Purpose The increasing incidence of knee injuries among children is well known by sports physicians. Papers dealing with this topic have often collected patient-reported outcomes measures (PROMs) in a retrospective manner; this limitation could lead to a misinterpretation of the results, because pediatric patients might not remember their preoperative conditions adequately. This study aims to evaluate the reliability and the reproducibility of the IKDC pediatric score when administered retrospectively at a 12-month follow-up. Methods From September 2018 and June 2019, all patients aged 7-18 scheduled for surgery due to diferent knee pathologies in a single center were considered eligible. Parents were contacted by phone for consent. An open-source platform was implemented to collect the responses: two surveys were created (Q1, Q2). They included general information and the Pedi-IKDC score. Q1 was completed prospectively, while Q2 was completed 12 months after surgery. The two questionnaires were identical, and patients were carefully advised to complete Q2 recalling their health status before surgery. ICC and the concordance correlation coeicient (ρ c ) were used to assess the reproducibility between the prospective and recalled scores. Results Sixty-six patients responded to Q1 and Q2, and the mean age was 12.9 ± 2.2 years at Q1 and 14.1 ± 2.2 years at Q2. The mean time between Q1 and Q2 was 14.1 ± 2.1 months. Between prospective-IKDC and recall-IKDC, the ICC coeicient was "poor" at 0.32 (CI 0.09 to 0.5) and the ρ c was "poor" at 0.4 (CI 0.29 to 0.51). Mean prospective-IKDC was 76.8 ± 23.52 mean recalled-IKDC was 60.4 ± 11.5 (P < 0.0001), while mean diference was -16.3 ± 2.09. Simple linear regression models showed that Δ-IKDC is independently associated with age at Q1 (R 2 = 0.2676; P0.0001) and prospective-IKDC (R 2 = 0.653; P < 0.0001). Conclusions Retrospective collection of the Pedi-IKDC score is not reliable and has high recall bias. This should be avoided in children with knee conditions. Level of evidence III.

Background and Objective Reconstruction of the anterior cruciate ligament (ACL) simultaneously with medial unicompartmental knee arthroplasty (UKA) has been suggested as an alternative treatment in patients with ACL deficiency and localized osteoarthritis (OA) in young patients. The objectives of this review were to report the current concepts on the topic and describe an original surgical technique of simultaneous medial UKA and ACL reconstruction. Methods A literature search was performed on PubMed, including articles written in English until June 2021. The articles regarding ACL reconstruction and UKA were reviewed using the narrative approach. Inclusion criteria: (I) original articles about ACL reconstruction and unicompartmental knee replacement; (II) written in English; (III) involving three or more cases. Two non-blinded authors reviewed the titles and abstracts of each article identified in the literature search. Key Content and Findings The articles regarding ACL reconstruction and UKA were reviewed using the narrative approach. Conclusions There is controversial evidence about performing the UKA simultaneously with an ACL reconstruction. Biomechanical and clinical studies show that the benefits of restoring good joint stability outweigh the possible risks associated with performing both surgeries at the same time. With this strategy, it is possible to obtain good clinical results with a high survival rate of the implant and patient satisfaction.

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