Mechanical Analysis and Clinical Application of Butterfly-Shaped Patellar Claw

Memory alloy patella claws for treating patella fractures have been used for more than 30 years with many desirable features including fast healing, quick recovery, and avoidance of top abrasion of Kirschner wires and other complications. However, there are many models and it is difficult to choose the accurate claw for the patient. In this study, a finite element model of the butterfly-shaped patellar claw made of shape memory alloy was established, its mechanical structure was analyzed, and its clinical application was monitored. We used Solidworks Simulation software for modeling and mainly analyzed the force of the compression ring of the butterfly-shaped patellar claw. Clinically, we chose a closed fresh patella fracture case. After finite element analysis, the maximum stress that the compression ring of the butterfly-shaped patellar claw can withstand is 568.1 MPa. In this range, it always has elastic deformation resistance. The butterfly-shaped patella claw is fixed on the patella and will not break when subjected to a maximum force of 150 N on the encircling arm, and at the same time, there will be no pressure failure due to plastic deformation. A total of 27 cases were clinically used for the assessment of the clinical efficacy of the newly designed butterfly-shaped patella claws. The average follow-up time was 15.5 months, and the average fracture healing time was 8-12 weeks. All patients can get out of bed with crutches within 2 to 3 days after surgery. Among them, there were 15 cases with excellent functional ratings, 10 cases with good ratings, 2 cases with acceptable ratings, and no cases with poor ratings. The designed butterfly-shaped patella claws can provide an effective method for the treatment of patella fractures.