The limit of tolerable micromotion for implant osseointegration: a systematic review

Abstract

Much research effort is being invested into the development of porous biomaterials that enhance implant osseointegration. Large micromotions at the bone-implant interface impair this osseointegration process, resulting in fibrous capsule formation and implant loosening. This systematic review compiled all the in vivo evidence available to establish if there is a universal limit of tolerable micromotion for implant osseointegration. The protocol was registered with the International Prospective Register for Systematic Reviews (ID: CRD42020196686). Pubmed, Scopus and Web of Knowledge databases were searched for studies containing terms relating to micromotion and osseointegration. The mean value of micromotion for implants that osseointegrated was 32% of the mean value for those that did not (112 ± 176 µm versus 349 ± 231 µm, p < 0.001). However, there was a large overlap in the data ranges with no universal limit apparent. Rather, many factors were found to combine to affect the overall outcome including loading time, the type of implant and the material being used. The tables provided in this review summarise these factors and will aid investigators in identifying the most relevant micromotion values for their biomaterial and implant development research.

Figure 1

Flowchart of the study selection process.

Figure 2

(A) Scatterplot of the animal data showing the micromotion value for osseointegrated (green, circle, n = 28) and non-osseointegrated (hollow circles, n = 23) samples. (B) Violin plot of the same data. Whilst micromotion was lower for the osseointegrated samples (Mann Whitney test p < 0.001), there was also considerable overlap between the groups.

Figure 3

(A) Applied values of micromotion in osseointegrated (OI, n = 17) and non-osseointegrated (Non-OI, n = 20) groups for the animal studies. Mann Whitney p value = 0.001 **. (B) Measured values of micromotion in OI (n = 11) and non-OI (n = 3) for the animal studies. Mann Whitney p value = 0.003 **.

Figure 4

Scatter plot graph of the correlation between micromotion values and percentage BIC for the animal studies. For the osseointegrated data (green filled circles) a positive correlation was found (Spearman’s ρ = 0.41, p value = 0.02). No correlation was observed for the non-osseointegrated data (empty circles), nor the full dataset (all circles).

Figure 5

Scatter plot demonstrating the correlation between observation time and percentage BIC for the animal studies. Spearman’s ρ = 0.40, p value = 0.01.