Similar outcomes after anterior cruciate ligament reconstruction in paediatric and adult populations: a 1-year follow-up of 506 paediatric operations in Denmark.

PURPOSE: To present 1-year results after all paediatric anterior cruciate ligament (ACL) reconstructions in Denmark (5.9 M inhabitants) for the 10½ year period, 1 July 2011 to 31 December 2021. METHODS: All children who had an ACL reconstruction were enrolled. They were asked to complete Pedi-IKDC preoperatively and at 1-year follow-up. Independent observers performed pivot shift test and instrumented laxity assessment preoperatively and at 1-year follow-up. RESULTS: The median age of the 506 children (47.2% girls) was 14.3 years (9.3-15.9). The Pedi-IKDC score increased from preoperatively 61.6 ± 15.8 (mean ± SD) to 85.9 ± 13.0 at 1-year follow-up (p < 0.0001). There were concomitant injuries (to meniscus and/or cartilage) in 49.9%, but these children had preoperative and follow-up Pedi-IKDC scores similar to the scores for children with isolated injury to ACL (n. s.). Instrumented anterior laxity was 4.3 ± 1.4 (mean ± SD) mm preoperatively and 1.4 ± 1.4 mm at follow-up (p < 0.0001). Preoperatively, 3% had no pivot shift whilst this was the case for 68% postoperatively (p < 0.0001). Twenty-five children (5.6%) had 4 mm instrumented laxity or more relative to the unoperated knee at follow-up. Two patients (0.4%) had an operatively treated deep infection, three (0.5%) were operated on for reduced range of motion and two (0.4%) had a revision ACL reconstruction. CONCLUSION: ACL reconstruction resulted in a clinically meaningful increase in Pedi-IKDC, an improved instrumented stability, a reduction in the grade of pivot shift and the complication rate was low at 1-year follow-up. The risk of graft insufficiency at 1-year follow-up was the same as in an adult population. LEVEL OF EVIDENCE: II.

Pedi-IKDC exhibits questionable measurement properties in a cohort of pediatric patients with ACL rupture.

BACKGROUND: Pedi-IKDC is commonly used to evaluate anterior cruciate ligament (ACL) deficiency in children. However, its construct validity has not been thoroughly assessed. The aim was to examine the measurement properties of the Pediatric International Knee Documentation Committee (Pedi-IKDC) by modern test theory (MTT) models, confirmatory factor analysis (CFA), and item response theory (IRT). METHODS: The cohort consisted of all children and adolescents in Denmark (n = 535, age 9-16) treated with physeal-sparing ACL reconstruction 2011-2020. Patient-reported outcome measure (PROM) data were collected before surgery and at 1 year follow-up. Structural validity of Pedi-IKDC was assessed with MTT models. Reliability was reported as McDonalds coefficient omega. Responsiveness was evaluated with standardized response means. RESULTS: Sufficient PROM data were available for 372 patients. The original unidimensional construct did not fit CFA model expectations neither before surgery (χ2 = 462.0, df = 163, p < 0.0001; RMSEA: 0.109, CFI: 0.910, TFI: 0.895) nor at follow-up. Neither did a two-factor CFA model with "Symptoms" and "Sports activities" as individual subscales (χ2 = 455.6, df = 162, p < 0.0001) nor a bifactor model (χ2 = 338.9, df = 143, p < 0.0001), although fit indices improved with the latter (RMSEA: 0.094, CFI: 0.941, TFI: 0.922). The IRT models confirmed this pattern. The scale was responsive (SRM 1.66 (95% CI: 1.46-1.88)). Coefficient omega values were 0.866 before surgery and 0.919 at follow-up. CONCLUSIONS: The Pedi-IKDC exhibited inadequate structural validity. Neither the original construct, a two-factor model, nor bifactor models fitted data well. We advise that data obtained by Pedi-IKDC are interpreted with caution.