Dahl William J, Silva Selina, Vanderhave Kelly L
Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, MI.
J Pediatr Orthop. 2014 Mar;34(2):134-8. doi: 10.1097/BPO.0000000000000083.
Distal femoral physeal fractures have a high incidence of physeal arrest. Several factors have been postulated to contribute to this high incidence, including fracture type, displacement, the undulating nature of the physis, and fracture reduction/fixation. The purpose of this study was to determine whether the position of percutaneous smooth pins across the physis contributes to physeal bar formation.
The previously validated New Zealand white rabbit model was used. Power analysis determined that 30 animals were required. All animals had a constant 0.045 smooth Kirschner (K) wire placed under fluoroscopic guidance from the distal lateral femur across the physis centrally. A second 0.045 K-wire was placed in a cross-pin configuration from the medial side in one of 2 positions: zone 1--crossing the physis centrally or zone 2--crossing the physis peripherally. Pins were removed after 4 weeks and micro computed tomography was performed at 8 weeks to assess for physeal bar formation. Histologic analysis was performed to confirm bar formation.
Two physeal bars (7%) were seen after removal of the constant (lateral pin). The peripheral pin resulted in bar formation in 2 animals (13%) and the central pin in 1 animal (7%). A χ² test was performed; there was no statistically significant difference between zones in terms of bar formation (P=0.5428).
Injury to the growth plate after distal femoral fracture may be unavoidable. Treatment is aimed to minimize further injury to the physis. Cross-pinning with smooth K-wires results in a low rate of physeal injury. Pins that cross the physis both centrally and peripherally appear to have the same risk for physeal bar formation.
This study reveals that physeal bar formation can be seen with smaller than previously reported cross-sectional damage to the distal femoral physis. This study highlights the need to carefully select and perform fixation of the distal femoral physis with as little additional trauma to the physis as possible.
股骨远端骨骺骨折发生骨骺早闭的几率很高。据推测，有几个因素导致了这一高发生率，包括骨折类型、移位、骨骺的起伏特性以及骨折复位/固定。本研究的目的是确定经皮光滑克氏针穿过骨骺的位置是否会导致骨骺桥形成。
采用先前经验证的新西兰白兔模型。功效分析确定需要30只动物。所有动物在透视引导下，从股骨远端外侧向骨骺中心置入一根恒定的0.045光滑克氏（K）针。第二根0.045 K针以交叉针构型从内侧置于两个位置之一：区域1——从中心穿过骨骺，或区域2——从周边穿过骨骺。4周后取出钢针，8周时进行微型计算机断层扫描以评估骨骺桥形成情况。进行组织学分析以确认桥的形成。
取出恒定（外侧）钢针后，发现两根骨骺桥（7%）。周边钢针导致2只动物（13%）形成骨骺桥，中心钢针导致1只动物（7%）形成骨骺桥。进行了χ²检验；在骨骺桥形成方面，各区域之间无统计学显著差异（P = 0.5428）。
股骨远端骨折后生长板损伤可能不可避免。治疗旨在尽量减少对骨骺的进一步损伤。用光滑K针交叉固定导致骨骺损伤的发生率较低。从中心和周边穿过骨骺的钢针似乎有相同的形成骨骺桥的风险。
本研究表明，对于股骨远端骨骺，当横截面损伤小于先前报道时也可出现骨骺桥形成。本研究强调需要谨慎选择并进行股骨远端骨骺固定，尽量减少对骨骺的额外创伤。
