Vertebral growth modulation by posterior dynamic deformity correction device in skeletally immature patients with moderate adolescent idiopathic scoliosis

Abstract

Study design Retrospective, comparative, multicenter. Introduction Growth modulating spinal implants are used in the management of scoliosis such as anterior vertebral body tethering. A motion-sparing posterior device (PDDC) was recently approved for the treatment of moderate AIS. The purpose of this study was to determine if the PDDC can modulate growth in skeletally immature patients with AIS. Methods From a database of patients treated with the PDDC over 4 years, we identified those who had a minimum of 2 years follow-up. Pre-operative and post-operative Cobb angles and coronal plane wedging of the apical vertebra were evaluated on standing full length radiographs. Independent sample t test and one-way ANOVA with post-hoc Tukey HSD analysis was used to compare three groups in varying skeletal maturity: Risser 0–1, Risser 2–3, and Risser 4–5. Results 45 patients (14.2-years old, 11–17) were evaluated with a mean pre-op curve of 46° (35°-66°). The average preoperative major curve magnitude, of either Lenke 1 or 5 curve type, was similar among the three groups 47.6°, 46° and 41.5°. Deformity correction was similar in the three groups, with reduction to 26.4°, 20.4° and 26.2°, respectively, at final follow-up [p < 0.05]. Pre-op wedging 7.4° (3.8°–15°) was reduced after surgery to 5.7° (1°–15°) (p < 0.05). Of those patients, Risser 0–1 (n = 16) had preoperative wedging of 9.5° (6°–14.5°) that was reduced to 5.4° (1°–8°) postoperatively (p < 0.05); Risser 2–3 (n = 15) had pre-op 7.7° (4°–15°) vs. post-op 7.0° (3°–15°); Risser 4–5 (n = 14) had pre-op 4.8° (3.8°–6.5°) vs. post-op 4.7° (3.7°–6.5°). Delta Wedging in Risser 0–1 stage was significantly different than for Risser 2–3 and for Risser 4–5. Conclusion The posterior dynamic deformity correction device was able to modulate vertebral body wedging in skeletally immature patients with AIS. This was most evident in patients who were Risser 0–1. In contrast, curve correction was similar among the three groups. This finding lends support to the device’s ability to modulate growth.

Anterior Vertebral Body Tethering for Treatment of Idiopathic Scoliosis in the Skeletally Immature

“…There is limited data with which to compare the complications of AVBT with other growth modulation techniques for AIS. Floman et al 24 reported results of 45 patients following implantation of a posterior dynamic correction system noting a 9% revision rate at 2 years, all for implant issues, but no conversion to fusion. Betz et al 25 reported a 14% complication rate in 28 patients treated with vertebral body stapling at mean 3.2 years postoperatively.…”

Fusionless All-Pedicle Screws for Posterior Deformity Correction in AIS Immature Patients Permit the Restoration of Normal Vertebral Morphology and Removal of the Instrumentation Once Bone Maturity Is Reached

“…The recently published posterior modulation system [ 10 ] has been demonstrated to modulate the anteroposterior plane by distraction, using pedicle screws at the ends of the concavity. This system raises certain issues that are related to the minimal number of implants used to correct the three-dimensional deformity; it obtains only partial correction of the anteroposterior plane, and the corrective forces that are applied have a lordotic effect.…”

“…This method has been experimentally demonstrated to produce vertebral modulation [ 7 , 8 , 9 ]. There is also recent clinical evidence showing vertebral modulation using distracting forces through pedicle screws located at the ends of the concavity [ 10 ].…”

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

“…Sufficient flexibility of the curve is required to facilitate correction both intraoperatively and during the postoperative physical exercises. Only 1 report on the distraction ratchet had been published at the start of our study; recently, 2 more studies, both retrospective case series, have been published [17][18][19] . Additionally, an in vitro biomechanical study demonstrated that the decrease in range of motion was much less in association with this implant as compared with fusion 20 .…”