Joost Peerbooms

39 PRP after total knee arthroplasty Platelet-rich plasma preparation In the group randomized to receive PRP the patient’s own platelets were collected using the GPS System (Biomet Biologics, Warsaw, Indiana). This device uses a desktop-size centrifuge with disposable cylinders to isolate the platelet rich fraction from a small volume of the patient’s anticoagulated blood drawn at the time of the procedure. First a 60 mL syringe was filled with 7 mL of anticoagulant citrate phosphate dextrose formula A and 53 mL of whole blood was drawn via an intravenous catheter in the medial cubital vein using a 17 G needle. Proper mixing with the anticoagulant was done by 8 times inverting the syringe. The platelet rich fraction was prepared according to the instructions for the use for the GPS System. In brief, blood was drawn into a 60mL bowl of the blood cell separator and centrifuged 15 min at a rate of 3200 RPM for sequestration. Approximately 6 mL PRP was obtained for each patient. The PRP was then buffered to physiologic pH using 8.4% sodium bicarbonate. Autologous thrombin was isolated from 4 mL PRP and 0.17 mL of 10% calcium chloride to antagonize the anticoagulant in the donated blood. Addition of calcified thrombin activated the platelets. The total time fromblood draw to injection in the patients was about 90 min. No specialized equipment, other than the centrifuge to process the GPS disposable, was required. A person that is certified for blood management performed all the procedures under sterile conditions. Injection technique Using an aerosol spraying at a distance of 10-15 cm with the knee flexed in 90 degrees, which expose the knee cavity, 6 mL PRP was applied to the dried wound site (synovium and bony cutting edges of femur and tibia); thereafter, the wound was closed in layers. After closure of the joint capsule the subcutaneous tissues of the patients randomized to receive PG were sprayed with the platelet-poor plasma (PPP) fraction (±10 mL). Rehabilitation Postoperative pain relief was achieved using a standard protocol (paracetamol 3 g daily and diclofenac 50 mg 3 x daily, with pantoprazol 40 mg daily as ulcer protective). All patients received thrombosis prophylaxis via a subcutaneous injection of 0.3 ml low- molecular-weight heparin daily before operation and continued until sufficient effect of oral anticoagulants (acenocoumarol) was achieved. The oral anticoagulants were used up to 12 weeks postoperatively. Rehabilitation, which was started the day after surgery using crutches, was according to the Joint Care program (Biomet, Indiana, USA). The physiotherapist was also blinded to which procedure was used. Wound score form A wound score form was used for scoring wound healing (Table 1). A pilot study showed the wound score form to be sufficiently reliable (K = 0.8, unpublished data). The score ranges from 0 to 100, where 0 represents a dry wound without any sign of infection, and 100 represents wound leakage with signs of infection. Points of changes of wound 3