Radiographic Comparison of Forefoot and Midfoot Width Changes with 4th Generation Minimally Invasive Bunion Surgery vs the Modified Lapidus Procedure

Research Type: Level 2 - Prospective comparative study, Meta-analysis of Level 2 studies or Level 1 studies with inconsistent results Introduction/Purpose: Minimally Invasive Bunion Surgery (MIBS) and the Modified Lapidus Procedure (MLP) have both been shown to treat bunions and narrow forefoot bony and soft tissue width. Conceptually, both procedures stabilise the 1st Tarsometatarsal Joint (TMTJ) with MIBS doing so through an increase in proximal IMA and "locking out" of the 1st TMTJ while the MLP does so through bony fusion. El Masry et al have recently reported on the increase in proximal midfoot bony and soft tissue width associated with MIBS however, this has not been looked at or compared to the MLP. This study looked to compare forefoot and midfoot bony and soft-tissue width between MIBS performed using a 4th generation technique to a MLP. Methods: A retrospective review of prospectively collected data for 21 consecutive MIBS using 4th generation technique on 16 feet between March 2022 and August 2024 and 24 consecutive MLPs on 20 feet between July 2021 and June 2024 were performed. Radiographic data collection included pre- and post-operative (at latest follow-up X-ray: 6-12 months post-op) HVA, IMA +/- proximal IMA, DMAA, Dist 1-2 (distance between 1st & 2nd metatarsal), forefoot bony (FFBW) & soft-tissue width (FFSTW), proximal/midfoot bony (MFBW) & soft-tissue width (MFSTW) and 1st:2nd Metatarsal ratio. Results: For the MLP: IMA, HVA & DMAA decreased from 17.97, 40.97 and 27.63 respectively to 7.48, 14.44 and 8.55 respectively. The mean dist 1-2 decreased from 18.37mm to 13.99mm. The mean FFBW & FFSTW decreased from 96.87mm & 107.69mm to 86.27mm & 98.79mm respectively. The mean MFBW & MFSTW decreased from 79.00mm & 95.17mm to 73.17mm & 90.97mm For MIBS: IMA, HVA & DMAA decreased from 15.79, 31.98 and 16.01 respectively to 4.75, 8.19 and 4.20 respectively. Mean proximal IMA increased to 24.01. The mean dist 1-2 increased from 17.62mm to 21.71mm. The mean FFBW & FFSTW decreased from 94.88mm & 105.47mm to 87.99mm & 102.19mm respectively. The mean MFBW & MFSTW however increased from 78.47mm & 95.00mm to 82.23mm & 96.18mm. Conclusion: Both MIBS and the MLP reduce HVA, IMA, DMAA and forefoot bony & soft-tissue width. However, MIBS was found to increase proximal IMA, distance between 1st & 2nd metatarsal and proximal/midfoot bony & soft-tissue width despite the surgical technique including meticulous medial ledge excision while the MLP reliably reduced these variables. The observed increase in proximal/midfoot width raises concerns that MIBS may "transfer the bunion from the forefoot to midfoot". Therefore, we recommend further investigation into the clinical impact of these findings as well as further study into this observation in larger studies.