Lidocaine patch is a safe and effective topical anesthetic agent for removal of metal staples after total knee replacement

This is a double-blind randomised control trial. After informed consent, the patients who undergoes primary total knee replacement will be assigned to either control group or experimental group randomly. The effectiveness and complication will be analysed.

If the patients are not medically fit for the study (including contraindications for lidocaine), they will be excluded.

Inclusion criteria:

1. Males and females, aged 50-100 years
2. The patients who undergo primary total knee replacement (performed by the same surgeon, Dr.Jiang)
3. Clear consciousness
4. No contraindication for staple removal on the post-operative day 7

Exclusion criteria:

1. Allergy to lidocaine
2. Patient with second or third degree atrio-ventricular block
3. Patients with severe Sinoatrial node block
4. Patients taking class I antiarrhythmia drugs
5. Pregnant patients
6. Patients undergoing revision total knee replacement
7. Contraindication for removal of staples on post-operative day 7