Cemented short‐stem total hip arthroplasty: Characteristics of line‐to‐line versus undersized cementing techniques using a validated CT‐based finite element analysis

Abstract

Short stems are becoming increasingly popular in total hip arthroplasty as they preserve the bone stock and simplify the implantation process. Short stems are advised mainly for patients with good bone stock. The clinical use of short stems could be enlarged to patients with poor bone stock if a cemented alternative would be available. Therefore, this study aimed to quantify the mechanical performance of a cemented short stem and to compare the “undersized” cementing strategy (stem one size smaller than the rasp) with the “line‐to‐line” technique (stem and rasp with identical size). A prototype cemented short stem was implanted in eight pairs of human cadaveric femora using the two cementing strategies. Four pairs were experimentally tested in a single‐legged stance condition; stiffness, strength, and bone surface displacements were measured. Subject‐specific nonlinear finite element models of all the implanted femora were developed, validated against the experimental data, and used to evaluate the behavior of cemented short stems under physiological loading conditions resembling level walking. The two cementing techniques resulted in nonsignificant differences in stiffness and strength. Strength and stiffness as calculated from finite element were 8.7 ± 16% and 9.9 ± 15.0% higher than experimentally measured. Displacements as calculated from finite element analyses corresponded strongly (R 2 ≥ .97) with those measured by digital image correlation. Stresses during level walking were far below the fatigue limit for bone and bone cement. The present study suggests that cemented short stems are a promising solution in osteoporotic bone, and that the line‐to‐line and undersized cementing techniques provide similar outcomes.

Calcar-guided short-stem total hip arthroplasty: Will it be the future standard? Review and perspectives

“…Using prototypes of the optimys stem fabricated using polished steel (Figure 12 ), a recent in vitro biomechanical study demonstrated that the concept of a line-to-line cementation technique could be further pursued for the development of a cemented short stem in THA[ 60 ]. This finding was confirmed in a validated, computed tomography-based, finite element analysis performed by Azari et al [ 61 ] that quantified the mechanical performance of this short stem design. The results suggested that cemented short stems are a promising alternative for use in osteoporotic bone and may, therefore, further expand the range of indications in the future.…”

Is it reasonable to shorten the length of cemented stems? A finite element analysis and biomechanical experiment

“…To date, there have been no new-generation cemented short stems used clinically. The utilization of the line-to-line technique in the development of cemented short stems may present a promising alternative for the treatment of osteoporotic bone conditions (Azari et al, 2021).…”