The relationship between extent of mobilisation within the first postoperative day and 30-day mortality after hip fracture surgery

OBJECTIVE: To determine the association between the extent of mobilisation within the first postoperative day and 30-day mortality after hip fracture.

DESIGN: Cohort study.

SETTING: Acute orthopaedic hospital ward.

PARTICIPANTS: Consecutive sample of 701 patients, 65 years of age or older, 80% from own home, 49% with a trochanteric fracture, and 61% with an American Society of Anesthesiology grade > 2.

INTERVENTION: n/a.

MAIN MEASURES: Cumulated ambulation score (CAS) (0-6 points) on the first postoperative day and 30-day postoperative mortality. A CAS = 0 reflects no functional mobility (bedridden), while a CAS = 6 reflects independent out-of-bed-transfer, chair-stand, and indoor walking status.

RESULTS: Overall, 86% of patients were mobilised to standing or seated in chair (CAS ≥ 1) on the first postoperative day. A CAS of 0, 1-3, and 4-6 was observed for 97 (14%), 519 (74%), and 85 (12%) patients, respectively. Overall, 61 (8.7%) patients died within 30 days with the highest mortality (23.7%, n = 23) seen for those not mobilised (CAS = 0). Only one patient (1.2%) with a CAS of 4-6 points died. Cox regression analysis adjusted for age, sex, residential status, pre-fracture CAS, fracture type, and American Society of Anesthesiology grade, showed that a one-unit increase in CAS was associated with a 38% lower risk of 30-day mortality (Hazard Ratio = 0.63, 95%Confidence Interval, 0.50-0.78).

CONCLUSION: Mobility on the first postoperative day was associated with 30-day postoperative mortality, with a lower risk observed for those completing greater mobility. National registries may consider extending collection of mobility on the first postoperative day from a binary indicator to the CAS which captures the extent of mobility achieved.