In-hospital waiting time to surgery and functional outcomes in geriatric hip fractures: a directed acyclic graph-based preplanned analysis from a prospective multicenter cohort study

Background:The early recovery of hip function after hip fracture surgery values more attention, especially for patients with delayed surgery of longer than 48 h. We aim to evaluate the associations of in-hospital surgical waiting time with the functional outcomes [Harris Hip Score (HHS), Parker Mobility Score (PMS), and EuroQol 5 dimensions VAS (visual analogue scale) score (EQ-5D VAS)] in elderly patients who sustained hip fractures. Materials and methods:Data on sociodemographic and clinical factors were prospectively collected using a multicenter hip fracture registry system. Participants in the cohort underwent a 12-month follow-up investigation. After adjusting potential confounders identified by the directed acyclic graphs, the associations between surgical waiting time longer than 48 h and functional outcomes were estimated by log-binomial regression and multivariable linear regression models with generalized estimating equations. Results:Of 863 survival participants with available functional data at 12 months after surgery, an increased risk was obtained from receiving surgery after 48 h and the poor functional outcomes (HHS<80: relative risk (RR)=1.56, 95% CI: 1.00-2.51; PMS<7: RR=1.49, 95% CI: 1.13-2.01; EQ-5D VAS<80: RR=1.97, 95% CI: 1.57-2.47). In-hospital waiting time greater than 48 h were time-invariantly associated with lower PMS during recovery (-0.44 units 95% CI: -0.70 to -0.18). In addition, delayed surgery was time-varying associated with HHS and EQ-5D VAS. Conclusions:The associations between in-hospital waiting time and postoperative functional score suggest that delayed surgery can lead to poor functional outcomes, especially in patients waiting longer than 72 h from injury. Delayed surgery mainly impacted hip function and mobility recovery with a slower speed in early recovery of the first 3 months. More attention should be paid to mechanisms behind the associations between delayed surgery on general healthy status.