Proximal tibial osteophyte volumes are correlated spatially and with knee alignment: a quantitative analysis suggesting the influence of biochemical and mechanical factors in the development of osteophytes

OBJECTIVE

To characterize the differences and correlations in osteophyte volumes between and within proximal tibial compartments, and to assess the correlations between osteophyte volumes and the femorotibial angle.

DESIGN

CT scans of 73 knees with predominantly medial femorotibial osteoarthritis (21 K/L2, 28 K/L3, 24 K/L4) were retrospectively analyzed using a new, reproducible method measuring total and subregional osteophyte volumes in the medial and lateral compartments. Non-parametric statistics was used for comparison and correlation analyses.

RESULTS

Total osteophyte volumes were larger in the medial than in the lateral compartment for all severity groups (p < 0.05). Additionally, statistically significant differences were observed among subregions of the lateral compartment in K/L3 and K/L4 knees. Statistically significant positive correlations were found between the medial and lateral total osteophyte volumes in K/L3 and K/L4 knees (ρ ≥ 0.44, p = 0.03), and among most subregional osteophyte volumes within each compartment in K/L3 knees. Markedly fewer statistically significant correlations were present in K/L2 and K/L4 knees. In K/L3 knees, the femorotibial angle was statistically significantly positively correlated with the total osteophyte volume in the medial compartment (ρ = 0.50, p = 0.01), with osteophyte volumes in most medial subregions, and with the osteophyte volume in the lateral posterior subregion (ρ = 0.40, p = 0.05).

CONCLUSIONS

Quantitative assessment of osteophytes may bring insight on factors influencing their development. Positive correlations of osteophyte volumes found between and within compartments suggest the influence of biochemical mediators acting on the entire joint, while positive correlations between the femorotibial angle and osteophyte volumes suggest a role of mechanical factors. These hypotheses are to be further confirmed.

Experimental cataracts in rats due to tryptophan-free diet

A tryptophan-free diet induces posterior subcapsular cataracts and reversible corneal opacities in young Wistar rats. Compared to the controls there is a significant decrease of body weight, lens fresh weight, and water-soluble lens protein. Protein separation by isoelectric focusing shows diminished alpha-, beta-, and gamma-crystallin fractions. If tryptophan is restored to the diet after 24 days, new clear lens fibers are laid down again, indicating that the mechanism of protein synthesis has not been permanently damaged by tryptophan-deficiency.