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Introduction
Adult scoliosis is a three-dimensional complex rotational deformity caused by an ongoing degeneration of the spine elements at maturity, on a former straight spine; with a Cobb angle > 10o on a coronal level, which furthermore alters the sagital and axial levels.1,2,3
Aebi classifies it into three groups:
Type I: degenerative, primary or de novo. It shows after skeletal maturity. It is secondary to degenerative changes on the discs and articular sides. It mostly appears on the lumbar spine.
Type II: idiopathic, progressive. It shows before skeletal maturity and becomes symptomatic at an adult age.
Type II: adult secondary scoliosis. It is secondary to structural deformities or metabolic disease.3
The prevalence for degenerative scoliosis varies from 2.5% to 15% in controlled populations versus 7.5% to 9.1% in individuals with associated lumbar pain.4,5
While deformity is the main symptom of idiopathic scoliosis in adolescents, there are several symptoms for the degenerative kind.3,6,7,8,9 However, the axial pain is the most frequent claim, reported in 40 to 90% of the cases, mainly when standing or sitting; and it diminishes when the patient releases the weight off the spine by taking a supine or side position. The pain shows on the convexity (75% of all cases) on the curve, on trigger points on muscle insertions around the iliac crest bone and sacrum. It may also be difuse on the affected spinal area.3,6
Conservative treatment includes both drugs and physical therapy.1,9,10,11 The epidural and facet injections for selective blocking of nerve roots act as short term pain relievers.3 Patients with non-treatable pain, radiculopathy and/or neurological impairment would undergo surgery.1,11,12
There is not a consensus for surgical indications; however, symptoms and clinical signs must be clearly understood.1,13 Surgery aims at the pressure relief of neural components through restoring and stabilizing the coronal and sagital balance.10 Surgical options include decompression, in situ decompression and decompression with fusion (anterior and/or posterior).1,13,14 Nowadays, it is known that coronal and sagital balance must be re-established in order for the deformity to be modified in a three-dimensional fashion and not only try to re-establish the sagital or coronal deformity.15
In the United States, the reported prevalence of adult degenerative scoliosis is estimated between 60 to 68%.1 Life expectancy in our population has increased together with advances in medical technology, resulting in changes in the population pyramid. The latter, together with the quest to improve quality of life within this group, makes adult degenerative scoliosis a more common problem for clinicians.5,16,17
The main goal of this study is to analyze the epidemiological, clinical and radiographic aspects in patients with the pathology, who have been diagnosed and taken care of in a referral institution in the last 20 years. The secondary purpose is to determine prevalence and spondylolisthesis level concomitant to adult scoliosis.
Material and methods
It is an analytic, observational, retrospective study. Information was gathered from the data base of admisssion to the Institute. The diagnosis from the data base was double checked by a spine surgeon and a neurosurgeon from the Institute yet, external to this study. The patient’s electronic and radiographic records were depicted. The inclusion criteria was: 40 to 80 year-old men and women, diagnosed with adult degenerative scoliosis who had surgical treatment in the spine surgery division of our institute due to lumbar, radicular pain and/or neurological impairment, from January 1994 to December 2013, whose electronic and radiographic records were complete.
The analyzed variables were: age, gender, spondylolisthesis presence, olisthesis presence, Cobb angle in the deformity (measured in degrees in the anteroposterior (AP) and lateral panoramic spine X-rays), curve levels and severity, type of treatment, hospitalization time and complications.
Proposed statistical analysis: The sample was grouped based on gender, age ranges (young adult = 18 to 45; middle adult = 46 to 60 and elderly ≥ 61), curve magnitude (slight: from 11o to 22o, moderate: 21o to 40o and severe: > 41o). Descriptive statistics was used for quantitative variables through measures of central tendency and dispersion. Qualitative variables were measured through percentages. To contrast the differences between groups, through nominal variables, the χ2 or Fisher’s Exact Test was used. For data with normal distribution, the comparison between medias for related data, with the Paired T-Test for the Cobb angle pre and post surgery values. If the normality requirement was not accomplished, the non parametric Wilcoxon signed-Rank Test was used A p < 0.05 was established as a significant difference. Data were analyzed with The SPSS v.21.0 (SPSS, Chicago, Illinois) statistical package.
Results
Prevalence of lumbar scoliosis in adults according to demographic variables.
Within the period from 1994 to 2013, it was estimated a prevalence of 87/100,000 (CI 95% 67.8-111) patients with adult degenerative scoliosis.
Degenerative lumbar scoliosis was more often found among women from that group 72.1% (44/61) and 27.9% (17/61) among men, at a ratio of 2.6:1. An increase in frequency by age group was observed: young adults: 3.3% (2/61), 26.2% (16/61) in middle adults and 70.5% (43/61) in the elderly (Table 1).
Table 1: Pre-operative radiologic parameters for operatively treated adults with scoliosis stratified based on age group.
| Severity of the curve | Slight (11-20o) n = 2 |
Moderate (21-40o) n = 59 |
Total (%) | p |
|---|---|---|---|---|
| Age group (years) | ||||
| Young adults (up to 45) | 0 | 2 (100%) | 2 (100) | 0.000 |
| Middle adults (46-60) | 0 | 16 (100%) | 16 (100) | 0.000 |
| Older age group (>60) | 2 (4.7%) | 41 (95.3%) | 43 (100) | 0.000 |
| Total | 2 (3.3%) | 59 (96.7%) | 61 (100) |
In the general population, the lowest and highest ages were 41 and 79 with a median of 64.9 ± 9.4 years old (CI 95% 62.2-66.8). In the gender based analysis, the lowest and highest ages in men were 46 and 79, with an average of 64.9 years (± 9.5 CI 95% 62.1-67.5); whereas in women the lowest and highest ages were 41 and 78, with a 64.9 year old average (± 9.4 CI 95% 62.2-66-8), (p = 0.953).
Prevalence of spondylolisthesis associated to degenerative lumbar scoliosis according to demographic variables
The prevalence of spondylolisthesis associated to degenerative lumbar scoliosis was 21% (13/61 patients). In the analysis by gender an increased prevalence among women was found to be 3.52% (8/44) compared to men with 0.8% (5/17).
The most affected level was that of L4-L5 with 61.5% (8/13 patients), one patient with listhesis L3-L4 and one with listhesis L5-S1, which represent 7.7% in each case. Listhesis in more than one segment was reported in 23.1% (3/13 patients). By age groups, there was an increase in the > 61 (61.5%) compared to a < 61 (38.5%). Listhesis was present in 7.7% (1/13) of the slight curves and in 92.3% (12/13) of the moderate ones.
Estimated risk based on demographic variables
Women showed 2.4 times the risk of suffering from degenerative lumbar scoliosis. (OR = 2.37, CI95% 1.35-4.15, p = 0.005), while men showed OR = 0.4, IC95% 0.24-0.73, p = 0.005).
Men showed 1.9 times the risk of suffering from spondylolisthesis associated to degenerative lumbar scoliosis (OR = 1.87, CI 95% 0.51-4.25, p = 0.005).
Radiologic variables
Olisthesis
The level with the highest presence of olisthesis was L-5-S1, with 62.3 % (38/61 patients). The second highest was L4-L5 with 29.5% corresponding to 18/61 patients. The L3-L4 level represented 8.2% with 5/61 patients. A 1.33 mm minimum and 8 mm maximum displacement and 4.5 ± 1.73 mm as the mean was reported.
Severity of scoliosis
The highest vertebral levels involved in the lumbar curves were 2 and 5. With an agulation measured with the Cobb technique, a curve from 16o to 40o with a 30.95o ± 4.9 mean (CI 95% 29.69-32.13) was documented. Men showed an average angulation of 31.23o ± 4.1 (CI 95% 29.31-33.21); women had an average angulation of 30.84o ± 5.8 (CI 95% 29.28-32.41), representing a non significant difference between genders (Table 2).
Surgical variables
To compare the correction obtained in the post surgical lumbar scoliosis deformity with two different techniques (only posterior approach or double approach), the pre surgery Cobb angle was measured. The latter showed values from 16o to 40o (mean = 30.95o ± 4.9). While, the post surgery Cobb angle went from 18o to 40o (mean = 31.13o ± 4.3). Student’s t Test for related samples was done for the Cobb angle analysis both pre and post surgery (p = 0.797), therefore, there was a significant change after surgery.
The type of approach used was posterior (82%) son 50 ocassions and 11 patients (18%) through a double approach (anterolateral transpsoas approach-ALPA and posterior). The number of in-hospital days go from 1 to 28 (mean = 3.30 days). 86.9% of the patients (53/61) did not have immediate or mediate post surgical complications; 7 patients (11.5%) had incidental durotomies at the moment of surgery and one patient (1.6%) developed a superficial infection of the surgical wound.
Discussion
This study presents the casuistry of those patients who were handled surgically in a referral and specialized Institute over a 20 year period and who were disgnosed with adult degenerative scoliosis.
The middle age of presentation in our populationn was 64.6 years old ± 9.4; which differs from what was reported by Tsutsui with a mean = 53.1 ± 15.4 years old and from that reported by Perennou with a mean = 53.1 ± 15.4 and Anwar 53.1 ± 15.4 years old.5,18,19 This could be explained due to the fact that our institute treats people who do not have social security and search for medical attention; though they are referred to a specialized institute at a late stage in the natural history of the disease.20
Depending on the age, the slight curve (11-20o) was present in two patients, with a minimum presentation age of 61 and a maximum of 78, with a mean = 69.50 years old. The severe curve (21-40o) in 59 patients had a minimum age of presentation of 41 and a maximum of 79, with a mean = 64.52, with p = 0.469.
The gender distribution in our study was 72.1% in women and 27.9% in men, similar to what was observed by Anwar, Perennou and Robin with reports of 70.3%, 72% and 63% of women in their respective studies.5,19,21
As in our population Li G. and Tsutsui did not find a statistical significant difference in terms of gender, nor age, for the level of severity of the curve.12,18
Scoliosis prevalence
The prevalence of scoliosis in our study was 0.087%, Perennou shows a 7.5% rate of scoliosis in the adult in patients with lower back pain and Kostuik reported a prevalence of 2.5% for lumbar scoliosis.4,19 Being a specialized Institute, selection criteria and late referral of patients with could explain the low prevalence of our population.
In our sample, the frequency of scoliosis for young adults was 3.3%, 26.2% for middle adults and 70.5% for the elderly. Anwar reported a scoliosis prevalence in the adult of 9.1%, 13.3% and 38.9% in young, middle and elderly adults respectively.5
Olisthesis
A higher presence of olisthesis in L5-S1 with 62.3% was observed in our study group, followed by L4-L5 with 29.5%. A 1 mm minimum and 8 mm maximum displacement was reported, with a mean = 4.5 mm. Pritchett reported a 39% of olistheis, mostly in L3-4 and L4-5. Whereas Grubb reported olisthesis mainly in L3 and L4 in 80% with a mean ≥ 5 mm.22,23
In our population, there was spondilolisthesis in 21.3%, being L4-L5 the most affected level with 13.1%. Pritchett reported listhesis in 55.5% of his sample, out of which, 28.5% in L4-L5 and multi level listhesis in 5%.22 Tsutsui reported more listhesis at L3-L4.18
Scoliosis severity
96.7% of the patients were classified with moderate scoliosis and 3.3% with light scoliosis. In contrast with what reported by Perennou where 56% suffered from light scoliosis and 44% the moderate and severe ones.19
In our population, the mean the Cobb angle was 30.93o ± 4.9o, compared to what was reported by Perennou: 21.2o ± 11.4o.19 Pritchett reported a mean in the curves of 24o in a study with 200 patients.22 On the other hand, Tsutsui reported an angle of 13.5o, in a detection study on healthy patients.18
Although there is no consensus on surgical indications, surgery is considered as possibly helpful for these patients. Li G reported on 34 patients who underwent surgery and found a statistical significant difference in the pre and post surgery Cobb angle of the high curvature in those patients who were treated with fusion of 6 and 7 levels, as well as improvement on the sagital balance, lead line and apical vertebra translation.12 The average fusion levels in our patient cohort are lower, being the mean = 3.36 levels, with this possibly being the reason for not finding improvement on the Cobb angle.
Li G reports complications of 17% being radiculopathy the main one with 12%, in our group, we found complication ratios of 13.1% with incidental durotomy at the top (11.5%).12
This study is limited because it is retrospective, without controls. A longitudinal, prospective study would provide more information on the patient’s profile and a comparative study could help determine different treatment effects.
The changes being held in the demographic characteristics of our population in terms of life expectandy, together with the quest to improve quality of life within the adult group of patients, makes adult degenerative scoliosis a more common problem for clinicians. Understanding the presentation of the disease and its epidemiologic behavior may help improve on time diagnosis and treatment, resulting in higher quality of life levels.
