Lee Jillian, Lillia Jonathon A, Bellemore Jeremy M, Little David G, Cheng Tegan L
Department of Orthopaedic Surgery, the Children's Hospital at Westmead, Sydney, NSW, Australia.
EPIC Lab, the Children's Hospital at Westmead, Sydney, NSW, Australia.
J Child Orthop. 2020 Oct 1;14(5):358-363. doi: 10.1302/1863-2548.14.190178.
Stable slipped capital femoral epiphysis (SCFE) is often treated with pinning, with the current gold standard being stabilization with a screw perpendicular to the physis. However, this can lead to impingement and a potentially unstable construct. In this study we model the biomechanical effect of two screw positions used for SCFE fixation. We hypothesize that single screw fixation into the centre of the femoral head from the anterior intertrochanteric line (the Universal Entry Point or UEP) provides a more stable construct than single screw fixation perpendicular to the physis with an anterior starting point.
Sawbone models of moderate SCFE were used to mechanically test the two screw constructs and an unfixed control group. Models were loaded to failure with a shear load applied through the physis in an Instron mechanical tester. The primary outcomes were maximum load, stiffness and energy to failure.
Screw fixation into the centre of the femoral head from the UEP resulted in a greater load to failure (+19%), stiffness (+13%) and energy to failure (+45%) than screw fixation perpendicular to the physis.
In this sawbone construct, screw fixation into the centre of the femoral head from the UEP provides greater biomechanical stability than screw fixation perpendicular to the physis. This approach may also benefit by avoiding an intracapsular entry point in soft metaphyseal bone and subsequent risk of impingement and loss of position.
稳定型股骨头骨骺滑脱（SCFE）通常采用穿针固定治疗，目前的金标准是使用垂直于骨骺的螺钉进行固定。然而，这可能会导致撞击和潜在的不稳定结构。在本研究中，我们模拟了用于SCFE固定的两种螺钉位置的生物力学效应。我们假设，从转子间前线（通用入点或UEP）向股骨头中心单螺钉固定比从前侧起始点垂直于骨骺的单螺钉固定提供更稳定的结构。
使用中度SCFE的Sawbone模型对两种螺钉结构和一个未固定的对照组进行力学测试。在Instron力学试验机中，通过骨骺施加剪切载荷将模型加载至破坏。主要结果是最大载荷、刚度和破坏能量。
与垂直于骨骺的螺钉固定相比，从UEP向股骨头中心螺钉固定导致更大的破坏载荷（+19%）、刚度（+13%）和破坏能量（+45%）。
在本Sawbone结构中，从UEP向股骨头中心螺钉固定比垂直于骨骺的螺钉固定提供更大的生物力学稳定性。这种方法还可能受益于避免在干骺端软骨质骨中的囊内入点以及随后的撞击和位置丢失风险。
