The split-line pattern of the distal femur: A consideration in the orientation of autologous cartilage grafts

Purpose: To identify the surface collagen orientations of the distal femur and create a generic cartilage split-line map that could be used as a reference guide for the proper alignment of autogenous cartilage transplants. Type of Study: Anatomic, cadaveric study. Methods: Eight fresh cadaveric knee joints were used to deter-mine the collagen fiber orientation of the superficial layer of the articular cartilage of the distal femur. A split-line technique was used, in which a dissecting needle dipped in India ink was inserted into the cartilage. The resulting split between collagen fibers identified the preferential orientation of the collagen fibers at each needle insertion point. Results: The results of the study show that a precise and consistent orientation of collagen fibers exists in areas that are known to experience significant joint load. Conclusions: Because the orientation of these split lines is thought to reflect the direction of tensile forces normally seen by the articular cartilage at a specific area, we hypothesize that proper orientation of autogenous cartilage plugs (with respect to split-line direction) may maximize resistance to these tensile forces and thus optimize the long-term health of these cartilage plugs.