Introduction: The amount of extravasated eosinophil leukocytes in soft tissue surrounding a metallic orthopaedic implant indirectly allows conclusions about the allergenicity of the implant. As yet the implications of the distance of the biopsy from the implant have not been studied.
Methods: In a prospective study we histocytologically evaluated soft tissue biopsies gained during routine removal of orthopaedic implant material in 81 patients. By means of a quantitative and semiquantitative method, material directly adjacent to and 1 cm distant from the implant was examined for eosinophil leukocytes.
Results: In respect to the number of eosinophil granulocytes, the two groups showed no significant discrepancies (p = 0.55). lnterestingly, correlation analysis revealed a significant difference in the number of eosinophiles between implant-adjacent and -distant tissue in some individuals. Consecutive semiquantitative analysis could show that there was no correlation concerning the number of eosinophiles between results gained at 1 cm distance from the implant and material in the direct vicinity of the biomaterial.
Conclusion: Our results suggest that when utilising a histocytological method to determine metal sensitivity of a biomaterial on surrounding soft tissue, not only material directly adjacent to the implant but also at a distance of approximately 1 cm should be evaluated.