Adding Satellite Rods to Standard Two-rod Construct With the Use of Duet Screws: An Effective Technique to Improve Surgical Outcomes and Preventing Proximal Junctional Kyphosis in Posterior-Only Correction of Scheuermann Kyphosis

Study Design. A retrospective matched-cohort comparative study. Objective. The aim of this study was to compare the surgical results after the use of duet screw based satellite rods and bilateral satellite rods (S-RC) versus a standard two-rod construct (2-RC) across osteotomy sites in a matched cohort with Scheuermann kyphosis (SK). Summary of Background Data. Multiple Ponte osteotomies are frequently employed to correct SK via a posterior-only approach, with a 2-RC across the osteotomy sites. Whereas, correction rate and junction problems remain as the major concerns. Methods. This study reviewed a consecutive series of patients with SK who had undergone posterior-only correction with multilevel Ponte osteotomy between 2009 and 2014 and had been followed over 24 months. Twenty-two patients receiving placement with an S-RC with the use of duet screws were identified and closely matched with 22 patients with a 2-RC in terms of age, apex, and magnitude of kyphosis. Comparisons were made with regards to deformity magnitude, correction results, complications, and clinical outcomes between the two groups. Results. No significant difference was found between groups in preoperative patient's factors (age, gender, apex, magnitude of kyphosis, and SRS-22 scores) and surgical factors (blood loss, operation time, osteotomy levels, and fused levels). Compared with the 2-RC group, the S-RC group had higher correction rate (55.4% ± 7.5% vs. 46.2% ± 5.1%, P < 0.001), less correction loss (1.0 ± 0.8° vs. 2.4 ± 1.4°, P < 0.001) during the follow-up, and higher improvement of back pain as well (P < 0.05). None were detected with pseudarthrosis or implant failure in either group, but proximal junctional kyphosis was less frequently seen in S-RC group (1 of 22) than 2-RC group (7 of 22) (P < 0.05). Conclusion. As a safe method, use of S-RC is effective in providing increased kyphotic correction across multiple Ponte osteotomy levels, and improving patient-reported outcomes of management satisfaction and back pain. The biomechanical benefits of stress dispersion, coupled with increased stability and weight bearing ability, make it a powerful technique preventing correction loss and proximal junctional kyphosis. Level of Evidence: 3

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