Effect of Postoperative Immobilization Time on PROMIS Scores and Clinical outcomes in Ankle Fracture Patients

BACKGROUND: Ankle fractures are among the most common injuries treated by orthopaedic surgeons, yet little guidance exists in postoperative protocols for ankle fractures concerning time of immobilization. Here, we aim to investigate the association between early mobilization and patient-reported outcomes. Our null hypothesis was that no difference in Patient-Reported Outcomes Measurement Information System (PROMIS) scores would be identified in patients when comparing the effect of time of immobilization. METHODS: A retrospective review identified ankle fractures that underwent surgical fixation between 2015 and 2020 at a level 1 trauma center and its associated facilities. One hundred nineteen patients from 9 providers met inclusion criteria for our final analysis. Forty-seven patients were immobilized for <6 weeks (early) and 68 patients were immobilized for ≥6 weeks (late). Our primary outcome measures included the PROMIS questionnaire, time of immobilization, and time to full weightbearing. Our secondary outcome measures included time to return to work, wound complications (infection, delayed healing), and complications associated with fracture fixation (loss of reduction, delayed union, reoperation, hardware failure). Repeated measures analysis of variance as well as linear mixed outcome regression were used to predict each of the PROMIS outcomes of anxiety, depression, physical function, and pain interference. Each model included the predictors of age, sex, race, body mass index (BMI), diabetes, rheumatoid arthritis, smoking status, payor, provider, time to radiographic union, time to return to work, time to full weightbearing, and early vs late immobilized groups. RESULTS: We found no differences in PROMIS scores between mobilization groups even when controlling for possible confounders such as age, BMI, rheumatoid arthritis, smoking status, and diabetes mellitus (P > .05). Furthermore, we found no differences in complications associated with fracture fixation (P > .05). Across our cohort, lower physical function scores were associated with higher BMI, increasing age, and longer time to return to work/play (P < .05). Our analysis further showed that depression, anxiety, pain interference, and physical function levels improve as a function of time (P < .05). Higher BMI was also noted to have a significant impact on PROMIS depression and anxiety when controlling for other variables. African Americans had greater pain interference scores (P < .05). CONCLUSION: Our study suggests that early mobilization in a walker boot after operative treatment of ankle fractures is a safe alternative to casting in non-neuropathic patients. When considering operative treatment of ankle fractures, factors such as increasing age and BMI are likely to negatively affect postoperative anxiety, physical function, and depression PROMIS scores regardless of immobilization time. LEVEL OF EVIDENCE: Level III, retrospective cohort study.