Adult spinal deformity (ASD), affecting the thoracic, thoracolumbar, or lumbar spine in the coronal and sagittal planes after skeletal maturity [1], has increased interest in the morbidity and burden with the population of rapid aging [2]. The prevalence of ASD with the Cobb angle > 10° is notably high in elderly individuals of age ≥ 60 years, accounting for up to 68% [3]. Then, ASD has a complex spectrum of disorders, principally consisting of adult idiopathic scoliosis, de novo degenerative scoliosis, and iatrogenic flatback [1]. Age-related factors to accelerate ASD further include osteoporosis, vertebral fracture, spondylosis, spondylolisthesis, mobility restriction, body imbalance, and neurodegenerative disorders [1]. Patients with ASD often complain of back pain, neurological disturbance, deformity, and disability, resulting in a negative influence on the health-related quality of life (HRQoL) [4]. Compared to nonoperative care, operative intervention provides significant improvements in the disability, pain, and HRQoL of ASD patients [5]. However, favorable impacts of ASD surgery on HRQoL largely come from the restoration of sagittal spinopelvic alignment, while the magnitude of coronal malalignment and extent of coronal correction are less critical parameters.6,7 Integrated with consistent findings of following studies [8-10], the association between HRQoL and sagittal alignment has been well validated. More recently, the importance of age-adjusted sagittal alignment has been emphasized [11-14]. Meanwhile, in a retrospective study of prospectively collected data, the correction of sagittal alignment was the most significant predictive factor for the improved HRQoL in patients with combined coronal and sagittal malalignment, although the correction of coronal alignment trended toward but did not reach the significance in those with coronal malalignment alone, due to the limited sample size [15]. Therefore, effectiveness of coronal plane correction in the HRQoL improvement is still undetermined.
A retrospective case-control study from a prospective multicenter database of ASD, by Scheer et al. [16], investigated postoperative 2-year radiographic, HRQoL, and complication outcomes of a unique cohort with scoliosis but also with age-appropriate sagittal alignment. These patients without sagittal malalignment were divided and compared based on the degree of the maximum coronal Cobb angle of 10°–30° and > 30°. Patients with 10°–30° mild scoliosis tended to be frailer with more comorbidities including arthritis, diabetes, and heart disease, who had worse preoperative leg pain Numerical Rating Scale (NRS), Oswestry Disability Index (ODI), and MOS 36-item Short Form health survey (SF-36) physical composite score than those with > 30° scoliosis. On preoperative radiographs, the maximum coronal curve of 10°–30° mild scoliosis existed mainly in the lumbar spine, but with a similar level of the coronal C7 plumb line change to > 30° scoliosis, indicating a short-segment but aggressive lumbar spine curve which would be difficult to compensate for the frailty. During correction surgery, patients with 10°–30° mild scoliosis had less surgical invasion, a smaller number of posterior fusion levels and Smith-Petersen osteotomy levels but larger number of decompression levels, and lower levels of the uppermost instrumented vertebra, whereas the most common location of the lowermost instrumented vertebra was the sacroiliac region. Postoperative 2-year radiographs presented the increased thoracic kyphosis in the group of > 30° scoliosis as well as the decreased maximum coronal Cobb angle in both the groups of 10°–30° and > 30° scoliosis. In patients with 10°–30° mild scoliosis, postoperative 2-year HRQoL measures of ODI, SF-36, Scoliosis Research Society-22R (SRS-22R), and back and leg pain NRS, except for the SF-36 mental composite score, SRS activity, and SRS mental, were improved with statistical significance compared to preoperative values; furthermore, surgical treatment significantly improved all HRQoL variables in those with > 30° scoliosis. The minimal clinically important difference (MCID) and substantial clinical benefit values for HRQoL instruments were also well met in both the scoliosis groups of 10°–30° (36%–74%) and > 30° (39%–78%), although patients with 10°–30° mild scoliosis had a lower rate to meet SRS appearance MCID. Then, a high percentage of surgical complications occurred in both the scoliosis groups of 10°–30° (64.3%) and > 30° (56.0%). In particular, rates of reoperation, implant failure, and neurological deficit were higher with marginal significance in patients with 10°–30° mild scoliosis than with > 30° scoliosis, indicating technically demanding surgery for 10°–30° mild scoliosis but with a short-segment, sharp coronal curve. This study is noteworthy which, for the first time, provides statistically robust data on the preoperative impairment and postoperative improvement of HRQoL in > 30° scoliosis patients and even in 10°–30° mild scoliosis patients, both without sagittal malalignment, undergoing ASD surgery primarily through the sacroiliac region.
The multicenter nature of this study is valuable but should be alerted, as there is a possible small variation in surgical indication and strategy for approaches, techniques, and fusion levels. Unjustified instrumentation is at risk of over treatment, which can lead to a considerable socioeconomic burden, particularly in ASD surgery [17]. Up to 3-level fusion and decompression surgery is commonly performed to treat degenerative spondylolisthesis with vertebral slippage and disc wedge or narrowing from L2 to L5 but with a relatively maintained harmony at L5–S1, providing substantial improvements in pain and function [18]. Unlike conventional fusion and decompression surgery [19,20], long-term results of ASD surgery are not fully uncovered. Further prospective, randomized, controlled trials regarding HRQoL outcomes of short-segment fusion versus long-segment fusion are warranted to identify an acceptable indication of ASD surgery in patients with short-segment, sharp coronal but not sagittal malalignment. This paper [16], published in the September 2023 issue of the Neurospine, has opened up new avenues to debate about impacts of ASD surgery on mild scoliosis and age-appropriate sagittal alignment.
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