Management of Methicillin-Resistant Staphylococcus aureus-infected femoral nonunion during lengthening in achondroplasia using circular external fixator: a case report.

BACKGROUND

Achondroplasia, the most common form of rhizomelic dwarfism, occurs in approximately 1 in 25,000 individuals. Clinical features include attenuated growth, rhizomelic limb shortening, and craniofacial abnormalities. Limb-lengthening surgery is widely employed to improve quality of life. However, reports on Methicillin-Resistant Staphylococcus aureus (MRSA) infections in femoral nonunions at lengthening sites are scarce.

CASE PRESENTATION

A 15-year-old boy with achondroplasia presented with MRSA-infected femoral nonunion. Bilateral femoral lengthening had been performed at age 13 using unilateral external fixators. Following a 7 cm lengthening of the right femur, surgical site infection occurred, with MRSA detected on postoperative day 127. Despite debridement and autologous iliac bone graft with non-locking screws, nonunion persisted. Referred to our hospital at age 15, the patient underwent radical debridement until punctate bleeding appeared, and vancomycin-loaded cement beads were implanted. A circular external fixator, effective even with bone weakened by prolonged non-weight bearing, was applied. Six weeks later, further debridement and vancomycin bead replacement were performed. Final fixation included refreshing the nonunion site and placing a cancellous bone graft from the contralateral iliac bone. Bone fusion progressed, and the ring was removed 9 months post-surgery. After seven years, no recurrence of infection was noted. Although slight knee flexion limitation persisted, the patient experiences no pain while walking and has become a healthy working adult.

CONCLUSION

This case highlights the effectiveness of radical debridement, antibiotic-loaded cement beads, autologous bone grafting, and circular external fixation in treating MRSA-induced nonunion at femoral lengthening sites in achondroplasia. Circular external fixators provide stable fixation even in cases of prolonged bone weakness.