Can an isolated modified Lapidus procedure alter hindfoot alignment? a retrospective radiographic study.

Purpose: The study aimed to evaluate the effect of first tarsometatarsal joint (TMT-1) arthrodesis using the modified Lapidus procedure on coronal hindfoot alignment, given the potential influence of medial column stabilization on talar positioning.

Study design: A retrospective radiographic analysis was performed.

Methods: We reviewed 54 feet in 40 patients (mean age 60.6 ± 9.78 years) who underwent an isolated modified Lapidus procedure with an average follow-up of 29.6 ± 13.9 months. Fixation was achieved using a compression screw and plantar plate. Preoperative and 12-month postoperative weight-bearing dorsoplantar, lateral, and Méary views were analyzed. Radiographic measurements were independently performed by two senior surgeons and assessed for inter-observer reliability. Importantly, only radiographic outcomes were evaluated.

Results: On Méary view, hindfoot valgus decreased significantly using the Méary's circle angle method (-2.0 ± 2.0° for observer 1 and -2.44 ± 1.84° for observer 2; p < 0.001 for both). Djian's hindfoot valgus angle also decreased significantly (-1.44 ± 0.98°, p < 0.001 for observer 1; -1.67 ± 4.09°, p = 0.004 for observer 2). Inter-observer reliability was good (ICC = 0.87 and 0.80, respectively).

Conclusion: The modified Lapidus procedure resulted in a significant radiographic reduction in hindfoot valgus, suggesting a stabilizing effect on the medial column and hindfoot. These radiographic findings may inform surgical planning in patients with hallux valgus and concomitant flatfoot, although further clinical validation is required.