Relationship between thoracic and lumbar vertebral posterior wall morphology and bone cement leakage into the spinal canal during the percutaneous kyphoplasty / 中国组织工程研究

ABSTRACT

BACKGROUND: Percutaneous kyphoplasty (PKP) is an effective method for treating osteoporotic vertebral compression fracture. Although satisfactory clinical outcomes can be achieved, bone cement leakage is still one of the main complications of PKP. Based on previous studies, there are many high risk factors for bone cement leakage into the spinal canal; however, less attention to the posterior wall morphology of different vertebral bodies may be an important reason for bone cement leakage into spinal canal. OBJECTIVE: To investigate the effect of thoracic and lumbar vertebral posterior wall morphology in the patients with osteoporotic vertebral compression fracture on bone cement leakage into the spinal canal during the PKP. METHODS: The clinical data of osteoporotic vertebral compression fracture patients with PKP were selected. There were 98 osteoporotic vertebral compression fracture patients with CT scan and three-dimensional reconstruction image data from T6 to L5. The three-dimensional reconstruction of CT and multiplanar reconstruction were used to measure the depth of the concave vertebral posterior wall (OC) and the corresponding middle-sagittal diameter of the vertebra (PC) of the non-fractured vertebral body, the ratio of OC to PC was calculated. All subjects were divided into thoracic group (T6-T12) and lumbar group (L1-L5) based on the location of measured vertebral, and the differences of the OC between groups were compared. 357 patients (548 vertebrae) with osteoporotic vertebral compression fracture without CT three-dimensional reconstruction underwent PKP within the same period. They were also divided into thoracic vertebra and lumbar vertebra groups. The degree of bone cement leakage into the spinal canal was compared between thoracic and lumbar vertebra groups. RESULTS AND CONCLUSION: (1)The morphological parameters of posterior vertebral wall in 98 patients showed that the depth of the concave vertebral posterior wall gradually (OC) deepened from T6toT12, with an average of 4.6 mm. The depth became gradually shallow from L1 to L5, with an average of 0.6 mm. The ratio of the depth of the concave vertebral posterior wall to the corresponding middle-sagittal diameter of the vertebra was approximately 16% (1/6) from T6toT12. The average value of ratios from Li to U was 3%. The ratios in lumbar vertebra were significantly decreased compared with thoracic vertebra (16%, 1/6). (2) Results form 357 patients who underwent PKP at the same time showed that the rate of bone cement leakage into spinal canal was 10.2% (31/304) in the thoracic vertebra group during the PKP, and the rate of lumbar vertebra group was 3.7% (9/244). In the thoracic group, the average maximal sagittal diameter of the bone cement intruded spinal canal was (3.1 ±0.2) mm, the average maximal area of the bone cement intruded spinal canal was (30.8±0.3) mm2, and the spinal canal encroachment rate was (22.5±0.2)%. In the lumbar group, the average maximal sagittal diameter of the bone cement intruded spinal canal was (1.4±0.1) mm, the average maximal area of the bone cement intruded spinal canal was (14.9±0.2) mm2, and the spinal canal encroachment rate was (11,4±0.3)%. There was significant difference between thoracic and lumbar groups (P<0.05). (3) The above results imply that due to the presence of OC structure in the middle and lower thoracic vertebra, it is possible to reduce the occurrence of bone cement leakage into spinal canal through avoiding bone cement distribution over the posterior 1/6 (16%) of vertebral body in PKP. The effect of the difference between thoracic and lumbar vertebral posterior wall morphology in osteoporotic vertebral compression fracture patients on bone cement leakage into the spinal canal during the PKP may be one of the reasons why the rate of bone cement leakage into spinal canal in thoracic vertebra significantly higher than that in lumbar vertebra. The study protocol was approved by the Ethics Committee of the Affiliated Hospital of Southwest Medical University (approval No. K2018008).