Do Patients With Functional Hallux Limitus Have a Low-Lying or Bulky FHL Muscle Belly?

Area of Science:

• Orthopedics
• Anatomy
• Radiology

Background:

• Functional hallux limitus (FHLim) describes limited hallux dorsiflexion under load.
• Limited excursion of the flexor hallucis longus (FHL) tendon in the retrotalar pulley is a suspected cause of FHLim.
• A low-lying or bulky FHL muscle belly may contribute to this limitation, but clinical and anatomical data are lacking.

Purpose of the Study:

• To correlate the presence of FHLim with objective morphologic findings using magnetic resonance imaging (MRI).

Main Methods:

• An observational study included 26 patients (27 feet), divided into positive and negative Stretch Test groups.
• MRI was used to measure the distance between the FHL muscle belly and the retrotalar pulley.
• The cross-sectional area of the FHL muscle belly was measured at 20, 30, and 40 mm proximal to the pulley.

Main Results:

• Patients with a positive Stretch Test (indicating FHLim) had a significantly shorter mean distance between the FHL muscle belly and the retrotalar pulley (6.0 mm vs. 11.8 mm, P = .039).
• The cross-sectional area of the FHL muscle belly was significantly larger in patients with FHLim at all measured points (20 mm: 190 mm² vs. 98 mm², P = .005; 30 mm: 300 mm² vs. 206 mm², P = .019; 40 mm: 395 mm² vs. 294 mm², P = .017).

Conclusions:

• Patients with FHLim exhibit a low-lying FHL muscle belly, which restricts excursion in the retrotalar pulley.
• Muscle bulkiness was comparable between groups and not identified as a contributing factor to FHLim.