Abstract
Category:
Bunion; Midfoot/Forefoot
Introduction/Purpose:
Following Minimally Invasive Bunionectomy (MISB), removal of hardware rates are about 5% and commonly due to midfoot pain near the distal metatarsal screw site. This distal screw head site corresponds to the proximal midshaft width measurement location, which has shown to increase postoperatively. One explanation for this increased width is medial subluxation of the first metatarsal at the tarsal-metatarsal (TMT) joint. This “TMT slippage” occurs as the metatarsal base is shifted medially to accommodate the metatarsal head lateralization at the metatarsal phalangeal joint. The force across the TMT joint overcomes the ligamentous stabilizers, allowing the metatarsal to “slip.” The aim of this study was to investigate the relation between TMT slippage and removal of hardware (ROH) rates.
Methods:
A retrospective analysis of prospectively collected data identified 38 patients undergoing MISB for hallux valgus (HV) with subsequent distal chevron screw removal and a control group of 40 MISB cases without hardware removal. Demographic data and surgical details were obtained via chart review. Pre- and at least 6-month post-operative radiographs were measured to obtain transverse TMT slippage on anteroposterior (AP) radiographs (Figures 1). Additionally, distal foot width, midshaft foot width, hallux valgus angle (HVA) and intermetatarsal angle (IMA) were measured. Independent samples t-tests and chi-square analyses were used to compare continuous and categorical characteristics, respectively, between patients who underwent removal of hardware. Multivariable logistic regression modeling was used to identify risk factors for undergoing hardware removal.
Results:
Interobserver reliability, measured by intraclass correlation coefficients (ICCs), was high for all measurements (ICC > 0.70). The change in TMT slip was significantly higher in the hardware removal (ROH) group compared to the control group (+1.39 versus +0.80, p=0.004) (Table 1). A greater decrease in distal foot width (narrower distal width postoperatively) was associated with an increased likelihood of hardware removal (OR: 0.76), while smaller reductions in HVA and IMA were linked to a higher likelihood of requiring ROH (OR: 1.12 and 1.42, respectively). Notably, a larger increase in TMT slip correlated with the highest likelihood of being in the ROH cohort (OR: 2.87) (Table 2). TMT slippage did not correlate with any other measurements (all p > 0.05).
Conclusion:
Our study highlights the relationship between MISB outcomes and TMT slippage. Patients requiring distal chevron screw removal showed significantly higher transverse TMT slippage. Interestingly, a smaller distal foot width reduction was associated with decreased hardware removal likelihood, suggesting a potential protective mechanism. Conversely, smaller corrections of both HVA and IMA were associated with higher chances of hardware removal. Notably, for every 1-centimeter increase in TMT slippage postoperatively, there was a nearly 3-fold increase in the likelihood of distal chevron screw removal. Further research is needed to understand the mechanisms underlying TMT slippage and its impact on HV correction outcomes.
