The radiological and clinical follow-up of osteonecrosis in cancer patients

<b>Background:</b> In patients with cancer, osteonecrosis (ON) lesions can affect multiple sites throughout the skeleton, including the long and short bones and the joints. The aims of this study were to explore the natural course of ON in patients treated for cancer by using radiological classification suitable for multisite ON lesions and to assess correlations between the ON grade and surgical procedures. <b>Material and methods:</b> Data were retrieved from hospital databases on 233 ON lesions in 54 patients (aged 2–73 years at cancer diagnosis; mean age: 25 years). ONs were graded according to the Niinimäki classification, based on magnetic resonance images. Medical records were reviewed to identify surgical procedures. <b>Results:</b> A total of 14 different ON sites were detected; the hip was the most common site (<i>n</i> = 51), followed by the femur (<i>n</i> = 45), tibia (<i>n</i> = 41) and knee (<i>n</i> = 37). Among the 233 ON lesions, 78.1% did not require surgical procedures. The remaining lesions required total joint arthroplasty (TJA; 40/233, 17.2%), core decompression (3.4%) and arthroscopy (1.3%). Most TJAs (33/40, 82.5%) were performed on the hip. ONs of the knee required TJAs only once; grade 3 knee ONs frequently healed (58%, 11/19). None of the diaphyseal or metaphyseal (grade 1–2) ONs of the long bones required surgery, and no fractures of those bones were identified. <b>Conclusions:</b> In conclusion, the natural history of ONs varied by the grade and site. Based on our findings, we would not recommend routine radiological follow-ups for grades 1–2 ON lesions that do not affect the joints, because the clinical consequences of those lesions appear to be minimal, although pain relief would be warranted. In contrast, joint deformations (grade 5) require surgery; therefore, intervention studies should focus on grades 3–4 ON lesions.