Ex Vivo Evaluation of Cementless Acetabular Cup Stability Using Impact Analyses with a Hammer Instrumented with Strain Sensors

Abstract

The acetabular cup (AC) implant stability is determinant for the success of cementless hip arthroplasty. A method based on the analysis of the impact force applied during the press-fit insertion of the AC implant using a hammer instrumented with a force sensor was developed to assess the AC implant stability. The aim of the present study was to investigate the performance of a method using a hammer equipped with strain sensors to retrieve the AC implant stability. Different AC implants were inserted in five bovine samples with different stability conditions leading to 57 configurations. The AC implant was impacted 16 times by the two hammers consecutively. For each impact; an indicator IS (respectively IF) determined by analyzing the time variation of the signal corresponding to the averaged strain (respectively force) obtained with the stress (respectively strain) hammer was calculated. The pull-out force F was measured for each configuration. F was significantly correlated with IS (R2 = 0.79) and IF (R2 = 0.80). The present method has the advantage of not modifying the shape of the hammer that can be sterilized easily. This study opens new paths towards the development of a decision support system to assess the AC implant stability.

Laser Resonance Frequency Analysis: A Novel Measurement Approach to Evaluate Acetabular Cup Stability During Surgery

“…Acetabular cup stability can be evaluated using a vibrator with RFA in a cadaver model [8] or a hammer tapping instrument using model bones [10]. Although both methods can reasonably measure acetabular cup stability, they are limited in utility due to several reasons.…”

“…The mechanical properties of the human bone and polyurethane foam are shown in Appendix A Table A1. The dimension of the foam and the adopted value of under-reaming were not determined because a previous study [10] did not show the value of under-reaming. Vibration induced by laser is focal and the amplitude is <1 μm, and the vibration does not lead to the polyurethane foam block.…”

“…Because there is no quantitative method to evaluate acetabular cup stability during surgery, this stability is currently measured through manual operator sensing. Although several quantitative methods have been established [8,9,10], they are not in clinical use. Others have evaluated acetabular cup stability according to torque [11] and pull-down force [12,13,14].…”

“…Conversely, adaptation of RFA for an acetabular cup is difficult because it is impacted into the pelvis and is located deep within the human body. For measuring acetabular cup stability, hammer tapping [10,21], and implant vibration [8,22,23,24] techniques have been used. Hammer tapping is subjective, is dependent on the surgeons, and is difficult to tap with the same power.…”

A cadaveric validation of a method based on impact analysis to monitor the femoral stem insertion

“…Based on these results, the piezoelectric force sensor was screwed on the impacting face of a hammer and the technique was adapted to predict the AC implant stability in vitro (Michel et al, 2016b). An alternative hammer instrumented by strain sensors was also developed to assess the AC implant stability (Tijou et al, 2017). In order to understand the phenomena occurring during the AC insertion, static (Nguyen et al, 2017a) and dynamic (Michel et al, 2017) finite element models have been developed.…”