Anterior variable-angle locked plating of complex patella fractures - Does the type of polar screw matter?

Background: Treatment of complex patella fractures represents a challenging clinical problem. Whereas controversy exists regarding the most appropriate fixation method, anterior plating is an emerging treatment option. A novel design of anterior variable-angle locking plates features radiating legs with integrated screw holes aiming at capturing fragments of the distal comminuted zone via either a locking or a cortical polar screw. The aim of this study was to compare the biomechanical performance of the novel anterior variable-angle locking plates used for fixation of complex patella fractures with either a locking or a cortical polar screw. Methods: Complex five-part AO/OTA 34-C3 patella fractures mimicking comminution around the distal pole were simulated in twelve human cadaveric knees. Specimens were randomized to two groups for treatment with an anterior variable-angle locking plate fixing the patella with either one locking or one cortical caudo-cranial bicortical polar screw. Biomechanical testing was performed over 5000 cycles by pulling on the quadriceps tendon, simulating active knee extension and passive flexion within the range from 90 degrees flexion to full extension. Interfragmentary movements were captured by motion tracking. Findings: No significant differences between the two fixation techniques were detected in terms of longitudinal and shear articular displacements, and relative rotations around the mediolateral axis measured between the proximal and distal fragments at the central patella aspect between 1000 and 5000 cycles, P >= 0.116. Interpretation: From a biomechanical perspective, anterior locked plating of complex patella fractures provides comparable fixation stability when using either a locking or a cortical polar screw.