Abstract
Revision of infected TKA is one of the most challenging operation as the surgeon should achieve two goals, ie eradication of infection and restoration of function.
For the eradication of infection, a minimum of two operations are needed in most of cases.
First stage of revision is meticulous debridement and insertion of antibiotic loaded cement.
During arthrotomy, thick fibrous and granulation tissues which is located in the suprapatella pouch, lateral site to the patella tendon and posterior joint space should be removed so as to get better exposure, to get rid of infection source and to get better functional result.
During debridement, I use highly concentrated antibiotic saline (1 gm vancomycin in 10cc saline), for irrigation of the operation field. I also pack the opening of the medullary canal so as to prevent the debris from entering into the medullary canal.
I use antibiotics with the ratio of 1:3.
To reduce the dead space in the medullary canal I insert a dowel shaped antibiotic loaded cement spacer made from one pack of cement and fill the medullary canal. Thereafter two packs of cement are used to make a block to fill the gap between femur and tibia. The cement block should be large enough to cover the distal femur and proximal tibia so as not to cause bone defect and knee dislocation during walking.
After first stage of operation, antibiotics are administered for 4∼8 wks until the CRP levels become normalized and clinical findings show no sign of infection.
The 2nd stage of operation is planned when clinical and laboratory signs of infection subside. The decision whether to reimplant the prosthesis or not is based on the operation findings and polymorphonuclear cell count on frozen section. However operation findings are considered more important than the frozen section results for reimplantation.
If operative findings are clean, I do reimplanation even though the polymorphonuclear cell count is more than 5 on high power field(hpf) on frozen section.
I have adopted numbering system to take specimen. Number 1 is specimen from suprapatella pouch, No 2 is that from gap between the femur and tibia, No 3 is that from femoral intramedullary canal, No 4 is that from tibial intramedullary canal, and No 5 is that from most unhealthy site.
In a retrospective analysis of 16 cases which received reimplantation despite of the prescence of more than five polymorphonuclear cells on intra-operative frozen sections, none of the cases had recurrence of infection at a final follow up of 2 years. The femoral medullary canal was the most prevalent site for higher polymorphonuclear cell count.
In conclusion, indication is the first step for successful reimplantion. Two stage revision is recommended and meticulous debridement is utmost important in first stage operation. Block type antibiotic loaded cement is sufficient for a good result.
Clinical, laboratory and operative findings are more important than polymorphonuclear cell count on frozen section to decide reimplantation.
I propose numbering system of the specimen site for frozen section, just as in tumor surgery.
