Effects of Tapping on the Holding Strength of Cancellous Bone Screws

T. C. Hearn; J. F. Surowiak; J. Schatzker

doi:10.1055/s-0038-1633123

Veterinary and Comparative Orthopaedics and Traumatology, Table of Contents

Vet Comp Orthop Traumatol 1992; 05(01): 10-12
DOI: 10.1055/s-0038-1633123

Original Research

Schattauer GmbH

Effects of Tapping on the Holding Strength of Cancellous Bone Screws

T. C. Hearn

¹Orthopaedic Biomechanics Research Laboratory, Division of Orthopaedics, Sunnybrook Health Science Centre, University of Toronto, Canada

,

J. F. Surowiak

¹Orthopaedic Biomechanics Research Laboratory, Division of Orthopaedics, Sunnybrook Health Science Centre, University of Toronto, Canada

,

J. Schatzker

¹Orthopaedic Biomechanics Research Laboratory, Division of Orthopaedics, Sunnybrook Health Science Centre, University of Toronto, Canada

› Author Affiliations

Abstract

Summary

The purpose of the study was to determine whether tapping affects the holding strength of cancellous bone screws in soft material. Paired extraction tests were conducted using 6.5 mm cancellous bone screws in porous polyurethane foam. One member of each pair had a pre-tapped pilot hole, the other was inserted in a self-tapping manner. The maximum value of tensile force during extraction with a servohydraulic materials testing machine was recorded as the screw holding strength.

Comparison of the holding strengths between the pre-tapped and self-tapping groups revealed a lower mean holding strength for the pre-tapped group (p <0.05). This result contrasts with previous studies which showed that pre-tapping increases the holding strength of bone screws in relatively stronger materials. The effect of tapping on the holding strength of bone screws is therefore dependant on the material properties of the host medium.

This study examined the effect of tapping the pilot hole on the extraction strength of 6.5 mm cancellous bone screws in soft, synthetic cancellous material. In contrast with previous studies in stronger materials, it was found that tapping significantly reduces the holding strength of bone screws. The effects of tapping depend on the material properties of the host medium.

Keywords

Internal fixation - holding strength - cancellous bone screws

Full Text

References

REFERENCES
1 Perren SM. Physical and biological aspects of fracture healing. Clin Orthop Rel Res 1979; 138: 175-96.
2 Hughes AN, Jordan BA. The mechanical properties of surgical bone screws and some aspects of insertion practice. Injury 1972; 4: 25-38.
3 Frandsen PA, Christoffersen H, Madsen T. Holding power of different screws in the femoral head: a study in human cadaver hips. Acta Orthop Scand 1984; 55: 349-51.
4 Evans M, Cunningham JL, Harris JD. The design and testing of external fixator bone screws. In: Proceedings of the European Society of Biomechanics. 6th Meeting Bristol: 1988: 35A.
5 Ansell RH, Scales JT. A study of some factors which affect the strength of screws and their insertion and holding power in bone. J Biomech 1968; 1: 279-302.
6 Nunamaker DM, Perren SM. Force measurements in screw fixation. J Biomech 1976; 9: 669-75.
7 Yovich JV, Turner AS, Smith FW, Davis DM. Holding power of orthopaedic screws: comparison of self-tapped and pre-tapped screws in foal bone. Vet Surg 1986; 15: 55-9.
8 Xu X, Rahn BA, Cordey J, Tepic S, Perren SM. Photoelastic model and morphological changes of bone following insertion of self-tapped and non-self-tapped screws. In: Proceedings of the European Society of Biomechanics. 6th Meeting Bristol: 1988. P 2.
9 Phillips J, Cordey JR, Rahn BA, Perren SM. Comparison of selftapping and pretapped screws in maxillo-facial surgery. In: Proceedings of the European Society of Biomechanics. 6th Meeting Bristol: 1988. P 13.
10 Surowiak JF, Hearn TC, Schatzker J. Comparison of bovine, human, and synthetic cancellous bone in the assessment of bone screw holding strength. In: Proceedings of the 24th Annual Meeting of the Canadian Orthopaedic Research Society. Vancouver: 1990: 15.