Arthroscopy-Assisted Core Decompression Combined with Octacalcium Phosphate/Gelatin Composite Implantation for Osteonecrosis of the Femoral Head: A Study Protocol for a Single-Center Externally Controlled Trial

Background/Objectives: Osteonecrosis of the femoral head is a progressive disease that frequently leads to femoral head collapse and secondary osteoarthritis. Although total hip arthroplasty provides reliable outcomes, its use in younger patients is limited due to concerns regarding implant longevity. Joint-preserving procedures such as core decompression have been widely used; however, their efficacy remains controversial. This study aims to evaluate a combined approach using arthroscopy-assisted core decompression and an osteoconductive bone substitute. Methods: This study is designed as a single-center, externally controlled trial conducted at Tohoku University Hospital. Patients with osteonecrosis of the femoral head (Japanese Investigation Committee Stage 1–3B, Type B–C2) will undergo arthroscopy-assisted core decompression combined with octacalcium phosphate/gelatin composite implantation. A total of 25 patients will be prospectively enrolled. Outcomes will be compared with a propensity score-matched historical control cohort. The primary outcome is disease progression within 1 year, defined as radiographic progression or conversion to total hip arthroplasty. Secondary outcomes include radiographic changes, clinical outcomes, and bone remodeling assessed by computed tomography. Expected Results: This study is expected to provide preliminary clinical evidence regarding the feasibility and potential effectiveness of arthroscopy-assisted core decompression combined with octacalcium phosphate/gelatin composite implantation for osteonecrosis of the femoral head. The intervention may promote bone remodeling and contribute to the prevention of femoral head collapse. Conclusions: The findings of this study may contribute to the development of improved minimally invasive joint-preserving treatment strategies for osteonecrosis of the femoral head and provide a basis for future large-scale clinical trials.