Increased failure rates due to metallic wear particle-associated adverse local tissue reactions (ALTR) is a significant clinical problem in resurfacing and total hip arthroplasty. Histological analysis and particle characterization are important elements for understanding the biological mechanisms of the reaction and different histological subtypes may have unique needs for longitudinal clinical follow-up and complication rates after revision arthroplasty.

Consecutive patients (N=285 cases) presenting with ALTR from three major hip implant classes, metal-on-metal resurfacing and total hip arthroplasty (THA) and non-metal-on-metal THA with dual modular neck were identified from our prospective Osteolysis Tissue Database and Repository and 53 cases were selected for wear particle nano-analysis.

Conventional histology: Tissue samples taken from multiple regions around the hip with extensive sampling performed at macroscopic examination were examined by light microscopy.

Particle analysis: Tissue samples selected after frozen section evaluation for cellularity and particle content were examined by scanning electron microscopy (SEM), backscatter scanning electron microscopy (BSEM), BSEM-energy-dispersive X-ray spectroscopy (EDS) element mapping examination, transmission electron microscopy (TEM), TEM-EDS element mapping, and X-ray diffraction spectrometry (XRD) examination.

ALTR encompasses three main histological patterns: 1) macrophage predominant, 2) mixed lymphocytic and macrophagic, and 3) predominant sarcoid-like granulomas. Duration of implantation and composition of periprosthetic cellular infiltrates was significantly different among the three implant types examined. Distinct differences in the size, shape, and element composition of the metallic particulate material were detected in each implant class, with correlation of the severity of the adverse reaction with element complexity of the particles.

ALTR encompasses a diverse range of histological patterns, which are reflective of both the implant configuration independent of manufacturer and clinical features such as duration of implantation. Distinct differences in the metallic particulate material can contribute to explain the histological features of the ALTR and variability of performance of the implants.

ALTR exhibits different histological patterns and is dependent on the characteristics of the wear particulate material of each implant class and host immunological reaction.