Broström with InternalBrace Augmentation Significantly Improves Ankle Stability Measured by the Cumberland Ankle Instability Tool Compared to Broström Without Augmentation

Research Type: Level 3 - Retrospective cohort study, Case-control study, Meta-analysis of Level 3 studies Introduction/Purpose: Limited data exist regarding whether primary Broström with InternalBraceTM augmentation bolsters ankle stability compared to Broström without augmentation. The Cumberland Ankle Instability Tool (CAIT) is a validated metric of ankle stability. Our study therefore aims to determine whether augmented Broström produces greater ankle stability measured by CAIT scores. To our knowledge, this investigation is the largest retrospective study evaluating the CAIT in non-augmented Broström vs. augmented Broström with InternalBrace, as well as the largest to assess the relative stability associated with InternalBrace augmentation as measured by preoperative CAIT scores. We hypothesized that augmented Broström would result in higher postoperative CAIT scores for patients compared to non-augmented. Methods: 574 patients who underwent lateral ankle ligament reconstruction at a single institution (2013-2024) were retrospectively reviewed by two independent investigators. Revisions, Evans procedures, allografts, nonanatomic reconstructions, flexor digitorum longus transfers, pes planus deformities, concomitant tibiotalar arthrodesis, associated ankle arthroplasties, and concomitant fractures or nonunions were excluded. Of 392 eligible patients contacted, 127 completed surveys assessing CAIT, self-reported ankle stability, and post-surgical activity levels and had completed preoperative CAIT. Patients were classified based on instability etiology: active individual (no anatomic deformity), osteochondral defect (OCD), or deformity (varus/valgus deformity, equinus contracture). T-tests and Pearson’s Chi-squared test were used for unadjusted comparisons. Analysis of covariance (ANCOVA) compared postoperative CAIT by procedure type, controlling for clinically relevant covariates, with interaction term (procedure type × preoperative CAIT) to test for differences by baseline instability. Post-hoc analyses were conducted to calculate estimated marginal means (EMM) and assess between-group differences at various preoperative CAIT percentiles. Results: In unadjusted comparisons, augmented (n=80) demonstrated superior outcomes than non-augmented (n=47), with higher postoperative CAIT (20.6±8.2 vs. 16.5±10.5, P=.02), greater self-reported ankle stability (88.8% vs. 72.3%, P=.03), and greater number of patients reporting increased postoperative activity (80% vs. 63.8%). ANCOVA demonstrated significant main effect of augmented on postoperative CAIT after controlling for clinically-relevant cofactors including preoperative CAIT (F(1,116)=6.39, P=.01). Augmented had significantly higher postoperative CAIT (EMM=21.3, 95% CI=19.0-23.6) compared to non-augmented (EMM=16.9, 95% CI=13.4-20.6). The benefit of augmentation varied by preoperative CAIT. At CAIT=2 (25th percentile) and CAIT=7 (50th percentile), augmented had significantly higher postoperative scores compared to non-augmented (MD=6.92, P<.001 and MD=4.25, P=.02, respectively); At CAIT=11 (75th percentile), difference between groups was no longer significant although augmented still resulted in higher scores (MD=2.12, P=.33). Conclusion: Broström with InternalBrace augmentation generates significantly improved ankle stability measured by CAIT compared to non-augmented Broström to a degree that reaches the minimal clinically important difference reported in the literature for CAIT. The benefit of augmentation is most pronounced in patients with high preoperative ankle instability (lower preoperative CAIT), as differences between augmented and non-augmented in postoperative CAIT was significantly greater in patients with preoperative CAITs in 25th and 50th percentiles. Likely due to its ability to exceed the native ATFL strength, InternalBrace augmentation also results in more patients self-reporting ankle stability and increased activity compared to primary, non-augmented Broström.