Original ArticleRevision Surgery Rates After Minimally Invasive Adult Spinal Deformity Surgery: Correlation with Roussouly Spine Type at 2-Year Follow-Up?
Introduction
Adult spinal deformity (ASD) surgery can be beneficial to patients; however, revision surgeries occur with regular frequency, leading to increased complications, morbidity, and costs. In many cases, failure to restore the spine to the proper spinopelvic balance can be a contributing factor, and spinopelvic parameters are often incorporated into preoperative planning. The Scoliosis Research Society (SRS)–Schwab classification system has been traditionally used, and surgical planning has relied heavily on preoperative measurements.1 These parameters include the sagittal vertical axis, pelvic tilt, and pelvic incidence (PI)-lumbar lordosis (LL) mismatch.1 Terran et al.2 prospectively analyzed a cohort of 527 patients with ASD and found that outcomes were associated with the SRS–Schwab classification, which correlated significantly with surgical decision-making.2 It has been shown that revision surgery is associated with failure to restore the spine to within the SRS–Schwab normalized parameters.3 However, even with the achievement of the proper balance and parameter values, the need for revision surgery has persisted. Because an inherent balance exists between the spine and pelvis, the relationship between the 2 is important to understand. The Roussouly classification of the normal human spine categorizes the spine into 4 spinal types (types 1–4).4 The types are based on the sacral slope, the shape of the spine, and the apex of the lordosis.5 These are inherent shapes in adults; however, it is unclear how much these shapes play a role in either accelerating or preventing degeneration and in the spine's response to surgical fusion via either adjacent segment degeneration or proximal junctional kyphosis (PJK).6 We investigated whether an association exists between the Roussouly types and revision surgery rates after minimally invasive spinal surgery (MISS) of ASD with a minimum of 2 years of follow-up data. To the best of our knowledge, the present study is the first report of a correlation analysis between the Roussouly classification and MISS spinal surgery for deformities.
Section snippets
Methods
A multicenter database of spinal deformity of patients who had undergone circumferential minimally invasive spinal (cMIS) deformity surgery and open deformity surgery was reviewed retrospectively. The inclusion criteria were age ≥18 years and 1 of the following: coronal Cobb angle >20°, sagittal vertical axis >5 cm, pelvic tilt >20°, PI-LL >10°, a minimum of 2 years of clinical and radiographic follow-up data available, cMIS surgery for ASD, and revision surgery before the last follow-up visit.
Results
A total of 104 patients were included. Of the 104 patients, 41 had had Roussouly type 1, 32 had had type 2, 23 had had type 3, and 8 had had Roussouly type 4. Preoperatively, the type 4 group had had the highest PI (type 1, 50°; type 2, 50°; type 3, 55°; type 4, 66°; P = 0.002) and LL (type 1, 39°; type 2, 27°; type 3, 48°; type 4, 56°; P < 0.001). However, the preoperative PI-LL mismatch was highest in those with type 2 (type 1, 11°; type 2, 24°; type 3, 7°; type 4, 9°; Table 1).
Discussion
Roussouly et al4 described the 4 types of spinal shapes that were inherent in the normal standing adult. The system was refounded by Laouissat et al.8 to include an anteverted pelvis in the classification system. Bari et al.9 performed a study of 64 patients and reported that the Roussouly classification system had very high interrater and intrarater reproducibility, making it reliable for spinal assessments. Although the original description of Roussouly types was intended for the normal human
Conclusions
Our results did not show a correlation between revision surgery for adjacent segment pathology in patients undergoing cMIS surgery for ASD and Roussouly type. We found that type 2 spines had a higher complication rate, which might have resulted from greater sagittal correction when type 2 spines might require less correction.
CRediT authorship contribution statement
Dean Chou: Conceptualization, Methodology, Software, Validation, Formal analysis, Investigation, Resources, Data curation, Writing - original draft, Writing - review & editing, Visualization, Supervision, Project administration, Funding acquisition. Alvin Y. Chan: Conceptualization, Methodology, Software, Validation, Formal analysis, Investigation, Resources, Data curation, Writing - original draft, Writing - review & editing, Visualization, Supervision, Project administration, Funding
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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.