Biomechanical evaluation of interlocking lag screw design in intramedullary nailing of unstable pertrochanteric fractures

TY - JOUR

T1 - Biomechanical evaluation of interlocking lag screw design in intramedullary nailing of unstable pertrochanteric fractures

AU - Hoffmann, Stefanie

AU - Paetzold, Robert

AU - Stephan, Daniel

AU - Püschel, Klaus

AU - Buehren, Volker

AU - Augat, Peter

PY - 2013/9/1

Y1 - 2013/9/1

N2 - OBJECTIVES: Intramedullary nails with special lag screw designs may provide improved mechanical performance and alleviate clinical problems. We hypothesize that the proximal design of trochanteric nails affects mechanical performance.METHODS: Ten pairs of human cadaveric femora were implanted with 2 different short intramedullary nails without (Gamma3) and with an interlocking lag screw (Intertan). An unstable, multifragmentary, pertrochanteric fracture was created. Bones were tested in a cyclic testing protocol with increasing loads until failure simulating 1 leg stance. Stiffness, failure load, cycles to failure, and fracture gap movements were measured.RESULTS: Initially stiffness of the interlocking lag screw nail was almost 40% larger (P = 0.005) compared with the noninterlocking nail. During the test, the difference in stiffness gradually decreased. Failure load (13%, P = 0.02) and cycles to failure (18%, P = 0.02) were larger for the interlocking nail construct. Rotation and varus collapse of the head were initially up to 84% lower (P = 0.013) for the interlocking technique. During the test, the rate of rotational instability gradually increased for both techniques.CONCLUSIONS: The interlocking lag screw design reduced movement of the femoral head and relative movement between fracture fragments. Beyond that the trapezoidal nail design of the Intertan reduced toggling within the trochanteric area and prolonged survival. Although this study showed a decrease in the retention of stability over time, failure did not occur until the equivalent of 2-3 months of reduced physical activity in which healing may have occurred under normal clinical conditions.

AB - OBJECTIVES: Intramedullary nails with special lag screw designs may provide improved mechanical performance and alleviate clinical problems. We hypothesize that the proximal design of trochanteric nails affects mechanical performance.METHODS: Ten pairs of human cadaveric femora were implanted with 2 different short intramedullary nails without (Gamma3) and with an interlocking lag screw (Intertan). An unstable, multifragmentary, pertrochanteric fracture was created. Bones were tested in a cyclic testing protocol with increasing loads until failure simulating 1 leg stance. Stiffness, failure load, cycles to failure, and fracture gap movements were measured.RESULTS: Initially stiffness of the interlocking lag screw nail was almost 40% larger (P = 0.005) compared with the noninterlocking nail. During the test, the difference in stiffness gradually decreased. Failure load (13%, P = 0.02) and cycles to failure (18%, P = 0.02) were larger for the interlocking nail construct. Rotation and varus collapse of the head were initially up to 84% lower (P = 0.013) for the interlocking technique. During the test, the rate of rotational instability gradually increased for both techniques.CONCLUSIONS: The interlocking lag screw design reduced movement of the femoral head and relative movement between fracture fragments. Beyond that the trapezoidal nail design of the Intertan reduced toggling within the trochanteric area and prolonged survival. Although this study showed a decrease in the retention of stability over time, failure did not occur until the equivalent of 2-3 months of reduced physical activity in which healing may have occurred under normal clinical conditions.

KW - Adult

KW - Biomechanical Phenomena

KW - Bone Nails

KW - Bone Screws

KW - Cadaver

KW - Equipment Design

KW - Fracture Fixation, Intramedullary

KW - Hip Fractures

KW - Humans

KW - Male

KW - Materials Testing

KW - Middle Aged

KW - Weight-Bearing

U2 - 10.1097/BOT.0b013e3182a1f54b

DO - 10.1097/BOT.0b013e3182a1f54b

M3 - SCORING: Journal article

C2 - 23860133

VL - 27

SP - 483

EP - 490

JO - J ORTHOP TRAUMA

JF - J ORTHOP TRAUMA

SN - 0890-5339

IS - 9

ER -