Abstract
Background:
Femoroacetabular impingement (FAI) is one of the major causes of hip pain. The pathogenesis of FAI remains unclear, and few animal models are available to study its mechanisms.
Purpose:
To evaluate bone deformity formation, labrum, and articular cartilage injury induced by mechanical and exercise stimulation, and to establish an FAI model in New Zealand White rabbits.
Study Design:
Controlled laboratory study.
Methods:
6-month-old (6M) and 1-month-old (1M) male rabbits were used. Three-dimensional printed polylactic acid scaffolds were surgically fixed to the acetabular rim, followed by postoperative treadmill training. Specimens were collected at 8 and 12 weeks. Bone deformities were assessed by micro-computed tomography. Histological evaluation included hematoxylin and eosin staining for morphology, Safranin O/Fast Green (SO/FG), and toluidine blue staining for proteoglycan and glycosaminoglycan deposition, and immunofluorescence for SRY-box transcription factor 9 (SOX9), aggrecan (ACAN), runt-related transcription factor 2 (RUNX2), and cluster of differentiation 31 (CD31) expression. Mechanical properties of the labrum and cartilage were evaluated by nanoindentation, with the Young’s modulus as the stiffness parameter.
Results:
Gross evaluation (control [Ctrl] vs FAI, 6M: P < .0001, 1M: P < 0001) and micro-CT revealed significant bone deformities and cartilage damage in the FAI group. SO/FG staining showed reduced proteoglycan deposition (Ctrl vs FAI, 6M: P = .0001, 1M: P = .0006), accompanied by decreased SOX9 (Sham vs FAI, 6M: P < .0001, 1M: P < .0001), ACAN (Sham vs FAI, 6M: P = .0392, 1M: P < .0001) expression, and increased RUNX2 (Sham vs FAI, 6M: P = .0007, 1M: P = .0014) and CD31 (Sham vs FAI, 6M: P = .0018, 1M: P = .0071) expression. The Young’s modulus of both the labrum (Ctrl vs FAI, 6M: P < .0001, 1M: P = .0061) and femoral head cartilage was reduced.
Conclusion:
A stable, reproducible, and easily operable rabbit model of FAI was established using combined mechanical and exercise stimulation, providing a practical platform for investigating the pathogenesis of FAI.
Clinical Relevance:
FAI animal models established through acetabular overcoverage surgery are expected to provide an effective tool for subsequent research into the pathogenesis of FAI, thereby laying a theoretical foundation for its early targeted treatment.
Keywords
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