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. 2009 Dec 1;91(12):2903–2914. doi: 10.2106/JBJS.H.01464

Fig. 2.

Fig. 2

A: Magnetic resonance imaging of the normal, noninvolved femoral head at forty-eight hours showing normal signal intensity of the epiphysis and metaphysis on a T1-weighted sequence after gadolinium enhancement. B: Photomicrograph of a portion of the ossification center of the normal femoral head showing bone trabeculae with osteocytes in their lacunae (open arrow), surface osteoblasts (curved arrow) and osteoclasts, and well-vascularized marrow (solid straight arrow). The marrow also contains hematopoietic and mesenchymal cells. The red blood cells are within thin-walled sinusoidal vessels. In this tissue preparation, the red blood cells are circular and stained light blue. The dark purple accumulations are the remaining fragments of calcified cartilage from the endochondral sequence. The inset shows new bone trabeculae with osteocytes, surface osteoblasts (curved arrow), and mesenchymal cells differentiating to osteoblasts between the two trabeculae. An osteoclast is seen at the lower right adjacent to both a cartilage remnant and woven bone. This corresponds to the magnetic resonance imaging in A (paraffin-embedded section, 1% toluidine blue stain). C: Magnetic resonance imaging at forty-eight hours after surgery showing complete ischemia of the involved femoral head with a complete lack of epiphyseal gadolinium enhancement (T1-weighted sequence after gadolinium enhancement). The intra-articular region of high signal intensity is the cut ligamentum teres and surrounding synovial reaction. D: Photomicrograph illustrating a portion of the femoral head ossification center after induction of ischemia. The surfaces of the bone trabeculae are completely devoid of osteoblasts, and many of the lacunae are either empty (black arrows) or show contracted pyknotic osteocytes (white arrows). The marrow is acellular or hypocellular, and the sinusoidal vessels (inset; arrows) are empty of red blood cells. Revascularization has not yet occurred, so the bone trabeculae remain intact (paraffin-embedded section, 1% toluidine blue stain).