Snap Back Versus Traditional Aspiration in Bone Marrow Harvesting: Quality Assessment and Clinical Outcomes

Background: The extent to which bone marrow aspiration technique affects the biological quality of bone marrow aspirate and its clinical relevance in knee osteoarthritis remains uncertain. This study compares the efficacy of the traditional aspiration method and the Snap Back technique at two anatomical harvest sites, the posterior iliac crest and the proximal tibia. Methods: This ancillary post hoc analysis was conducted within a randomized trial comparing posterior iliac crest and proximal tibia harvest sites in 60 patients with unicompartmental knee OA. Aspiration technique (traditional vs. Snap Back) was selected intraoperatively and not randomized. BMA samples were analyzed for MSCs, mononuclear cells (MNCs), platelet concentration, and marrow purity. Clinical outcomes were assessed at baseline and six months using the Visual Analog Scale and the Western Ontario and McMaster Universities Osteoarthritis Index. Results: The posterior iliac crest yielded significantly higher MSC and MNC concentrations compared to the tibia, with superior purity and PLT counts observed using the Snap Back technique. Within each anatomical site, Snap Back aspiration provided improved cellular recovery over the traditional method. However, differences in clinical outcomes between groups were modest and did not consistently reach statistical significance. Conclusions: Both harvest site and aspiration technique were associated with substantial differences in the cellular composition of BMA. The withdrawal from posterior iliac crest combined with the Snap Back technique optimizes MSC yield and marrow purity, though clinical improvements appear independent of cellular concentration in the short term. These findings suggest that standardized aspiration protocols may be relevant for the biological efficacy of orthobiologic therapies in knee OA.