Prospective video-based analysis of coronal lower limb alignment may be as accurate as radiography in children

Temporary hemiepiphysiodesis is a growth-guided surgical technique to address lower limb malalignment in children with remaining growth potential. It is a minimally invasive approach that relies on full standing radiography of the lower limb, resulting in exposure to ionizing radiation. Radiation-free, video-based alternative techniques have recently evolved which seem to have potential to be applied in clinical pathways, but they are still very expensive and have a complex setup.In this prospective pilot study, a low budget and uncomplicated method to assess malalignment of the lower limb was compared to radiologic measurements in 40 children aged from 8 to 16 years with idiopathic genu varum or valgum. Dynamic and static video-based assessments of the children were conducted, during their routine visits provided they had undergone full standing radiographs of the lower limb. Measurements of the primary (HKA = hip-knee angle) and secondary knee angles (e.g. medial proximal tibia angle) were compared. It was observed that the video-based hip-knee-ankle angle correlated very closely with radiographic values, as well as a significant positive correlation (p < 0.001) between all techniques (radiographic/dynamic/static). Moreover, the HKA measurements revealed excellent to high inter- and intrarater reliability.Concerning the HKA, this low-budget technique may represent a reliable alternative for longitudinal evaluation of lower limb malalignment in children. Considering the measurement errors in video-based analyses, it may be suggested that radiographic follow-up is only indicated until the target HKA approximates 2°. In summary, this novel technique has the potential to be the first step towards implementing radiation-free setups within clinical routine to evaluate lower limb malalignment. Future studies will need to determine whether the reliability and quality of video-based techniques are high enough to guide operative decision making.