Calcification of the acetabular labrum of the hip: prevalence in the general population and relation to hip articular cartilage and fibrocartilage degeneration

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.

Response to “Letter to the editor: Labral calcification plays a key role in hip pain and symptoms in femoroacetabular impingement”

“…Previous study stated that the amount of calcification in the labrum instead of histological degeneration grade had significant influence on the preoperative Harris Hip Score (HHS) in patients with end-stage OA [3,4]. Therefore, how much amount of calcium crystal deposition in the labrum produce adverse effect on hip function in patients with FAI needs further study.…”

“…We should point that the FAI patients enrolled in our study had a mean age of 33 years as opposed to 62 years in the work mentioned by Drs. Zhong and Ouyang [3]. These significant differences in age should be considered when trying to compare "healthy" and "FAI" labral tissues.…”

Chondrokalzinose

“…Nach klinischen Standardscores erhoben, korreliert die Menge des Knorpelmineralgehalts an Hüfte und Kniegelenk mit dem subjektiv empfundenen Schmerzniveau [15,16]. Wenn man die Lokalisation der ektopen Mineralisation weiter differenziert und die Kalzifikation des Labrum acetabulare von der Kalzifikation des Gelenkknorpels im Hüftgelenk separat betrachtet und parallel analysiert, wird evident, dass der Faserknorpel des Labrums besonders anfällig für Kalzifikation ist (Faktor 1,55 mehr Mineralgehalt gegenüber dem hyalinen Gelenkknorpel) und dass die Labrummineralisation stärker als die Gelenkknorpelmineralisation mit dem subjektiven Schmerzniveau korreliert [17,18].…”

Kalziumkristalle im Gelenk

“…Der Prozess der Kalzifizierung findet in allen Gelenken statt. Eine Kalzifizierung des Knorpels ist während der Knie-, Hüft-, Schulter-und auch Großzehen-Arthrose gezeigt worden [17,[19][20][21]. Dieser Mechanismus ist vermutlich mit der enchondralen Ossifikation während der Knochenentstehung zu vergleichen, bei der es ebenfalls zu einer Hypertrophie von Chondrozyten und anschließender Mineralisierung des Knorpels kommt.…”