Abstract
BackgroundMeniscal calcification is considered to play a relevant role in the pathogenesis of osteoarthritis of the knee. Little is known about the biology of acetabular labral disease and its importance in hip pathology. Here, we analyze for the first time the calcification of the acetabular labrum of the hip (ALH) and its relation to hip cartilage degeneration.MethodsIn this cross-sectional post-mortem study of an unselected sample of the general population, 170 ALH specimens and 170 femoral heads from 85 donors (38 female, 47 male; mean age 62.1 years) were analyzed by high-resolution digital contact radiography (DCR) and histological degeneration grade. The medial menisci (MM) from the same 85 donors served as an intra-individual reference for cartilage calcification (CC). Scanning electron microscopy (SEM), energy dispersive analysis (ED) and Raman spectroscopy were performed for characterization of ALH CC.ResultsThe prevalence of CC in the ALH was 100% and that in the articular cartilage of the hip (ACH) was 96.5%. Quantitative analysis revealed that the amount of ALH CC was higher than that in the ACH (factor 3.0, p < 0.001) and in the MM (factor 1.3, p < 0.001). There was significant correlation between the amount of CC in the fibrocartilage of the left and right ALH (r = 0.70, p < 0.001). Independent of age, the amount of ALH CC correlated with histological degeneration of the ALH (Krenn score) (r = 0.55; p < 0.001) and the ACH (Osteoarthritis Research Society International (OARSI), r = 0.69; p < 0.001). Calcification of the ALH was characterized as calcium pyrophosphate dihydrate deposition.ConclusionThe finding that ALH fibrocartilage is a strongly calcifying tissue is unexpected and novel. The fact that ALH calcification correlates with cartilage degeneration independent of age is suggestive of an important role of ALH calcification in osteoarthritis of the hip and renders it a potential target for the prevention and treatment of hip joint degeneration.
Highlights
Meniscal calcification is considered to play a relevant role in the pathogenesis of osteoarthritis of the knee
CC was detected in 100% of the left and right acetabular labrum of the hip (ALH) (85/85), in 88.2% of the left and right articular cartilage of the hip (ACH) (75/85), in 94.1% of the left medial menisci (MM) (80/85) and in 97.6% of the right MM (83/85)
We have previously reported that articular cartilage calcification can be looked at as the result of a systemically driven process [25, 26], which was reconfirmed by the present data, exemplified by correlation between the amount of CC in the ALH and that in the MM and the contralateral ALH in this unselected cohort of donors (Fig. 3a, b)
Summary
Meniscal calcification is considered to play a relevant role in the pathogenesis of osteoarthritis of the knee. Little is known about the biology of acetabular labral disease and its importance in hip pathology. We analyze for the first time the calcification of the acetabular labrum of the hip (ALH) and its relation to hip cartilage degeneration. Osteoarthritis (OA) is a major health problem and represents the most common joint disease in western populations [1]. OA affects the whole joint and involves hyaline cartilage, subchondral bone, the joint capsule, periarticular ligaments and fibrocartilage [2]. One factor of interest is cartilage calcification (CC). It is detectable in 100% of the hyaline cartilage of end-stage hip and knee OA [3, 4]. Calcium crystals have the potential to induce a pro-inflammatory intra-articular milieu [5,6,7,8] and to alter the biomechanical properties of the cartilage [9, 10], both of which may result in OA [11]
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