Novel screw-cable integrated system(SCIS) for minimally invasive treatment of patella transverse fractures: a finite element analysis

BACKGROUND: The most recommended method for treating transverse patella fractures is modified tension band wiring (MTBW). However, the optimal instrument for use with MTBW is still undetermined. Hence, we aimed to design a novel screw-cable integrated system (SCIS) and compare its biomechanical characteristics with Kirschner-wire, SCIS, and Cable-Pin systems in treating transverse patellar fracture. METHODS: A finite-element (FE) model of transverse patella fracture was created. The fracture model was fixed with either K-wire, SCIS, or Cable-pin. Different tension force loading (400 N and 800 N), direction(0° and 45°), and screw or K-wire depth(5 mm and 10 mm) were set. The maximum displacement of the fragment and maximum gap opening were measured by using FE analysis. RESULTS: Compared with the K-wire and Cable-pin system, SCIS increased the stability of the fractured patella by reducing fragment displacement and gap opening. Under 400 N loading in the direction 45°, SCIS with screw placing at 5-mm depth reduced the maximum fragment displacement (0.43 mm) by 49.62% and 26%, respectively, compared with the K-wire (0.22 mm) and Cable-pin (0. 22 mm) group. Meanwhile, the gap opening in SCIS (0.05 mm) was reduced by 83% and 59.8% (0.05 to 0.18) compared with the K-wire (0.30 mm) and Cable-pin (0.18 mm) group. CONCLUSION: SCIS demonstrated improved biomechanical stability for treating transverse patellar fractures compared to MTBW with Kirschner wire and the Cable-Pin system. Finite element analysis showed SCIS substantially reduced fracture fragment displacement and gap opening under various loading conditions.