Surgical treatment of ossification of the ligamentum flavum associated with dural ossification in the thoracic spine.

Between January 2006 and December 2009, dural ossification (DO) was found intraoperatively in 26 of 98 patients with thoracic spinal stenosis due to ossification of the ligamentum flavum (OLF). MRI showed single-level (n = 2), two-level (n = 8) and multilevel (n = 16) areas of low signal intensity in the ligamentum flavum of the thoracic spine. Of the 68 ossified segments in the study population, 11 (16.2%) were located in the upper thoracic spine (T1-T4), nine (13.2%) were located in the midthoracic spine (T5-T8), and 48 (70.6%) were located in the lower thoracic spine (T9-L1). All patients underwent en bloc resection of the areas affected by OLF and DO. All patients underwent posterior decompression; we did not use instrumented fusion to restore the stability of the involved segments after decompression for any patient. The dural defect was not repaired. The neurological status had improved at follow up (22-66 months; mean, 46.7 months) from a preoperative mean Japanese Orthopaedic Association score of 5.46 ± 1.73 points to 8.92 ± 1.38 points at the last follow up (t = 13.87, p < 0.05). The mean values for preoperative and postoperative kyphosis of the involved vertebrae were 6.6 ± 1.5° and 8.2 ± 1.4°, respectively; the mean increase in kyphosis was only 1.7 ± 1.4°. Thus, the surgical techniques discussed in this paper for treatment of OLF associated with DO in the thoracic spine, are effective.