Do Patients’ Perceptions of Leg Length Correlate with Standing 2- and 3-dimensional Radiographic Imaging?

Abstract Background This study compared two- and three-dimensional (2D and 3D) radiographic measurements of anatomical and functional leg length and knee coronal and sagittal alignments, and correlated these measurements with patients’ leg-length perceptions. Methods Patients without symptomatic spinal pathology, previous surgery of the spine and lower extremities (140 lower extremities) were evaluated on EOS® images obtained in standing position. Numerous measurements of each limb were compared to the contralateral limb. All 2D/3D measures were evaluated and compared for repeatability and reproducibility. Results Mean 2D functional and anatomical lengths were 78.7 cm (64.7-88.4, CI 95%: 77.4-80) and 78.3 cm (64.9-87.9, CI 95%: 77-79.6), respectively. Mean 3D functional and anatomical lengths were 78.9 cm (65.1-88.7, CI 95%: 77.6-80.2) and 78.9 cm (65.6-88.3, CI 95%: 77.8-80.5), respectively (p < 0.001). Mean 2D and 3D knee varus/valgus angles were -1.9 ° (-26.4-9.1, CI 95%: -3.5 to -0.7) and -0.9 ° (-19.2-11.8, CI 95%: -2.4-0.2), respectively (p = 0.004). Multiple regression analysis found that patients with >10° of flexum/recurvatum were 2.1× more likely to perceive unequal length (p < 0.1). Patients with irreducible varus/valgus knee deformity were 4× more likely to perceive unequal length (p < 0.04). Conclusions EOS® imaging allows more accurate assessment of anatomical and functional lengths. Patients’ perceptions of lower extremity length may correlate more closely with coronal and sagittal alignments of the knee than with femoral or tibial length. This study highlights the importance of physical examination of all the joints and 3D measurements in functional standing position.