Subtalar Arthroereisis with Calcaneus Stop Screws-Can the Angles on Pre- and Post-Surgical X-Ray Images Be Reliably Measured by Artificial Intelligence?

Background/Objectives: Flexible symptomatic flat foot in children can be surgically treated with calcaneus stop screws. This raises the question of whether pre- and postoperative radiographs (X-ray) can be analyzed in two planes using AI. Methods: In this monocentric retrospective study, angle measurements generated by Bone Metrics AI (Gleamer) were compared with manual measurements using Centricity™ (GE Healthcare). A total of 659 X-rays from 124 operated feet (2014-2024) were available, of which 422 were analyzable by AI and 299 met defined quality criteria. Bland-Altman plots were used to assess agreement. Linear and logistic regression analysis examined the influence of age, gender, accessory navicular bone, additional foot pathologies, and flat foot severity on comparability of the measurement methods and measurability by the AI. Finally, radiographs meeting and missing quality criteria were compared. Results: AI measurements were comparable to manual measurements for calcaneus inclination, hallux valgus, 1st-2nd and 1st-5th metatarsal angle both pre- and post-operatively. For the talus-1st metatarsal and medial arch angles, AI results differed significantly (p < 0.001 and p ≤ 0.013) from manual measurement. AI generated talus-1st metatarsal angle was measured larger by 6.14°, 95% [-7.14; -5.14] pre-operatively and 2.80°, 95% [-3.79; -1.81] post-operatively. Medial arch angle was smaller by 1.63° pre-operatively, 95% [1.03; 2.23] and 0.52° post-operatively, 95% CI [0.11; 0.93] with AI. Post-operative measurability was not significantly lower than pre-operative. AI measured angles on incorrectly taken radiographs as often or more often than on correctly taken ones. Discussion: Screw implantation did not negatively impair measurability or AI accuracy. However, age, gender, and flat foot severity influenced AI performance. Bad radiograph quality did not affect AI measurability negatively, indicating that AI cannot yet distinguish between X-rays suitable and unsuitable for angle measurements. Conclusions: Manual measurements are still indispensable in the diagnosis of children's flat feet. In the future, continuous training of the AI is expected to bring it into line with manually measured radiological values.