Three-dimensional analysis of subchondral cysts in hip osteoarthritis: An ex vivo HR-pQCT study

Abstract

Introduction Subchondral cysts are deeply related to the pathogenesis of osteoarthritis (OA), but the factors contributing to cyst formation are not well known. A three-dimensional analysis of subchondral cysts at the micro-structural level was conducted using high-resolution peripheral quantitative CT (HR-pQCT), and their relationships with cartilage attrition and subchondral bone microstructure were investigated. Methods Femoral heads extracted from ten female patients with hip OA were scanned using HR-pQCT at a voxel size of 41 μm. The volume fractions, numbers, and sizes of the cysts were measured in the subchondral bone region under the area of cartilage loss. Furthermore, the areas of cartilage loss, as well as the microstructure of the subchondral bones, were also measured, and their correlations with the cysts were analyzed. Results The volume fractions of cysts within subchondral bone regions varied from 2% to 33%, the numbers of cysts varied from 6 to 87, and the sizes varied from 1 mm3 to 657 mm3. There was a positive correlation between the number of cysts and bone volume (r>0.8, p<0.01). Conclusion The degree of cyst formation showed a wide distribution in number and volume, and there was a close relationship between multiple cyst formation and bone sclerosis, which might be caused by reactive bone formation that occurred around each cyst.

Decrease in Local Volumetric Bone Mineral Density in Osteoarthritic Joints Is Associated with the Increase in Cartilage Damage: A Peripheral Quantitative CT Study

“…We observed subchondral bone cysts in all of OA samples, which are consistent with other reports on OA hip (Chiba et al, 2014). These fluid-filled voids in subchondral bone, which are typically referred to as "subchondral bone cysts, " are normally reported in OA patients.…”

Correlation between vertebral bone microstructure and estimated strength in elderly women: An ex-vivo HR-pQCT study of cadaveric spine

“…It also allows us to analyze the microstructure of bone samples ex vivo, similar to micro-CT [8]. While micro-CT is mainly used for small experimental animals, HR-pQCT can be used for large bone samples, such as the human cadaver spine [9][10][11][12][13][14][15][16]. It has been reported that HR-pQCT results in fewer errors in measurements of bone morphology compared to the histological method [17].…”

Response to Letter to the Editor: ‘Is subchondral bone mineral density associated with nocturnal pain in knee osteoarthritis patients?’

“…With regards to quantifying cyst presence, this was completed using a custom semi-quantitative approach combining methods from Kornaat et al 5 and results from Chiba et al 6 . A single researcher (JDJ) retrospectively evaluated all CT scans (mainly sagittal and coronal reconstructions) for cyst presence, size and number.…”

“…With the assumption that cysts are predominantly spherical in shape, segmented areas were converted to equivalent cyst diameters and volumes. Individual cyst sizes were classified as: none, 0e1.25 mm diameter, 0e1 mm 3 volume, as per Chiba et al 6 ; mild, 1.25e2.5 mm diameter, 1e8 mm 3 volume; moderate, 2.5e5 mm diameter, 8e65 mm 3 volume; large, >5 mm diameter, >65 mm 3 volume, as per Kornaat et al 5 . In instances where there were multiple cysts, the volumes of individual cysts were summed and total cyst volume dictated the specific grouping.…”

“…The paper referred by Chen and colleagues identifying cysts as a main factor contributing to pain in OA did not actually find an association between pain and cysts (the associations were between pain and joint effusion as well as osteophyte presence in the patellofemoral compartment) 5 . In recent years there appears to be more focus on evaluating the role of cysts in OA (see works by Chiba et al 6,7 and McErlain et al 8e10 ), which is partly why we included a discussion of our preliminary observations regarding cysts in the paper. Our aim was to initiate discussion and offer potential direction to other researchers evaluating links between pain and structural abnormalities.…”