RESUMEN
BACKGROUND: Pedicle screw fixation combined with cement-augmented is an effective method for the treatment of severe osteoporotic vertebral fractures, but there is no uniform standard. The range of fixed segments is one of the focus of clinical controversy. OBJECTIVE: To establish a three-dimensional finite element model of the short-segment and long-segment cement-augmented pedicle screw fixation for osteoporotic thoracolumbar fracture, and to analyze the biomechanical characteristics of adjacent segment structures, fractured vertebral bodies and internal fixation devices. METHODS: The T 9 -L 5 segment of a volunteer without obvious degenerative disease was selected for CT scan. The CT images of Dicom format were obtained, and the engineering software was imported to establish a finite element geometric model to simulate the thoracolumbar fracture and the short-segment and long-segment cement-augmented pedicle screw fixation models. The relevant material parameters were set and the biomechanical characteristics of the two groups were compared and analyzed. RESULTS AND CONCLUSION: (1) The stress on the vertebrae was mainly concentrated on the periphery of the vertebral body and the small facet of the attachment. In the four directions flexion, extension, left-sided and right-sided curvature, the maximum stress of the proximal and distal adjacent vertebrae in the long-segment group was greater than that in the short-segment group. The stress of the intervertebral disc was mainly concentrated in the peripheral annulus. The maximum stress of the proximal and distal adjacent intervertebral discs was greater in the short -segment than in the long-segment, but the high stress area of the long-segment was larger than that of the short-segment. Therefore, long-segment fixation might accelerate the degeneration of adjacent segments.(2) The vertebral bodies of the long-segment group and the short-segment group were displaced to different extents, and the displacements in the left and right directions were the most obvious. In the six movement directions, the displacement and maximum stress of the injured segment of the short-segment group were greater than those of the long-segment group. So the long-segment fixation could better maintain the stability of the fractured vertebra. (3) The stress on the internal fixing device was mainly concentrated on the screws at both ends and the part of the rod. The maximum stress of the long-segment group was greater than that of the short-segment group, but the main stress area of the screws at both ends was smaller compared with the short- segment group.and the displacements in the left and right directions were the most obvious. In the six movement directions, the displacement and maximum stress of the injured segment of the short-segment group were greater than those of the long-segment group. So the long- segment fixation could better maintain the stability of the fractured vertebra. (3) The stress on the internal fixing device was mainly concentrated on the screws at both ends and the part of the rod. The maximum stress of the long-segment group was greater than that of the short-segment group, but the main stress area of the screws at both ends was smaller compared with the short-segment group.and the displacements in the left and right directions were the most obvious. In the six movement directions, the displacement and maximum stress of the injured segment of the short-segment group were greater than those of the long-segment group. So the long- segment fixation could better maintain the stability of the fractured vertebra. (3) The stress on the internal fixing device was mainly concentrated on the screws at both ends and the part of the rod. The maximum stress of the long-segment group was greater than that of the short-segment group, but the main stress area of the screws at both ends was smaller compared with the short-segment group.So the long-segment fixation could better maintain the stability of the fractured vertebra. (3) The stress on the internal fixing device was mainly concentrated on the screws at both ends and the part of the rod. The maximum stress of the long-segment group was greater than that of the short-segment group, but the main stress area of the screws at both ends was smaller compared with the short-segment group. So the long-segment fixation could better maintain the stability of the fractured vertebra. (3) The stress on the internal fixing device was mainly concentrated on the screws at both ends and the part of the rod. The maximum stress of the long-segment group was greater than that of the short-segment group, but the main stress area of the screws at both ends was smaller compared with the short-segment group.
RESUMEN
Objective: To compare the effectiveness of short-segment and long-segment bone cement-augmented fixation combined with vertebroplasty in treatment of stage Ⅲ Kümmell disease. Methods: A clinical data of 44 patients with stage Ⅲ Kümmell disease met the selection criteria between January 2014 and December 2017 was retrospectively analyzed. Eighteen cases were treated with short-segment bone cement-augmented fixation combined with vertebroplasty (short-segment group) and 26 cases were treated with long-segment bone cement-augmented fixation combined with vertebroplasty (long-segment group). There was no significant difference in gender, age, disease duration, fracture segment, bone mineral density (T value), Frankle grading, and preoperative pain visual analogue scale (VAS) score, Oswestry disability index (ODI), anterior edge height of injured vertebrae, kyphosis Cobb angle, and thoracolumbar kyphosis (TLK) between the two groups ( P>0.05). The operation time, intraoperative blood loss, bone cement injection volume, bone cement leakage rate, VAS score, ODI, anterior edge height of injured vertebrae, kyphosis Cobb angle, and TLK were compared between the two groups. Results: The operation time and the intraoperative blood loss in the short- segment group were significant lower than those in the long-segment group ( P0.05). All patients were followed up 12-36 months, with an average of 24.4 months. The VAS score, ODI, anterior edge height of injured vertebrae, kyphosis Cobb angle, and TLK significantly improved at 1 week after operation and last follow-up in the two groups ( P0.05). At last follow-up, the neurological function of the two groups recovered, and there was no significant difference in Frankle grading between the two groups ( P>0.05). There were 3 cases (16.67%) of non-surgical vertebral fractures in the short-segment group and 6 cases (23.08%) in the long-segment group, showing no significant difference between the two groups ( P>0.05). Bone rejection occurred in 1 case in the short-segment group, and neither internal fixation failure nor collapse of the injured vertebrae occurred during follow-up. Conclusion: Both short-segment and long-segment bone cement-augmented fixation combined with vertebroplasty can achieve good effectiveness in treatment of stage Ⅲ Kümmell disease, and can maintain the height of the injured vertebra and prevent the collapse of the injured vertebra. Compared with long-segment fixation, short-segment fixation has the advantages of shorter operation time and less intraoperative bleeding.