**5.6.1 Malondialdehyde determination in periprosthetic tissue**

Tissue malondialdehyde levels were determined by Khoschsorur's method (Khoschsorur et al., 2000). The samples were chromatographed on a high performance liquid chromatographer (HPLC) (Spectrochrom, Brackley, UK) interfaced to a LiChrosorb RP18 column. Fluorometric detection was performed with excitation at 527 nm and emission at 551 nm.

Evidence Linking Elevated Oxidative Stress and Aseptic Loosening of Hip Arthroplasty 305

In contrast, stroma rich of connective tissue, abundance of fibroblasts with less frequent

Fig. 2. Periprosthetic tissue from 72-year-old male, 9 years after implantation of cementless prosthesis. Adjacent to the implant synovia-like membrane with 1-2 cell layers (arrow), interstitial matrix rich of fibrous tissue with abundance of fibroblasts and macrophages

Analysis of selected sections from ten representative cases by electron microscopy established damaged collagen fibers and presence of collagen cross-links. Their relative

Fig. 3. Electron micrograph (x39 000) showing periprosthetic tissue taken from stable cementless hip replacement 86 months after implantation. The picture shows damaged

collagen fibers (open arrows) with numerous cross-links (black arrows).

digested wear debris (open arrow) (haematoxylene staining, x500).

**6.2 Electron microscopic examination** 

macrophages were more prevalent in the fibrous pseudocapsule (Fig. 2).

Arbitrary values obtained were compared with a series of standard solutions (Sigma-Aldrich, St. Louis, MO). Results were expressed as nmol/mg hydroxyproline.

### **5.6.2 Malondialdehyde determination in pseudojoint fluid**

Joint fluid malondialdehyde levels were determined by the modified method of Yagi (Yagi, 1982). The samples were read with fluorometric detection at 515/553 nm. As a standard solution Tetraetoxypropane in concentration of 0.1 μmol/L was used. Results were expressed as nmol/L.
