Abstract Purpose To compare intraoperative and postoperative posterior tibial slope (PTS) measurements and determine whether unintended postoperative changes occur relative to preoperative values. Methods A total of 79 patients (81 knees) underwent open‐wedge high tibial osteotomy (owHTO) using patient‐specific instrumentation (PSI) for varus malalignment were included. PTS was assessed pre, intra and postoperatively on short lateral knee radiographs using standardised calibrated software. The hip‐knee‐ankle angle (HKA) and the medial proximal tibia angle (MPTA) were measured pre and postoperatively on weight‐bearing long leg radiographs (LLR). Results Preoperative (10.3° 7.3−11.7°) and intraoperative (9.1° 6.7–11.2°) PTS measurements were significantly lower than postoperative (10.8° 8.5–13.3°) values ( p < 0.001). Intraoperative PTS was also significantly lower than the preoperative one (9.1° 6.7–11.2° vs. 10.3° 7.3−11.7°) ( p < 0.01). Intraoperative PTS underestimated the postoperative PTS by a mean of 1.8° (95% CI: −2.1° to – 1.5°). Both HKA and MPTA changed significantly postoperatively (−7.4 ± 3.8° vs. 0.4 ± 2.6° p < 0.001, 84.4 ± 2.8° vs. 91.0 ± 2.8° p < 0.001). Conclusion Intraoperative PTS measurements significantly underestimated postoperative PTS, by a mean of 1.8°, indicating that visual intraoperative assessment based on fluoroscopy should be interpreted with caution when used to evaluate postoperative PTS. Level of Evidence Level IV.
Neopoulos et al. (Wed,) studied this question.