Achilles tendon allografts with and without InternalBrace augmentation for revision anterior cruciate ligament reconstruction: a randomized pilot trial

To describe short-term patient-reported and MRI outcomes after single-stage revision ACL reconstruction using Achilles tendon allografts with calcaneal bone blocks and to explore differences associated with additional InternalBrace augmentation. This prospective randomized exploratory pilot trial included patients undergoing first-time revision ACL reconstruction. Participants were allocated by simple 1:1 randomization to reconstruction with or without InternalBrace augmentation. Thirty participants with final follow-up were analyzed, including 16 in the InternalBrace group and 14 in the non-InternalBrace group. The prespecified primary outcomes were patient-reported outcome measures comprising the IKDC, Lysholm, Tegner Activity Scale, KOOS subscales, and SF-36 Physical and Mental Component Summary scores. Longitudinal patient-reported outcomes were analyzed using baseline-adjusted linear mixed-effects models including treatment group, follow-up visit, and their interaction. P values across the primary patient-reported outcomes were adjusted using the Benjamini–Hochberg procedure. MRI graft appearance, tunnel diameters, range of motion, and clinical stability findings were secondary outcomes. IKDC, Lysholm, all KOOS subscales, and the SF-36 Physical Component Summary score improved from baseline to final follow-up after false-discovery-rate adjustment, whereas Tegner activity did not change significantly and the SF-36 Mental Component Summary score decreased. At 54 weeks, the adjusted IKDC score was 78.9 in the no-InternalBrace group and 77.5 in the InternalBrace group, corresponding to an adjusted between-group difference of − 1.4 points (95% CI, − 10.4 to 7.6; p = 0.754). No patient-reported outcome showed a significant 54-week between-group difference or treatment-by-time interaction after multiplicity adjustment. MRI classified 15 grafts as tight, 10 as elongated, and 5 as insufficient; MRI classification did not differ significantly between groups (simulated Fisher exact p = 0.231). Mean active flexion was 136.5° without InternalBrace and 135.3° with InternalBrace. Patient-reported knee outcomes improved at short-term follow-up, although half of the grafts were classified as elongated or insufficient on MRI. No clear short-term advantage of InternalBrace augmentation was identified in patient-reported outcomes, range of motion, clinical stability, or MRI classification. The small sample, short follow-up, absence of instrumented laxity measurements, and wide confidence intervals preclude conclusions regarding equivalence or definitive treatment effectiveness. Trial registration: ClinicalTrials.gov, NCT07564336. Retrospectively registered on 27/04/2026.