Background: Slipped upper femoral epiphysis is the most common disorder affecting adolescent hips. When diagnosed on a subacute basis, it provides significant challenges for the orthopaedic surgeon. Addressing kinked retinacular vessels with an open subcapital reorientation in the past has resulted in high rates of avascular necrosis. As our understanding of these injuries has improved, management has evolved with Dunn’s description of reorientation through a posterior approach with a trochanteric osteotomy. This approach has been further enhanced with creation of a retinacular soft-tissue flap. Still, there is a paucity of evidence in the literature, becaise there are no large case series reproducing initial promising results. Purpose: This video overview and case presentation demonstrates the modified Dunn approach for patients presenting with subacute slipped upper femoral epiphysis. Methods: The anatomy of, diagnosis of, and treatment options for slipped upper femoral epiphysis are reviewed. We discuss surgical indications and considerations, including in situ pinning, the Parsch technique, and the modified Dunn approach. A 16-year-old young man with a painful right hip was found to have a slipped upper femoral epiphysis. He was able to ambulate, albeit with pain. On presentation, an MRI was obtained confirming the subacute nature of this injury, and after a thorough discussion of risks, benefits, and prognosis, the patient elected to proceed with a modified Dunn capital realignment procedure. Results: An anatomic reduction of the epiphysis was achieved without undue tension on the reticular vessels. Metaphyseal blood flow after stable reduction was noted to be good. At 4 months after surgery, hardware was removed and there was no motion noted at the physis. Conclusion: The modified Dunn capital realignment procedure is a challenging procedure that, if done appropriately, can preserve the retinacular blood supply while fusing the physis in an anatomic position. Appropriate soft-tissue dissection is crucial to good functional outcome.