The surgical treatment of adolescent idiopathic scoliosis (AIS) aims to prevent curve progression and deterioration in pulmonary function.1 Harrington and segmental hook instrumentations represent the historical surgical instrumentations, which have provided stable and long-lasting correction of scoliosis with acceptable back pain and health-related quality of life (HRQoL) parameters for thoracic curves.2 However, for lumbar and double major curves there has been a high prevalence of breakdown, degeneration, and loss of lumbar lordosis below the construct. In a recent study, these techniques did not improve the long-term HRQoL as compared with untreated individuals and brace-treated patients with juvenile and AIS.3
Posterior spinal fusion with pedicle screws allows a 3-dimensional correction of the deformity and represents the current standard of surgical treatment.4 Pedicle screw instrumentation provides typically 75% correction of scoliosis with low reoperation rates.5 Recently, a 5-year follow-up of patients treated with pedicle screw instrumentation showed improvement in back pain and HRQoL compared with patients with untreated AIS.6 It remains unclear, whether this improved surgical technique provides superior long-term results after 5-year follow-up in pain and HRQoL as compared with untreated patients with AIS.7
The aim of this study was to evaluate the outcomes of back pain and quality of life after a minimum of 10-year follow-up period after pedicle screw instrumentation for AIS as compared with untreated patients with AIS and healthy individuals. Our hypothesis was that surgical treatment results in the reduced experience of back pain and improved HRQoL as compared with untreated AIS patients.
PATIENTS AND METHODS
Patients
This study included 64 consecutive patients prospectively enrolled from 2 academic medical centers. These patients (aged between 10 and 18 yr) were surgically treated for AIS with a minimum of 10-year follow-up. They underwent a posterior spinal fusion with bilateral segmental pedicle screw instrumentation using a combination of vertebral column derotation techniques along with selective translation, compression, and distraction (CD Legacy, Medtronic, Sofamor-Danek, Memphis, TN).6 For thoracic curves, the last substantially central sacral vertical line touching the vertebra was selected for the lowest instrumented vertebra (LIV). All procedures were performed by the same senior orthopedic spine surgeon. The study received approval from the Ethics Committee of the Hospital District.
Outcome Parameters
Perioperative, radiographic, and Scoliosis Research Society (SRS)-24 outcomes from preoperative to 2-year follow-up were collected prospectively. After a minimum of 10-year follow-up, the 64 patients were invited to clinical evaluation and to complete and return the SRS-24 questionnaire, numerical pain rating scale, query on possible reoperation, and pain drawing indicating localization and categorization of the pain (sharp pain, ache, numbness, and insensitivity).6 The thoracic rib hump during the forward bending test was measured at 6 months, 2 years, and 10 years postoperatively.
Standard standing posteroanterior and lateral radiographs were taken of the spine preoperatively, at 6 months, at 2 years, and at a minimum 10-year follow-up in the surgically treated cohort. Bending radiographs were obtained to evaluate the flexibility of the curves preoperatively. Radiographic variables collected included angles of the proximal thoracic, main thoracic, and lumbar curves as well as sagittal and coronal balance.8 Sagittal measures included thoracic kyphosis (T5–T12) and lumbar lordosis (T12–S1). The curves were classified according to the Lenke classification.9
Patient-Reported Outcome Measures
The SRS-24 is a disease-specific HRQoL questionnaire used to assess the current state of the patient with AIS and the effects of scoliosis surgery, consisting of 24 questions with a maximum score of 120.10 The questionnaire has 7 domains: pain, general self-image, function from back condition, general level of activity, postoperative self-image, postoperative function, and satisfaction. Each domain score ranges from 1 to 5, with higher scores indicating better patient outcomes. A score of 3 or less in the SRS-24 pain domain (1 = severe pain; 5 = pain-free) was considered clinically relevant11 and a numerical pain rating score (NRS) of 4 or more (1 = no pain; 9 = severe pain) was considered moderate to severe pain. The NRS has been validated as a pain measure in children aged 7 to 17 years.12
Controls
Untreated individuals with AIS and healthy control subjects were obtained from our previous study.3 The untreated patients with AIS had been observed in orthopedic departments separate from the surgical cohort and were included in the database between 2006 and 2011. Inclusion criteria were a Cobb angle of at least 10° and scoliosis that was of idiopathic origin. The patients had been diagnosed between 10 and 17 years of age. These 347 subjects had not been brace treated. The data on the Cobb angle of the major curve was collected from the last available radiograph (at a mean age of 19.4 yr).3 The 272 healthy controls were selected from a population register and were invited to complete and return the SRS-22r questionnaire. Using these databases, we matched 53 untreated patients for age (±2 yr) and sex, and 53 healthy controls for age (±2 yr) and sex (Table 1). The age was matched to the age of the surgically treated patient at the final follow-up. The control groups of untreated patients with AIS and healthy individuals had filled out the SRS-22r. The SRS-22r questionnaire is an improved and modified version of the original SRS-24 questionnaire.7,10
TABLE 1 -
Demographics of the Study Population
*
| Variable |
Surgical treatment group at 10 yr follow-up (N = 53) |
Untreated AIS group (N = 53) |
Healthy control group (N = 53) |
P
†
|
| Age† (yr) |
26.9±2.1 |
26.4±4.2 |
27.6±6.1 |
0.21 |
| Sex (M:F) |
8:45 |
8:45 |
8:45 |
1.00 |
| Major curve |
| Preoperative (°) |
57±8.5 |
32±13 |
— |
— |
| 6 mo postoperative (°) |
15±5.7 |
— |
— |
— |
| 2 yr postoperative (°) |
15±5.6 |
— |
— |
— |
| 10 yr postoperative (°) |
15±6.3 |
— |
— |
— |
| Correction (%) at 10 yr follow-up |
74±11 |
— |
— |
— |
| Levels fused |
11.6±1.3 |
— |
— |
— |
| Lenke classification |
| 1 |
26 |
— |
— |
— |
| 2 |
10 |
— |
— |
— |
| 3 |
10 |
— |
— |
— |
| 4 |
1 |
— |
— |
— |
| 5 |
2 |
— |
— |
— |
| 6 |
4 |
— |
— |
— |
*Data are presented as mean and SD unless otherwise stated.
†Kruskal-Wallis test.
AIS indicates adolescent idiopathic scoliosis.
To compare surgically treated patients at 10-year follow-up with untreated patients and healthy controls without scoliosis, we used the preoperative first 15 questions on SRS-24, which are either the same or close to the questions in the SRS-22r questionnaire (questions #1, 2, 4, 5, 6, 8, 9, 11, 12, 14, 15, 17–20). These questions were used to form 4 preoperative domains of the SRS-24 questionnaire: Pain domain (SRS-24 questions 1, 3, 6, 8, and 11; SRS-22r questions 1, 4, 8, 11, and 14), general self-image (SRS-24 questions 5, 14, and 15; SRS-22r questions 6, 19, and 20), general function (SRS-24 questions 7, 12, and 13; SRS-22r questions 9, 15, and 18), and general activity (SRS-24 questions 4, 9, and 10; SRS-22r questions 5, 12, and 17).11,13 Finally, the mean total score of 8 exactly the same questions with similar scoring in both questionnaires were compared.
Statistics
Data are presented as mean and SD or 95% CI, medians, and lower and upper quartiles or frequencies, as appropriate. Age, sex, and group differences were tested with a multiway analysis of variance and group comparisons were adjusted with the Tukey-Kramer method. Normal distribution assumption was checked visually together with the Shapiro-Wilk test. To study whether the mean change of different SRS domain scores occurred over the study, we used a hierarchical linear mixed model with repeated measurements. Compound symmetry covariance structure was used for time. After the main analyses, pairwise comparisons between time points were conducted. Pearson correlation coefficients were calculated when examining the association between two numerical variables. Changes in categorized pain scores were compared with 2 time points with the McNemar test. All statistical tests were performed as 2-tailed, with a significance level set at 0.05. The analyses were performed using SAS System (SAS Institute Inc., Cary, NC).
RESULTS
Out of the 64 surgically treated, 53 patients (mean follow-up, of 12.2 yr; range, 10–14.0 y) were clinically and radiographically examined. The mean preoperative Cobb angle of the major curve was 57 ± 8.5° and the mean age of the patients was 14.7 ± 1.9 years. The mean major curve was 15 ± 6.3° at the final follow-up (Table 1). There were no significant differences in age or sex between the treatment group, the untreated AIS patients, or the healthy individuals (Table 1). The untreated patients with AIS had a mean major curve of 32 ± 13°, including 17 (32%) patients with a main curve exceeding 40°.
For the 53 operatively treated patients, who visited the outpatient clinic at 10-year follow-up, the preoperative SRS-24 questionnaire was available for 45 (85%) patients, 6 months follow-up for 50 (94%), and 2-year follow-up for 47 (89%) patients (Figure 1). The mean length of follow-up for radiographic, HRQoL (SRS-24 questionnaire), reoperation, and deep wound infection data was 12.2 years (range, 10–15 yr). Two (3.1%) out of the 64 patients required a reoperation: 1 patient had a transient neurological deficit with full recovery, requiring T12 pedicle screw removal. One patient was operated for pseudoarthrosis. One patient had a cerebrospinal fluid leak treated during the index surgery and 1 patient had an iatrogenic pneumothorax. There were no postoperative deep wound infections during the follow-up in the cohort.
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Figure 1: Flow diagram of the study population.
Pain Outcomes and Quality of Life in the Surgically Treated Cohort
The SRS-24 total score remained at a high level during the first 2-year follow-up but reduced significantly during the 10-year follow-up. The pain domain score improved from preoperative to 2-year follow-up, declining to preoperative levels at 10-year follow-up (P = 0.85). Only the self-image domain score showed a significant improvement from preoperative to 2 years and remained significantly higher at the 10-year follow-up (P < 0.001) (Table 2). Fifteen (33%) of the patients reported moderate to severe pain preoperatively, 8 (17%) patients at 2 years postoperatively, and 19 (36%) patients at 10 years postoperatively in NRS.
TABLE 2 -
SRS Domains in Surgically Treated Patients
*
| SRS-24 domain |
Preoperative (n = 44) |
6 mo follow-up (n = 51) |
2 yr follow-up (n = 48) |
10 yr follow-up (n = 53) |
P
†
|
| Pain |
3.92±0.73 |
4.31±0.51 |
4.43±0.49 |
3.89±0.75 |
0.85 |
| Self-image |
3.71±0.68 |
4.02±0.70 |
4.00±0.81 |
4.09±0.77 |
<0.001 |
| Function |
4.06±0.48 |
4.09±0.37 |
4.23±0.35 |
4.12±0.45 |
0.13 |
| Activity |
4.69±0.58 |
4.16±0.80 |
4.74±0.45 |
4.53±0.69 |
0.14 |
| Postop self-image |
NA |
3.41±0.56 |
3.30±0.41 |
3.28±0.65 |
NA |
| Postop function |
NA |
2.05±1.04 |
2.74±0.67 |
2.85±0.89 |
NA |
| Satisfaction |
NA |
4.42±0.55 |
4.32±0.61 |
4.19±0.69 |
NA |
| Total score |
4.06±0.51 |
3.93±0.39 |
4.10±0.34 |
3.90±0.47 |
0.040 |
*Values are given as mean and SD.
†Comparison between preoperative and 10-year follow-up.
NA indicates not applicable; SRS, Scoliosis Research Society.
No correlation was found among the 10-year follow-up SRS pain domain or total score and preoperative major curve, postoperative rib hump, lumbar lordosis, thoracic kyphosis, and coronal or sagittal balance. There was no difference in the SRS-24 domains in patients with a smaller (major curve of 15° or less) or a larger residual major curve (>15°) at the final follow-up. The Mean (SD) SRS-24 pain score was 3.85 (0.73) in patients with a smaller residual curve (major curve 15° or less) versus 4.06 (0.69) with a larger residual curve (>15°) at final follow-up (P = 0.317). No radicular symptoms to the extremities were reported in the pain drawings. Two (3.8%) of the patients were using prescription drugs for back pain at the 10-year follow-up.
At 10-year follow-up the SRS-24 domains for pain, satisfaction, and total scores were significantly higher in patients with LIV of L2 or higher as compared with patients with LIV of L3 or lower (P < 0.029 for all comparisons) (Table 3). Thoracic kyphosis averaged 20.8 ± 7.1° in patients with LIV L2 or above and 22.4 ± 10.2° in patients with LIV L3 or L4 (P = 0.54). Lumbar lordosis in patients with LIV of L2 or above was 53 ± 15° and in patients with LIV of L3 or below 54 ± 13° (P = 0.84). The mean coronal balance was in patients with LIV of L2 or above 9.4 mm (range, 0–26) and in patients with LIV of L3 or below 11 mm (range, 0–35) from the central sacral vertical line (P = 0.40) at 10-year follow-up. Sagittal balance was slightly positive in both groups at the final follow-up: 5.5 ± 14.6 mm in patients fused to L2 or above and 8.2 ± 17.7 mm when fused to L3 or L4 (P = 0.55).
TABLE 3 -
SRS Domains in Patients Fused to LIV L2 or Higher and LIV L3 or Lower
*
| SRS-24 domain |
LIV L2 or higher (N = 24) |
LIV L3 or lower (N = 29) |
P
†
|
| Pain |
4.20±0.53 |
3.69±0.81 |
0.023 |
| Self-image |
4.25±0.70 |
4.07±0.91 |
0.29 |
| Function |
4.21±0.27 |
4.07±0.55 |
0.45 |
| Activity |
4.64±0.77 |
4.40±0.67 |
0.066 |
| Postop self-image |
3.46±0.52 |
3.10±0.71 |
0.066 |
| Postop function |
3.00±0.83 |
2.69±0.93 |
0.19 |
| Satisfaction |
4.43±0.49 |
3.99±0.77 |
0.029 |
| Total Score |
4.10±0.30 |
3.75±0.52 |
0.015 |
*Values are given in mean and SD.
†Mann-Whitney test.
LIV indicates lowest instrumented vertebra; SRS, Scoliosis Research Society.
Comparison of Pain and Health-Related Quality of Life (SRS-24) in Surgically Treated Versus Untreated Versus Healthy Controls
Of the surgically treated patients, 32% (17 of 53) scored <4 in the SRS pain domain. In the control group with untreated patients with AIS, 51% (27 of 53) scored under 4 in the pain domain compared with 8% (4 of 53) in the group with healthy controls.
The mean scores in the SRS-24 domains for pain, self-image, and activity were significantly higher in the surgically treated patients as compared with untreated patients with idiopathic scoliosis (P < 0.045 for all comparisons). However, the surgically treated patients had significantly lower pain and function domain scores than healthy individuals at 10-year follow-ups (P < 0.001 for both comparisons). The mean scores of the 8 exactly same questions in both questionnaires showed significantly reduced scores in the group with untreated patients as compared with the surgically treated patients (P = 0.035) (Table 4). Table 4 does not contain postoperative SRS domains (postoperative self-image, postoperative function, and satisfaction) to allow a comparison of the untreated AIS subjects.
TABLE 4 -
Comparison of SRS Domain Scores Between Groups
*
| SRS domain |
Surgical treatment at 10 yr follow-up |
Untreated |
Healthy controls |
P
†
|
P
‡
|
| Pain§
|
4.02±0.78 |
3.72±0.86 |
4.65±0.50 |
0.045 |
<0.001 |
| Self-image |
4.09±0.77 |
3.81±0.82 |
4.38±0.52 |
0.034 |
0.074 |
| Function |
4.12±0.45 |
4.44±0.89 |
4.92±0.22 |
<0.001 |
<0.001 |
| Activity |
4.53±0.69 |
3.89±1.08 |
4.65±0.40 |
0.0012 |
0.77 |
| Total of 8 same questions |
4.13±0.65 |
3.81±0.75 |
4.54±0.43 |
0.035 |
<0.001 |
*Values are given as mean and SD.
†Comparison of surgical treatment group with untreated group.
‡Comparison of surgical treatment group with healthy control group.
§Pain domain does not contain postoperative questions.
SRS indicates Scoliosis Research Society.
DISCUSSION
This study indicates that the positive effect of surgery on back pain diminishes during long-term follow-up in surgically treated AIS patients, while HRQoL remains at a high level 10 years after surgery. Only the self-image domain showed a significant improvement from preoperative to 10-year follow-up, whereas the majority of the domains improved only from preoperative to 2-year follow-up and then declined to the preoperative level. Compared with untreated patients with AIS the quality of life and back pain was statistically significantly better in the surgically treated cohort. The self-image and activity scores of AIS patients treated with spinal fusion were on the same level as healthy controls, while the total score remained at a lower level.
A considerable amount of our patients with AIS report significant pain preoperatively. Of the patients, 28% rated their pain to be moderate to severe before surgery. This is comparable to the results in a published study, where 23% of the patients with AIS reported back pain at the time of diagnosis.14 In other studies, the prevalence of preoperative pain has been reported to be between 35% and 80% in AIS patients.15,16 The prevalence of back pain in AIS patients and the causal relationship to the back deformity remain unclear.
There are studies evaluating the prevalence of postoperative pain after scoliosis surgery with pedicle screws, but in these, the follow-up has been 2 years or less.17–19 In the studies published with over 10-year follow-ups, the surgical technique has not been the current standard.20,21 In a previous study, 190 untreated patients with scoliosis were compared with 166 surgically treated patients.7 In this cohort, no difference was found between the groups on pain, function, or mental health domains of SRS-22r. The untreated cohort consisted of patients who had chosen not to proceed with surgical treatment. We suspect that the patients who preferred nonsurgical treatment were more likely to have nonsymptomatic curves and less pain. In a review article from 2013, it was stated that evidence is lacking regarding the effect of surgery on pain prevalence.22 Of the cohorts, 81% included reported postoperative improvements in pain 2 years after surgery. However, the improvement was considered clinically important only in one of the cohorts. Minimally clinically important difference values have been published for SRS-22r in adolescents with a threshold for pain domain at 0.20.23 Minimally clinically important difference values for SRS-24 are lacking. In a previous study with the current standard treatment, the pain domain score improved by a mean value (95% CI) of 0.29 (0.07, 0.52) at a 5-year follow-up.6 In the current study, we observed an improvement of the mean 0.51 in the SRS-24 pain domain at a 2-year follow-up. This increase in pain score was lost at a 10-year follow-up. Our study indicates that the back pain seems to increase during long-term follow-up to preoperative levels in contrast to anticipated progressive improvement in pain. A similar phenomenon has been observed in surgical treatments of other spinal conditions, such as lumbar spinal stenosis.24 More long-term follow-up data are needed on this topic.
There is significant controversy about whether the caudal fusion level affects the HRQoL and pain in surgically treated AIS patients. Previous studies have not shown any correlation between the experience of pain and caudal fusion level.25,26 In contrast, an increase in pain after longer fusion to L4 and L5 has been described.27 Patients reported in these studies were operated with Harrington instrumentation, which corrects scoliosis by application of distractive forces on the lateral and frontal planes, thus leading to loss of physiological lumbar lordosis and possibly to early degenerative changes in the lumbar spine resulting in pain. In our current study, the pain domain improved at a 2-year follow-up but returned to the preoperative level at a 10-year follow-up. Patients fused to L3 or L4 had statistically lower pain, satisfaction, and total SRS-24 score compared with the L2 and above group. The selection of LIV was according to the Lenke classification.9 It is possible that the curve type itself (structural thoracolumbar curve) has a different HRQoL in the long term. In addition, a lower fusion level leaves fewer discs below the fusion, which may present as a risk factor for future low back pain. This needs further evaluation.
A limitation of our study is the somewhat different questionnaires used. However, we chose to keep the same original SRS-24 questionnaire in the surgical cohort to provide comparable data from preoperative to 10-year follow-ups. To provide comparable questionnaires we chose questions from both questionnaires, which were the same to build up pain, activity, self-image, and function domains. We used the 15 preoperative questions of SRS-24 and the preoperative domains of SRS-24. Our results were supported using 8 of the 15 preoperative questions, which were exactly alike with similar scoring. In the remaining 7 questions, the scoring was not identical, but close enough to make a valid comparison.
The untreated AIS patients had been diagnosed between 10 and 17 years of age and had not been brace treated.3 The data on the Cobb angle of the major curve were collected from the last available radiograph (at a mean age of 19.4 yr).3 Seventeen (32%) of these patients had a curve of 40° suggesting the risk of further deformity progression. Unfortunately, further radiographic follow-up is not available for this untreated cohort. Similarly, bending radiographs were not available and, therefore, Lenke classification could not be provided for this cohort. The response rate of untreated patients was 65% and this may cause a bias in terms of more symptomatic patients returning to the HRQoL assessment.
The study has many strengths. It is a prospective study with consecutively enrolled patients. They were all operated by the same senior orthopedic spine surgeon and the surgical technique was identical, posterior spinal fusion surgery with segmental pedicle screws. The follow-up was a minimum of 10 years with a high participation rate. We used validated standardized questionnaires and the data comprises of patients’ own reports and results are compared with age and sex-matched untreated and healthy controls.
Posterior spinal fusion with pedicle screws for AIS improves back pain and HRQoL as compared with patients with untreated AIS. However, HRQoL remains at a lower level in surgically treated patients as compared with healthy controls.
Key Points
- Patients who had undergone posterior spinal fusion with current treatment standards for adolescent idiopathic scoliosis over 10 years ago were compared with age and sex-matched untreated scoliosis patients and healthy subjects.
- The SRS-24 domains of pain, self-image, function, and activity remained at a high level over the 10-year follow-up.
- Patients with LIV of L2 or above had significantly higher SRS-24 pain, satisfaction, and total scores than patients with LIV of L3 or below at 10-year follow-up.
- Pain, self-image, general activity, and total scores were significantly better at 10-year follow-up in the surgically treated patients as compared with untreated patients, whereas untreated patients scored better in the function domain than the surgically treated patients.
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