Surgical management of moderate adolescent idiopathic scoliosis with a fusionless posterior dynamic deformity correction device: interim results with bridging 5–6 disc levels at 2 or more years of follow-up

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OBJECTIVE

A posterior dynamic deformity correction (PDDC) system was used to correct adolescent idiopathic scoliosis (AIS) without fusion. The preliminary outcomes of bridging only 3–4 discs in patients with variable curve severity have previously been reported. This paper examines a subgroup of patients with the authors’ proposed current indications for this device who were also treated with a longer construct.

METHODS

Inclusion criteria included a single AIS structural curve between 40° and 60°, curve flexibility ≤ 30°, PDDC spanning 5–6 levels, and minimum 2-year follow-up. A retrospective review was conducted and demographic and radiographic data were recorded. A successful outcome was defined as a curve magnitude of ≤ 30° at final follow-up. Any serious adverse events and reoperations were recorded.

RESULTS

Twenty-two patients who met the inclusion criteria were operated on with the PDDC in 5 medical centers. There were 19 girls and 3 boys, aged 13–17 years, with Risser grades ≥ 2. Thirteen had Lenke type 1 curves and 9 had type 5 curves. The mean preoperative curve was 47° (range 40°–55°). At a minimum of 2 years’ follow-up, the mean major curve measured 25° (46% correction, p < 0.05). In 18 (82%) of 22 patients, the mean final Cobb angle measured ≤ 30° (range 15°–30°). Trunk shift was corrected by 1.5 cm (range 0.4–4.3 cm). The mean minor curve was reduced from 27° to 17° at final follow-up (35% correction, p < 0.05). For Lenke type 1 patterns, the mean 2D thoracic kyphosis was 24° preoperatively versus 27° at final follow-up (p < 0.05), and for Lenke type 5 curves, mean lumbar lordosis was 47° preoperatively versus 42° at final follow-up (p < 0.05). The mean preoperative Scoliosis Research Society-22 questionnaire score improved from 2.74 ± 0.3 at baseline to 4.31 ± 0.4 at 2 years after surgery (p < 0.0001). The mean preoperative self-image score and satisfaction scores improved from preoperative values, while other domain scores did not change significantly. Four patients (18%) underwent revision surgery because of nut loosening (n = 2), pedicle screw backup (n = 1), and ratchet malfunction (n = 1).

CONCLUSIONS

In AIS patients with a single flexible major curve up to 60°, the fusionless PDDC device achieved a satisfactory result as 82% had residual curves ≤ 30°. These findings suggest that the PDDC device may serve as an alternative to spinal fusion in select patients.

ABBREVIATIONS AIS = adolescent idiopathic scoliosis; IMAST = International Meeting on Advanced Spine Techniques; PDDC = posterior dynamic deformity correction; SRS-22 = Scoliosis Research Society-22.
Article Information

Contributor Notes

Correspondence Yizhar Floman: Assuta Hospital, Tel Aviv, Israel. yizharfloman@gmail.com.INCLUDE WHEN CITING Published online January 10, 2020; DOI: 10.3171/2019.11.SPINE19827.Disclosures Dr. Floman is a co-founder of ApiFix. Dr. El-Hawary reports being a consultant for Medtronic Canada, DePuy Synthes Spine, ApiFix Ltd., Globus Medical, and Wishbone Medical, and holding stock options in ApiFix Ltd. and Wishbone Medical. Dr. Millgram reports having direct stock ownership in ApiFix. Dr. Lonner reports being a consultant to DePuy Synthes, Ethicon, Zimmer Biomet, and ApiFix; having direct stock ownership in Spine Search and Paradigm Spine; having private investments in Paradigm Spine; serving on the Scientific Advisory Board, Speaker’s Bureau, and receiving royalties from DePuy Synthes for the development of the Expedium Plus Implant System; serving as a Scientific Advisory Board Member for ApiFix; serving on the Board of Directors of Spine Search and the Setting Scoliosis Straight Foundation; and serving on the Speaker’s Bureau for K2M. Dr. Betz reports being a consultant for ApiFix, DePuy Synthes Spine, Globus Medical, SpineGuard, and Wishbone Medical; having stock options in Abyrx, ApiFix, Electrocore, Medovex, Orthobond, SpineGuard, and Wishbone Medical; receiving royalties from DePuy Synthes Spine, Globus Medical, SpineGuard, and Thieme Medical Publishers; serving on the Speakers Bureau for DePuy Synthes Spine and Globus Medical; and having a child who is employed by DePuy Synthes Spine.
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