Effect of the First Tarsometatarsal (Modified Lapidus) Arthrodesis on Hindfoot Alignment.

The purpose of this study is to demonstrate the effect of first tarsometatarsal (modified Lapidus) arthrodesis on hindfoot alignment. We reviewed the radiographs of 39 patients, 40 feet (16 right feet and 24 left feet in 6 males and 34 females; mean age 43 years) who underwent hallux valgus reconstruction and isolated first tarsometatarsal arthrodesis. Patients who had ancillary osseous procedures were excluded from the study, with the exception of proximal phalangeal osteotomy to address hallux interphalangeus. The mean time to follow up was 33.78 weeks (8.45 months), median 21.5 weeks. Statistically significant differences were found between preoperative and postoperative measurements for talar declination (-3.3 ± 3.5), lateral talocalcaneal angle (-3.1 ± 3.9), lateral Meary's angle (-4.2 ± 4.9), medial cuneiform height (3.5 ± 4.6), medial cuneiform to fifth metatarsal distance (4.7 ± 4.5), AP talocalcaneal angle (-2.8 ± 5.3), and percentage of talar head uncovering (-6.6 ± 7.6). Our results suggest that first tarsometatarsal arthrodesis can affect hindfoot alignment on AP and lateral radiographs.