The Significant Of Stability Differentiation In Percutaneous Vertebral Augmentation For Osteoporotic Vertebral Compression Fractures

Part 1 Risk factors of occurrence of insufficient cement distribution in the fractured area after percutaneous vertebroplasty for osteoporotic vertebral compression fracturesBackgroundInsufficient cement distribution in the fractured area leading to unstable immobilization of the index vertebra has been advocated to be responsible for unsatisfied pain relief and recollapse of the augmented vertebral bodies after percutaneous vertebroplasty for osteoporotic vertebral compression fractures, which conforms to the theories of stability and immobilization in Chinese Orthopedics. However, little is known about risk factors of occurrence of insufficient cement distribution in the fractured area.ObjectiveThe present study aimed to identify independent risk factors of emergence of insufficient cement distribution in the fractured area after percutaneous vertebroplasty for osteoporotic vertebral compression fractures.MethodsPatients who underwent percutaneous vertebroplasty for single-level osteoporotic vertebral compression fracture from January 2012 to September 2014 in our hospital and met this study’s inclusion criteria were retrospectively reviewed. Associations of insufficient cement distribution in the fractured area with co-variates(age, sex, bone mass density with a T-score, amount of injected cement, cement leakage, fracture level,fracture age, fracture severity grade, and location of the fractured area) and the influence of insufficient cement distribution in the fractured area on pain relief were analyzed.ResultsA total of 225 patients were included. Insufficient cement distribution in the fractured area was found in 26 (11.6%) patients. Fractured area located in superior portion of the index vertebra was significantly associated with occurrence of insufficient cement distribution in the fractured area(P=0.041). No further significant associations between the studied co-variates and emergence of insufficient cement distribution in the fractured area were seen in the adjust analysis(P>0.05). In addition, patients with insufficient cement distribution in the fractured area had significant higher immediate postoperative visual analog scale of back pain compared with those with sufficient cement distribution in the fractured area (P<0.001)ConelusionThe incidence of insufficient cement distribution in the fractured area is higher in patients with the fractured area located in superior portion of the index vertebra and insufficient cement distribution in the fractured area might be responsible for unsatisfied pain relief after percutaneous vertebroplasty for osteoporotic vertebral compression fractures.Part 2 Biomechanical effects of cement distribution in the fractured area on osteoporotic vertebral compression fractures:a three-dimensional finite element analysisBackgroundInsufficient cement distribution in the fractured area leading to unstable immobilization of the index vertebra was thought to be the reason for unrelieved pain and recollapse of the augmented vertebral bodies, which conforms to the theories of stability and immobilization in Chinese Orthopedics. Asymmetrical cement distribution around the fractured area was also assumed to be the main risk factor of recollapse of the augmented vertebral bodies. To date, however, few biomechanical studies have been performed to research the reasons why insufficient cement distribution in the fractured area and asymmetrical cement distribution around the fractured area can induce above complications.ObjectiveThe theories of stability and immobilization in Chinese Orthopedics are summaries of experiences from physicians over the ages. Microcosmic differentiation emphasized that Traditional Chinese Medicine shoud be integrated into the modern advanced diagnosis and treatment technologies. The theory of stability differentiation in Chinese Orthopedics proposed in recent years suggested that the stability of injuries and immobilization could be assessed by biomechanical experiments. The purpose of this study is to investigate the biomechanical effects of cement distribution in the fractured area on osteoporotic vertebral compression fractures using three-dimensional finite element method according to the theory of stability differentiation in Chinese Orthopedics proposed in recent years.MethodsOsteoporotic T11-L1 finite element model was constructed and osteoporotic vertebral compression fracture was simulated in T12. Then, three patterns of cement distribution in the fractured area including sufficient distribution, insufficient distribution and asymmetrical distribution (upward distribution and downward distribution) were simulated in T12. Five models were got for the test eventually. The magnitudes and distributions of the von Mises stress in cortical bone and cancellous bone and maximum displacement of T12 fractured area were calculated for the five models under compression, flexion, extension, lateral bending loading conditions, respectively.ResultsCompared with fractured vertebra before percutaneous vertebral augmentation, distribution of von Mises stress in cancellous bone was transferred to be concentrated at cancellous bone surrounding cement after percutaneous vertebral augmentation while it was not changed in cortical bone. Compared with sufficient distribution group, maximum von Mises stress in cancellous bone and cortical bone and maximum displacement of fractured area increased significantly in insufficient distribution group, while asymmetrical cement distribution around the fractured area in upward distribution and downward distribution groups mainly increased maximum von Mises stress in cancellous bone significantly. Similar results could be seen in all loading conditions.ConelusionInsufficient cement distribution in the fractured area may lead to unrelieved pain after percutaneous vertebral augmentation in treatment of osteoporotic vertebral compression fractures as maximum displacement of fractured area increased significantly. Both insufficient cement distribution in the fractured area and asymmetrical cement distribution around the fractured area are more likely to induce recollapse of augmented vertebra because they increased maximum von Mises stress in cancellous bone and/or cortical bone of augmented vertebra significantly.