CRP and infection: Meanwhile, the effect of elevated C-reactive protein on LOS is dual: on the one hand, preoperative C-reactive protein > 5 mg/L suggests an elevated risk of infection [42,43]; on the other hand, chronic inflammation [44] and pain exacerbation [45] reflected by elevated C-reactive protein can act synergistically—the former through pro-inflammatory factor release exacerbating the postoperative inflammatory response [46], and the latter impeding functional recovery, which together prolong LOS [45].