Bylski-Austrow Donita I, Glos David L, Bonifas Anne C, Carvalho Max F, Coombs Matthew T, Sturm Peter F
Orthopaedics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, 45229-3030 USA.
University of Cincinnati, Cincinnati, OH, USA.
Scoliosis. 2015 Feb 11;10(Suppl 2):S16. doi: 10.1186/1748-7161-10-S2-S16. eCollection 2015.
Surgical treatments for early onset scoliosis (EOS), including growing rod constructs, involve many complications. Some are due to biomechanical factors. A construct that is more flexible than current instrumentation systems may reduce complications. The purpose of this preliminary study was to determine spine range of motion (ROM) after implantation of simulated growing rod constructs with a range of clinically relevant structural properties. The hypothesis was that ROM of spines instrumented with polyetheretherketone (PEEK) rods would be greater than metal rods and lower than noninstrumented controls. Further, adjacent segment motion was expected to be lower with polymer rods compared to conventional systems.
Biomechanical tests were conducted on 6 skeletally immature porcine thoracic spines (domestic swine, 35-40 kg). Spines were harvested after death from swine that had been utilized for other studies (IACUC approved) which had not involved the spine. Paired pedicle screws were used as anchors at proximal and distal levels. Specimens were tested under the following conditions: control, then dual rods of PEEK (6.25 mm), titanium (4 mm), and CoCr (5 mm) alloy. Lateral bending (LB) and flexion-extension (FE) moments of ±5 Nm were applied. Vertebral rotations were measured using video. Differences were determined by two-tailed t-tests and Bonferroni correction with four primary comparisons: PEEK vs control and PEEK vs CoCr, in LB and FE (α=0.05/4).
In LB, ROM of specimens with PEEK rods was lower than control at each instrumented level. ROM was greater for PEEK rods than both Ti and CoCr at every instrumented level. Mean ROM at proximal and distal noninstrumented levels was lower for PEEK than for Ti and CoCr. In FE, mean ROM at proximal and distal noninstrumented levels was lower for PEEK than for metal. Combining treated levels, in LB, ROM for PEEK rods was 35% of control (p<0.0001) and 270% of CoCr rods (p<0.01). In FE, ROM with PEEK was 27% of control (p<0.001) and 180% of CoCr (p<0.01).
PEEK rods decreased flexibility versus noninstumented controls, and increased flexibility versus metal rods. Smaller increases in ROM at proximal and distal adjacent motion segments occurred with PEEK compared to metal rods, which may help decrease junctional kyphosis. Flexible growing rods may eventually help improve treatment options for young patients with severe deformity.
早期脊柱侧弯（EOS）的手术治疗，包括生长棒植入，存在许多并发症。有些并发症是由生物力学因素导致的。一种比当前器械系统更灵活的植入物可能会减少并发症。这项初步研究的目的是确定植入具有一系列临床相关结构特性的模拟生长棒后脊柱的活动范围（ROM）。假设是，用聚醚醚酮（PEEK）棒植入的脊柱ROM将大于金属棒且小于未植入器械的对照组。此外，与传统系统相比，聚合物棒相邻节段的活动预计会更低。
对6个骨骼未成熟的猪胸椎（家猪，35 - 40千克）进行生物力学测试。脊柱是从用于其他未涉及脊柱的研究（经机构动物护理和使用委员会批准）的猪死后采集的。在近端和远端水平使用配对椎弓根螺钉作为锚定物。在以下条件下对标本进行测试：对照组，然后是PEEK（6.25毫米）、钛（4毫米）和钴铬（5毫米）合金的双棒。施加±5牛米的侧弯（LB）和屈伸（FE）力矩。使用视频测量椎体旋转。差异通过双尾t检验和Bonferroni校正进行确定，有四个主要比较：PEEK与对照组以及PEEK与钴铬合金在LB和FE方面（α = 0.05 / 4）。
在LB中，每个植入水平下PEEK棒标本的ROM低于对照组。在每个植入水平下，PEEK棒的ROM大于钛棒和钴铬棒。PEEK棒近端和远端未植入器械水平的平均ROM低于钛棒和钴铬棒。在FE中，PEEK棒近端和远端未植入器械水平的平均ROM低于金属棒。综合处理水平，在LB中，PEEK棒的ROM是对照组的35%（p < 0.0001），是钴铬棒的270%（p < 0.01）。在FE中，PEEK棒的ROM是对照组的27%（p < 0.001），是钴铬棒的180%（p < 0.01）。
与未植入器械对照组相比，PEEK棒降低了灵活性，与金属棒相比则增加了灵活性。与金属棒相比，PEEK棒在近端和远端相邻运动节段的ROM增加较小，这可能有助于减少交界性后凸。灵活的生长棒最终可能有助于改善重度畸形年轻患者的治疗选择。
