A radiographic assessment of the change in metatarsal length following the modified Lapidus procedure

Abstract

Background: The modified Lapidus is a surgical procedure for managing moderate to severe hallux valgus deformities, especially in the presence of first tarsometatarsal joint arthritis or hypermobility. It has good long term results, but reportedly can lead to transfer metatarsalgia due to inherent shortening of the first metatarsal. Methods: A retrospective analysis of all adult patients who underwent a modified Lapidus procedure, during a three year period was performed. Clinical notes were evaluated to look for non-union or any other complications related to the surgery. Pre and postoperative standard weight bearing radiographs were used to establish the relative metatarsal length (RML), intermetatarsal angle (IMA), hallux valgus angle (HVA) and distal metatarsal articular angle (DMMA). A total of 69 modified Lapidus procedures were identified, with 32 included in the study. Results: The mean pre and postoperative RML was -0.77mm and -4.86mm respectively. The average RML shortening due to the procedure was -4.09 (p< 0.0001).The mean pre and postoperative IMA was 15 and five degrees respectively (p < 0.0001).The mean pre and postoperative HVA was 33 and nine degrees respectively (p < 0.0001). One patient reported transfer metatarsalgia, which was attributed to elevation of the first metatarsal. Conclusion: In this series there was a statistically significant degree of shortening (p< 0.05) of the relative length of the first metatarsal, without any clinical implications. The low rate of transfer metatarsalgia following the modified Lapidus procedure could be attributed to the sagittal plane correction and stability obtained by performing a first tarsometatarsal (TMT) fusion. Level of evidence: Level IV, retrospective case series