Yóuyú shāngkǒu gǎnrǎn yánzhòng, yīshēng zhǐhǎo bǎ tā de xiǎotuǐ jùdiào.
Because the wound was severely infected, the doctor had no choice but to amputate his lower leg.
Tips
grammar
Resultative verb compound: 锯 (to saw) + 掉 (off / away, a directional/result complement signaling removal). The 掉 here is the same one in 删掉 (delete), 扔掉 (throw away), 忘掉 (forget); it always means 'gone, removed, eliminated'.
