Abstract
ObjectiveWhen a hip screw needs to be changed, choosing between the conventional (C-type) and helical blade (H-type) types is difficult. In this biomechanical study, we compared these two screw types relative to the type of the initial screw used.MethodsC- or H-type screws were inserted (leading screw) in three types of polyurethane bone models (Sawbone, Pacific Research Laboratories, Inc., Washington, USA: 130 × 180 × 40 mm) of different bone mineral densities (pounds per cubic feet [PCF] 5, 80 kg/m3; PCF 10, 160 kg/m3; and PCF 15, 240 kg/m3), and then successively or alternately inserted (following screw) after the leading screw removal. An original model (original C and H) of a leading screw without removal was created as a control. The strengths of resistance to pullout (PO) and rotational stress were measured. For each experimental condition, there were 30 experimental models.ResultsThe original C screw was superior in PO strength, and the original H-type screw was superior in rotational strength. When the C- or H-type screw was the leading screw, using the C-type screw again as the following screw (C1-C2, H1-C2) showed the greatest resistance to PO, and using the H-type screw as the following screw (C1-H2, H1-H2) showed superior resistance to rotational strength. However, the rotational strength of the C2 screw decreased by more than 50% compared with that of the original C screw. Moreover, the PO and rotational strengths of the H2 screw decreased to less than 30% overall compared with those of the original H screw.ConclusionThe H-type screw should be used for second-time screw insertion procedures in cases where it is difficult to choose between PO and rotational strengths.
Highlights
Femoral intertrochanteric fractures (IT Intertrochanteric fractures (Fx)) are representative osteoporotic fractures in elderly patients, and their incidence has markedly increased in aging societies [1]
The representative types of hip screws inserted into the femoral head in the nail system for hip (NSH) system are the conventional-type (C-type) and helical blade-type (H-type) screw; the most stable insertion site is the center-center of the femoral head [3]
In specific conditions, such as when the femoral head bone defect is small and the bone quality is adequate for reinserting the hip screw, a method of attempting osteosynthesis is by replacing the NSH system currently in place while replacing the length of the intramedullary nail
Summary
Femoral intertrochanteric fractures (IT Fx) are representative osteoporotic fractures in elderly patients, and their incidence has markedly increased in aging societies [1]. Osteosynthesis revisional surgery through open reduction and internal fixation preserves the native femoral head; plates with 95° blades are useful when they target bone in the inferior portion of femoral heads that have not been violated by prior fixation devices [9]. In specific conditions, such as when the femoral head bone defect is small and the bone quality is adequate for reinserting the hip screw, a method of attempting osteosynthesis is by replacing the NSH system currently in place while replacing the length of the intramedullary nail. In this biomechanical study, we attempted to determine the best screw type to use in second-time insertions in relation to the original type, by comparing C (trochanteric gamma 3 locking nail) and H (PFN antirotation) type screws in a polyurethane synthetic bone model
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