Effect of Length of Side Plate on Treating Hip Intertrochanteric Fracture with Dynamic Hip Screw-A Finite Element Study

以不同長度側鋼板之動態髖骨釘治療骨粗隆骨折－有限元素分析

施世亮(Shih-Liang Shih) ； 鄭誠功(Cheng-Kung Cheng) ； 陳振昇(Chen-Sheng Chen)

《北市醫學雜誌》 12卷1期 (2015/03) Pp. 28-41

https://doi.org/10.6200/TCMJ.2015.12.1.03

摘要

目的：以兩個螺孔的動態髖骨釘治療股骨粗隆間骨折在臨床上已經得到令人滿意的結果，生物力學方面的實驗數據也支持這個治療的觀念，然而以兩個螺孔的動態髖骨釘治療粗隆間骨折仍然陸續有側螺釘斷裂的病例報告。究竟側螺釘斷裂與側鋼板的長度是否有關？目前仍未可知。本研究目的是運用三維的電腦數值實體股骨模型模擬以不同長度側鋼板之動態髖骨釘固定粗隆間骨折，以有限元素分析來評估動態髖骨釘之側鋼板長度是否影響其穩定度。方法：本研究以一位健康男性的股骨電腦斷層掃描造影建立一個三維立體股骨的數值模型，並在模形上製造粗隆間骨折。此股骨模型分別植入兩個螺孔、三個螺孔及四個螺孔側鋼板之動態髖骨釘之模型後，分別於此三個模型之股骨頭部施與模擬正常步態著地期（stance phase）及擺盪期（swing phase）的負載以測量不同側鋼板長度之動態髖骨釘的強度。此外，此三個模型也分別進行有限元素分析的疲勞測試。結果：側鋼板有四個螺孔的動態髖骨釘提供了最穩定的骨折固定，然而最遠端的側螺釘也承受了最大的應力；兩個螺孔的動態髖骨釘展現了最長的疲勞壽命，並且比其他兩組模型讓股骨本身承擔更多的受力。此外，三個模型的動態髖骨釘應力分析顯示最遠端的兩個側螺釘承受了主要的應力。結論：對於穩定型的股骨粗隆間骨折，以側鋼板具兩個螺孔的動態髖骨釘固定的骨折處位移最大，但與三個螺孔的動態髖骨釘的位移差距不大。此外，兩個螺孔的動態髖骨釘承受最久的疲勞測試以及最少的應力，植入側鋼板具兩個螺孔的動態髖骨釘的股骨幹顯示出較其他兩個模型更多的應力，亦即最少的應力遮蔽效應。

關鍵字

髖骨骨折 ； 粗隆間骨折 ； 動態髖骨釘 ； 兩螺孔側鋼板 ； 有限元素法

並列摘要

Objectives: Treating hip intertrochanteric fracture (HIF) with dynamic hip screw (DHS) with two-hole side plate has gained satisfactory clinical results. Biomechanical tests also supported the use of DHS with two-hole side plate in treating HIF. However, complications with screws breakage have been reported; whether the events were related to the length of side plate remained unknown. The purpose of this study was to assess the stress distribution at dynamic hip screws with different length of side plate and movement of fracture fragments fixed by these implants. Methods: Finite element (FE) analysis was used to evaluate the reliability and durability of the implants. FE models of fractured proximal femur implanted with DHS with two, three and four-hole side plate and fractured healed model were built through CT scan images, and loads of single leg in stance and swing phase were applied to the FE models to evaluate the strength of HIF with DHS. Fatigue analysis of the three FE models was also performed. Results: DHS with four-hole side plate provided the best stability but also bore the greatest stress at its most distal screw. DHS with two-hole side plate exhibited the longest period of fatigue life cycle and shared more stress to the femur than the other two FE modes. Stress distribution showed that only the two distal screws of the side plate played major roles in holding the femur. Conclusion: In simple HIF fracture type, fragment of the fractured model fixed with DHS with two-hole side plate had the largest displacement, but not much different from that of three-hole side plate. Nevertheless, DHS with two-hole side plate revealed most life cycles and the lowest stress. Moreover, femoral shaft implanted with DHS with two-hole side plate sustained more even stress than those implanted with the other two implants.

並列關鍵字

Hip fracture ； proximal femur fractures ； hip intertrochanteric fracture ； sliding hip screw ； dynamic hip screw ； finite element ； two-hole side plate