Avascular necrosis in kidney transplant recipients: Incidence and risk factors in the modern immunosuppression era.

Objectives: This study aims to assess the incidence and risk factors for avascular necrosis (AVN) in kidney transplant recipients (KTRs) under modern immunosuppression.

Patients and methods: Between January 1993 and April 2023, a total of 769 KTRs (496 males, 273 females; mean age: 38.15±12.29 years) who underwent transplantation were retrospectively analyzed. The diagnosis of AVN was established using X-rays and magnetic resonance imaging to evaluate patients presenting with pain in one or more joints. Risk factors for AVN were analyzed in a cohort of 290 transplant recipients after 2007 under tacrolimus-based treatment to standardize immunosuppression (178 males, 112 females; mean age: 40.6±12.0 years).

Results: The incidence of AVN was 8.2% (n=21) from 1993 to 2007 and 4.1% (n=21) from 2008 to 2023, retrospectively. The median duration from transplantation to the diagnosis of AVN was 15 (range, 1 to 68) months, with the femoral head being the predominant site affected. The reduction in AVN incidence, along with the replacement of cyclosporine by tacrolimus and the reduction in total corticosteroid dosage, was evident in recent era. The increased body mass index (BMI) (p=0.005), the onset of late acute rejection (p=0.024), and the administration of greater cumulative corticosteroid doses at both three (p=0.001) and 12 months (p<0.001) were correlated with the incidence of AVN in recipients undergoing tacrolimus-based maintenance immunosuppression. Multivariate analysis indicated that an elevated BMI (odds ratio [OR]=1.130, 95% confidence interval [CI]: 1.013-1.261; p=0.028) and a cumulative methylprednisolone dosage exceeding 4.5 g within 12 months (OR=12.692, 95% CI: 2.146-75.069; p=0.005) were significant predictors of AVN.

Conclusion: The incidence of AVN in kidney transplant recipients has significantly diminished in the modern immunosuppressive era and the elevated total corticosteroid dosage remains the principal risk factor for AVN among kidney transplant recipients. The implementation of preventive strategies and screening in high-risk populations should be coordinated between transplant specialists and orthopedic surgeons.