Perioperative antibiotic stewardship by dental hygienists and prosthetic-joint infection risk in South African arthroplasty patients: a target-trial emulation of prophylaxis decision thresholds

Dental hygienists in South Africa increasingly make antibiotic-prophylaxis decisions for patients with prosthetic joints, yet the decision threshold that would justify prophylaxis has never been formally characterised. the present analysis treats the threshold as a design parameter and evaluates, through a target-trial emulation framework, how precisely a before-after-control-impact (BACI) design can recover the effect of hygienist-led stewardship on prosthetic-joint infection (PJI) under a declared variance structure. The analysis is a design and power evaluation, not an observational study: no patient data were used. Under between-cluster SD = 6.0, residual SD = 4.5 and intraclass correlation = 0.640, power was estimated across 2000 replications per design cell for cluster counts of 8, 16, 24 and 32 and effect sizes of 3, 5 and 8 percentage points. Fifty-two clusters were required for 80% power at a 5-percentage-point effect. The intraclass correlation of 0.640 dominated the design: at 8 clusters, only the 8-percentage-point effect approached adequate power, whereas 32 clusters resolved the 5-percentage-point effect. The stewardship threshold and the design threshold are the same quantity viewed from different ends, and that South African dental-hygiene research should be powered for the 5-percentage-point effect rather than the 8-percentage-point effect that current study sizes can detect.