In Vitro Evaluation of the Acetabular Cup Primary Stability by Impact Analysis

Abstract

The implant primary stability of the acetabular cup (AC) is an important parameter for the surgical success of press-fit procedures used for the insertion of cementless hip prostheses. In previous studies by our group (Mathieu, V., Michel, A., Lachaniette, C. H. F., Poignard, A., Hernigou, P., Allain, J., and Haiat, G., 2013, "Variation of the Impact Duration During the in vitro Insertion of Acetabular Cup Implants," Med. Eng. Phys., 35(11), pp. 1558-1563) and (Michel, A., Bosc, R., Mathieu, V., Hernigou, P., and Haiat, G., 2014, "Monitoring the Press-Fit Insertion of an Acetabular Cup by Impact Measurements: Influence of Bone Abrasion," Proc. Inst. Mech. Eng., Part H, 228(10), pp. 1027-1034), the impact momentum and duration were shown to carry information on the press-fit insertion of the AC within bone tissue. The aim of the present study is to relate the impact momentum recorded during the AC insertion to the AC biomechanical primary stability. The experimental protocol consisted in testing 13 bovine bone samples that underwent successively series of 15 reproducible mass falls impacts (5 kg, 5 cm) followed by tangential stability testing. Each bone sample was tested with different hole sizes in order to obtain different stability configurations. The impact momentum and the tangential primary stability reach a maximum value for an interference fit equal to around 1 mm. Moreover, a correlation between the impact momentum and the stability was obtained with all samples and all configuration (R2 = 0.65). The implant primary stability can be assessed through the measurement of the impact force signal analysis. This study opens new paths for the development of a medical device which could be used as a decision support system to assist the surgeon during the insertion of the AC implant.

Finite element model of the impaction of a press-fitted acetabular cup

“…In the present paper, the impact momentum I was devised following the results obtained in previous studies [24][25][26]. However, several parameters were modified to take into account the specific configuration described herein.…”

“…The AC implant insertion obtained with reproducible mass drops could first be assessed by following the impact contact duration [23]. Then, the impact momentum was found to be a more precise indicator [24] of the implant status because it could predict the implant in vitro stability [25]. The approach was also validated by comparing the results obtained using an instrumented impact hammer and pull-out tests [26].…”

Assessing the Acetabular Cup Implant Primary Stability by Impact Analyses: A Cadaveric Study

“…By realizing reproducible mass drops, the contact duration was found to be a useful indicator to follow the AC implant insertion [20]. A second indicator based on the impact momentum was then shown to be more accurate [21] to follow the AC implant insertion conditions and to assess the AC implant primary stability [22]. In order to develop a device that could be used intraoperatively in a patient specific manner, a hammer was then instrumented and the technique was adapted to predict the AC implant stability using such impact hammer [22, 23].…”

The effect of dynamic hip motion on the micromotion of press-fit acetabular cups in six degrees of freedom

“…A 1 mm press-fit was chosen rather than a 2 mm press-fit to ensure that full seating of the cup was achieved. Furthermore, a few studies have reported increased stability of cups implanted with a 1 mm press-fit compared to a 2 mm press-fit [2,9,25] . Prior to testing, the peripheral diameters of each acetabular cavity were measured using a digitiser (Incise, Renishaw, Wotton-under-Edge, UK) to confirm the accuracy of the machining; the mean peripheral diameter was 52.99 ± 0.02 mm.…”