Placzek R, Ruffer M, Deuretzbacher G, Heijens E, Meiss A L
CMSC, Paediatric Orthopaedic Section, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13533 Berlin, Germany.
Arch Orthop Trauma Surg. 2006 Aug;126(6):369-73. doi: 10.1007/s00402-006-0142-5. Epub 2006 Apr 21.
Lengthening procedures are often complicated by loosening of pins. It has been reported that coating with hydroxyapatite improves fixation and reduces the rate of pin-track infection.
We compared 47 hydroxyapatite-coated Schanz screws (HA screws) in 12 monolateral fixators mounted at the University Hospital Hamburg-Eppendorf with 45 standard stainless steel screws in 9 monolateral fixators mounted at the St Josefs-Hospital Wiesbaden by measuring the insertion and extraction torque values. The average implantation period was 7 months for the hydroxyapatite-coated screws and 5.4 months for the uncoated screws. We established the quotient of the maximum extraction torque over insertion torque which shows the change in the fixation strength with respect to time, the fixation index. It eliminates the influence of the varying pin-bone contact.
There was no significant difference in the rate of infection. In the Schanz screws without signs of infection the index was 1.92 for the HA screws and 0.76 for the stainless steel screws (P = 0.0002) giving evidence of the improvement of the fixation by the coating.
HA coating resulted in improved fixation of Schanz screws in bone and may be useful in prolonged external fixation of the lower leg. The fixation index proved to be a simple tool for the evaluation of the fixation strength of Schanz screws.
延长手术常因克氏针松动而变得复杂。据报道，羟基磷灰石涂层可改善固定效果并降低针道感染率。
我们通过测量置入和拔出扭矩值，比较了汉堡 - 埃彭多夫大学医院安装在12个单侧固定器中的47根羟基磷灰石涂层斯氏针（HA针）与威斯巴登圣约瑟夫医院安装在9个单侧固定器中的45根标准不锈钢针。羟基磷灰石涂层针的平均植入期为7个月，未涂层针的平均植入期为5.4个月。我们建立了最大拔出扭矩与置入扭矩的商，该商显示了固定强度随时间的变化，即固定指数。它消除了不同针 - 骨接触的影响。
感染率无显著差异。在没有感染迹象的斯氏针中，HA针的指数为1.92，不锈钢针的指数为0.76（P = 0.0002），这证明了涂层改善了固定效果。
HA涂层可改善斯氏针在骨内的固定效果，可能有助于小腿的长期外固定。固定指数被证明是评估斯氏针固定强度的一个简单工具。
