Case Report: Atlantoaxial Instability in a 4-Year-Old Child Treated With Harms Technique

Abstract

A 4-year-old child with a chronic inflammatory syndrome and osteolytic lesions of unknown cause presented with C1-C2 instability and myelopathy. She was treated successfully with posterior atlantoaxial screw arthrodesis with Harms technique. Atlantoaxial instability in children is rare and is usually treated with conventional wiring techniques or transarticular screw fixation (Magerl technique). The latter shows very high fusion rates, but it is technically demanding and has a potential risk of injury to the vertebral artery (VA). In addition, in some cases the procedure cannot be used because of anatomical unsuitability or the presence of fixed subluxation of C1 on C2. To overcome these limitations, Harms developed a technique of fixation with pedicle screws. The technique is easier to apply than transarticular screw fixation and lowers the risks of injury to the VA. Fusion rates are comparable. The authors used polyaxial-head screws and rods for posterior fixation of the atlantoaxial complex in a 4-year-old child. Successful posterior fusion of C1-C2 and decompression of the myelum was achieved. Fixation of the atlantoaxial complex using the Harms technique is an efficient alternative to previously reported fusion techniques for the pediatric population. (J Prosthet Orthot. 2007;19:48-50.) KEY INDEXING TERMS: atlantoaxial instability, cervical fusion, Harms technique, posterior screw fixation O ur patient was born with a chronic inflammatory syndrome and osteolytic lesions of unknown cause. Computed tomography (CT) scan showed osteolytic lesions in the metaphysis of radius and tibia and thickening of all costochondral junctions. This was histologically diagnosed as reactive periostitis. She was treated with high-dose corticosteroids for 2.5 years, complicated by hypertension and osteoporosis. She developed a vertebral collapse of C5-C6 and anterior subluxation of C1 on C2 (Figure 1) after a mild trauma. It was not clear whether the atlantoaxial instability was a result of an inflammatory process.Lateral flexion-extension radiographs were obtained to confirm diagnosis. Magnetic resonance imaging showed a mild myelopathy at C1-C2 region. Physical examination proved involvement of the pyramidal tract with gait abnormality, hyperreflexia, and motor weakness. SURGICAL TECHNIQUEThe C1-C2 subluxation was treated under general anesthesia with a posterior spondylodesis. An Axon-system (Synthes, Inc, West Chester, PA) with four polyaxial-head screws (3.5 mm outer diameter) was used for fixation of the C1 lateral mass and the C2 pedicle. Drilling was guided by anatomic landmarks and fluoroscopy. Polyaxial screws of appropriate length were inserted, then C1 was lowered onto C2 before fixation to the 3-mm rods. Finally, allograft bone chips mixed with bone marrow aspirate were added. Postoperative cervical immobilization was provided with a Minerva cast for 3 weeks.