Calcified cartilage in patients with osteoarthritis of the hip compared to that of healthy subjects. A design-based histological study

• Published in: Bone (New York, N.Y.) Vol. 143; p. 115660
• Main Authors: Klose-Jensen, Rasmus, Hartlev, Louise Brøndt, Thomsen, Jesper Skovhus, Nyengaard, Jens Randel, Boel, Lene Warner Thorup, Laursen, Mogens, Laurberg, Trine Bay, Stengaard-Pedersen, Kristian, Hauge, Ellen-Margrethe
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-02-2021
• Subjects: Calcified cartilage; Femur head; Histology; Human; Osteoarthritis; Stereology; Human; Stereology; Histology; Calcified cartilage; Osteoarthritis; Femur head
• ISSN: 8756-3282; 1873-2763
• DOI: 10.1016/j.bone.2020.115660

Calcified cartilage is suggested to be involved in the pathogenesis of osteoarthritis (OA) by facilitating endochondral ossification at the bone-cartilage unit. Therefore, the objective was to quantify the volume and surface area of the calcified cartilage in the femoral head in OA patients and healthy subjects.
We used design-based stereological principles, i.e., systematic uniform random sampling and vertical uniform random sections of the entire femoral head. We investigated the articular and calcified cartilage and femoral head surface area and volume, excluding fovea capitis and marginal osteophytes, in 20 patients with OA and 15 healthy subjects.
The volume of the calcified cartilage was significantly larger for the patients with OA compared with the healthy subjects (mean difference [95% CI]) (284 [110,457] mm3, p = 0.002). The upper and lower surface area of the calcified cartilage, i.e. the tidemark and cement line, were both significantly larger for OA patients compared with the healthy subjects (17.8 [8.4,27.3] cm2, p < 0.001) and (38.7 [20.8,56.7] cm2, p = 0.002), respectively. The volume of the calcified cartilage and the volume of the femoral head were significantly correlated for the patients with OA (Spearman's ρ = 0.51, p = 0.021), but not for the healthy subjects (ρ = 0.41, p = 0.123).
Patients with OA had a larger femoral head surface area and more calcified cartilage compared to healthy subjects. The volume of the calcified cartilage correlated positively with the volume of the femoral head for patients with OA, but not for healthy subjects. This strongly supports the existing view that bone growth in OA is associated with endochondral ossification.
•Patients with osteoarthritis (OA) had larger volume and surface area of the calcified cartilage in the femoral head.•The larger surface area of the calcified cartilage reflected a more considerable irregularity of both the tidemark and the cement line.•The volume of the calcified cartilage correlated with the size of the femoral head for patients with OA only.•The larger calcified cartilage with more irregular borders support that bone growth in OA is associated with endochondral ossification.