Hoffa's fracture in a five-year-old child diagnosed and treated with the assistance of arthroscopy: A case report

BACKGROUND: Hoffa's fracture is a coronal-oriented fracture of the femoral condyle. It is rarely observed in pediatric patients that isolated coronal fracture of the medial femoral condyle accompanies an intact lateral femoral condyle. Only a few cases involving Hoffa's fracture of the medial femoral condyle have been reported in patients with undeveloped skeletons. Such a fracture cannot be observed by routine imaging examinations, thus resulting in possible misdiagnosis and further treatment challenges. CASE SUMMARY: A 5-year-old boy with Hoffa's fracture of the medial femoral condyle suffered from right knee pain and severe swelling after being hit by a heavy object. The patient was misdiagnosed and initially treated in a local primary healthcare center. No improvement in his right knee’s extension was observed following conservative treatment for 2 wk. The patient was transferred to our hospital, re-diagnosed using arthroscopy, and underwent open reduction and internal fixation. The therapeutic outcome was satisfactory with the screws removed 7 mo after fixation. At the final follow-up of 40 mo, the range of motion in the knee had recovered. There was no varus-valgus instability. CONCLUSION: Hoffa's fracture is rarely seen in children aged 5 years, let alone in the medial condyle, and can easily be misdiagnosed due to limited physical and imaging examinations. Suspected Hoffa's fracture in preschool children should be confirmed based on arthroscopic findings. Open reduction and internal fixation should be performed to protect the articular surface and prevent long-term complications.