在外科手術中，鎖定式骨板(Locking plate)廣泛應用於各種不同類型與部位的骨折治療，與傳統的動態加壓式骨板(dynamic compression plate)相比，鎖定式骨板的螺絲頭與骨板藉由螺紋結合為一體，可增加整體結構的剛性，提供較高的穩定度。鎖定式骨板常見的破壞為疲勞破壞，破壞的起始位置好發於截骨附近骨板上的螺紋孔洞。因此本研究之目的為探討使用螺絲頭鎖入骨板截骨處的空螺絲洞藉此提升鎖定式骨板疲勞強度的方法，以及鈦合金能否使用相同方法克服螺紋結構上的凹口效應。
在本文中，分為生物力學測試以及有限元素分析兩部分，在生物力學測試方面，總共對六種骨板進行降伏測試與疲勞測試，而在實驗後得到位移、負載之關係而計算出其彎曲勁度、降伏強度與疲勞壽命；在有限元素方面利用SolidWorks建立三維骨板模型並匯入ANSYS進行模擬，其負載情形與邊界條件與機械測試雷同，藉由有限元素分析得到最大von-Mises應力與位移之分析數值，並將生物力學測試結果與有限元素分析結果進行相關性比較。
由機械測試結果得知，將不鏽鋼骨板的空螺絲洞鎖入螺絲頭後，與未鎖入螺絲頭的骨板比較，疲勞壽命將得到顯著提升。鈦合金骨板在鎖入螺絲頭後疲勞壽命並沒有得到提升。提高螺絲頭鎖入扭力對疲勞壽命並無顯著影響。有限元素分析結果顯示，塞入螺絲頭後並不會降低骨板的最大von-Mises應力。微維克氏硬度分析結果發現，不鏽鋼骨板塞入螺絲頭後螺紋處產生加工硬化，鈦合金骨板則無。生物力學測試與有限元素分析結果相互比對後，發現加工硬化是使不鏽鋼骨板疲勞壽命提升的原因，而塞入螺絲頭並不會降低骨板的最大von-Mises應力，驗證了鈦合金骨板疲勞壽命無法提升的結果。

Locking plate is widely used for the treatment of various kinds of bodily fractures. Locking plate can provide more stiffness and stability than dynamic compression plate, because its locking screw can lock on plate by thread hole. Fatigue breakage was the most commonly seen mode of failure and mostly occurs through the screw holes around the fracture site. The purpose of this study was to increase the locking plate fatigue strength with screw head insertion. And to investigate if the screw head insertion can improve notch effect in titanium alloy plate.
In biomechanical testing, plates were tested for both stiffness and fatigue mechanical properties. In finite element analysis, three-dimensional plate model used same structures and conditions with those applied in the biomechanical tests. After processing, the von-Mises stresses and displacement were recorded and correlated with the mechanical test results.
From the results of biomechanical test, plugging the empty holes could increase the fatigue life of the stainless steel plates but not in titanium alloy plate. The insertion torque was increased from 4 Nm to 12 Nm, the stainless steel plates fatigue life could also be increased, but the differences were still not significant. In the finite element analysis, plugging the empty holes did not decrease the von-Mises stress. The micro Vickers-hardness shows that the stainless steel plate work hardening occurs after screw head insertion but not in titanium alloy plate.

[1] K. A. Egol, E. N. Kubiak, E. Fulkerson, F. J. Kummer, and K. J. Koval, "Biomechanics of locked plates and screws," J Orthop Trauma, vol. 18, pp. 488-93, Sep 2004.
[2] S. Walsh, R. Reindl, E. Harvey, G. Berry, L. Beckman, and T. Steffen, "Biomechanical comparison of a unique locking plate versus a standard plate for internal fixation of proximal humerus fractures in a cadaveric model," Clin Biomech (Bristol, Avon), vol. 21, pp. 1027-31, Dec 2006.
[3] A. L. Freeman, P. Tornetta III, A. Schmidt, J. Bechtold, W. Ricci, and M. Fleming, "How much do locked screws add to the fixation of "hybrid" plate constructs in osteoporotic bone?," J Orthop Trauma, vol. 24, pp. 163-9, Mar 2010.
[4] C. K. Chao, C. C. Hsu, J. L. Wang, and J. Lin, "Increasing bending strength of tibial locking screws: mechanical tests and finite element analyses," Clin Biomech (Bristol, Avon), vol. 22, pp. 59-66, Jan 2007.
[5] C. C. Hsu, C. K. Chao, J. L. Wang, S. M. Hou, Y. T. Tsai, and J. Lin, "Increase of pullout strength of spinal pedicle screws with conical core: biomechanical tests and finite element analyses," J Orthop Res, vol. 23, pp. 788-94, Jul 2005.
[6] A. R. Tolat, A. Amis, S. Crofton, and J. Sinha, "Failure of humeral fracture fixation plate in a young patient using the Philos system: case report," J Shoulder Elbow Surg, vol. 15, pp. e44-7, Nov-Dec 2006.
[7] T. De Baere, F. Lecouvet, and O. Barbier, "Breakage of a volar locking plate after delayed union of a distal radius fracture," Acta Orthop Belg, vol. 73, pp. 785-90, Dec 2007.
[8] K. Yukata, K. Doi, Y. Hattori, and S. Sakamoto, "Early breakage of a titanium volar locking plate for fixation of a distal radius fracture: case report," J Hand Surg Am, vol. 34, pp. 907-9, May-Jun 2009.
[9] H. A. Vallier, T. A. Hennessey, J. K. Sontich, and B. M. Patterson, "Failure of LCP condylar plate fixation in the distal part of the femur. A report of six cases," J Bone Joint Surg Am, vol. 88, pp. 846-53, Apr 2006.
[10] G. Button, P. Wolinsky, and D. Hak, "Failure of less invasive stabilization system plates in the distal femur: a report of four cases," J Orthop Trauma, vol. 18, pp. 565-70, Sep 2004.
[11] C. Sommer, R. Babst, M. Muller, and B. Hanson, "Locking compression plate loosening and plate breakage: a report of four cases," J Orthop Trauma, vol. 18, pp. 571-7, Sep 2004.
[12] J. M. Banovetz, R. Sharp, R. A. Probe, and J. O. Anglen, "Titanium plate fixation: a review of implant failures," J Orthop Trauma, vol. 10, pp. 389-94, 1996.
[13] F. B. Christensen, M. Dalstra, F. Sejling, S. Overgaard, and C. Bunger, "Titanium-alloy enhances bone-pedicle screw fixation: mechanical and histomorphometrical results of titanium-alloy versus stainless steel," Eur Spine J, vol. 9, pp. 97-103, Apr 2000.
[14] P. Q. Chen, S. J. Lin, S. S. Wu, and H. So, "Mechanical performance of the new posterior spinal implant: effect of materials, connecting plate, and pedicle screw design," Spine (Phila Pa 1976), vol. 28, pp. 881-6; discussion 887, May 1 2003.
[15] M. Tompkins, D. J. Paller, D. C. Moore, J. J. Crisco, and R. M. Terek, "Locking buttons increase fatigue life of locking plates in a segmental bone defect model," Clin Orthop Relat Res, vol. 471, pp. 1039-44, Mar 2013.
[16] J. Bellapianta, K. Dow, N. A. Pallotta, P. P. Hospodar, R. L. Uhl, and E. H. Ledet, "Threaded screw head inserts improve locking plate biomechanical properties," J Orthop Trauma, vol. 25, pp. 65-71, Feb 2011.
[17] K. Meyers, T. Achor, J. Ahn, K. Khalsa, D. Lorich, T. Wright, et al., "The Effect of Locking Inserts and Overtorque on the Fatigue Behavior of Locking Compression Plates," 56th Annual Meeting of the Orthopaedic Research Society, vol. Poster NO.1768, 2010.
[18] J. Cartner, A. Messina, C. Baker, T. A. Russell, P. Tornetta III, and W. M. Ricci, "Does insertion torque affect the mechanics of locking hole inserts and fatigue performance of bridge plate constructs?," Bone Joint Sci, vol. 2, 2011.
[19] R. Firoozabadi, E. McDonald, T. Q. Nguyen, J. M. Buckley, and U. Kandemir, "Does plugging unused combination screw holes improve the fatigue life of fixation with locking plates in comminuted supracondylar fractures of the femur?," J Bone Joint Surg Br, vol. 94, pp. 241-8, Feb 2012.
[20] J. K. Eichinger, J. P. Herzog, and E. D. Arrington, "Analysis of the mechanical properties of locking plates with and without screw hole inserts," Orthopedics, vol. 34, p. 19, Jan 2011.
[21] P. Tornetta III, W. M. Ricci, B. Jones, Y. Zheng, and A. Whitten, "Filling empty holes in locked plates: Does it improve fatigue properties?," Annual Meeting of the Orthopaedic Trauma Association, vol. Poster NO.33, 2008.
[22] P. Chao, B. P. Conrad, D. D. Lewis, M. Horodyski, and A. Pozzi, "Effect of plate working length on plate stiffness and cyclic fatigue life in a cadaveric femoral fracture gap model stabilized with a 12-hole 2.4 mm locking compression plate," BMC Vet Res, vol. 9, p. 125, 2013.
[23] J. L. Stambough, A. M. Genaidy, R. L. Huston, H. Serhan, F. El-khatib, and E. H. Sabri, "Biomechanical assessment of titanium and stainless steel posterior spinal constructs: effects of absolute/relative loading and frequency on fatigue life and determination of failure modes," J Spinal Disord, vol. 10, pp. 473-81, Dec 1997.
[24] C. Kanchanomai, V. Phiphobmongkol, and P. Muanjan, "Fatigue failure of an orthopedic implant – A locking compression plate," Engineering Failure Analysis, vol. 15, pp. 521-530, 2008.
[25] G. F. Vander Voort and R. Fowler, "Low-load Vickers microindentation hardness testing," AM & P, vol. 170, pp. 28-33, Apr 2012.
[26] C. Gaebler, S. Stanzl-Tschegg, G. Heinze, B. Holper, T. Milne, G. Berger, et al., "Fatigue strength of locking screws and prototypes used in small-diameter tibial nails: A biomechanical study," J Trauma, vol. 47, pp. 379-384, Aug 1999.
[27] D. Pienkowski, G. C. Stephens, T. M. Doers, and D. M. Hamilton, "Multicycle mechanical performance of titanium and stainless steel transpedicular spine implants," Spine (Phila Pa 1976), vol. 23, pp. 782-8, Apr 1 1998.
[28] R. Frigg, "Development of the Locking Compression Plate," Injury, vol. 34, pp. 6-10, 2003.