Nonoperative Management of an Acute Complete Achilles Tendon Rupture With Mesenchymal Stem Cells and Extracellular Vesicles: A Case Report.

An acute complete rupture of the Achilles tendon with a large intertendinous gap is conventionally regarded as a surgical indication, yet operative repair carries a significant burden on wound-healing and potential for neurovascular complications, whereas nonoperative care may be limited by re-rupture and incomplete functional recovery. Human umbilical cord-derived mesenchymal stem/stromal cells (hUC-MSCs) and their secreted extracellular vesicles (EVs) exert immunomodulatory, pro-angiogenic and pro-tenogenic paracrine effects that could support tendon healing. A healthy 45-year-old recreationally active male sustained an acute complete rupture of the right Achilles tendon while playing tennis. A 3.0-T magnetic resonance imaging (MRI) confirmed a full-thickness mid-substance rupture located 6.1 cm proximal to the calcaneal insertion, with a 3.7 cm gap. He delayed treatment and opted out of surgical management and was offered nonoperative care with a combined biologic regimen: two ultrasound-guided intralesional injections of hUC-MSC-derived EVs (a total of 30 × 10⁹ vesicles) deposited into the tendon gap, both stumps, and the peritendon along with three consecutive daily intravenous (IV) infusions of hUC-MSCs (approximately 1.7 × 10⁶ cells/kg of total body weight) as a paracrine priming adjuvant, alongside an injury-guided functional rehabilitation program.  Pain measured using the numeric rating scale (NRS) decreased from 10/10 at baseline to 0/10 at six months post-intervention. At final follow-up (approx 14 months) the patient had returned to regular weight training and jogging without pain or functional limitations. On physical examination, the Thompson Test was negative, the Achilles Tendon Total Rupture Score (ATRS) and the American Orthopaedic Foot & Ankle Society (AOFAS) ankle-hindfoot scores were both calculated as 100/100, and instrumented biomechanical testing showed near-symmetric lower-limb range of motion and balance. Follow-up MRI demonstrated a remodeled tendon with restoration of continuity and no residual gap. No mild or severe adverse events were reported during or after procedures. In this single case report, a combined regimen of systemic hUC-MSCs and intralesional hUC-MSC-derived EVs was associated with imaging-confirmed tendon healing and full functional recovery of an acute complete Achilles tendon rupture managed nonoperatively. This treatment protocol serves as a hypothesis-generating observation with potential for validation in controlled prospective studies.