Cheng Kevin K, Berven Sigurd H, Hu Serena S, Lotz Jeffrey C
Department of Orthopaedic Surgery, University of California, 513 Parnassus Ave., 11th Floor, San Francisco, CA 94143, USA.
Department of Orthopaedic Surgery, University of California, 513 Parnassus Ave., 11th Floor, San Francisco, CA 94143, USA.
Spine J. 2014 Mar 1;14(3):522-30. doi: 10.1016/j.spinee.2013.06.089. Epub 2013 Nov 15.
It is well-established that disc mechanical properties degrade with degeneration. However, prior studies utilized cadaveric tissues from donors with undefined back pain history. Disc degeneration may present with pain at the affected motion segment, or it may be present in the absence of back pain. The mechanical properties and matrix quantity of discs removed and diagnosed for degeneration with patient chronic pain may be distinct from those with other diagnoses, such as spinal deformity.
To test the hypothesis that discs from nondeformity segments have inferior mechanical properties than deformity discs owing to differences in matrix quality.
STUDY DESIGN/SETTING: In vitro study comparing the mechanical and matrix properties of discs from surgery patients with spinal nondeformity and deformity.
We analyzed nucleus and annulus samples (8-11 specimens per group) from surgical discectomy patients as part of a fusion or disc replacement procedure. Tissues were divided into two cohorts: nondeformity and deformity. Dynamic indentation tests were used to determine energy dissipation, indentation modulus, and viscoelasticity. Tissue hydration at a physiologic pressure was assessed by equilibrium dialysis. Proteoglycan, collagen, and collagen cross-link content were quantified. Matrix structure was assessed by histology.
We observed that energy dissipation was significantly higher in the nondeformity nucleus than in the deformity nucleus. Equilibrium dialysis experiments showed that annulus swelling was significantly lower in the nondeformity group. Consistent with this, we observed that the nondeformity annulus had lower proteoglycan and higher collagen contents.
Our data suggest that discs from nondeformity discs have subtle differences in mechanical properties compared with deformity discs. These differences were partially explained by matrix biochemical composition for the annulus, but not for the nucleus. The results of this study suggest that compromised matrix quality and diminished mechanical properties are features that potentially accompany discs of patients undergoing segmental fusion or disc replacement for disc degeneration and chronic back pain. These features have previously been implicated in pain via instability or reduced motion segment stiffness.
椎间盘的力学性能会随着退变而下降，这一点已得到充分证实。然而，先前的研究使用的是来自背痛病史不明确的捐赠者的尸体组织。椎间盘退变可能在受影响的运动节段出现疼痛，也可能在没有背痛的情况下存在。因患者慢性疼痛而被切除并诊断为退变的椎间盘的力学性能和基质数量，可能与其他诊断（如脊柱畸形）的椎间盘不同。
检验以下假设：由于基质质量的差异，非畸形节段的椎间盘力学性能低于畸形椎间盘。
研究设计/地点：一项体外研究，比较脊柱非畸形和畸形手术患者椎间盘的力学和基质特性。
作为融合或椎间盘置换手术的一部分，我们分析了手术切除椎间盘患者的髓核和纤维环样本（每组8 - 11个标本）。组织被分为两个队列：非畸形和畸形。使用动态压痕试验来确定能量耗散、压痕模量和粘弹性。通过平衡透析评估生理压力下的组织水合作用。对蛋白聚糖、胶原蛋白和胶原交联含量进行定量。通过组织学评估基质结构。
我们观察到，非畸形髓核中的能量耗散显著高于畸形髓核。平衡透析实验表明，非畸形组的纤维环肿胀明显更低。与此一致的是，我们观察到非畸形纤维环的蛋白聚糖含量较低，胶原蛋白含量较高。
我们的数据表明，与畸形椎间盘相比，非畸形椎间盘的力学性能存在细微差异。这些差异部分可由纤维环的基质生化组成来解释，但髓核并非如此。这项研究的结果表明，基质质量受损和力学性能下降是接受节段性融合或椎间盘置换治疗椎间盘退变和慢性背痛患者的椎间盘可能具有的特征。这些特征先前被认为与疼痛通过不稳定或运动节段刚度降低有关。
