Quantifying increased lateral column instability in Adult Acquired Flatfoot Deformity (AAFD)

Area of Science:

• Orthopedics
• Biomechanics
• Foot and Ankle Surgery

Background:

• Adult acquired flatfoot deformity (AAFD) involves ligamentous failure and tendon overload, primarily affecting the posterior tibial tendon and spring ligament.
• Increased lateral column (LC) instability is a characteristic of AAFD but remains undefined and unquantified.

Purpose of the Study:

• To quantify the increased LC motion in unilateral symptomatic planus feet.
• To utilize the contralateral unaffected foot as an internal control for comparison.

Main Methods:

• Case-matched analysis of 15 patients with unilateral stage 2 AAFD and an unaffected contralateral foot.
• Measurement of lateral foot translation to assess spring ligament competency.
• Assessment of medial and LC dorsal sagittal instability via direct measurement of metatarsal head motion and video analysis.

Main Results:

• A statistically significant increase in dorsal LC sagittal motion (5.6 mm) was observed in affected feet compared to unaffected feet (p < 0.001).
• Significant increases were also found in lateral translation score (42.8 mm, p < 0.001) and medial column dorsal sagittal motion (6.8 mm, p < 0.001).
• Video analysis confirmed a statistically significant increase in LC dorsal sagittal motion in affected feet.

Conclusions:

• This study provides the first quantification of statistically significant increased dorsal LC motion in feet with AAFD.
• Understanding this increased LC motion and its association with talonavicular/spring ligament laxity can improve foot assessment.
• These findings may contribute to the development of future preventative treatment strategies for AAFD.