How Reliable Are The Threaded Locking Screws?

Abstract

To avoid locking screw deformation, high threaded screws must not be used as locking screws. In cases of unreliable patients, 5-mm low threaded screws should not be used in the nailing of comminuted or oblique femur shaft fractures. All 5-mm unthreaded screws and 5.5-mm low threaded stainless steel screws can be used safely in full weight-bearing conditions of unreliable patients.

Tibia Intramedüller Çivileme Sisteminde Proksimal Kilitleme Vidalarının Dirençlerinin Karşılaştırılması: Biyomekanik Çalışma

“…The same experimental design was used by many researches with polyethylene tube [7][8][9], aluminium tube [13] -12] to obtain yield strength and yield point. With the polyethylene tube and aluminium tube to obtain true yield point was not likely as it was unreliable if the deformation that appears on the stress-strain graph belonged to polyethylene tube and its holes deformations or the locking screw deformation itself [10][11][12].…”

“…It was stated that the stress on 1-mm deformation was defined as "yielding strength" instead of "true yield point [7-9, 14, 15]. It was concluded that due to the trapping of screws within the tube holes, the diameter of the metal tube hole must be 7 mm in order to clearly determine the true yield point [10][11][12].…”

“…Then we calculated the inner and outer diameter of the stainless steel tube used in the experiment. We used a stainless steel tube (inner diameter of 34 mm, outer diameter 39 mm and 420 mm in length) that represented the level of proximal tibia, like the same test system used by previous studies [7][8][9][10][11][12]. 18 mm below of the stainless steel tube upper tip were two opposite holes in diameters of 7 mm.…”

“…On the tibia interlocking nail there is one proximal locking screw oblong hole 6,5 mm in diameter and 16 mm in length. The tibia interlocking nail was supported from its proximal and distal part by two metal ring shaped devices that don't allow movement of the nail to sides on the stainless tube [10][11][12]. Metal rings had external diameter of 32 mm and internal diameter of 14 mm and were 12 mm high simulating the cross sectional area of a standart tibia.…”

“…The screws passed through the metal tube holes of 7 mm diameter and proximal locking screw oblong hole of the tibia nail. The speed of loading on 3 -point bending tests was 1 mm/ minute resampling previous studies [7][8][9][10][11][12]. Loading was conducted from the upper tip of the tibia nail by axial compression machine ( Figure 2).…”