Objective To compare the stability of patellar transverse fracture model fixed by hollow screw combined with “8” and “0” tension band wire fixation systems by finite element analysis (FEA). Methods Computerized tomography (CT) images were acquired from a 48-year-old healthy male volunteer. A geometric model of patella was firstly built in the computer-aided design (CAD) system, and then imported into the Ansys system. The finite element model of patellar was built without the soft tissue and cartilage. Patellar transverse fracture model was created by intersecting the patella on the median transverse section. The proximal end of the patella was fixed and tractive force was loaded on the distal end of the patella. The models were set in the condition of 90° knee flexion during non-weight-bearing extension with the middle part of the patellar articular surface contacting to a cartilage-covered distal femur. Results When the patella transverse fracture was fixed with “8” or “0” tension band wire fixation system, under distraction force of 200 N, the maximum relative displacement of screws were 0.32 mm and 0.20 mm, that of wires were 0.36 mm and 0.21mm and that of patella were 0.35 mm and 0.22 mm, respectively. The maximum equivalent stress of screws were 778.01 Mpa and 941.88 Mpa, that of wires were 311.51 Mpa and 336.24 Mpa, and that of patella was 3.81 Mpa and 3.66 MPa, respectively. Stress concentration was observed in screws and wires in both groups. Conclusions When combined with hollow screw in the treatment of patellar transverse fracture, the “0” tension band wire fixation system is more stable than the “8” fixation system based on FEA.
Key words
Patella fracture; /
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Tension band wire fixation system; /
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Finite element analysis
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