Descriptive Quantitative Analysis of First Metatarsal Sagittal Plane Motion.

Evaluation of the sagittal plane motion of the first ray is a commonly accepted physical examination technique performed during the assessment and treatment of the hallux valgus deformity. Excessive or abnormal motion in this location, termed "hypermobility," has also traditionally been strongly associated with surgical decision-making and serves as a widely accepted indication for performance of the first metatarsal-medial cuneiform arthrodesis procedure. The objective of this investigation was to perform an analysis of first ray sagittal plane motion from a large population in order to determine the descriptive quantitative characteristics of the data set. First metatarsal sagittal plane motion was measured from a group of 149 subjects (298 feet) with a Klaue device. The mean total first metatarsal sagittal plane motion was 9.37 ± 2.39 mm (3.97-18.76). The data set was found to demonstrate many of the characteristics of a normally distributed population based on the histogram distribution, skewness (0.651), and kurtosis (0.761). No difference was observed between measurement of total sagittal plane motion between right and left feet (9.13 ± 2.37 mm vs 9.61 ± 2.40 mm; p = .081), nor between male and female subjects (9.29 ± 2.27 mm vs 9.58 ± 2.70 mm; p = .352). No substantial correlation was observed between total sagittal plane motion and subject age (Pearson correlation -0.053; p = .522). Results indicate that first ray sagittal plane motion might be best considered as a continuous variable as opposed to categorical variable, and might help objectify the difference between "normal" and "abnormal" motion.