[VASCULARITY STUDY ON PERIPROSTHETIC TISSUES AROUND ASEPTIC LOOSENING AFTER TOTAL HIP ARTHROPLASTY]

To observe the vascularity in periprosthetic tissues of aseptic loosening after total hip arthroplasty (THA) and to explore the relationship between expression of vascularity and osteolysis.

Between October 2009 and June 2012, interface tissues were obtained from 22 patients (22 hips) who underwent revision of THA because of prosthetic aseptic loosening, including 12 males and 10 females with the age range of 53-81 years and prosthesis survival range of 6-14 years. The interface tissues were divided into osteolysis group and non-osteolysis group based on preoperative X-ray findings and intraoperative observation. The synovial tissues were harvested from another 8 patients (3 males and 5 females, aged 58-72 years) with osteoarthritis undergoing THA as control group. HE stainging was used to observe the histological character, and low-wear or high-wear was identified according to metal or polyethylene particles amount in osteolysis group. The CD34 immunohistochemical staining was used to mark the blood vessels. Microvessel density and microvessel index were calculated with the use of image analysis software. RESULTS :Histological observation showed that wear particles and numerous macrophages/multinucleated giant cells accumulated in the membrane of osteolysis group, while many fibroblasts and synovial cells existed in non-osteolysis group. The microvessels density and microvessel index were significantly lower in non-osteolysis group than those in osteolysis group and control group (P < 0.05), and there was no significant difference in microvessel density and microvessel index between osteolysis group and control group (P > 0.05). There were less microvessel density and microvessel index in heavy-loaded metal or polyethylene wear particles areas than those in low-loaded metal or polyethylene wear particles areas (P < 0.05), and there for either polyethylene or metal particles (P > 0.05).

The phagocytosis of macrophage in periprosthetic tissues need vicinal microvessels formation and blood supply to some extent. Vascular injury and decreased blood supply at the implant-bone interface seem to be one of the reasons for insufficient implant osseointegration and aseptic loosening.