Full-field measurement of micromotion around a cementless femoral stem using micro-CT imaging and radiopaque markers

Abstract

a b s t r a c tA good primary stability of cementless femoral stems is essential for the long-term success of total hip arthroplasty. Experimental measurement of implant micromotion with linear variable differential transformers is commonly used to assess implant primary stability in pre-clinical testing. But these measurements are often limited to a few distinct points at the interface. New techniques based on microcomputed tomography (micro-CT) have recently been introduced, such as Digital Volume Correlation (DVC) or markers-based approaches. DVC is however limited to measurement around non-metallic implants due to metal-induced imaging artifacts, and markers-based techniques are confined to a small portion of the implant. In this paper, we present a technique based on micro-CT imaging and radiopaque markers to provide the first full-field micromotion measurement at the entire bone-implant interface of a cementless femoral stem implanted in a cadaveric femur. Micromotion was measured during compression and torsion. Over 300 simultaneous measurement points were obtained. Micromotion amplitude ranged from 0 to 24 mm in compression and from 0 to 49 mm in torsion. Peak micromotion was distal in compression and proximal in torsion. The technique bias was 5.1 mm and its repeatability standard deviation was 4 mm. The method was thus highly reliable and compared well with results obtained with linear variable differential transformers (LVDTs) reported in the literature. These results indicate that this micro-CT based technique is perfectly relevant to observe local variations in primary stability around metallic implants. Possible applications include pre-clinical testing of implants and validation of patient-specific models for pre-operative planning.

Digital Volume Correlation: Review of Progress and Challenges

“…In the following, feature tracking (e.g., see Refs. [217,116,216,62,146]) will not be reviewed. The discussion will focus on different variants of DVC in which mechanical information is gradually included.…”

“…Some attempts were made (e.g., by adding particles [18,77,25,146] or revealing grain boundaries [135] for x-ray µCT) but at the expense of changing the behavior of the investigated material. This is particularly true when studying ductile of brittle fracture [94].…”

Effect of cavity preparation and bone mineral density on bone‐interface densification and bone‐implant contact during press‐fit implantation of hip stems

“…The distinct medial and lateral contact has been previously observed by Gortchacow et al who also found larger gaps on the anterior and posterior sides of straight stems. However, other groups have shown more contact on the anterior than the posterior side, and therefore this variable may be highly dependent on the surgeon's technique, whereas distinct medial and lateral contact is found in all studies.…”

Micromotion-induced peri-prosthetic fluid flow around a cementless femoral stem

“…The choice of local gap size and micromotion levels was made so as to span the variety of results measured experimentally in a previous study (Malfroy Camine et al 2016). …”

“…The initial and boundary conditions were similar, except for the amplitude and direction of micromotion, which were defined according to the interpolation function of 3D bone-implant micromotion around the stem, measured locally using a micro-CT based experimental technique ( Figure S1) (Malfroy Camine et al 2016). …”