Does metatarsus primus elevatus really exist in hallux rigidus? A weightbearing CT case-control study

Area of Science:

• Orthopedics
• Radiology
• Biomechanics

Background:

• Metatarsus primus elevatus (MPE) is debated in hallux rigidus (HR) etiology.
• Weight-bearing radiographs (WBR) have limitations in measuring MPE.
• Weight-bearing CT (WBCT) offers a more accurate assessment of forefoot spatial relationships.

Purpose of the Study:

• To comparatively assess MPE and other forefoot variables in HR versus controls using WBCT.
• To evaluate the diagnostic capability of MPE for symptomatic HR.

Main Methods:

• Retrospective case-control study of 25 HR patients and 30 controls.
• WBCT parameters, including MPE, were measured by two independent investigators.
• Receiver Operating Characteristic (ROC) curve analysis determined the MPE diagnostic threshold.

Main Results:

• HR group showed significantly increased hallux valgus angle (HVA) and MPE compared to controls.
• First metatarsal declination and 1st/2nd metatarsal declination ratio were decreased in the HR group.
• Dorsal translation of the first metatarsal at the first tarsometatarsal joint occurred in 70% of HR patients.

Conclusions:

• WBCT confirmed significantly elevated MPE in the HR group.
• An MPE threshold of 4.19 mm on WBCT is diagnostic for symptomatic HR.
• Dorsal translation at the first TMT joint may contribute to increased MPE in HR.