Bone cement enhanced pedicle screw fixation combined with vertebroplasty for elderly patients with malignant spinal tumors / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Older patients with malignant spinal tumors are difficult to treat because they have many co-morbidities including osteoporosis. The purpose of this research is to discuss the technique and clinical outcome of bone cement enhanced pedicle screw fixation combined with vertebroplasty (the Sandwich Procedure) for elderly patients with severe osteoporosis and malignant spinal tumors.</p><p><b>METHODS</b>This study includes 28 consecutive elderly patients with malignant thoracic or lumbar spinal tumors. There were nine patients with myelomas, and 19 patients with metastatic bone tumors. The Sandwich Procedure began with curettage of the tumor and a vertebroplasty with bone cement (polymethyl methacrylate, PMMA), followed by PMMA enhanced pedicle screw fixation. Patients were evaluated with the visual analogue scale (VAS), oswestry disability index (ODI), American Spinal Cord Injury Association (ASIA) neurological function classification, and the radiographic degree of kyphosis (Cobb angle). Data were analyzed using paired t-test to compare the pre- and post-operative values. The complications, local recurrences, and the survival status were also recorded.</p><p><b>RESULTS</b>There was no operative mortality, and the mean operative time was 210 minutes (range 150 - 250 minutes). The average blood loss was 1550 ml (range 650 - 3300 ml). The average amount of cement for vertebroplasty was 3.6 ml (range 3 -5 ml). The VAS, ODI, and ASIA scores were significantly improved after surgery (P < 0.05). However, we found no differences between the pre and post-operative Cobb angles. The shortest survival time was 3 months, and we found no evidence of local recurrence in this group of patients.</p><p><b>CONCLUSION</b>The Sandwich Procedure is a safe operation and provides symptomatic relief in these difficult patients, permitting further treatment with chemotherapy or radiotherapy.</p>

Comparison of stability of sacroiliac screws in the treatment of bilateral sacral fractures in a finite element model / 中华外科杂志

<p><b>OBJECTIVE</b>To compare the stability of sacroiliac screws fixation for the treatment of bilateral vertical sacral fractures to provide reference for clinic application.</p><p><b>METHODS</b>A finite element model of Tile C pelvic ring injury (bilateral type Denis II fracture of sacrum) was produced. The bilateral sacral fractures were fixed with sacroiliac screws in 4 types of models respectively: two bidirectional sacroiliac screws fixation in the S₁ segment, two bidirectional sacroiliac screws fixation in the S₂ segment, one sacroiliac screw fixation in the S₁ segment and one sacroiliac screw fixation in the S₂ segment, two bidirectional sacroiliac screws fixation in S₁ and S₂ segments respectively. By the ABAQUS 6.9.1 software, in the case of standing on both feet, 600 N vertical load was imitated to be imposed to the superior surface of the sacrum and downward translation and backward angle displacement of the middle part of the sacral superior surface and everted angle displacement of the top of iliac bones were extracted for analysis. The stability of sacroiliac screws fixation was compared according to the principle of the better stability the smaller displacement.</p><p><b>RESULTS</b>The stability of 2 bidirectional sacroiliac screws fixation in S₁ and S₂ segments respectively was markedly superior to that of 2 bidirectional sacroiliac screws fixation in S₁ or S₂ segment and was also markedly superior to that of one sacroiliac screw fixation in S₁ segment and one sacroiliac screw fixation in S₂ segment. The vertical and everted stability (the downward translation: 0.531 mm; the everted angle displacement: 0.156° (left side), 0.163° (right side)) of sacroiliac screws fixation in two bidirectional sacroiliac screws fixation in the S₂ segment was superior to that of two bidirectional sacroiliac screws fixation in the S₁ segment (the downward translation: 0.673 mm; the everted angle displacement: 0.200° (left side), 0.232° (right side)). The rotational stability of two bidirectional sacroiliac screws fixation in the S₁ segment (the backward angle displacement: 0.269°) was superior to that of two bidirectional sacroiliac screws fixation in the S₂ segment (the backward angle displacement: 0.287°). Moreover, the rotational stability of one sacroiliac screw fixation in the S₁ segment and one sacroiliac screw fixation in the S₂ segment was inferior to that of two bidirectional sacroiliac screws fixation in the S₁ segment or two bidirectional sacroiliac screws fixation in the S₂ segment, and the vertical and everted stability of one sacroiliac screw fixation in the S₁ segment and one sacroiliac screw fixation in the S₂ segment was between that of two bidirectional sacroiliac screws fixation in the S₁ segment and two bidirectional sacroiliac screws fixation in the S₂ segment.</p><p><b>CONCLUSIONS</b>Two bidirectional sacroiliac screws fixation in S₁ and S₂ segments respectively is recommended to be utilized for fixing bilateral sacral fractures of Tile C pelvic ring injury as far as possible. It is suggested to choose sacral segments in which sacroiliac screws fixed according to vertical, rotational and everted stability degree of sacral fractures.</p>