The Statistical Fragility of Minimally Invasive vs Open Hallux Valgus Surgical Correction Outcomes

Research Type: Level 2 - Prospective comparative study, Meta-analysis of Level 2 studies or Level 1 studies with inconsistent results Introduction/Purpose: Hallux valgus is one of the most common forefoot deformities treated by foot and ankle surgeons. Definitive treatment involves surgical correction, which aims to reduce pain, realign the foot, re-establish foot function, and, ideally, preserve joints. Many surgical procedures have been described over the years, most of which have shown good outcomes. Comparative trials studying minimally invasive versus open techniques have been performed and are crucial for understanding the benefits each technique might offer. However, their overlooked statistical fragility can undermine clinical reliability. Minor outcome changes may overturn statistically significant findings, leading to unreliable evidence impacting patient care. This study assessed the fragility of minimally invasive vs open hallux valgus surgical correction outcomes in comparative trials, hypothesizing high sensitivity to such changes. Methods: PubMed and MEDLINE were searched via PRISMA methodology for comparative trials on minimally invasive versus open hallux valgus surgical correction procedures reporting continuous and dichotomous outcomes. Fragility analyses were conducted using a two-tailed Fisher’s exact test or Welch’s t-test to evaluate the statistical significance of reported outcomes at a threshold of p < 0.05. The Fragility Index (FI) quantified the number of outcome reversals needed to change statistical significance from significant to nonsignificant or vice versa (reverse Fragility Index). The Fragility Quotient (FQ) was calculated as the FI divided by the study sample size. Subgroup analysis was conducted by outcome category, which was grouped into: (a) clinical outcomes (which included range of motion, peri-operative and post-operative complications, pain scores, i.e., VAS, and function scores, i.e., AOFAS score and MOXFQ), (b) radiologic outcomes (which included hallux valgus angle, intermetatarsal angle, toe length, and tibial sesamoid position), or (c) patient satisfaction. Results: 19 studies were included which analyzed a total of 1,416 cases and 136 outcomes. The median FI was 6 (IQR: 0-10) with a FQ of 0.10 (IQR: 0.024-0.20) for continuous outcomes and 4 (IQR: 1-5) with a FQ of 0.07 (IQR: 0.02-0.90) for dichotomous outcomes (Table 1a). In continuous outcomes, clinical outcomes had a median FI of 11 (IQR: 6-23) and radiologic outcomes had a median FI of 4 (IQR: 0-9). In dichotomous outcomes, clinical outcomes had a median FI of 4 (IQR: 3-5), radiologic outcomes had a median FI of 4 (IQR: 3-6), and patient satisfaction had a median FI of 3 (IQR: 2-4) (Table 1b). Patients lost to follow-up exceeded the FI in 23.5% of outcomes on average. Conclusion: This analysis is the first to analyze the fragility of minimally invasive vs open hallux valgus surgical correction outcomes in comparative studies. We showed that the statistical findings in these studies are fragile and warrant cautious interpretation. A small number of outcome reversals would have altered the significance of results and this number was lower than the number of patients lost to follow-up a quarter of the time. Standardized reporting of p values alongside FI and FQ metrics is recommended to help clinicians evaluate the robustness of study findings. This approach will lead to the improved reliability of research results.