Modified anteromedial and anterolateral elbow arthroscopy portals show superiority to standard portals in guiding arthroscopic radial head screw fixation.

PURPOSE: Arthroscopic fixation of radial head radial head fractures is an appealing alternative to open reduction and internal fixation, which presents the advantage of minimal surgical trauma. The aim of this study was to evaluate if modifications to the standard anteromedial (AM) and anterolateral (AL) portals could allow screw placement for radial head fracture osteosynthesis closer to the plane of the radial head articular surface. METHODS: Eight fresh-frozen specimens were prepared to mimic arthroscopic setting. Standard AL (ALst) and AM (AMst) and distal AL (ALdi) and AM (AMdi) portals were established. Eleven independent examiners were asked to indicate the optimal trajectory, when aiming to place a cannulated screw parallel to the radial head surface for radial head osteosynthesis. A three-dimensional digital protractor was used to measure the angle between the indicated position and a Kirschner wire placed parallel to the radial head articular surface (α). The Shapiro-Wilk normality test was used to evaluate the normal distribution of the samples. Means, standard deviations, and 95% confidence intervals (95% CI) were calculated for each portal. A coefficient of variation (CoV) was calculated to determine agreement among observers and intra-observer variability. RESULTS: Mean α angles were 25.1 ± 11.5° for AMst, 13.8 ± 4.8° for AMdi, 17.1 ± 13.4° for ALst, -2.6 ± 9.2° for ALdi. No overlapping in the 95% CI of ipsilateral standard and distal portals was observed, indicating that the difference between these means was statistically significant. The distal portals showed smaller inter-observer CoV as compared to the standard ones (AMst: 10.0%; AMdi: 4.6%; ALst: 12.5%; ALdi: 10.6%). Intra-observer CoV was similar for all portals (AMst: 5.5%; AMdi: 6.1%; ALst: 7.7%; ALdi: 7.1%). CONCLUSIONS: The use of distal AM and AL portals permits to obtain α angles closer to the radial head articular surface than standard AM and AL portals. This is expected to allow screw placement in a flatter trajectory, which should correlate with a superior biomechanical performance of fixation. Good reproducibility of Kirschner wire placement from distal portals was observer among different examiners. Modifications to the standard AM and AL elbow arthroscopy portals allow to place screws for radial head fracture osteosynthesis in a position which should guarantee superior biomechanical performance of fixation.