Background The aim of this study was to investigate the biomechanical performance of novel anterior variable-angle locking plates versus tension band wiring used for fixation of simple and complex patella fractures. Methods Sixteen pairs of human cadaveric knees were used to simulate two-part simple transverse AO/OTA 34-C1 and five-part complex AO/OTA 34-C3 patella fractures. The complex fracture pattern was characterized with a medial and a lateral proximal fragment, together with an inferomedial, an inferolateral and an inferior fragment mimicking comminution around the distal patella pole. Eight pairs with simple fractures were split for fixation via either tension band wiring (TBW) through two parallel cannulated screws or anterior variable-angle locked plating, whereas other eight pairs with complex fractures were split for either TBW through two parallel cannulated screws plus circumferential cerclage wiring, or anterior variable-angle locked plating using a cortical caudo-cranial polar screw. Each specimen was tested over 5000 cycles with a range of motion from 90° flexion to full extension by pulling on the quadriceps tendon. Interfragmentary movements were captured by motion tracking. Results For both fracture types, the longitudinal and shear articular displacements, measured between the proximal and distal fragments at the central patella aspect between 1000 and 5000 cycles, together with the relative rotations of these fragments around the mediolateral axis were all significantly smaller following anterior variable-angle locked plating versus TBW, p ≤ 0.01. Conclusions From a biomechanical perspective, anterior locked plating of both simple and complex patella fractures resulted in less interfragmentary displacement under extended cyclic loading.

Treatment of simple and complex patella fractures represents a challenging clinical problem. Controversy exists regarding the most appropriate fixation method. Tension band wiring, aiming to convert the pulling forces on the anterior aspect of the patella into compression forces across the fracture site, is the standard of care, however, it is associated with high complication rates. Recently, anterior variable-angle locking plates have been developed for treatment of simple and comminuted patella fractures. The aim of this study was to investigate the biomechanical performance of the novel anterior variable-angle locking plates versus tension band wiring used for fixation of simple and complex patella fractures.Sixteen pairs of human cadaveric knees were used to simulate either two-part transverse simple AO/OTA 34-C1 or five-part complex AO/OTA 34-C3 patella fractures by means of osteotomies, with each fracture model created in eight pairs. The complex fracture pattern was characterized with a medial and a lateral proximal fragment, together with an inferomedial, an inferolateral and an inferior fragment mimicking comminution around the distal patellar pole. The specimens with simple fractures were pairwise assigned for fixation with either tension band wiring through two parallel cannulated screws, or an anterior variable-angle locking core plate. The knees with complex fractures were pairwise treated with either tension band wiring through two parallel cannulated screws plus circumferential cerclage wiring, or an anterior variable-angle locking three-hole plate. Each specimen was tested over 5000 cycles by pulling on the quadriceps tendon, simulating active knee extension and passive knee flexion within the range from 90° flexion to full knee extension. Interfragmentary movements were captured by motion tracking.For both fracture types, the articular displacements, measured between the proximal and distal fragments at the central aspect of the patella between 1000 and 5000 cycles, together with the relative rotations of these fragments around the mediolateral axis were all significantly smaller following the anterior variable-angle locked plating compared with the tension band wiring, p < 0.01From a biomechanical perspective, anterior locked plating of both simple and complex patella fractures provides superior construct stability versus tension band wiring.