Comparison of 30° and 70° arthroscopes in canine hip arthroscopy: a 3D-printed model study

Hip arthroscopy is a valuable diagnostic and surgical tool in veterinary medicine; however, the optimal arthroscope viewing angle for the canine coxofemoral joint has not been established. We hypothesised that a 70° arthroscope would provide superior visualisation of the hip joint cavity compared to the standard 30° arthroscope when inserted via a dorso-lateral approach. To test this hypothesis, five 3D-printed canine hip joint models were developed using computed tomography (CT) scans of large-breed dogs. The articular surfaces were embossed with a 1 × 1 mm checkerboard pattern to enable objective quantification of the visible area. Arthroscopy was performed with 2.7-mm-diameter 30° and 70° arthroscopes at four positions (3, 6, 9, and 12 o'clock), and the visible area was calculated by counting visible tiles. Statistical analysis was performed using a mixed-effect general linear model. There was no significant overall difference in the visible area between the two arthroscope viewing angles (P = 0.977). However, arthroscope position significantly affected the visible area (P < 0.001), and a significant interaction between viewing angle and position was identified (P = 0.001). Notably, the visible area produced by the 70° arthroscope was significantly smaller than that produced by the 30° arthroscope at the 12 o'clock position (P = 0.026). However, at the 3 o'clock position, the visible area produced by the 70° arthroscope appeared to be larger than that produced by the 30° arthroscope. Nevertheless, this difference was not significant (P = 0.085). The results suggest that, in this experimental model, the 70° arthroscope provided a comparable overall visible area of the artificial hip joint surface to the 30° arthroscope during dorso-lateral canine hip arthroscopy. Further comparative studies, particularly on calibrated cadaveric hip joints, are required.