Gottschalk Hilton Phillip, Sagoo Daljeet, Glaser Diana, Doan Josh, Edmonds Eric W, Schlechter John
Department of Pediatric Orthopaedic Surgery, Rady Children's Hospital San Diego, San Diego, CA, USA.
J Pediatr Orthop. 2012 Jul-Aug;32(5):445-51. doi: 10.1097/BPO.0b013e318257d1cd.
Several studies have examined the biomechanical stability of smooth wire fixation constructs used to stabilize pediatric supracondylar humerus fractures. An analysis of varying pin size, number, and lateral starting points has not been performed previously.
Twenty synthetic humeri were sectioned in the midolecranon fossa to simulate a supracondylar humerus fracture. Specimens were all anatomically reduced and pinned with a lateral-entry configuration. There were 2 main groups based on specific lateral-entry starting point (direct lateral vs. capitellar). Within these groups pin size (1.6 vs. 2.0 mm) and number of pins (2 vs. 3) were varied and the specimens biomechanically tested. Each construct was tested in extension, varus, valgus, internal, and external rotation. Data for fragment stiffness (N/mm or N mm/degree) were analyzed with a multivariate analysis of variance and Bonferroni post hoc analysis (P<0.05).
The capitellar starting point provided for increased stiffness in internal and external rotation compared with a direct lateral starting point (P<0.05). Two 2.0-mm pins were statistically superior to two 1.6-mm pins in internal and external rotation. There was no significant difference found comparing two versus three 1.6-mm pins.
The best torsional resistances were found in the capitellar starting group along with increased pin diameter. The capitellar starting point enables the surgeon to engage sufficient bone of the distal fragment and maximizes pin separation at the fracture site. In our anatomically reduced fracture model, the addition of a third pin provided no biomechanical advantage.
Consider a capitellar starting point for the more distally placed pin in supracondylar humerus fractures, and if the patient's size allows, a larger pin construct will provide improved stiffness with regard to rotational stresses.
多项研究已对用于稳定小儿肱骨髁上骨折的光滑钢丝固定结构的生物力学稳定性进行了研究。此前尚未对不同的克氏针尺寸、数量和外侧起始点进行分析。
将20个合成肱骨在鹰嘴窝中部切开，以模拟肱骨髁上骨折。对标本进行解剖复位并用外侧入路构型进行穿针固定。根据特定的外侧入路起始点（直接外侧与肱骨小头）分为2个主要组。在这些组中，改变克氏针尺寸（1.6与2.0毫米）和克氏针数量（2与3），并对标本进行生物力学测试。对每个固定结构进行伸展、内翻、外翻、内旋和外旋测试。用多因素方差分析和Bonferroni事后分析（P<0.05）分析骨折块刚度数据（N/mm或N·mm/度）。
与直接外侧起始点相比，肱骨小头起始点在内外旋时提供了更高的刚度（P<0.05）。在内外旋时，两根2.0毫米克氏针在统计学上优于两根1.6毫米克氏针。比较两根与三根1.6毫米克氏针时未发现显著差异。
在肱骨小头起始组中发现了最佳的抗扭转能力，同时克氏针直径增加。肱骨小头起始点使外科医生能够固定足够的远端骨折块骨质，并使骨折部位的克氏针间距最大化。在我们的解剖复位骨折模型中，增加第三根克氏针未提供生物力学优势。
对于肱骨髁上骨折，考虑将肱骨小头作为更靠远端克氏针的起始点，并且如果患者体型允许，更大尺寸的克氏针固定结构在旋转应力方面将提供更好的刚度。
