Maldague et al
) first reported the intravertebral vacuum cleft sign, and the authors considered gas accumulation (vacuum cleft sign) in the vertebral body on plain X-rays as pathognomonic of Kümmell’s disease. The vacuum phenomenon is more evident in the extended position and may reduce or disappear in the flexed position. The gas noted on the plain radiographs was expected to be hypointense on both the MRI T1 and T2 sequences. However, the majority of authors have reported either a homogeneous fluid or gas signal on the MRI sequences of patients with the intravertebral vacuum phenomenon. Malghem et al
) plausibly explained this phenomenon. Patients with the vacuum sign were serially imaged, and the MRI demonstrated that the initially gas-filled cleft appeared hypointense. However, following prolonged supine positioning, a hyperintense signal appeared on the T2 sequences, indicating the presence of fluid instead of gas. We also observed this phenomenon in one patient. The lumbar MRI T2-weighted image showed a mixed signal of gas and liquid at T12. After 8 min, the thoracic MRI T2-weighted image showed a hyperintense liquid signal at T12, which suggests that the contents (fluid and gas within the vertebral body) are variable over time.
Whether intravertebral clefts are a pathognomonic sign of Kümmell’s disease is controversial. Certain studies have demonstrated that intravertebral clefts are a benign sign, whereas others have reported that intravertebral clefts occur rarely in patients with spinal infections and in patients with multiple myeloma (8
). We identified a patient (excluded from the study) with a CT that displayed a vacuum phenomenon () and an MRI that displayed a liquid sign (). The patient was diagnosed with Kümmell’s disease based on the clinical and radiological signs. The vacuum cleft was filled well with PMMA (). However, the pathology report revealed non-Hodgkin’s lymphoma (). To the best of our knowledge, no non-Hodgkin’s lymphoma with vacuum cleft has been reported. Therefore, intravertebral clefts are not pathognomonic of Kümmell’s disease, but they are highly suggestive of the disease. Thus, we consider that it is necessary to confirm Kümmell’s disease with bone necrosis under biopsy.
The pathogenesis of the vertebral vacuum phenomenon remains controversial and it has been mainly theorized to involve vertebral avascular necrosis (4
), vertebral fracture nonunion or pseudarthrosis (6
) or intradiscal gas leakage through the endplate fractured into the vertebral body (20
). In the current study, only two patients had factors that predispose to bone necrosis (long-term corticosteroid application history). The remaining patients had no other predisposing factors. The theory of vertebral avascular necrosis alone does not explain the pathogenesis of the disease. In the current study, nine patients exhibited a gas signal in the affected vertebral body based on CT but only three cases had gas in the adjacent disk. Therefore, the theory that intravertebral gas originates from the adjacent disk alone does not explain the intravertebral vacuum phenomenon. In addition, we compared the preoperative standing lateral radiographs and intraoperative prone lateral radiographs, as well as the preoperative extension and flexion radiographs, of five patients. We found that vertebral height varied with postural changes, in accordance with the report by Yang et al
). These findings support the theory of vertebral fracture nonunion or pseudarthrosis. Thus, we advocate the complete filling of the cleft with cement to maximize stabilization of the pseudarthrosis. In the current study, the mean amount of cement injected was 7.2 ml. According to the literature, as well as our imaging results and clinical data, the pathogenesis of the vertebral cleft phenomenon requires a combination of avascular bone necrosis, fracture non-healing and adjacent intradiscal gas diffusion.
The treatment strategies for Kümmell’s disease differ between patients with neurological symptoms and those without neurological symptoms. For patients without neurological symptoms, the objective is to eliminate motion at the fracture site and restore the spinal curvature. Certain authors have reported that PVP (4
) or PKP (5
) achieves good clinical results for Kümmell’s disease without neurological symptoms. For neurologically impaired patients, the aim of surgery is to decompress the spinal cord, restore the spinal physiological curvature and maintain spinal stability. The surgical modes include anterior, posterior or combined anterior and posterior approaches. Anterior decompression and fusion with intervertebral tricortical graft or ceramic glass spacers has favorable results. These procedures are the most efficient for decompressing the spinal cord since the locus of pathology (deficient anterior and middle spinal columns) is directly addressed, and they provide anterior column support. Anterior approach surgery has a high fusion rate (95.5–100%) and the postoperative kyphosis correction angle has a mean of 10.4–18°. At final follow-up, the corrected degree decreased by 4.8–8°. The drawback of the anterior approach in pleural and extrapleural operations is that it may cause pulmonary complications in injuries of the thoracolumbar junction, where most cases of intravertebral vacuum occur, and it may affect gastrointestinal function in retroperitoneal surgery. Moreover, in the anterior approach, the stabilization of the spine may fail due to the osteoporotic bone. Surgeries that use the posterior approach include decompression and PSO (2
). The fusion rate of the posterior approach operation is 62.5–100%, and the immediate postoperative kyphosis correction angle is 14.6–25.7°. The average loss of correction at final follow-up is 2.4–8.8°. PSO surgery often requires the fixation of the vertebral bodies above and below the affected vertebra; thus, adjacent vertebral disease often occurs. A combined anterior and posterior approach has a good fusion rate (100%), with a kyphosis angle correction of 11.2° postoperatively and a loss of 4.2° at final follow-up. However, the surgery time is longer (351 min) and the blood loss is higher (2892 ml) (14
Patients with Kümmell’s disease with neurological symptoms are often older and have a variety of diseases; thus, the patients do not easily tolerate the aforementioned surgical methods. Therefore, the development of a minimally invasive and effective treatment is required. Surgeons have performed open posterior decompression and short-segment fixation for Kümmell’s disease with neurological symptoms, followed by vertebroplasty (15
) or kyphoplasty (17
) under direct visualization. This surgical method provides several advantages. Posterior decompression relieves nerve compression with short segment fixation and fusion reduces the fusion segment and the influence of long segmental spinal function. Vertebral bone cement provides anterior support to minimize posterior pedicle screw stress. Furthermore, bone cement leakage may be avoided under direct vision. Matsuyama et al
) used calcium phosphate cement, which polymerizes at lower temperatures. The results included effective pain relief (from 8.6, preoperatively, to 2, postoperatively, on the VAS), nerve function and kyphosis restoration (vertebral height from 41% preoperatively to 74% postoperatively and 68% at final follow-up). In the current study, we used PMMA for vertebroplasty which achieved effective pain relief (the mean preoperative VAS score of 8.49 was reduced to 2.09 one day postoperatively and 2.29 at final follow-up) and good postoperative kyphosis correction (the anterior and central vertebral body height were enhanced by ~1 cm and Cobb’s angle correction was 18.29° one day postoperatively). Follow-up examinations were conducted for ≥18 months. At the final follow-up, a slight reduction in the vertebral height and a kyphosis correction of 1.11° were observed compared with those at one day after the surgery. However, these differences were not statistically significant. The patients recovered neurologically, and nerve function improved by least one Frankel grade at final follow-up. The mean surgery time was 110 min (range, 90–140 min) and the mean estimated blood loss was 250 ml (range, 150–500 ml). Thus, posterior decompression with short-segment fixation and fusion combined with vertebroplasty is an effective treatment for Kümmell’s disease with neurological symptoms, especially for patients who are not able to tolerate long surgery times and massive blood loss. However, a previous study hypothesized that the osteolysis rate among patients with Kümmell’s disease is greater than the rate of bone callus formation. Following PVP or PKP, accelerated osteolysis occurs and may displace the bone cement (21
). Two case reports have focused on bone cement displacement following PVP (22
) or PKP (23
) alone for Kümmell’s disease without neurological deficits. Therefore, greater numbers of patients and longer follow-up times are required to verify the efficiency of posterior decompression with short segmental pedicle screw fixation and fusion combined with vertebroplasty for Kümmell’s disease with neurological deficits.