Microfracture at the Acetabular Rim as Biological Augmentation of Labral Reconstruction Improves Autograft Vascularization and Integration: A Porcine Model.

BACKGROUND: Labral reconstruction is used for irreparable acetabular labral tears, but graft incorporation is often limited by insufficient vascular ingrowth. Bone marrow stimulation at the acetabular rim may enhance revascularization and promote biological healing.

PURPOSE: To determine whether acetabular rim microfracture improves vascularization and tissue integration of labral autografts compared with reconstruction alone in a porcine model.

METHODS: A total of 36 skeletally mature pigs were randomized to labral reconstruction with acetabular rim microfracture (RCMC) or reconstruction alone (RC). A 10-mm segment of the acetabular labrum was resected to create a standardized defect. In the RCMC group, the acetabular rim was microfractured with multiple 2-mm holes, followed by autograft reconstruction with an Achilles tendon graft fixed to the rim. In the RC group, the same reconstruction was performed without microfracture. Hips were harvested at 6, 12, and 24 weeks for macroscopic and histological analysis.

RESULTS: At 12 and 24 weeks, RCMC hips more often showed complete defect filling and smoother articular surfaces than RC hips. Histologically, RCMC grafts showed more mature fibrocartilaginous remodeling, whereas RC grafts remained predominantly fibrous on the articular side with a persistent gap from adjacent cartilage. At 6 weeks, vascular distribution was more uniform in RCMC, whereas in RC it was mainly confined to the capsular side; by 24 weeks, both groups showed a native labrum-like peripheral vascular pattern. Compared with RC, RCMC showed a progressive increase in type 2 collagen, indicating more advanced fibrocartilaginous matrix remodeling. Terminal deoxynucleotidyl transferase dUTP nick-end labeling staining showed that apoptosis was higher early in RCMC and then gradually declined, whereas RC showed delayed increases.

CONCLUSION: Acetabular rim microfracture enhanced early and uniform revascularization of labral autografts and was associated with more advanced fibrocartilaginous remodeling and more labrum-like integration than reconstruction alone.

CLINICAL RELEVANCE: In this porcine segmental labral reconstruction model, acetabular rim microfracture was associated with enhanced histological vascularization, matrix remodeling, and interface integration. These preclinical findings support further investigation of rim microfracture as a potential biological adjunct to labral reconstruction; however, biomechanical and clinical studies are required before its functional effectiveness or clinical applicability can be established.

STUDY DESIGN: Controlled laboratory study.