Kummer F J, Olsson O, Pearlman C A, Ceder L, Larsson S, Koval K J
Hospital for Joint Diseases, New York, NY 10003, USA.
Acta Orthop Scand. 1998 Dec;69(6):580-4. doi: 10.3109/17453679808999259.
We compared two different subtrochanteric fracture fixation techniques, an intramedullary hip screw system (IMHS) and an extramedullary, dual sliding screw-plate system (MSP), to determine relative fixation stability. 6 matched pairs of osteosynthesized osteopenic cadaver femurs were axially loaded to 1000 N with concurrent, simulated abductor forces of 0%, 50%, or 86% of the applied head force. The initial loading sequence was made with uniaxial dynamization--the lag screw of the MSP locked and distal locking of the IMHS nail. Femoral head displacement and medial femoral strain were measured for intact femur controls, after fixation of a 2-part reverse oblique subtrochanteric fracture and finally a 3-part reverse oblique subtrochanteric fracture with a lateral wedge defect. The samples were then loaded at 750 N for 10(4) cycles with both devices uniaxially locked, followed by 10(4) cycles with both devices fully biaxially dynamized (unlocked). For the 2-part subtrochanteric fracture pattern, both devices exhibited similar inferior displacements of the femoral head (average 2.0 mm) and medial femoral strain (approximately 70% of intact). Increasing abductor forces decreased medial compressive strain but did not significantly affect head displacement. For the 3-part fracture model, the MSP demonstrated significantly less inferior displacement of the head (1.6 mm vs. 2.1 mm) and both devices demonstrated significantly decreased medial strain. After cycling, head displacement increased approximately 50% in both devices and medial strain increased slightly. After unlocking and cycling, the MSP group showed significant lateral displacement of the proximal fragment. The IMHS and MSP devices provide similar stability for fixation of 2-part and 3-part reverse oblique subtrochanteric fractures. In a biaxially dynamized, 3-part reverse oblique fracture, displacement of the proximal fragment can occur with the MSP.
我们比较了两种不同的转子下骨折固定技术，即髓内髋螺钉系统（IMHS）和髓外双滑动螺钉钢板系统（MSP），以确定相对固定稳定性。6对匹配的经骨合成的骨质疏松尸体股骨在轴向加载至1000 N，同时施加相当于股骨头作用力0%、50%或86%的模拟外展肌力量。初始加载顺序为单轴动力化——MSP的拉力螺钉锁定，IMHS钉进行远端锁定。测量完整股骨对照组、固定两部分型反向斜行转子下骨折后以及最终固定伴有外侧楔形缺损的三部分型反向斜行转子下骨折后的股骨头位移和股骨内侧应变。然后将样本在750 N下加载10⁴个循环，两种装置均单轴锁定，随后再进行10⁴个循环，两种装置均完全双轴动力化（解锁）。对于两部分型转子下骨折模式，两种装置的股骨头均表现出相似的向下位移（平均2.0 mm）和股骨内侧应变（约为完整状态的70%）。增加外展肌力量可降低内侧压缩应变，但对股骨头位移无显著影响。对于三部分骨折模型，MSP的股骨头向下位移明显更小（1.6 mm对2.1 mm），且两种装置的内侧应变均显著降低。循环加载后，两种装置的股骨头位移均增加约50%，内侧应变略有增加。解锁并循环加载后，MSP组近端骨折块出现明显的侧向位移。IMHS和MSP装置在固定两部分型和三部分型反向斜行转子下骨折时提供相似的稳定性。在双轴动力化的三部分型反向斜行骨折中，MSP可能会出现近端骨折块的位移。
