Avascular bone necrosis of the femoral head after renal transplantation: Is it avoidable?

Background: Avascular osteonecrosis (AVN) is a serious osseous complication after renal transplantation (RT). Its prevalence clearly decreased from 20% to 4 % possibly due to the use of calcinurin inhibitors (CNI), reduction of steroid doses and use of steroid free regimens. The aim of our study was to evaluate the frequency of AVN among our kidney transplant recipients and to determine the risk factors for its occurrence. Patients and methods: Among 1785 kidney transplant recipients who received renal allografts between March 1976 and December 2005, 40 patients (2.24%) developed AVN with a mean age of 31.3 ± 10.2 years. Eighty kidney transplant recipients without AVN were selected to be a matched control group. The localization of AVN was the femoral head in all cases. Results: AVN was diagnosed at a mean of 20.4 months after transplantation. The following risk factors were statistically significant; sirolimus-based regimen, hypercholesterolemia, overweight with body mass index (BMI)>26 and those with HLA A9, HLA B35 and DR B15. Conclusions: We concluded that the proper management of hypercholesterolemia, maintenance of ideal body weight as well as avoidance of sirolimus-based immunosuppressive regimen in genetically predisposed patients may be an effective preventive strategy to avoid AVN. -----------------Correspondence and offprint requests to: Dr. Ayman F. Refaie, M.D, Consultant Nephrologist, Urology and Nephrology Center, Mansoura University, 35516, Mansoura, Egypt. Tel.: 20-50-2262226 Fax: 20-50-2263717 E-mail: [email protected] Introduction Renal transplantation (RT) is the treatment of choice for most patients with end stage renal disease (ESRD). However, it is attended by complications which are many and varied osseous complications after RT include osteoporotic fractures and osteonecrosis. It has been estimated that osteonecrosis of the femoral head affect up to 20% of recipients. Symptomatic cases of avascular necrosis (AVN) of femoral head are almost always serious complications, accounting for considerable functional restriction and eventual disability, ultimately leading to femoral collapse and total hip arthroplasty in over 80% of cases [1]. X-rays are usually normal at the early stage of bone disease, whereas magnetic resonance imaging (MRI) is more sensitive and specific for the diagnosis of AVN [2]. The known risk factors for AVN include high cumulative steroid dose, blood urea nitrogen level, hypofibrinolysis caused by variant plasminogen activator inhibitor-1 genotype and allograft rejection. In children, the risk factors for osteonecrosis are poorly known, although age under 10 years seems to decrease the risk and higher cumulative steroid doses to increase the risk of AVN [3]. If the diagnosis is made in early phase, treatment by bisphosphonate infusion and vascular bone grafting may be beneficial. Secondary deformities and osteoarthritis are treated with corrective osteomies and total joint replacement [4]. We retrospectively reviewed our renal transplant recipients followed between March 1976 and December 2005 to identify the frequency and the risk factors for the occurrence of AVN.