Effect of long-term physiological activity on the long-term stem stability of cemented hip arthroplasty: in vitro comparison of three commercial bone cements

Abstract

Long-term endurance of the cement mantle is fundamental for the survival of cemented hip prostheses. Current protocols to characterize bone cements are unsuitable to predict the actual clinical outcome. The aim of this study was to assess if it is possible to rank cement types having diverse clinical outcome by using a simplified in vitro physiological test. Composite femurs were implanted with identical stems (Lubinus-SPII), using different commercial cement types: CMW1 to represent cement with poor clinical outcome; Simplex-P and Cemex-RX to represent cements with a positive clinical outcome. Implanted femurs were subjected to a validated protocol that simulated a demanding but physiological loading spectrum. Inducible micromotions and permanent migrations were recorded throughout the test. After test completion, the cement mantles were sectioned and inspected with dye penetrants to quantify the fatigue-induced cracks. Micromotions did not differ significantly between cement types (possibly because a successful prosthesis was chosen that is very stable in the host bone). Significant differences were observed in terms of cement cracks: CMW1 induced significantly more numerous and larger cracks than Simplex-P and Cemex-RX; no difference was observed between Simplex-P and Cemex-RX. This indicates that this protocol: (a) can discriminate between 'good' and 'bad' cements and (b) yields consistent results when comparable cements are tested. The proposed protocol overcomes the limitations of existing standardized material tests for bone cements. New cements can be assessed in comparison with other cements with known (positive/negative) clinical outcome, tested with the same protocol.

Standard and line‐to‐line cementation of a polished short hip stem: Long‐term in vitro implant stability

“…Although differences were not extremely large, we observed more fatigue damage in the Line‐to‐line than in the Standard‐mantle . This finding is in agreement with previous in vitro tests where different cement mantle thickness were compared, and especially in regions where the cement mantle was thin . More cracks have also been observed in retrievals, when the cement mantle is thin .…”

“…Similarly, also the extent of cement damage observed at the end of the cyclic loading was that typically observed when a clinically successful stem such as the Lubinus SPII was tested in vitro . The finding of small cement cracks around stable implants is consistent with who found cracks around autopsy‐retrieved stable implants.…”

Method to Analyze the Fatigue Cracks in Acrylic Bone Cement

“…2(c)]. More details regarding the study on three types of bone cement have been described in Bialoblocka-Juszczyk et al 21…”

Comments on ‘Experimental versus computational analysis of micromotions at the implant - bone interface’

“…This statement is inaccurate for the other paper: 2 in fact, as shown in that paper, 2 the reference frame of each of the four LVDTs was connected to the bone close (500 micron) to the stem–bone interface (as opposed to the bone surface) by means of a tiny sleeve inserted onto the transcortical holes (Figure 1). We used the same type of fixation for the LVDTs in a number of later studies on cemented and cementless stems, 4–14 many of which are published in this Journal, which Tarala et al 1 did not mention. Therefore, the statement that ‘None of these experimental methods allow for micromotion measurement at the actual implant–bone interface’ seems unjustified.…”