Vertebral pseudarthrosis in the osteoporotic spine.

Study Design: Radiologic and operative findings of intravertebral cleft in the osteoporotic spine were investigated and the pathomechanism discussed.
Objectives: To clarify the pathologic features of the intravertebral cleft.
Summary of Background Data: Intravertebral "vacuum" cleft is one of the common radiographic findings in the osteoporotic spine. It is thought that the cleft is a rare lesion of an ununited fracture, or pseudarthrosis. Evidential findings of the disease, however, have never been reported.
Methods: Simple bone grafting was performed in five cases (average age, 76.8 years) of thoracolumbar intravertebral cleft in osteoporotic spine in patients who had been suffering from prolonged pain of the back or leg. Preoperative radiologic evaluation using flexion-extension radiograph and magnetic resonance imaging was performed in all patients. At operation, the cleft and the components of the structure were macroscopically and microscopically observed. The fluid content in the cleft was biochemically analyzed.
Results: In all patients, preoperative flexion-extension radiographs showed intravertebral instability at the location of the clefts that indicated gas density in three cases and water density in two cases. Magnetic resonance imaging showed that, for the most part, the cleft was low intensity on the T1-weighted image and high intensity on the T2-weighted scans, regardless of the radiographic findings. At operation, abnormal movement was observed at the cleft of the affected body, which was covered with hypertrophic membrane. The serous fluid within the cleft was aspirated before the excision of soft tissue. The thick membrane was excised and showed that the cleft was lined by smooth fibrocartilaginous tissue and the great degree of motion between the fracture ends that is consistent with the pathologic appearance of pseudarthrosis.
Conclusions: The unstable cleft in the affected vertebral body of the osteoporotic spine with magnetic resonance findings of low intensity on the T1-weighted scans and high intensity on the T2-weighted scans suggests that the cleft is a false joint lined by fibrocartilaginous tissue with notable movement consistent with pseudarthrosis.