Incidence of Acute Post-zoledronic acid reactions following hip fractures at a National Orthopaedic centre.

Introduction:

Adverse effects(AE) of zoledronic acid(ZA) administration, including electrolyte abnormalities and pyrexia, are well documented in the literature. A retrospective audit of all hip fracture patients that underwent fixation at the Royal Victoria Hospital, Belfast between 01/06/25 and  31/08/25 was performed. Incidence of fragility-fracture patients who received IV ZA post-op and recording subsequent reactions during their inpatient stay was reported.  

Methodology.

A total of 222 patients underwent fixation for hip fractures. 17 were excluded due to fracture eligibility e.g. high-trauma or elective. 59 patients were excluded due to ZA eligibility e.g. Creatinine clearance<35ml/min, poor dentition or received ZA within the previous year. 11 patients refused ZA.  146 patients received ZA(mean 5.8 days post-op) with bone profiles collected pre- and post-ZA administration.  

Results:

Serum bone profiles were collected in 101 patients following ZA(mean 4 days post-administration). 45 patients were either discharged pre- or missed bone profile collection. A mean decrease of 0.13mmol/L in adjusted calcium levels was observed following ZA administration, with 6 patients(5.9%) developing new hypocalcaemia. Additionally, 24 patients(23.7%) developed new hypophosphatemia(18 mild 0.6-0.8mmol/L), 5 moderate(0.3-0.59mmol/L) and 1 severe(<0.3mmol/L).  2 patients with pre-existing mild hypophosphatemia developed severe hypophosphatemia following ZA. 4 patients identified as hypophosphataemic pre-ZA administration did not have repeat bone profiles performed following ZA. Of the 146 patients who received ZA, 12 developed pyrexic symptoms following ZA with no other identifiable aetiology(8.2%). 2 patients developed acute kidney injuries secondary to ZA administration. 

Conclusion:

Incidence of AE following ZA administration remain high in fragility-fracture patients. Bone profile abnormalities remain common, most notably hypophosphataemia. Hypophosphataemia is likely multifactorial and may be attributed to poor nutrition/re-feeding picture in our frail cohort.  A significant proportion of our cohort did not receive adequate follow-up to identify BP abnormalities, which prospective studies may wish to monitor and manage at increasing intervals post-ZA administration.