View Options - Click to expand
Print Options - Click to expand
E-Mail Options - Click to expand

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

Bram Hentenaar, MD
F. Cumhur Öner, MD, PhD
Annet van Royen, MD, PhD

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.)

Our 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 TECHNIQUE

The 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.

OUTCOME

Three months after surgery, the patient presented with normal motor function of the lower extremities and a successful cervical fusion on radiograph ( Figure 2 ). At 5 years' follow-up, there are no complications regarding the cervical spine with the instrumentation still in situ.

DISCUSSION

Atlantoaxial instability may occur in children for several reasons: traumatic injuries, congenital malformations, rheumatoid diseases, connective tissue disorders, and after infection (Grisel syndrome). The treatment is a major challenge in pediatric spinal surgery. Smaller physical size, abnormal anatomy, and growth potential are three important issues faced by pediatric spine surgeons. Despite these problems, the reported success rate using different surgical and nonsurgical techniques is high.1–8

Traditionally, surgical treatment is done with interlaminar structural bone grafting and sublaminar wire stabilization (Brooks procedure)9 or structural bone grafting without wiring (Gallie procedure).10 Both procedures are followed by adjunctive halo vest immobilization.6–8 Lowry et al.6 reviewed the outcomes of 25 pediatric patients who underwent fusion for atlantoaxial or occipitocervical instability with either Brooks or Gallie fusion and postoperative immobilization in a halo jacket. Fusion was achieved in 21 (84%) patients. This technique requires the use of structural bone grafting and an intact arch of C1. However, the passage of wires or cables into the spinal canal causes an increased risk of neural injury, especially in cases of myelopathy.11

More recent studies have reported fusion rates as great as 100% for treatment with transarticular screw fixation.3,4 Gluf and Brockmeyer4 documented a series of 67 patients with 100% fusion with transarticular screw fixation either as a primary method of fixation or as an anchor for craniocervical constructs. To maximize stability, all but one atlantoaxial constructs were supplemented with autologous iliac crest bone graft and multistranded cable wiring. Only two patients were treated after surgery with a halo orthosis. Risks of VA injury were minimized by careful preoperative planning of the screw trajectory on multiplanar CT reconstructions and the use of intraoperative fluoroscopy. In seven cases, unilateral screw placement was done because of anatomical unsuitability.4,5 VA injury occurred in 2 of the 67 patients.

Harms and Melcher12 presented a new technique of posterior atlantoaxial stabilization with minipolyaxial screws and rods. It overcomes the limitations of the transarticular screw fixation in anatomically unsuitable patients and fixed subluxations of C1 on C2. The technique minimizes the risk of injury to the VA and allows intraoperative reduction. They reported 37 patients. The average age was 49 years (range, 2–90 years; 2 patients, <11 years). Successful cervical fusion was reached in all cases, and there were no problems regarding placement of the screws or neurologic deterioration. Only cancellous bone grafts were used, no structural bone grafts. Postoperative immobilization was done with soft cervical collars in 36 cases and a halo vest in 1 case.

One concern that surgeons raise regarding cervical fusion in children is the postoperative growth potential and potential spinal deformity. No growth deformities have been reported. Long-term follow-up in pediatric patients with cervical fusion is necessary to determine if there are any developmental complications related to screw fixation.

We chose a Minerva cast for postoperative immobilization because of the patient's inability to comply with a cervical collar. We believe this method is a good alternative to overcome anatomical difficulties and potential complications associated with transarticular screw fixation. In addition, there is no need for the Harms technique to be supplemented with structural bone graft or sublaminar wiring, so it can safely be used in cases of myelopathy or deficient C1 lamina.

CONCLUSIONS

The Harms technique is effective for obtaining fusion of the atlantoaxial complex in the pediatric population, especially in cases of vertebral congenital anomalies or anatomical unsuitability for other techniques. Even in small children the lateral mass of C1 and the pedicle of C2 are of sufficient size to accept regular polyaxial cervical screws.

Correspondence to: F. Cumhur Öner, MD, PhD, Department of Orthopaedics, University Medical Center Utrecht, PO Box 85500, Utrecht 3508GA, The Netherlands; e-mail:


BRAM HENTENAAR, MD, is affiliated with the Department of Orthopaedics, University Medical Center Utrecht, Utrecht, The Netherlands.

F. CUMHUR ÖNER, MD, PhD, is affiliated with the Department of Orthopaedics, University Medical Center Utrecht, Utrecht, The Netherlands.

ANNET VAN ROYEN, MD, PhD, is affiliated with the Department of Pediatrics, University Medical Center Utrecht, Utrecht, The Netherlands.

References:

  1. Rahimi SY, Stevens EA, Yeh DJ, et al. Treatment of atlantoaxial instability in pediatric patients. Neurosurg Focus 2003;15(6):ECP1.
  2. Meyer B, Vieweg U, Rao JG, et al. Surgery for upper cervical spine instabilities in children. Acta Neurochir (Wien) 2001; 143(8):759–766.
  3. Wang J, Vokshoor A, Kim S, et al. Pediatric atlantoaxial instability: management with screw fixation. Pediatr Neurosurg 1999;30(2):70–78.
  4. Gluf WM, Brockmeyer DL. Atlantoaxial transarticular screw fixation: a review of surgical indications, fusion rate, complications, and lessons learned in 67 pediatric patients. J Neurosurg Spine 2005;2(2):164–169.
  5. Brockmeyer DL, York JE, Apfelbaum RI. Anatomical suitability of C1–2 transarticular screw placement in pediatric patients. J Neurosurg 2000;92(1 Suppl):7–11.
  6. Lowry DW, Pollack IF, Clyde B, et al. Upper cervical spine fusion in the pediatric population. J Neurosurg 1997;87(5):671–676.
  7. Floman Y, Kaplan L, Elidan J, Umansky F. Transverse ligament rupture and atlanto-axial subluxation in children. J Bone Joint Surg Br 1991;73(4):640–643.
  8. Smith MD, Phillips WA, Hensinger RN. Fusion of the upper cervical spine in children and adolescents. An analysis of 17 patients. Spine 1991;16(7):695–701.
  9. Brooks AL, Jenkins EB. Atlanto-axial arthrodesis by the wedge compression method. J Bone Joint Surg Am 1978;60(3): 279–284.
  10. Gallie WE. Fractures and dislocations of the cervical spine. Am J Surg 1939;3:495–499.
  11. Smith MD, Phillips WA, Hensinger RN. Complications of fusion to the upper cervical spine. Spine 1991;16(7):702–705.
  12. Harms J, Melcher RP. Posterior C1–C2 fusion with polyaxial screw and rod fixation. Spine 2001;26(22):2467–2471.