Orthopedic Intervention in an Organic Acid Disorder: Challenges in the Management of Hip Dislocation in a Child with Late Onset Methylmalonic Acidemia.

Introduction: Hip dislocation is a rare secondary complication due to neuromuscular dysfunction in organic acid disorders like methylmalonic acidemia (MMA). Surgical intervention in patients with metabolic-driven basal ganglia lesions present with unique challenges for both physiological stability and mechanical success. Case Report: A 11-year-old boy with late-onset MMA presented with generalized spasticity, involuntary movements, and a left hip deformity in flexion, adduction, and internal rotation. Imaging confirmed a left hip dislocation associated with coxa valga and caput valga. The patient was managed initially with muscle relaxants followed by surgical intervention consisting of a closed reduction, proximal femoral varus osteotomy, adductor tenotomy and a medial femoral caput epiphysiodesis. Post-operative management utilized an abduction brace; however, persistent spasticity created significant challenges in maintaining hip stability and compliance to orthosis. Conclusion: Surgical management of hip dislocation in MMA requires addressing both the bony deformity and the underlying neuromuscular forces. While anatomical reduction is achievable, aggressive management of spasticity is critical to prevent recurrence in the acute post-operative period.