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>

Repairing segmental radial bone defect with poly (3-hydroxybutyrate-co-3-hydroxyvalerate)/sol-gel bioactive glass composite porous scaffold / 中国医学科学院学报

<p><b>OBJECTIVE</b>To investigate the capability of the bone regeneration of poly (3-hydroxybutyrate-co-3-hydroxyvalerate/sol-gel bioactive glass (PHBV/SGBG) composite porous scaffold.</p><p><b>METHODS</b>PHBV/ SGBG composite porous scaffold was implanted into the segmental radial bone defect of the New Zealand white rabbits, PHBV/hydroxylapatite (PHBV/HA) as experimental control. The degradability, biocompatibility, and bone regeneration capability of the implants were evaluated through radiological, histological, computerized graphic, and biomechanical analysis.</p><p><b>RESULTS</b>The new bone formation occurred as early as 4 weeks after implantation of PHBV/SGBG composite porous scaffold. The defect was filled with new bone 8 weeks after the implantation, and was completely repaired 12 weeks after operation. The new bone had normal bone structure and the medullar cavity regenerated. The biomechanical study showed that the anti-compression force of radial specimen in PHBV/SGBG groups was significantly higher than in PHBV/ HA groups (P < 0.05), but no significant difference existed between PHBV/SGBG group and autograft bone group (P>0.05). The PHBV/SGBG composite porous scaffold degraded no sooner than 4 weeks after the implantation and most of scaffold was absorbed after 12 weeks. The proportion of the scaffold to new bone decreased from 60% by week 4 to 8% by week 12.</p><p><b>CONCLUSIONS</b>PHBV/SGBG composite porous scaffold is a degradable bone substitute. It can achieve early bone generation and complete repair. It can be used as an ideal scaffold for tissue-engineering bone.</p>