The Effect of Platelet Dose on Outcomes after Platelet Rich Plasma Injections for Musculoskeletal Conditions: A Systematic Review and Meta-Analysis

Berrigan W, et al. · Current Reviews in Musculoskeletal Medicine

PRP trials across musculoskeletal conditions, stratified by absolute platelet dose rather than by preparation brand. On WOMAC at 6 months or later, 5 studies below 5 billion platelets favoured PRP (mean difference 6.93, 95 percent CI 0.05 to 13.8, P = 0.05), 6 studies at 5 to 10 billion showed no difference (MD -0.32, 95 percent CI -4.06 to 3.42, P = 0.87) and 6 studies above 10 billion favoured PRP (MD 14.8, 95 percent CI 1.47 to 28.12, P = 0.03). On VAS pain, the sub-5-billion stratum showed no difference (MD 0.18, 95 percent CI -0.71 to 1.08, P = 0.69) while 5 to 10 billion (MD 0.31, 95 percent CI 0.06 to 0.57, P = 0.01) and above 10 billion (MD 1.32, 95 percent CI 0.13 to 2.50, P = 0.03) both did. Meta-regression at 6 months found larger WOMAC decreases with higher platelet dose; at 12 months the same trend held with a lower slope. Begg and Egger statistics showed no study bias and a jackknife analysis left the summary effects unchanged.

Population

PRP trials across musculoskeletal conditions with reported platelet dose

Intervention

Higher platelet dose PRP

Comparator

Lower platelet dose PRP

Limitations

A between-study comparison, not a randomised dose comparison: no trial in this literature randomises platelet dose in knee osteoarthritis, so dose is confounded with everything else that differs between studies, including preparation method, indication and injection protocol. The strata are small, at four to six studies each, and the pattern is not monotonic — on WOMAC the middle stratum was null while both the lowest and the highest favoured PRP, which a clean dose-response would not produce. The review pools across musculoskeletal conditions rather than knee osteoarthritis alone. No structural endpoint.