Comparative Study Between Pedicle Subtraction Osteotomy (PSO) and Closing-Opening Wedge Osteotomy (Fish-Mouth PSO) for Sagittal Plane Deformity Correction

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Study Design.A retrospective study.Objective.To evaluate the safety and efficacy of closing-opening wedge osteotomy (fish-mouth pedicle subtraction osteotomy [PSO]), for sagittal plane deformity correction and to compare the radiographical outcomes for patients undergoing conventional- and fish-mouth PSO.Summary of Background Data.The closing-opening wedge osteotomy has been developed to achieve a large magnitude of correction at a single level for patients with severe fixed sagittal imbalance.Methods.We retrospectively reviewed the medical records and the radiographs of patients who underwent PSO by a single surgeon between June 2012 and December 2015. Forty patients were included and were divided into 2 groups according to surgical technique (fish-mouth– vs. conventional PSO group). Radiographical measurements included pelvic incidence, thoracic kyphosis, lumbar lordosis, global kyphosis (GK), sagittal vertical axis, osteotomized vertebra angle (OVA), and the height of the osteotomized vertebra (HOV).Results.The preoperative, immediate postoperative, ultimate follow-up and correction of thoracic kyphosis, lumbar lordosis, thoracolumbar junction, and sagittal vertical axis did not show significant differences between the groups. Preoperative GK and OVA were significantly larger in fish-mouth group (GK: 47.1° ± 28.8° vs. 23.7° ± 16.0°, P < 0.05 and OVA: 31.7° ± 14.5° vs. 9.0° ± 11.4°, P < 0.05). The correction of GK and OVA were significantly larger in fish-mouth PSO group (GK: 48.8° ± 24.5° vs. 34.8° ± 17.4°, P < 0.05 and OVA: 42.9° vs. 25.0°, P < 0.05). Preoperative HOV between the groups was not significantly different; however, postoperative HOV was significantly greater in fish-mouth PSO group (2.3 vs. 1.7 cm, P < 0.05). Postoperative transient paraparesis occurred in 3 (20%) and 6 (24%) patients of fish-mouth PSO and PSO group, respectively.Conclusion.Fish-mouth PSO can provide a larger magnitude of correction compared to classic PSO without compromising spinal cord function for fixed sagittal plane deformity.Level of Evidence: 3

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