REPRODUCIBILITY OF THE BASIC X-RAY PARAMETERS OF LOWER EXTREMITY DEFORMATIONS IN CHILDREN WITH SKELETAL DYSPLASIA

Introduction: axial deformities in the lower extremities of children lead to an uneven distribution of the load in different compartments of the knee joint, which can contribute to the development of osteoarthritis. Regardless of the cause of their occurrence, the main goal of treatment is the restoration of the mechanical axis. Various calculation methods are used to determine the amount of deformity, its apex and the degree of required correction. The aim: to evaluate the reproducibility of the basic X-ray parameters characterizing the deformities of the lower extremities in the frontal plane in children with skeletal dysplasia based on the calculation of inter-rater reliability.

Materials and methods: the article presents calculations of the main angulometric parameters of the knee joint (deviation of the mechanical axis — MAD, distal mechanical angle of the femur — mLDFA, proximal angle of the tibia — MPTA) in 18 patients with skeletal dysplasia (30 lower extremities) that had axial deformities of the lower extremities in the frontal plane at the level of the knee joint. The control group included the results of similar calculations of the angulometric parameters in 19 children (30 lower extremities) with valgus and varus deformities of the knee joint without skeletal dysplasia (idiopathic axial deformations, posttraumatic deformities, malformations of the lower limbs). The estimation of inter-expert reliability was made in the SPSSv. 23.

Results: the analysis demonstrated that calculation of reference parameters in children without primary lesion of the growth plate has a high degree of inter-rater reliability: an intra-class correlation coefficient with a 95% confidence interval (ICC [95% CI]) when calculating the reference angles of mMPTA and mLDFA was 0.981% [0.971–0.991] and 0.993% [0.989–0.997] respectively, for MAD 0.996% [0.993–0.998]. When calculating the same parameters in children with skeletal dysplasia, the results differed. Thus, the intra-class correlation coefficient for the deviation of the mechanical axis was 0.861% [0.763–0.926] (which corresponds to the normal reproducibility of this parameter), for mMPTA — 0.586% [0.295–0.781], for mLDFA — 0.796% [0.653–0.892]. This indicates a low reproducibility and may lead to errors in the planning of correction of axial deformities of the lower limbs in children with skeletal dysplasia.

Conclusion: when calculating the severity of axial deformities in the lower extremities in children with skeletal dysplasia, the most reproducible parameter is the determination of the deviation of the mechanical axis of the lower extremities as compared to the studied angulometric methods.