Comparative study between fixed-angle and polyaxial screws in distal radius fixation with two volar locking plates

Abstract

IntroductionWhen treating a distal radius fracture with a volar locking plate (VLP), numerous plate-screw designs are available. To date, there is not a screw fastening system with a clear superiority among the others. HypotesisFixed-angle screws are superior to polyaxial screws in distal radius VLP fixation with respect to screw protrusion and reduction preservation. Material and methodsA prospective cohort study based on eighty patients was performed. The first forty patients were treated by polyaxial VLP (PA group) were the next forty by a fixed-angle VLP (FA group). Fixation was performed by the flexor carpi radialis approach. Screws were placed 2mm shorter than actual measurement and intraoperative AP, lateral and tilt wrist views were done routinely. A computed tomography (CT) was conducted searching for screw protrusion. Loss of reduction was calculated from the difference between post-operative x-rays values and those at the 6-month follow-up. The total follow-up was 12 months with no losses. ResultsPostoperative CT detected dorsal screw protrusion in 17 patients in PA group and 16 patients in FA group that intraoperative radiographs were assumed as correct (p=0.48). The mean invasion of dorsal cortex was of 2.2mm (1–7mm) for PA group and 2.6mm (1–5mm) for FA group (p=0.70). As from those protruding screws, the mean size was registered founding that fixed-angle screws had protrusions with shorter screws 20 vs. 22mm (p<0.05). Intraarticular screw protrusion was registered in 3 and 2 patients respectively (p>1.0). Experienced loss of reduction in volar tilt (p=0.42), radial inclination (p=0.75) and ulnar variance (p=0.83) were equivalent in both groups while a better preservation of the radial height in the PA group was observed (p<0.05). DiscussionsIn terms of screw protrusion rate, both fastening systems where similar. However, fixed-angle group invaded the dorsal cortex with shorter screws. Polyaxial screws were associated with a better preservation of the radial height. Finally, this study reinforces the idea that dorsal and articular screw protrusion is more frequent than we expected. Level of evidenceII; therapeutic, prospective cohort study.