Total hip arthroplasty with tantalum rod extraction via direct anterior approach based on preoperative DCE-MRI and AI: a case report.

Introduction and importance: Osteonecrosis of the femoral head (ONFH) is a debilitating condition characterized by compromised blood supply to the femoral head, leading to bone marrow or osteocyte death, and ultimately resulting in ischemia, necrosis, and potential collapse of the femoral head. Dynamic contrast-enhanced MRI (DCE-MRI) is a minimally invasive test that has the advantage of providing a microenvironmental picture of the femoral head that cannot be detected by conventional imaging (e.g., X-rays, CT, MR), and accurately assessing the viability and function of the local tissues, thus helping to select the appropriate surgical intervention. In this context, tantalum rod implantation has been employed as a treatment option for ONFH, aiming to provide structural support and potentially improve blood supply to the necrotic area. However, there are few reports in the literature on the evaluation of the efficacy of tantalum rod implantation in combination with DCE-MRI.

Case presentation: A patient with bilateral SONFH, diagnosed according to the ARCO classification, presented with significant pain and limited mobility. Despite undergoing tantalum rod implantation in both hips, the patient reported minimal improvement in symptoms and continued to experience discomfort. Preoperative DCE-MRI was conducted to assess blood supply in the femoral heads, revealing inadequate perfusion in the necrotic areas. Given the poor response to tantalum rod implantation, a decision was made to proceed with DAA-THA to remove the tantalum rods and femoral heads. Intraoperative findings confirmed the presence of necrotic bone and lack of significant revascularization in the affected areas. The retrieved femoral head specimens were subjected to pathological and micro-CT analysis, which further confirmed the extent of necrosis and the inadequacy of blood supply.

Clinical discussion: The use of tantalum rods in the treatment of ONFH is based on their osteoconductive properties and potential to promote revascularization. However, the success of this treatment is highly dependent on the preoperative blood supply status of the femoral head. DCE-MRI played a crucial role in this case by providing a clear picture of blood perfusion in the necrotic areas, which helped in identifying patients who may not benefit from tantalum rod implantation. The pathological and micro-CT analysis of the retrieved femoral head specimens provided additional insights into the reasons behind the inefficacy of tantalum rod implantation. Specifically, the lack of significant revascularization and the extent of necrosis highlighted the limitations of this treatment option in certain patient populations. The decision to proceed with DAA-THA was based on the patient's poor response to tantalum rod implantation and the need for a definitive surgical intervention. The use of the AIHIP system for preoperative planning facilitated a precise and efficient surgical approach, minimizing trauma and optimizing postoperative recovery.

Conclusion: This case study highlights the importance of comprehensive preoperative assessment using DCE-MRI in guiding the selection of surgical interventions for ONFH. Specifically, DCE-MRI can identify patients who may not respond favorably to tantalum rod implantation due to inadequate blood supply in the necrotic areas. In such cases, alternative treatment options such as DAA-THA should be considered.