Poor angiogenesis and bony ingrowth are the major factors causing unsatisfactory healing between the tendon graft and the bone tunnel surface. Exogenous biological factors, biomaterials, and cells have been considered as new strategies to promote healing quality in recent years. However, it remains challenging for their clinical use because of insufficient in-situ retention time and release efficiency. Increasing attention has been paid to the hydrogel microspheres (HMPs) as potential drug-loading deliveries in biomedicine due to their minimally invasive manner, extended drug retention time, and high loading efficiency. In this review, the healing mechanism between the tendon graft and the bone tunnel is introduced, which is followed by a brief summarization of current methods applied for enhancement of the healing quality. Then, the preclinical studies focusing on HMPs as novel drug carriers are summarized to address the aforementioned concerns in the treatment of tendon–bone healing. Of note, the challenges and perspectives of HMPs in clinical conversion are also outlooked. Collectively, this review may inspire researchers and clinicians to develop clinical available HMPs in orthopedics such as sports medicine from both material and biomedical aspects.

中文翻译：

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水凝胶微球在前交叉韧带重建术后肌腱-骨愈合中的机遇与挑战

血管生成不良和骨向内生长是导致肌腱移植物与骨隧道表面之间愈合不理想的主要因素。近年来，外源性生物因子、生物材料和细胞被认为是促进愈合质量的新策略。然而，由于原位保留时间和释放效率不足，它们的临床应用仍然具有挑战性。水凝胶微球 (HMPs) 因其微创方式、延长药物保留时间和高负载效率而作为生物医学中潜在的载药递送方式受到越来越多的关注。在这篇综述中，介绍了肌腱移植物和骨隧道之间的愈合机制，然后简要总结了目前用于提高愈合质量的方法。然后，总结了以 HMPs 作为新型药物载体的临床前研究，以解决上述在腱骨愈合治疗中的问题。值得注意的是，还展望了 HMP 在临床转化中的挑战和前景。总的来说，这篇综述可能会激发研究人员和临床医生从材料和生物医学方面开发用于骨科（如运动医学）的临床可用 HMP。