Novel Ultrasound Anatomical Measurement of the Deep Transverse Metatarsal Ligament: An Intra-Rater Reliability and Inter-Rater Concordance Study

Insufficient space below the Deep Transverse Metatarsal Ligament (DTML) could be an etiological factor for Morton's Neuroma (MN). To date, there is a lack of studies measuring the space below the DTML. For this reason, this study assesses the intra- and inter-rater concordance and reproducibility of measurements of the space below the DTML between the third and the fourth metatarsal heads (M3 and M4) using ultrasound imaging to assess and verify the reliability and reproducibility of measurements of the space under the DTML. Forty feet from twenty patients were examined using ultrasound by three trained evaluators at two different times. The two measurements taken on each foot were: base (b)-distance between M3 and M4, and height (h)-distance between the DTML and the plantar skin surface. This was a quantitative, observational, analytical study. The concordance rate between observers for measurements of height and base were 98.5% and 99.5%, respectively. The mean area obtained of the space was 54.6 mm(2) and 57.2 mm(2) for both the left and right foot (p > 0.05). Reproducibility over time calculated in pre- and post-measurements showed an intraclass correlation coefficient of 1.00 (95%CI: 0.99-1.00), which leads us to conclude that the measurements are perfectly reproducible. Both measurements (height and base) of the space under the DTML, performed by ultrasound, are reliable and reproducible.