Knee flexion during skin preparation improves anterior antiseptic coverage: A controlled fluorescent dye study

Periprosthetic joint infection (PJI) is a rare but devastating complication of total knee arthroplasty (TKA) and a leading cause of TKA failure. Thorough skin preparation is a key preventative measure; however, the influence of limb position on antiseptic coverage has not been evaluated. This study compared the effectiveness of anterior knee antiseptic coverage in flexion and extension using a validated fluorescent dye model.

A prospective single-centre trial at Colchester General Hospital recruited ten healthy adult volunteers (20 knees) who underwent standardised preparation with 0.5 % chlorhexidine gluconate in 70 % ethanol after fluorescent dye application. The knees were prepared either in full extension or in maximal flexion in a fixed sequence. Ultraviolet (UV) imaging and digital analysis were used to quantify the residual dye as a surrogate for incomplete antiseptic coverage. Intra and interrater reliabilities were assessed using intraclass correlation coefficients (ICC).

Eighty preparations (40 flexion, 40 extension) were analysed, with flexion yielding significantly less residual dye than extension (median [IQR: interquartile ratio] 1.7 % [IQR 0.1-7.2] vs. 9.8 % [IQR 2.6-19.0], p < 0.0001). The subgroup analysis confirmed consistent findings across both investigators. The intrarater reliability was good to excellent (ICC 0.62-0.89), whereas the interrater reliability was poor (ICC 0.07-0.35). No adverse events were reported.

Maximal knee flexion during skin preparation significantly improved anterior surface antiseptic coverage compared with extension. This simple, cost-neutral modification can be readily incorporated into TKA workflows, as we have done previously. Further studies with microbiological endpoints and broader patient populations are warranted to establish the effect on PJI prevention.