Nitrate patch prevents steroid‐related bone necrosis

Avascular necrosis of the femoral head is a common complication with disabling effect for young patients after high‐dose corticosteroid treatment. We could show that steroids have a vasoconstrictive effect on lateral epiphyseal arteries of the femoral head which could lead to ischemia and subsequent necrosis. In this study we investigated the preventive effect of a nitrate patch on steroid‐related bone necrosis in a rabbit model. New Zealand White rabbits (male; 3–4.5 kg bodyweight) were injected with 20 mg/kg bodyweight methylprednisolone (GC group; n  = 6). Control animals ( n  = 6) were treated with phosphate‐buffered saline. A third group (GC + N; n  = 6) additionally received a nitrate patch (0.675 mg/day). Four weeks after i.m. methylprednisolone injection the animals were sacrificed. For histology and immunohistochemistry, tissue samples were fixed in 3% paraformaldehyde, embedded in paraffin, sectioned, dewaxed, and stained with Ladewig. For quantification of empty lacunae, a histologic sign of FHN, histomorphometry was performed. Histomorphometry revealed a significant increase of empty lacunae in glucocorticoid‐treated animals compared to controls and GC + N‐treated animals. No significant difference in empty lacunae count was detected between the GC + N group and controls. HE staining revealed the different osteocyte amount in the GC versus GC and nitrate patch‐treated groups. This study demonstrates an increased number of empty osteocyte lacunae representing a pathologic feature of osteonecrosis, in the GC group. Less empty lacunae were counted in the GC animals after additional treatment with a nitrate patch. This finding suggests that nitrate co‐treatment has the potential to prevent steroid‐associated FHN. © 2011 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29: 1517–1520, 2011