Postoperative lumbar spinal stenosis after intertransverse fusion with granules of hydroxyapatite: a case report

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/3483360258050263 webciteA 76-year-old man with lumbar spinal stenosis was admitted to our hospital with low back pain and bilateral sciatica. For his low back and bilateral leg pain, he had undergone L4/L5 non-instrumented intertransverse fusion with granules of HA for lumbar spinal stenosis in another hospital seven years before. After surgery, his complaint disappeared completely, however, after two years, he once again felt low back pain and increasing bilateral sciatica. On admission, he showed intermittent claudication after 20 meters, and lateral roentgenograms showed instability, suggesting failure of the attempted posterolateral intertransverse fusion. Computed tomography showed that hardly any bone had formed around the HA and no bony intertransverse bridge existed between the transverse process and HA (black arrow heads; Figure 1A). Magnetic resonance imaging (MRI) of the T2 wedged axial plane revealed a high intensity area between the mass of hydroxyapatite and the transverse process. Enhancement with gadolinium was observed around the transplanted HA, suggesting failure of the intertransverse fusion (Figure 1B). Decompression and instrumented intertransverse fusion with autologous iliac bone for L4/L5 were performed after removal of the HA granulation. Both sides of the granules of HA that formed an en bloc mass were resected obtusely and evaluated histologically.In hematoxylin and eosin staining of the sagittal section of the resected mass, fibrous tissue with hyaline degeneration surrounded the cavity where the HA had existed. Multinuclear giant cells and lymphocytes infiltrated some parts of the marginal layer of the cavity, and partially formed foreign-body granulomas. New bone formation was observed in a limited area in the cavity where the HA had been, or just beside the fibrous tissue. Most of this new bone was necrotic. Bone marrow formation was