| Summary: | Category: Bunion, Midfoot/Forefoot Introduction/Purpose: Hypermobility of the first ray is related to problems such as transfer metatarsalgia and painful callosity. Methods to assess this condition have different advantages and disadvantages. Ultrasound, in addition to providing real time, dynamic imaging and allowing for patient interaction, can be used to evaluate first ray hypermobility. However, there have been no studies specifically investigating the accuracy of ultrasound evaluation of hypermobility of the first ray. The aim of this study was to determine the accuracy of ultrasound in diagnosis and evaluation of first ray hypermobility and to compare the results with diagnosis and evaluation using the Klaue device. Methods: The baseline characteristics and radiographic parameters of twenty-eight hallux valgus patients (56 feet) were determined. Hypermobility of the first ray was assessed using both a Klaue device and ultrasound. Subjects were classified into two groups: normal mobility and hypermobility. Hypermobility in this study was defined as a translation of > 9.3 mm as measured with a Klaue device. Sonographic evaluation, including dorsal translation, plantar gapping, and medial gapping of the first metatarsal cuneiform joint, was accomplished and compared to measurements made with a Klaue device. A Paired-Student’s t-test was used to identify significant differences in baseline data between patients with and without hypermobility and patient with and without symptoms. Logistic regression was used to analyze ultrasound parameters and to find a cut-off point to define hypermobility. Results: Significant differences in foot width and hallux valgus angle were found between the normal mobility and hypermobility groups. The cut-off points for each ultrasound parameter to diagnose hypermobility of the first ray were determined to be = 1 mm increase in dorsal translation (sensitivity= 76.47%, specificity= 72.72%) or = 1 mm increase in medial gapping (sensitivity= 50%, specificity= 90%) and = 0.8 mm increase in plantar gapping of the first metatarsocuneiform joint (sensitivity= 75.75%, specificity= 39.13%). When we used = 1 mm increase in dorsal translation together with = 0.8 mm medial gapping to diagnose hypermobility of the first ray, we found that accuracy improved (sensitivity= 72.72%, specificity= 88.88%, PPV=88.88%, NPV=72.27%). Our cut- off point ultrasound parameters reliant on baseline Klaue device measurement. Conclusion: In conclusion, these three sonographic parameters have acceptable power to identify hypermobility as represented by the area under ROC curve. The assessment of hypermobility of the first ray is possible using ultrasound. Hypermobility of first ray should be suspected if there is = 1 mm increase in dorsal translation, = 1 mm increase in medial gapping, and = 0.8 mm increase in plantar gapping of the first metatarsocuneiform joint. The ultrasound technique using three parameters of first ray motion in the vertical and horizontal planes provides increased accuracy for first ray mobility assessment.
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