Efficacy of Platelet-Rich Plasma, Mesenchymal Stromal Cells, and Hyaluronic Acid in Preventing Adhesions After Zone II Flexor Tendon Repair: A Narrative Review.

Zone II flexor tendon injuries remain among the most challenging conditions in hand surgery due to the region's complex anatomy and high rates of postoperative complications, particularly adhesion formation and the resulting loss of range of motion. Although platelet-rich plasma (PRP), mesenchymal stromal cell (MSC) therapies, and hyaluronic acid (HA) have demonstrated therapeutic potential in other musculoskeletal conditions, their effectiveness in preventing postoperative adhesions following zone II flexor tendon repair, specifically, remains unclear. A comprehensive review of the literature was conducted using PubMed and Google Scholar to identify randomized controlled trials, prospective and retrospective cohort studies, and original research evaluating the use of PRP, MSCs, or HA in zone II flexor tendon repair. Only full-length English-language studies specifically addressing zone II injuries were included. Studies were excluded if they did not focus explicitly on zone II flexor tendon injuries, lacked clearly reported outcomes, or failed to assess postoperative adhesion formation and functional recovery. Search terms included but were not limited to "Zone II flexor tendon," "PRP Zone II flexor tendon repair," "stem cell Zone II flexor tendon repair," "hyaluronic acid Zone II flexor tendon repair." Data from both human and animal studies were collected to compare postoperative adhesion formation and functional outcomes. Studies across all compounds showed inconsistent results in animal and human trials. PRP for zone II flexor tendon repair showed limited and inconsistent benefits, with most preclinical and clinical trials reporting no significant improvement in adhesion prevention or range of motion. Higher leukocyte concentrations in PRP were associated with increased inflammatory activity, potentially promoting scar formation. In contrast, mesenchymal stromal cell therapies, particularly adipose- and synovium-derived MSCs, demonstrated promising preclinical effects by modulating inflammation, reducing scar-related gene expression, limiting apoptosis, and enhancing tendon gliding though statistical significance was not always achieved. HA showed the most promising results with a majority of animal and human studies consistently reducing adhesion formation and improving tendon excursion and functional outcomes in the long-term. Across all the examined studies, no agent- PRP, MSCs, or HA- consistently prevented postoperative adhesions or reliably improved range of motion following zone II flexor tendon repair, specifically. The complex anatomy of zone II, inconsistent functional outcomes, limited mechanistic understanding, and wide methodological variation among studies, continue to limit the ability to draw definitive conclusions. Cost and accessibility further complicate the clinical adoption of these adjuncts. Current evidence does not support the routine use of PRP, MSCs, or HA for preventing postoperative adhesions after zone II flexor tendon repair. Nevertheless, while research on this topic remains limited, a few existing studies have shown promising trends that warrant further investigation. Future research should incorporate age-specific analyses, standardized agent formulations, clearer mechanistic evaluation, and optimized delivery methods to better determine whether these adjuncts can consistently and reliably improve outcomes in this anatomically challenging region.