Boch A L, Hermelin E, Sainte-Rose C, Sgouros S
Service de Neurochirurgie, Hôpital Necker-Enfants Malades, Paris, France.
J Neurosurg. 1998 Jun;88(6):975-82. doi: 10.3171/jns.1998.88.6.0975.
The authors studied new and calcified shunt catheters to identify the prevalence of failures caused by aging materials in the shunt. Complications associated with these devices have various origins. Among late complications, fracture or migration of the system is related to the subcutaneous adhesion of the distal tubing in a growing child. A review of a cohort of 64 children who underwent shunt placement in 1980 with barium-impregnated distal catheters showed that 10 of these patients underwent reoperation for complications related to aging of the shunt material. This group represents 15% of the whole series and 30% of those children who were followed for more than 3 years. The true impact of aging of materials on shunt function is probably underestimated.
The authors performed physical, chemical, and mechanical analyses of the retrieved aged catheters and also of new catheters, resulting in the following findings: 1) calcifications were observed only on the external surface of the catheter, predominantly in its subcutaneous segment at the level of the neck and anterior chest wall; 2) calcifications contained particles of free silicon and barium sulfate, signifying fragmentation of the polymer; 3) the microstructure of the silicone polymer was modified: microfractures and alteration of the polymeric network were observed; 4) silanol groups were observed on the external surface of the catheter; and 5) the mechanical properties of the silicone rubber were degraded, and the aged catheters were more brittle than the new ones, with ruptures at elongations and fracture energy much lower than that seen in new catheters. Furthermore, in vitro testing with a metastable solution of simulated body fluid demonstrated the critical impact of pH variations in liquid media and surface degradation of the catheters on the precipitation of hydroxylapatite crystals.
Although most shunt complications can be addressed by better patient management and surgical technique, late complications appear to be partly related to aging of the material. Distal tubing calcifications have been observed in barium-impregnated catheters. The industry recently responded to these observations by introducing plain silicone-coated shunt tubing; further evaluation will show what improvement can be expected.
作者研究了新型和钙化的分流导管，以确定分流装置中老化材料导致故障的发生率。与这些装置相关的并发症有多种原因。在晚期并发症中，系统的断裂或移位与成长中儿童远端导管的皮下粘连有关。对1980年接受分流置入术且远端导管含钡的64名儿童队列进行的回顾显示，其中10例患者因分流材料老化相关并发症接受了再次手术。该组占整个系列的15%，占随访超过3年儿童的30%。材料老化对分流功能的真正影响可能被低估了。
作者对回收的老化导管以及新型导管进行了物理、化学和力学分析，结果如下：1）钙化仅在导管外表面观察到，主要在颈部和前胸壁水平的皮下段；2）钙化包含游离硅颗粒和硫酸钡颗粒，表明聚合物发生了碎裂；3）硅聚合物的微观结构发生了改变：观察到微裂缝和聚合物网络的改变；4）在导管外表面观察到硅醇基团；5）硅橡胶的力学性能下降，老化导管比新型导管更脆，其伸长断裂和断裂能量远低于新型导管。此外，用模拟体液的亚稳溶液进行的体外测试表明，液体介质中的pH值变化和导管表面降解对羟基磷灰石晶体沉淀具有关键影响。
尽管大多数分流并发症可通过更好的患者管理和手术技术来解决，但晚期并发症似乎部分与材料老化有关。在含钡导管中观察到远端导管钙化。该行业最近通过引入普通硅胶涂层分流导管来回应这些观察结果；进一步评估将显示预期会有哪些改进。
