NeuroSpine Surgery Research Group (NSURG), Sydney, New South Wales, Australia.
Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia.
Orthop Surg. 2019 Jun;11(3):510-515. doi: 10.1111/os.12467. Epub 2019 Jun 9.
Cement augmentation is a technique used to increase the stability and purchase of pedicle screws in poor quality bone. Various methods can be applied for cement delivery, such as cement injection before screw placement and the use of fenestrated screws. However, potential problems can arise with the use of cement augmentation.
A 66-year-old man with a lower trunk deformity, severe kyphosis, and sagittal imbalance following fusion (L ), with minimal comorbidities, was referred to our unit 9 months after surgery. Pain and progressive kyphosis were investigated clinically and radiographically with computed tomography (CT) scans to assess the status of the hardware and fusion. CT imaging revealed that cement was present only at the distal tip of the fenestrated screws at the L4 vertebral level. A non-union was present along with loosening and a halo around the body of the pedicle screws, and there was evidence of pullout of inferior screws.
Single-level cement augmentation of pedicle screw in a posterior construct and distal tip cement augmentation of the screw results in a fixed pivot point. Micromotion in cranio-caudal loading during flexion and extension may result in screw toggling with the single-level cement-augmented tip as a fulcrum. This may cause screw loosening, which can lead to pullout and loss of construct stability. The halo around the screw suggests bone loss and/or a fibrous tissue interface, which further complicates revision surgery. Stress shielding and polymethylmethacrylate cement present additional difficulties. The findings of this technical note question the risks and benefits of cement-augmented fenestrated pedicle screw fixation for spinal fusion. Although incidences of such cases are uncommon, surgeons should perform this technique with caution. Accurate restoration of lumbar lordosis during index procedures is important to minimize the risk of construct failure.
骨水泥强化是一种用于增加质量较差的椎弓根螺钉稳定性和把持力的技术。可以应用各种方法进行骨水泥输送，例如在螺钉放置之前进行骨水泥注射和使用开窗螺钉。然而，骨水泥强化的使用可能会带来潜在问题。
一位 66 岁男性，因 L 融合术后出现下躯干畸形、严重后凸畸形和矢状面失衡，合并轻度合并症，术后 9 个月转入我科。临床和影像学检查（包括计算机断层扫描 (CT)）评估了患者的硬件和融合情况，发现患者存在疼痛和进行性后凸，CT 影像显示仅在 L4 椎骨水平的开窗螺钉的远端尖端存在骨水泥。存在非融合，螺钉松动，椎弓根螺钉体周围有光环，下侧螺钉有拔出的迹象。
后路内固定中单一水平的椎弓根螺钉骨水泥强化和螺钉远端尖端骨水泥强化会形成固定枢轴点。屈伸时颅尾加载的微动可能导致螺钉以单一水平骨水泥强化尖端为枢轴发生摆动。这可能导致螺钉松动，从而导致螺钉拔出和结构稳定性丧失。螺钉周围的光环表明存在骨丢失和/或纤维组织界面，这进一步增加了翻修手术的复杂性。应力屏蔽和聚甲基丙烯酸甲酯骨水泥也带来了额外的困难。本技术说明的结果对骨水泥强化开窗椎弓根螺钉固定脊柱融合的风险和益处提出了质疑。尽管此类病例的发生率不高，但外科医生在进行此项技术时应谨慎操作。在指数手术中准确恢复腰椎前凸有助于最大程度地降低结构失败的风险。
