Description:
<jats:title>Abstract</jats:title><jats:sec>
<jats:title>Background</jats:title>
<jats:p>Secondary anterior cruciate ligament (ACL) ruptures are a relevant clinical concern after surgical treatment of a primary ACL rupture. However, there is a lack of scientific evidence related to the role of muscle strength prior to revision surgery in a second ACL rupture. The aim of this study was to assess differences in knee extensor and flexor strength in patients <jats:italic>before</jats:italic> primary and secondary ACL reconstruction compared to healthy controls.</jats:p>
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<jats:title>Methods</jats:title>
<jats:p>In total, <jats:italic>n</jats:italic> = 69 age, weight and sex matched individuals were included in the study: <jats:italic>n</jats:italic> = 23 patients with isolated primary ACL rupture, <jats:italic>n</jats:italic> = 23 with secondary ACL rupture, and <jats:italic>n</jats:italic> = 23 matched healthy controls. Maximal isokinetic knee extension and flexion torque normalized to body mass was assessed for both legs.</jats:p>
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<jats:title>Results</jats:title>
<jats:p>For patients with secondary ACL ruptures, torques were reduced in the non-injured (extension: 1.94 Nm/kg vs. 2.46 Nm/kg, <jats:italic>p</jats:italic> < 0.05, flexion: 1.25 Nm/kg vs. 1.59 Nm/kg, <jats:italic>p</jats:italic> < 0.05) and the injured leg (extension: 1.70 Nm/kg vs. 2.46 Nm/kg, <jats:italic>p</jats:italic> < 0.05, flexion: 1.14 Nm/kg vs. 1.59 Nm/kg, <jats:italic>p</jats:italic> < 0.05) compared to healthy controls. For patients with a primary ACL rupture torques were reduced in the non-injured (extension: 1.92 Nm/kg vs. 2.46 Nm/kg, <jats:italic>p</jats:italic> < 0.05, flexion: 1.24 Nm/kg vs. 1.59 Nm/kg, <jats:italic>p</jats:italic> < 0.05) and the injured leg (extension: 1.38 Nm/kg vs. 2.46 Nm/kg, <jats:italic>p</jats:italic> < 0.05, flexion: 1.01 Nm/kg vs. 1.59 Nm/kg, <jats:italic>p</jats:italic> < 0.05) compared to healthy controls. There were no differences between patients with primary and secondary ruptures, except of the knee extension on the injured leg showing higher values after a secondary ACL rupture (1.38 Nm/kg vs. 1.70 Nm/kg, <jats:italic>p</jats:italic> < 0.05).</jats:p>
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<jats:title>Conclusions</jats:title>
<jats:p>The findings indicate that maximal knee torques were significantly reduced in patients with primary and secondary ACL ruptures before surgical reconstruction for the non-injured and injured leg as compared to healthy controls. Further investigations are needed to assess strength abilities before and after a second revision within a prospective design.</jats:p>
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