Biomechanical Testing Facility, Orthopaedic Trauma Institute, San Francisco General Hospital, San Francisco, CA, USA.
Spine (Phila Pa 1976). 2011 Apr 15;36(8):E519-23. doi: 10.1097/BRS.0b013e3181f65de1.
Biomechanical laboratory research.
To characterize the structural stiffness of opening and closing wedge osteotomies and the independent effect of rod diameter.
Traditionally, C7 opening wedge osteotomy (OWO) has been performed for patients with ankylosing spondylitis. For patients without ankylosing spondylitis, closing wedge osteotomy (CWO) may be considered for more controlled closure. Biomechanical characteristics of the two osteotomy alternatives have not yet been analyzed.
Nondestructive pure moment flexion/extension (FE), lateral bending (LB), and axial rotation (AR) tests were conducted to 4.5 Nm on cadaveric specimens (C4-T3). All specimens underwent posterior bilateral screw-rod fixation with 3.5 mm and 4.5 mm Ti rods, whereas half received OWO and half received CWO.
Independent of osteotomy type, constructs with 4.5 mm rods exhibited a significant increase in stiffness compared to 3.5 mm rods in all bending modes (P < 0.01). Relative to 3.5 mm rods, 4.5 mm constructs showed an increase in stiffness of 31 ± 12% for FE, 37 ± 39% for LB, and 31 ± 11% for AR. At the osteotomy site, there was a 43 ± 23% increase in FE stiffness, 45 ± 36% in LB, and 41 ± 17% in AR. Independent of rod diameter, CWO was significantly stiffer than OWO (42% for the construct and 56% across the osteotomy) in FE bending only (P < 0.05).
The surgeon can expect a similar increase in stiffness in switching from 3.5 mm to 4.5 mm rod independent of osteotomy type. The increased stiffness of CWOs has an anatomic basis. OWOs disrupt the anterior longitudinal ligament (ALL) and leave a significant anterior gap whereas CWOs create a wedge through the vertebral body and leave the ALL and the discs above and below the osteotomy intact. The closure in CWOs leaves no anterior gap providing greater axial loading stability. This greater bone on bone contact in CWOs is likely a significant reason for the anterior stiffness and may provide greater fusion rates in the nonankylosing spondylitis patient population.
生物力学实验室研究。
描述撑开和楔形截骨术的结构刚度以及杆直径的独立影响。
传统上，C7 撑开楔形截骨术（OWO）用于治疗强直性脊柱炎患者。对于没有强直性脊柱炎的患者，可能会考虑闭合楔形截骨术（CWO）以实现更可控的闭合。这两种截骨术替代方法的生物力学特性尚未得到分析。
对尸体标本（C4-T3）进行非破坏性纯力矩前屈/伸展（FE）、侧屈（LB）和轴向旋转（AR）测试，至 4.5Nm。所有标本均采用双侧后路螺钉-棒固定，使用 3.5mm 和 4.5mmTi 棒，其中一半接受 OWO，一半接受 CWO。
无论截骨术类型如何，使用 4.5mm 棒的结构在所有弯曲模式下与 3.5mm 棒相比，刚度均显著增加（P<0.01）。与 3.5mm 棒相比，4.5mm 结构的 FE 刚度增加 31±12%，LB 增加 37±39%，AR 增加 31±11%。在截骨部位，FE 刚度增加 43±23%，LB 增加 45±36%，AR 增加 41±17%。无论棒直径如何，仅在 FE 弯曲时，CWO 比 OWO 显著更硬（结构增加 42%，截骨处增加 56%）（P<0.05）。
无论截骨术类型如何，从 3.5mm 切换到 4.5mm 棒，外科医生都可以预期刚度有类似的增加。CWOs 的增加的刚度具有解剖学基础。OWOs 破坏前纵韧带（ALL）并留下明显的前间隙，而 CWOs 通过椎体形成楔形并使 ALL 和截骨上方和下方的椎间盘保持完整。CWOs 的闭合没有前间隙，提供更大的轴向负载稳定性。CWOs 中更大的骨与骨接触可能是前刚度的一个重要原因，并可能为非强直性脊柱炎患者群体提供更高的融合率。
