Association of non-anaemic iron deficiency with postoperative outcomes after fast-track hip and knee arthroplasty: a prospective cohort study

BACKGROUND: Preoperative iron deficiency anaemia is a common risk factor for worse postoperative outcomes. However, the influence of preoperative iron deficiency without anaemia on postoperative outcomes after hip and knee arthroplasty is uncertain.

METHODS: We used the Fast-track Center for Hip and Knee Replacement Database registry from eight Danish departments for this prospective cohort study. Anaemia and iron deficiency were defined as haemoglobin of <130 g L-1 and transferrin saturation <20%, respectively. Patient characteristics were collected using patient-reported questionnaires and information on prescribed medication, laboratory results and follow-up using electronic healthcare records. Quantile regression was used to analyse changes in median days alive and at home at postoperative day 30 (DAH30) and day 90 (DAH90), adjusting for procedure, hospital, and comorbidity. Additional endpoints included length of hospital stay >2 days, 30-day readmission rate, and self-evaluated health (EuroQol Visual Analogue Scale [EQ-VAS]) at 90 days.

RESULTS: The cohort included 964 iron deficient and 3919 iron replete participants undergoing primary unilateral hip or knee arthroplasty. Median DAH30 was 29.0 (interquartile range 29.0-30.0) days in both groups, but differently distributed (P<0.001). Adjusted difference in median DAH was -0.00 (95% confidence interval -0.00 to -0.00; P=0.001) and -0.00 (95% confidence interval -0.00 to -0.00; P=0.006) days for DAH30 and DAH90, respectively. There was no association between iron deficiency and any of the other endpoints.

CONCLUSIONS: The influence of iron deficiency on days alive and at home at 30 and 90 days after fast-track hip or knee arthroplasty was statistically significant, but of minimal clinical importance. Correction of preoperative iron deficiency without anaemia is unlikely to improve common postoperative outcomes in these procedures.

CLINICAL TRIAL REGISTRATION: NCT05613439.