To elucidate the relationship between changes in the mechanical properties of the tibialis anterior tendon and deformity in patients with hallux valgus, a case-control study is planned to quantitatively measure tendon stiffness using shear-wave elastography (SWE). Two groups will be compared: adults with radiographically confirmed hallux valgus (HVA (Hallux valgus angle) ≥15°) and age- and gender-matched healthy controls. The primary outcome is the elasticity modulus of the tibialis anterior tendon measured by SWE (kPa). Measurements will be performed using a high-frequency linear probe, with the probe positioned parallel to the tendon fibers and the foot in the standard ankle position, with three repetitions performed on each subject; the mean of stable frames will be used in the analysis. Secondary variables will be the relationships between tendon thickness/cross-sectional area, clinical angle parameters (HVA, IMA (intermetatarsal angle)), and functional scores. In the reliability sub-study, intra- and inter-observer ICC (Intraclass Correlation Coefficient), SEM (Standard Error of Measurement), and MDC (Minimal Detectable Change) will be calculated.

The sample size was calculated for a two-sample, two-tailed t-test with α=0.05 and 80% power assumptions, targeting a clinically meaningful medium-to-high effect size (Cohen d=0.60); at least 45 patients (45 with hallux valgus + 45 healthy) were planned. Parametric/non-parametric tests appropriate for the distribution and ANCOVA for potential confounders (age, gender, BMI, foot dominance) will be used in the analyses. The study is expected to objectively demonstrate whether tibialis anterior tendon stiffness changes in hallux valgus, thereby clarifying the muscle-tendon contributions to pathomechanics and laying the groundwork for targeted strategies in both conservative and surgical treatment planning.

Inclusion Criteria:

• Aged 18 years or older and able to provide written informed consent
• Compliance with procedures and ability to maintain standard position during measurement
• HV group: Weight-bearing radiograph showing HVA ≥15° (with IMA increase) - Control: no deformity, HVA <15°
• Selection of a single index foot in the same individual (highest HVA/symptomatic in HV; dominant in control)
• Availability or ability to obtain current radiographic measurements within the last 3 months

Exclusion Criteria:

• Previous foot/ankle surgery on the same lower extremity or significant trauma/fracture within the last 12 months
• Rheumatological/metabolic diseases (RA, spondyloarthritis, gout), neuropathy/peripheral vascular disease
• Drug/procedure affecting tendons: systemic or local corticosteroids within the last 6 months; fluoroquinolone use within the last 3 months
• Other significant foot deformity (advanced pes planus/cavus, hallux rigidus/varus) or professional intensive training (exclude or subgroup at your discretion)

Patients who visited the orthopedics outpatient clinic at Kastamonu Education and Research Hospital during the study period and were requested to undergo tibialis anterior tendon elastography examination

yes

Data will become available persistantly on 1.6.2026.

Upon reasonable request principal investigator will share the data.