Comparison of Different Locking Mechanisms in Total Hip Arthroplasty: Relative Motion between Cup and Inlay

Abstract

The resulting inflammatory reaction to polyethylene (PE) wear debris, which may result in osteolysis, is still considered to be a main reason for aseptic loosening. In addition to the primary wear in hip joint replacements caused by head-insert articulation, relative motions between the PE liner and the metal cup may cause additional wear. In order to limit this motion, various locking mechanisms were used. We investigated three different locking mechanisms (Aesculap, DePuy, and Zimmer Biomet) to address the resulting relative motion between the acetabular cup and PE liner and the maximum disassembly force. A standardized setting with increasing load levels was used in combination with optically based three-dimensional measurements. In addition the maximum disassembly forces were evaluated according to the ASTM F1820-13 standard. Our data showed significant differences between the groups, with a maximum relative motion at the maximum load level (3.5 kN) of 86.5 ± 32.7 µm. The maximum axial disassembly force was 473.8 ± 94.6 N. The in vitro study showed that various locking mechanisms may influence cup-inlay stability.Materials 2020, 13, 1392 2 of 9 locking mechanisms are used. It is assumed that a firm connection of the components will reduce the relative motion and the particle migration inside the cup system [13,14]. Another rather rare reason for revision is the dislocation between cup and PE liner, which presumably can be attributed to the acetabular locking mechanism.The aim of this study was to evaluate specific locking mechanisms regarding the resulting relative motion between the acetabular cup and the PE liner. In addition, the maximum dissembling forces were investigated. For this purpose, three implant designs were tested, to determine if different types of locking mechanisms affect the magnitude of relative motion and dissembling force.

Liner dissociation in a large-diameter ceramic-bearing acetabular component: a report of five cases

“…Acetabular component modularity was introduced in THA to allow bearing exchange in case of premature polyethylene wear and to simplify implant inventory. In metal backed MoP acetabular component, early postoperative polyethylene liner dissociations have been attributed to intra-operative liner malseating or poor locking mechanism design while late dissociations are believed to be associated with femoral neck impingement against the liner or edge loading causing liner micro motion and liner locking mechanism wear [ 12 – 14 ]. An important factor in polyethylene liner dissociation is the suboptimal locking mechanism of multi-bearing acetabular shells implant design.…”

How to Prevent Aseptic Loosening in Cementless Arthroplasty: A Review

“…The micromotion between the acetabular cup and inlay produces wear debris which generate a biologic host response responsible for a periprosthetic bone loss that further leads to aseptic loosening [22].…”

“…Jaeger et al tested three different locking mechanisms between the cup and inlay: Allofit ® -S Alloclassic ® with cross-linked Durasul ® -PE liner (Zimmer Biomet); Pinnacle ® -Multihole combinates with a cross-linked Marathon ® -PE liner (DePuy Synthes) and Plasmafit ® Plus7 with a conventional ultra-high-molecular-weight polyethylene (UHMWPE) liner (Aesculap) [20]. The micromotion was less in the Aesculap combination, followed by DePuy and Zimmer Biomet [22].…”

Polyethylene Liner Dissociation in the Early Post-Operative Period Following Total Hip Arthroplasty: A Case Report and Literature Review

“…There are several different locking mechanisms designed to fixate polyethylene liners to the acetabular shell. A polyethylene liner is locked into the acetabular shell by locking rings and tabs, taper lock, circular fit, or by increasing the friction fit between the metal and polyethylene component, or by increasing the conformity between the metal shell and PE liner [ 1 ]. Multiple factors can contribute to this malfunction of the locking mechanism, and these factors can be classified as technique-related (improper seating and component malposition), design-related, and wear-related or delayed impingement due to changes in hip-spine relationships.…”