Characterization of the acetabular labrum articular surface and its translation into biomimetic graft design

The acetabular labrum contributes to hip joint stability and lubrication, yet its articular surface properties remain poorly characterized. Understanding and replicating these surface features is critical for developing functional labral grafts.

Native bovine labra were analyzed to assess surface microstructure, lubricin distribution, local stiffness, and coefficient of friction (COF). Scanning electron microscopy, immunohistochemistry, micromechanical indentation, and pin-on-disc testing were employed, with cartilage and meniscus samples as controls. In parallel, hybrid scaffolds combining melt electrowriting (MEW) microgrids with electrospun (SES) nanofibre caps were fabricated. These constructs were structurally and mechanically evaluated by SEM, T-peel adhesion tests, tensile testing, and pin-on-disc friction measurements for comparison.

The bovine labrum exhibited a dense nanofibrillar surface (∼70 nm fibres), abundant lubricin, and a low COF (0.15 ± 0.03), significantly lower than cartilage or meniscus. Trypsin digestion depleted lubricin, increasing COF and reducing local stiffness. Biomimetic MEW-SES constructs demonstrated successful nanofibre capping (∼0.83 µm fibres) over MEW grids (∼16.5 µm fibres). Adhesion between layers was moderate (3-4 mN/mm) and independent of MEW spacing. Nanofibre capping enhanced tensile modulus in dense MEW grids from 2.292 to 3.261 MPa and significantly reduced COF from 0.203 to 0.117, values within the physiological range of native tissue.

The acetabular labrum possesses unique tribological properties that can serve as a blueprint for graft design. Hybrid MEW-SES constructs replicate key structural and functional features, providing a promising approach toward engineered labral grafts. Future work should integrate biological evaluation and long-term tribological testing under physiologic conditions.