Linguistics

Engineering

Philosophy

Olecranon

Materials science

Stress (linguistics)

Patella fracture

Displacement (psychology)

Surgery

Transverse plane

Finite element method

Psychology

Anatomy

Elbow

Tension band wiring

Psychotherapist

Internal fixation

Patella

Sagittal plane

Composite material

Orthodontics

Structural engineering

Compression (physics)

Fracture (geology)

Medicine

Tension (geology)

Kirschner wire

Journal of Orthopaedic Surgery and Research

The position of Kirschner wires (K-wires) has an influence on the outcome of modified tension-band wiring (MTBW) in fixing patella fractures. However, the instruction for K-wires positioning is not clear enough. This study tried to clarify the effect of K-wires positioning and provide evidence for a more definite instruction.The sagittal position (SP) suitable for placing K-wires was evenly divided into SP 1-5 from anterior to posterior, and the finite element models of midpatella transverse fractures fixed by the figure-of-eight or figure-of-zero MTBW were built up at each SP. Separating displacement of the fracture, stress of the fracture, and stress of the internal fixations were measured at 45° knee flexion by using finite element analysis.The separating displacement of the fracture was smaller at SP 3-5 (23% smaller than SP 1-2). From SP 1 to 5, the compression of the fracture surfaces increased (R = 0.99, P = 0.001); the improper stress area of the fracture surfaces decreased (R = - 0.96, P = 0.01), and so was the stress of K-wires (R = - 0.93, P = 0.02). However, the stress of stainless steel wires showed a stable trend.The SP of K-wires plays a role in the function of MTBW in the surgical management of transverse patella fracture. At 45° knee flexion, posteriorly placed (close to the articular surface) K-wires enable optimal stability and stress for the fracture, which provides basis for the positioning of K-wires in clinical practice.

Where should Kirschner wires be placed when fixing patella fracture with modified tension-band wiring? A finite element analysis