Oakland Robert J, Furtado Navin R, Timothy Jake, Hall Richard M
School of Mechanical Engineering, University of Leeds, United Kingdom.
J Neurosurg Spine. 2008 Nov;9(5):493-501. doi: 10.3171/SPI.2008.9.11.493.
The vertebral column is the most common site for secondary bone metastases and lesions arising from hematological malignancies such as multiple myeloma (MM). These infiltrations can be lytic in nature and cause severe weakening of the vertebral body, an increased risk of fracture, and spinal cord compression leading to neurological deficit. Qualitatively it is apparent that increasing infiltration of these lytic lesions will have a deleterious effect on the mechanical behavior of the vertebrae. However, there is little quantitative information about the relationship between tumor deposits and the impact on the mechanical behavior of the vertebrae. In addition, there have been limited biomechanical assessments of the use of vertebroplasty in the management of these malignancies. The purpose of this preliminary study was to evaluate the mechanical behavior of lesion-infiltrated vertebrae from 2 malignant cancers and to investigate the effectiveness of vertebroplasty with and without tumor debulking.
Individual vertebrae from 2 donor spines--one with MM and another with bone metastases secondary to bladder cancer-were fractured under an eccentric flexion load, from which failure strength and stiffness were derived. Alternate vertebrae defined by spinal level were assigned to 2 groups: Group 1 involved removal of lesion material with Coblation (ArthroCare Corp.) preceding vertebroplasty; Group 2 received no Coblation prior to augmentation. All vertebrae were fractured postaugmentation under the same loading protocol. Micro-CT assessments were undertaken to investigate vertebral morphology, fracture patterns, and cement distribution.
Multiple myeloma involvement was characterized by several small lesions, severe bone degradation, and multiple areas of vertebral shell compromise. In contrast, large focal lesions were present in the vertebrae with metastatic bladder cancer, and the shell generally remained intact. The mean initial failure strength of the vertebrae with metastases secondary to MM was significantly lower than in vertebrae with bone metastases secondary to bladder cancer (Load = 950 +/- 300 N vs 2200 +/- 750 N, p < 0.0001). A significant improvement in relative fracture strength was found postaugmentation for both lesion types (1.4 +/- 0.5, p < 0.001). Coblation provided a marginally significant increase in the same parameter postaugmentation (p = 0.08) and qualitatively improved the ease of injection and guidance of cement.
In the vertebral column, metastatic lesions secondary to bladder cancer and MM showed variations in the pattern of infiltration, both of which led to significant reductions in fracture strength. Account should be taken of these differences to optimize the vertebroplasty intervention in terms of the cement formulation, delivery, and any additional surgical procedure.
脊柱是继发性骨转移瘤以及血液系统恶性肿瘤（如多发性骨髓瘤，MM）所致病变最常见的部位。这些浸润性病变本质上可为溶骨性，会导致椎体严重弱化、骨折风险增加以及脊髓受压并引发神经功能缺损。定性来看，显然这些溶骨性病变浸润程度增加会对椎体的力学行为产生有害影响。然而，关于肿瘤沉积物与椎体力学行为影响之间的定量信息却很少。此外，对于椎体成形术在这些恶性肿瘤治疗中的应用，生物力学评估也很有限。本初步研究的目的是评估来自两种恶性肿瘤的病变浸润椎体的力学行为，并研究椎体成形术在有无肿瘤减容情况下的有效性。
取自2个供体脊柱的单个椎体——一个患有MM，另一个患有继发于膀胱癌的骨转移瘤——在偏心屈曲载荷下发生骨折，由此得出破坏强度和刚度。按脊柱节段确定的交替椎体被分为2组：第1组在椎体成形术前用低温等离子射频消融术（ArthroCare公司）清除病变组织；第2组在强化治疗前未进行低温等离子射频消融术。所有椎体在强化治疗后按照相同的加载方案进行骨折。进行显微CT评估以研究椎体形态、骨折模式和骨水泥分布。
多发性骨髓瘤累及表现为多个小病变、严重的骨质破坏以及多个椎体壳受损区域。相比之下，继发于膀胱癌的椎体中存在大的局灶性病变，且椎体壳通常保持完整。继发于MM的椎体转移瘤的平均初始破坏强度显著低于继发于膀胱癌的骨转移瘤的椎体（载荷分别为950±300 N和2200±750 N，p<0.0001）。两种病变类型在强化治疗后相对骨折强度均有显著改善（1.4±0.5，p<0.001）。低温等离子射频消融术在强化治疗后同一参数上有略微显著的增加（p = 0.08），并且在定性上改善了骨水泥注射的便利性和导向性。
在脊柱中，继发于膀胱癌和MM的转移性病变在浸润模式上存在差异，这两种情况均导致骨折强度显著降低。在骨水泥配方、输送方式以及任何额外的手术操作方面，应考虑这些差异以优化椎体成形术干预。
