How Reliable Are The Threaded Locking Screws?

Year 2015, Volume: 49 Issue: 5, 552 - , 24.09.2015

Ahmet Karaarslan Ahmet Karakaslı Tolga Karcı , Hakan Aycan Erhan Sesli

Abstract

Objectives: A frequent problem for interlocking nailing, that affects the treatment of the fracture is locking screw deformation. The research question is whether bending resistance is different between high, low and unthreaded locking screws of interlocking femoral nails.
Materials and methods. : We used 90 screws for nine groups, ten screws for each group in this experimental study. We performed three-point bending tests on six group of 5 mm screws (titanium, stainless steel, crossed with unthreaded, low threaded and high threaded) and the same three thread types of 5.5 mm stainless steel screws in a steel tube that has 30 mm inner diameter, which imitates the level of lesser trochanter. We determined the yield points at three-point bending tests that permanent deformation started in the locking screws   using an axial compression testing machine.
Results: The mean yield point value at 3-point bending test of 5 mm low threaded stainless steel locking screws  was 2071N and 53% less than unthreaded ones (3169 N).The mean yield point value of 5 mm high threaded stainless steel locking screws was 556 N and 272% less than low threaded ones (2071 N).
Conclusion: To avoid locking screw deformation, high threaded screws must not be used as locking screws. Five mm low threaded screws in nailing of comminuted or oblique femur shaft fractures of unreliable patients should not be used. All 5 mm unthreaded screws and 5.5 mm low threaded stainless steel screws can be used safely in full weight conditions of unreliable patients.

 

 

Keywords

Femur shaft fractures;femur nail, locking screw;three-point bending test

References

• Colchero F, Orst G, Reboul C, Villalobos F, Vidal J. In- tramedullary locking nailing. Experimental study. Surgi- cal technic. Results. [Article in French] Rev Chir Orthop Reparatrice Appar Mot 1983;69:547–55. [Abstract]
• Kempf I, Grosse A, Taglang G, Favreul E. Gamma nail in the treatment of closed trochanteric fractures. Results and indications of 121 cases. Orthop Traumatol Surg Res 2014;100:75–83.
• Whittle AP, Wester W, Russell TA. Fatigue failure in small diameter tibial nails. Clin Orthop Relat Res 1995;315:119–28.
• Boenisch UW, de Boer PG, Journeaux SF. Unreamed in- tramedullary tibial nailing--fatigue of locking bolts. Injury 1996;27:265–70.
• Whittle AP, Russell TA, Taylor JC, Lavelle DG. Treat- ment of open fractures of the tibial shaft with the use of interlocking nailing without reaming. J Bone Joint Surg Am 1992;74:1162–71.
• Court-Brown CM, Will E, Christie J, McQueen MM. Reamed or unreamed nailing for closed tibial fractures. A prospective study in Tscherne C1 fractures. J Bone Joint Surg Br 1996;78:580–3.
• Chao CK, Hsu CC, Wang JL, Lin J. Increasing bending strength of tibial locking screws: mechanical tests and finite element analyses. Clin Biomech (Bristol, Avon) 2007;22:59–66.
• Hou SM, Wang JL, Lin J. Mechanical strength, fatigue life, and failure analysis of two prototypes and five conventional tibial locking screws. J Orthop Trauma 2002;16:701–8.
• Taylor SJ, Walker PS, Perry JS, Cannon SR, Woledge R. The forces in the distal femur and the knee during walking and other activities measured by telemetry. J Arthroplasty 1998;13:428–37.
• Taylor SJ, Walker PS. Forces and moments telemetered from two distal femoral replacements during various activi- ties. J Biomech 2001;34:839–48.
• Noble PC, Alexander JW, Lindahl LJ, Yew DT, Granberry WM, Tullos HS. The anatomic basis of femoral compo- nent design. Clin Orthop Relat Res 1988;235:148–65.
• Rubin PJ, Leyvraz PF, Aubaniac JM, Argenson JN, Estève P, de Roguin B. The morphology of the proximal femur. A three-dimensional radiographic analysis. J Bone Joint Surg Br 1992;74:28–32.
• Umer M, Sepah YJ, Khan A, Wazir A, Ahmed M, Jawad MU. Morphology of the proximal femur in a Pakistani population. J Orthop Surg (Hong Kong) 2010;18:279– 81.
• Sen RK, Tripathy SK, Kumar R, Kumar A, Dhatt S, Dhil- lon MS, et al. Proximal femoral medullary canal diameters in Indians: correlation between anatomic, radiographic, and computed tomographic measurements. J Orthop Surg (Hong Kong) 2010;18:189–94.
• Lin J, Hou SM. Bending strength and holding power of a prototype tibial locking screw. Clin Orthop Relat Res 2002;403:232–9.
• Gaebler C, Stanzl-Tschegg S, Heinze G, Holper B, Milne T, Berger G, et al. Fatigue strength of locking screws and prototypes used in small-diameter tibial nails: a biome- chanical study. J Trauma 1999;47:379–84.
• Griffin LV, Harris RM, Zubak JJ. Fatigue strength of com- mon tibial intramedullary nail distal locking screws. J Or- thop Surg Res 2009;4:11.
• Hsu CC, Yongyut A, Chao CK, Lin J. Notch sensitivity of titanium causing contradictory effects on locked nails and screws. Med Eng Phys 2010;32:454–60.