Traumatologique
  • Influence of taper design and loading on taper micromotion

    2022, Journal of the Mechanical Behavior of Biomedical Materials
View all citing articles on Scopus
*

No benefits or funds were received in support of this study.

**

Reprint requests: Andrew H. Schmidt, MD, Department of Orthopaedic Surgery, Hennepin County Medical Center, 701 Park Avenue, Minneapolis, MN 55415. E-mail: [email protected]

View full text