• Anke Rüttershoff, Dominik Geisel, Lucca Lacheta, Doruk Akgün, Ulrich Stöckle, Oliver Miltner, Adrian Alexander Marth, and Suchung Kim.
• Centrum für Muskuloskelettale Chirurgie, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, Berlin, 13353, Deutschland. anke.ruettershoff@charite.de.
• Arch Orthop Trauma Surg. 2024 Sep 1; 144 (9): 448344904483-4490.

PurposeThough previous studies on surgical quadriceps tendon repair reported good to satisfactory results its impact on knee extensor strength and patellofemoral joint is unknown. The purpose of the study was to assess the clinical and functional outcome by quantifying subjective knee related outcome, isokinetic extensor strength complemented by magnetic resonance imaging (MRI).MethodsFor this retrospective clinical trial twenty-one patients with a mean age of 59.1 (±14.9) years were carried out for follow-up evaluation. For clinical outcome numeric rating scale for pain (NRS), Kujala anterior knee pain score, Knee osteoarthritis outcome score (KOOS) with its subscores, Tegener Activity Score (TAS), Isokinetic extensor strength testing (ISO) and the Limb symmetry index (LSI) were utilized. Muscle volume (Vmqf), atrophy and cartilage status were assessed on MRI. Tendon integrity and implant loosening were evaluated. Statistical analysis was carried out using Student´s t-test, Pearson and Spearman correlation coefficient.ResultsMean follow-up was 56.2 (± 17.5) months. Clinical outcomes in mean were as follows: NRS 1.7 (±2.0), Kujala score 75.8 (± 15.8) points; KOOS 62.9 (±30.6) % (Subscores: (KOOSPain 84 (± 18.3)%, KOOSSymptoms 63.4 (± 15.3) %, KOOSADL 79.8% (± 19.4)%, KOOSSports&Rec 61.5 (± 28.8))%, TAS 3.7 (± 1.2). Mean ISO difference was 3.7 (±32.3) %). 41.2% of patients had an LSI < 90% and showed non-significantly (p > 0.05) better outcomes in NRS, Kujala score and KOOS than patients with LSI < 90%. ISO correlated with better subjective outcome (r > 0.5) but not with MRI findings. Vmqf asymmetry > 10% was seen in 41,2% of patients. Degenerative muscle and cartilage changes were few and low grade. One tendon showed partial retear. Patients showed no signs of implant loosening.ConclusionDistal quadriceps tendon repair leads to satisfactory subjective outcome in patients with low to moderate activity levels. Tendon integrity was reliably restored. However, extensor strength deficits remain in more than 40% of patients. Atrophy signs of advanced fatty infiltration were recorded in 15% and patellofemoral cartilage defects in 20% of all patients, indicating that previous assessment tools do not display functional outcome adequately.© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

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