Time to Radiographic Union Following Minimally Invasive META Procedure for Hallux Valgus

Abstract

Background: The use of fourth-generation minimally invasive hallux valgus surgery with metaphyseal extra-articular transverse and Akin osteotomy, recently dubbed "META," is a new generation of minimally invasive surgical (MIS) technique and a recent focus of foot and ankle orthopaedic literature associated with good functional outcomes and low complication rates. Literature in orthopaedic trauma has indicated that 2 or 3 neocortices on postoperative radiographs are associated with high likelihood of union. In this study, we conducted a retrospective analysis to investigate the time to bony union for patients undergoing fourth-generation MIS hallux valgus repair as well as the relationship between intraoperative degree of first-metatarsal displacement and time to bony union.

Methods: We retrospectively analyzed 217 consecutive patients with moderate to severe hallux valgus who underwent fourth-generation MIS first distal metatarsal and Akin osteotomy between 2020 and 2023 and were followed for up to 1 year. Radiographic measurements included the scale of displacement between the proximal and distal portions of the first metatarsal as a percentage and the number of neocortical bridge formations at the osteotomy site. Postoperative weightbearing radiographs were recorded at 6 weeks, 3 months, 6 months, and 1 year to assess time to union and patient clinical outcomes. Two orthopaedic surgeons independently reviewed the radiographs to assess progression to bony union. Any discrepancy in analysis was resolved by a third-party clinician. Complete union was defined as the presence of at least 2 new cortical bridge formations on postoperative X-ray films. Patients were divided into 3 groups based on the percentage of shift on the first metatarsal head (≤50%, 51%-75%, ≥76%) for the purpose of our analysis.

Results: Union (≥2 cortices) was observed in 17%, 70%, and 90% of patients at 6 weeks, 3 months, and 6 months, respectively. At final follow-up (mean 13 ± 6.9 weeks), 92% achieved union. No significant differences in time to union were observed across metatarsal shift groups.Complications include 3 nonunions, 3 revisions, 16 cases that necessitated removal of hardware, 1 case of superficial wound infection, 1 case of deep wound infection, and 6 deformity recurrences.

Conclusion: Time to union after META procedure typically occurred by 13 weeks, independent of shift magnitude. Surgeons may consider ≥2 cortices and absence of symptoms as sufficient indicators for advancing weightbearing. These findings may assist in patient counseling and postoperative planning.Level of Evidence: Level IV, retrospective case series.

Keywords: bunion; foot and ankle; hallux valgus; minimally invasive; time to union.

Visual Abstract

This is a visual representation of the abstract.

Figure 1 and 2.

Postoperative weight bearing anteroposterior and lateral radiographs showing 4 neocortical bridge callus formations following fourth-generation minimally invasive hallux valgus correction surgery.

Figure 3.

Anteroposterior radiographs showing first-metatarsal shift percentage, recorded as the distance from the medial aspect of the distal metatarsal to the lateral aspect of the proximal metatarsal divided by the width of the first metatarsal at the level of the osteotomy. (A) Less than or equal to 50%, (B) 50%-75%, and (C) greater than 75% first-metatarsal shift.

Figure 4.

Percentage of patients achieving bony cortex formation across the metatarsal shift category.

Figure 5.

Mean time to union by metatarsal shift category.

Figure 6.

Mean time to 1, 2, or 3 cortical formations regardless of metatarsal shift.