Platelet-rich plasma (PRP) is an autologous solution of platelets, concentrated over baseline, that delivers a high dose of anti-inflammatory and anabolic proteins. High-quality data support its use for pathology like knee osteoarthritis (OA), but vast heterogeneity among PRP processing methods and product content make synthesizing clinical data very challenging. Most processing techniques rely upon centrifugation and often involve manual processing steps, such as resuspension or extraction of platelets, which can introduce further heterogeneity in the final product. The Angel cPRP device is a fully automated device that uses both centrifugation and principles of flow cytometry in its PRP processing. However, the system has a wide range of preprocessing settings that alter PRP composition and there are no recommendations or standards on which settings should be used for OA. The aims of this manuscript are to (1) describe a unified PRP processing technique using this system and (2) report preliminary outcomes using that unified protocol when treating knee OA.

For the processing of PRP, all patients had whole blood drawn under aseptic conditions (104 cc whole blood for unilateral OA, 156 cc whole blood for bilateral OA) that was then processed at the unified setting of 0% hematocrit, first spin performed at 4000 rpm for 11 minutes and the second spin at 3000 rpm for 2 minutes. The device automatically separated the resulting PRP that was then injected. For the second aim of this work, 90 knees (63 patients) met the criteria for inclusion. International Knee Documentation Committee (IKDC) subjective scores completed at baseline and 3 months were collected and analyzed.

Overall, IKDC score improved from 42.3±14.1 preinjection to 59.7±17.5 at 3 months postinjection (P<0.001). Of the 90 knees injected with PRP, 57% met the criteria for a positive response at 3 months with an average final IKDC score of 66.5±15.0 (Δ 24.7±10.9). Increased patient age (P=0.008) and body mass index (P=0.008) were associated with lower 3-month subjective IKDC scores.

A single PRP injection created with the unified preparation protocol described here resulted in significant improvement in preliminary patient-reported outcomes. There was a positive response in 57% of patients. Higher age and body mass index were associated with worse outcomes. Given the wide range of preprocessing settings available on this device, the protocol described here can serve as an initial guide for clinical and research implementation.