In vivo evaluation of a vibration analysis technique for the per-operative monitoring of the fixation of hip prostheses
1 Division of Biomechanics and Engineering Design (BMGO), Katholieke Universiteit Leuven, Celestijnenlaan 300C, bus 2419, 3001 Heverlee, Belgium
2 Group T Leuven Engineering College (Association K.U. Leuven), Vesaliusstraat 13, 3000 Leuven, Belgium
3 BIOMAT Research Cluster, Katholieke Universiteit Leuven, Kapucijnenvoer 7, 3000 Leuven, Belgium
4 Dept Biomedical Kinesiology, Katholieke Universiteit Leuven, Tervuursevest 101, 3000 Leuven, Belgium
5 Department of Orthopaedics, Katholieke Universiteit Leuven, Weligerveld 1, 3212 Lubbeek, Belgium
Journal of Orthopaedic Surgery and Research 2009, 4:10 doi:10.1186/1749-799X-4-10Published: 9 April 2009
The per-operative assessment of primary stem stability may help to improve the performance of total hip replacement. Vibration analysis methods have been successfully used to assess dental implant stability, to monitor fracture healing and to measure bone mechanical properties. The objective of the present study was to evaluate in vivo a vibration analysis-based endpoint criterion for the insertion of the stem by successive surgeon-controlled hammer blows.
A protocol using a vibration analysis technique for the characterisation of the primary bone-prosthesis stability was tested in 83 patients receiving a custom-made, intra-operatively manufactured stem prosthesis. Two groups were studied: one (n = 30) with non cemented and one (n = 53) with partially cemented stem fixation. Frequency response functions of the stem-femur system corresponding to successive insertion stages were compared.
The correlation coefficient between the last two frequency response function curves was above 0.99 in 86.7% of the non cemented cases. Lower values of the final correlation coefficient and deviations in the frequency response pattern were associated with instability or impending bone fracture. In the cases with a partially cemented stem an important difference in frequency response function between the final stage of non cemented trial insertion and the final cemented stage was found in 84.9% of the cases. Furthermore, the frequency response function varied with the degree of cement curing.
The frequency response function change provides reliable information regarding the stability evolution of the stem-femur system during the insertion. The protocol described in this paper can be used to accurately detect the insertion end point and to reduce the risk for intra-operative fracture.