High Failure Rates of a Unilateral Posterior Peri-Apical Distraction Device (ApiFix) for Fusionless Treatment of Adolescent Idiopathic Scoliosis

Background: Conventional surgical treatment for adolescent idiopathic scoliosis (AIS) consists of correction of the spinal deformity with rigid spinal instrumentation and fusion. Less-invasive and fusionless surgery could potentially improve patient outcomes. The purpose of the present study was to evaluate the efficacy of a recently U.S. Food and Drug Administration (FDA)-approved posterior peri-apical self-distracting device (ApiFix) that is designed to gradually correct the deformity without spinal fusion. Methods: In a prospective cohort study of 20 patients with AIS (Risser stage 1-4; Lenke 1 or 5; major curve Cobb angle, 40 degrees to 55 degrees; and Bunnell scoliometer rotation, <15 degrees) were managed with the ApiFix device. Clinical and radiographic performance was assessed. Results: Twenty patients with a mean age (and standard deviation) of 14.8 +/- 1.4 years were followed for a mean of 3.4 +/- 1.0 years. The average major curve was reduced from 45.4 degrees preoperatively to 31.4 degrees at 2 weeks postoperatively and 31.0 degrees at the time of the latest follow-up. The average minor curve measured 31.3 degrees preoperatively, 26.1 degrees at 2 weeks postoperatively, and 24.2 degrees at the time of the latest follow-up. Ten patients had serious complications that required revision surgery, including osteolysis (n = 6), screw and/or rod breakage (n = 2), failure of the ratchet mechanism (n = 1), and pain without explainable cause (n = 1). During revision surgery, metallosis was observed in all patients and cultures showed growth of Cutibacterium acnes in 6 patients. Because of the high failure rate, the study was terminated early. Conclusions: The use of the unilateral peri-apical concave self-distracting ratchet rod initially was associated with promising clinical and radiographic results. However, no distraction was observed and the high rate of serious adverse events within 2 years was considered to be unacceptable for further clinical application of this device in our institution, despite recent FDA approval.

Automated summary

The study evaluated a new self-distracting device ApiFix for treating AIS, showing promising clinical and radiographic results initially. However, due to a high rate of serious complications within 2 years, the study was terminated early, indicating the device's unsuitability for further clinical application despite recent FDA approval.