Intramedullary nailing for subtrochanteric fracture in autosomal dominant Type II osteopetrosis: Case report of 2 patients

RATIONALE: Autosomal dominant type II (AD II) osteopetrosis is a rare inheritable metabolic bone disease characterized by hard but brittle bone and a narrow medullary canal. Intramedullary nailing (IMN) is a difficult but attractive option for the treatment of subtrochanteric fractures in patients with AD II osteopetrosis. PATIENT CONCERNS AND DIAGNOSIS: Two patients with AD II osteopetrosis sustained subtrochanteric fractures after a fall. INTERVENTIONS: IMN was performed through the sequential use of instruments such as a 4.9-mm drill bit, small reamer, and larger reamer for over-reaming. OUTCOMES: In the first case, IMN left some gap at the fracture site. Dynamization was performed to treat the delayed union at 6 months postoperatively. The fracture healed at 10 months after the dynamization. In the second case, IMN was successful without a gap, and the fracture healed at 8 months. LESSONS: Although IMN is difficult to perform owing to partial obliteration of the medullary canal in AD II osteopetrosis, it can be performed with sequential widening of the medullary canal using various instruments. In addition, the fracture gap should not be left uncorrected during IMN to attain fracture union.