Development and Validation of a Method for Preclinical Durability Evaluation of Linked Semiconstrained Total Elbow Replacement Prostheses

Abstract

Total elbow replacement (TER) is a clinically successful procedure yet isolated, gross mechanical complications associated with implant durability persist. The objectives of this study were to (1) develop a clinically relevant in vitro methodology to replicate the reported damage modes and (2) demonstrate durability improvements of a next-generation linked, semiconstrained design. Two TER prostheses were tested on a biaxial test frame at 1.4 Hz in 37 AE 3 deionized water through 0 to 130 flexion/extension at various load levels simulating high demand, posttraumatic patients until either component failure or run out to 200 000 cycles. The damage patterns of tested components were qualitatively compared to retrieved components to establish the clinical validity of the methodology. The run out load of design 1 was equivalent to 100 N weight in hand (WIH). Specimens tested at higher load levels exhibited multimodal damage consistent in appearance with the clinical literature. The minimum run out load of design 2 was 110 N WIH with no significant damage observed on the components. The methodology developed here was shown to reproduce the clinical damage modes associated with TER in high demand, posttraumatic patients. The method was able to distinguish performance differences within and between 2 different linked, semiconstrained designs.

Comparing damage on retrieved total elbow replacement bushings with lab worn specimens subjected to varied loading conditions

“…The JRF angle with respect to the humerus was consistent with the pattern described by Kincaid and An . A medial‐lateral force was coupled with the pure VV moment, based on visual interpretation of how VV loads were applied by Varadarajan et al…”

“…Their study did not prescribe an exact magnitude for applied loading, but a general pattern for joint reaction force (JRF) and JRF angle, both as a function of weight‐in‐hand (WIH) and flexion angle. Results presented by Varadarajan et al using a similar loading pattern indicated that the 200 K cycle run‐out load for this implant occurred with a maximum joint reaction force (JRF) of 1,511 N (10.2 kg WIH) and a sinusoidal ±4.9 Nm varus‐valgus (VV) moment, during cyclical flexion–extension from 0° to 130°. Higher loading than this induced component failure (including snap‐pin failure) before 200 K cycles.…”

“…Davis previously estimated up to 1,400 elbow flexion–extension cycles per day (∼500 K cycles/year) during nominal ADL with some WIH, and approximately 20 cycles per day (∼7,300 cycles/year) of ADL involving significant (>4.5 kg) WIH. Varadarajan et al performed TER testing simulating significant WIH (10.2 kg) at 0.7 Hz for 200 K cycles. Popoola et al performed TER testing with a smaller WIH (5.5 kg) at 1 Hz for 3M cycles.…”

“…Appropriate pre‐clinical testing of TER is vital to ensuring future TER designs address these durability concerns; however, there exists no standardized pre‐clinical durability testing protocols for TER prostheses. Kincaid and An published elbow biomechanics data which may serve as a foundation for clinically relevant pre‐clinical testing protocols for TER implants using joint motion simulators; however, few studies have reported outcomes of durability tests based on their data . Furthermore, the effects of infrequent but higher‐demand elbow loading scenarios (such as sit‐to‐stand) are unknown.…”