Alternatives to Spinal Fusion Surgery in Pediatric Deformity

Randal R. Betz, MD; M. Darryl Antonacci, MD; Laury A. Cuddihy, MD

Disclosures

Curr Orthop Pract. 2018;29(5):430-435. 

In This Article

Posterior Dynamic Concave Distraction (Apifix ltd, Misgav, Israel)

The posterior dynamic concave distraction device relies on two to four pedicle screws placed on the concave side of the curve connected to a mini-ratcheting device through polyaxial ring connectors that allow for gradual curve correction with specific physical therapy exercises (Figure 2A–C). Biomechanical testing on cadaveric human thoracic spines showed that the device has significantly less restriction of motion compared to standard posterior spinal fusion, although it does limit some flexion and extension by 40% and lateral bending by 18% as compared to an uninstrumented spine.[43] Additionally, testing revealed that adjacent vertebral segment stresses are not significantly altered as happens with fusion.[43] This lack of adjacent level stress is likely secondary to the unique polyaxial joint that prevents mechanical stresses from being transferred to the pedicle screw except with pure axial compression. Each device or screw connection allows 50 degrees of freedom in all directions.

Figure 2.

(A) Anteroposterior radiograph of a 15-year-old girl with 50-degree Lenke 1 curve, Risser 4. (B) Two years after surgery with ApiFix. The curve is stable at 28 degrees. (C) Lateral view at 2 yr follow-up. (Courtesy of Yizhar Floman, MD).

Floman et al.[44,45] reported good short-term results using the device in patients with AIS with preoperative curves ranging from 43 to 53 degrees. At final follow-up between 6 mo to 2 yr, all of the patients were pain free, with curve correction of 22 to 33 degrees.

Posterior Dynamic Concave Distraction Indications

The current indications for posterior dynamic concave distraction surgery (CE mark approval in Europe) include patients with AIS between the ages of 10 and 17 yr with single curves, Lenke 1 and 5 curves measuring 40 to 60 degrees, and correction to 35 degrees or less on side bending films. The device may also be used as an internal brace in patients with smaller curves who are non compliant with external bracing.

Posterior Dynamic Concave Distraction Complications

There appear to be few complications with the posterior periapical concave distraction procedure owing to its minimally invasive nature. Reports show short surgical times with less potential for infection and blood loss compared to standard posterior spinal fusions for Lenke 1 curves.[46] Furthermore, due to the fact that no fusion is attempted, there is no risk for pseudarthrosis. If a standard posterior spinal fusion is necessary at a later time, it can still be performed.

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