Morphometric and Cellular Evaluation of Delaminated Cartilage From the Acetabulum

Delaminated acetabular cartilage flaps are associated with inferior outcomes of arthroscopic treatment of femoroacetabular impingement syndrome. Recently, concomitant arthroscopic minced cartilage implantation has shown encouraging early clinical results under such circumstances.

The purpose of this study is to investigate the morphology, outgrowth, and functionality of chondrocytes from delaminated acetabular cartilage flaps in comparison to controls, in order to assess their suitability for minced cartilage implantation. It was hypothesized that despite morphologic differences, chondrocyte viability and functionality do not differ between groups.

Controlled laboratory study.

Delaminated acetabular chondral flaps were obtained from 11 patients undergoing hip arthroscopy. Control samples were taken either from the acetabulum in patients undergoing total hip arthroplasty for avascular necrosis (2 samples) or from patients undergoing minced cartilage implantation at the knee (12 samples). Synchrotron radiation microcomputed tomography (SR-µCT) analyses and histologic evaluations were conducted. In vitro investigations assessed cell proliferation, metabolic activity, and redifferentiation potential in 3-dimensional spheroid cultures.

Microcomputed tomography revealed a significantly increased mean number of chondrocyte lacunae in delaminated acetabular cartilage compared to control samples, along with a significant reduction of lacunar diameter. Morphometric and histologic analyses demonstrate cell-free, necrotic areas with fiber structures within delaminated acetabular cartilage samples. Regarding the number of outgrown cells, metabolic activity, and proliferation capacity, no differences between delaminated acetabular cartilage and control samples were observed. Initially cultured chondrogenic spheroids of cells from delaminated acetabular cartilage samples had lower protein and proteoglycan content compared to controls, but no differences were observed for spheroids cultured with TGF-β1 supplementation.

Delaminated acetabular cartilage exhibits altered morphology. However, cell numbers, outgrowth potential, and population doublings of chondrocytes isolated from delaminated acetabular cartilage were comparable to those of controls. Redifferentiation of chondrocytes isolated from delaminated acetabular cartilage relies on TGF-β1 stimulation.

Delaminated acetabular flaps are strongly degenerated, characterized by atrophic chondrocyte lacunae and tissue necrosis, indicating that autograft utilization is unfavorable. However, cell outgrowth and functionality suggest that delaminated acetabular cartilage flaps provide a suitable tissue source for minced cartilage implantation after augmentation with TGF-β1.