**6.7 Correlations**

308 Recent Advances in Arthroplasty

Mean value of hydroxyproline in both groups was 13.9 mg/g (±10.2 SD), and in controls,

Fig. 6. The concentration of lipid peroxidation product - malondialdehyde in joint fluid. Values were measured in nmol/L. The lower and upper lines in the boxes represent the 25th

The tissue concentrations of the different metals for the Co-Cr and Ti-alloy prostheses are shown in Table 2. The mean level of MDA in the 23 implants made of titanium alloy was 0.059 µg/mg, and of the 9 implants made of Co-Cr alloy, 0.023 µg/mg. However, this

Table 2. Concentrations of various metals in periprosthetic tissues from Co-Cr alloy and titanium alloy prostheses. Values measured in µg/g wet tissue. Data represented as mean ±SD.

**Ti V Fe Cr Co** 

70.1 189.5 4.4 8.7 na na na

381.8 911.9 20.6 46.5 11.2 12.2 2.7 4 \* 4.1 5.6

na na 13.5 11.2 75.3 160 \* 33.2 34.5

and 75th percentiles, respectively, with the median marked in the box.

**6.5 Hydroxyproline determination** 

55.6 mg/g (±38.6 SD) ( p<0.013).

p<0.001

Composition Stem/Cup

*Ti / Ti alloy* (N 23)

*Co-Cr / Ti alloy*

(N 9)

(N 8)

*Co-Cr / Co-Cr alloy*

**6.6 Metal particle analysis** 

difference was not significant (p=0.145).

\* p<0.013 in comparison between groups

In the 40 hips, levels of MDA correlated with levels of GSH and GSSG (rho=0.509, p<0.0001, and rho=0.421, p<0.001, respectively). Because oxidative stress is a significant contributor to tissue fibrosis, a second set of correlations was calculated that measured the correlation between oxidative stress and hydroxyproline content. There was a correlation between GSH, GSSG, as well as MDA levels and periprosthetic collagen content. GSH/GSSG ratio and MDA level correlated with degree of osteolysis (rho=0.337, p=0.007, and rho=0.374, p=0.017, respectively). GSSG and MDA levels were higher in hips with greater annual wear of the polyethylene.
