Background: Although radiographic measurements are used in multiple epiphyseal dysplasia (MED) during correction of lower-limb alignment, the reliabilities of the measurements are unclear.
Questions/purposes: We determined interobserver and intraobserver reliabilities of the measurement methods used in evaluation of lower-limb alignment in MED.
Methods: After consensus building, we included 10 radiographic measurement methods widely used to evaluate lower-limb alignment: mechanical tibiofemoral angle, anatomic tibiofemoral angle, mechanical axis deviation, joint line convergence angle, mechanical lateral distal femoral angle, anatomic lateral distal femoral angle, mechanical medial proximal tibial angle, anatomic medial proximal tibial angle, epimetaphyseal angle, and tibial metadiaphyseal angle. A study group consisting of 30 patients with MED was compared with a control group consisting of 30 sex- and age-matched patients with genu varum and genu valgum. Mean age in both groups was 11 years (study group: SD, 2 years; range, 6-16 years; control group: SD, 2 years; range, 6-15 years). Interobserver and intraobserver reliabilities of all radiographic measurement methods were obtained and expressed by intraclass correlation coefficients (ICCs).
Results: Mechanical tibiofemoral angle, anatomic tibiofemoral angle, and mechanical axis deviation were associated with high interobserver reliability (ICCs, 0.987, 0.985 and 0.982, respectively). Epimetaphyseal angle had the lowest reliability (ICC, 0.280). Intraobserver reliability exhibited similar trends, with mechanical axis deviation and mechanical tibiofemoral angle having the highest ICCs and epimetaphyseal angle the lowest.
Conclusions: Mechanical tibiofemoral angle, anatomic tibiofemoral angle, and mechanical axis deviation are reasonably reliable measures of alignment in MED. The lateral distal femoral angle and medial proximal tibial angle (mechanical and anatomic) can be used as complementary measurement methods.
Level of evidence: Level II, diagnostic study. See Instructions for Authors for a complete description of levels of evidence.