DOI: https://doi.org/10.21203/rs.3.rs-1476067/v1
Study Design: A prospective single-center study. Level of Evidence IV
Purpose: To reveal frontal and sagittal patterns of spinal deformity depends on neuromuscular nosology for surgery and outcomes planning.
Methods: The evaluation criteria were: age, gender of patients, volume of blood loss, duration of hospital stay, measurement of the deformity curve, thoracic kyphosis and lumbar lordosis (Cobb angle), pelvic obliquity relative to the horizontal line, the percentage of the curve correction. The Cobb angle was measured preoperatively, prior to discharge from the hospital (up to 21 postoperative days) and one year after surgery.
Results: The cohort of 71 patients with spinal deformities due to neuromuscular diseases included four groups: muscular dystrophy (MD), spinal muscular atrophy (SMA), Duchenne muscular dystrophy (DMD) and cerebral palsy (CP). The most characteristic deformity in the frontal plane was C-shaped thoracolumbar scoliosis with the pelvis rotation, rotation of the vertebrae increased according to the magnitude of scoliosis. Lumbar hyperlordosis were common for CP patients, whereas decreased thoracic kyphosis or even thoracic lordosis occurs more frequently in DMD patients. Moderate scoliosis correction was noted in all groups. There was no significant improvement in functional status according to FIM.
Conclusion: The findings showed that rigid hyperlordosis the key problem of spinal deformities in neuromuscular patients. Scoliosis and pelvic obliquity can be well corrected in NMS by pedicle screw construction with standard maneuvers and pelvic screw fixation.
Neuromuscular scoliosis (NMS) can be defined as a secondary deformity of the spine with a leading scoliotic component caused by muscle imbalance due to neuropathic or myopathic conditions .
The scoliosis develops in about 20–25% patients with cerebral palsy (CP) and in nearly all children with DMD (Duchenne muscular dystrophy) and spinal muscular atrophy (SMA) 1–3. Loss of trunk balance, pain and discomfort in the back, as well as problems of verticalization are indications for orthopedic correction of spinal deformity in NMD patients .
The authors aimed to analyze mixed NMS cohort, consisting of patients with various types of muscular dystrophy (MD), CP, DMD and SMA, focusing on radiological characteristics of spinal deformities in each of these diseases before and after surgery.
The study was carried out prospectively in 2018–2019 yy, in patients with NMS due to MD, CP, DMD and SMA, who surgically treated in our center. Inclusion criteria were: confirmed MD, CP, DMD or SMA diagnosis (neurological and/or genetic examination), age ≤ 18 years old, the presence of spinal deformity, signed informed consent to participate in the study. Only patients who were indicated for surgery and who eventually underwent surgery were included.
Indications for surgical correction of deformity were progressive scoliosis with curve ≥ 40° Cobb, lumbar hyperlordosis with pronounced sagittal imbalance.
A standard examination performed for all patients included anterior-posterior and lateral X-rays of the spine, the anterior-posterior X-ray of hip joint and computed tomography (CT) scans of the spine and the chest and magnetic resonance imaging (MRI) of the spine. X-rays of the spine were taken while standing or sitting with or without support, lying in some patients. Before hospitalization, a standard examination was performed by a pulmonologist and a cardiologist, including, among other things, spirometry, blood and urine tests, electrocardiography and echocardiogram, densitometry in some patients.
All patients underwent surgical correction of spinal deformity with posterior pedicle screw fixation. The evaluation criteria included: age, gender of patients, volume of blood loss (mL), hospitalization length, and measurement of the deformity curve, thoracic kyphosis and lumbar lordosis (Cobb angle), pelvis obliquity relative to the horizontal line (Cobb angle), the percentage of deformity correction. The Cobb angle was measured preoperatively, prior to discharge from the hospital (up to 21 postoperative days) and one year after surgery.
The significance of differences between data groups evaluated using the criteria depending on the number of observations and distribution type of parameter values within groups. Statistical calculation was performed using Microsoft Excel software and SPSS Statistics.
The nosological profile of 71 patients with NMS was as follows: 13 patients with MD, 12 with SMA, 14 with DMD and 32 with CP(Table 1). Male predominated (63% vs 37%). The average age was 14.0 ± 3.61 years old. The angle of the main scoliotic curve ranged from 13.8⁰Cobb to 152.6⁰Cobb (mean 70.87 ± 27.99⁰Cobb, Table 2).
MD (n = 13) | SМА (n = 12) | DMD (n = 14) | CP (n = 32) | Total(n = 71) | |
---|---|---|---|---|---|
Males | 9 | 7 | 9 | 20 | 45 |
Females | 4 | 5 | 5 | 12 | 26 |
Age (years old) | 14.0 ± 4.40 | 11.3 ± 4.37 | 15.4 ± 1.55 | 14.5 ± 3.17 | 14.0 ± 3.61 |
NMS group | MD (N = 13) | SМА (N = 12) | DMD (N = 14) | CP (N = 32) | Total (N = 71) |
---|---|---|---|---|---|
Measurements | Mean ± SD | Mean ± SD | Mean ± SD | Mean ± SD | Mean ± SD |
Major scoliotic curve, Cobb | 69.67 ± 24.29 (N = 12) | 78.20 ± 26.47 (N = 12) | 53.41 ± 24.66 (N = 14) | 76.20 ± 29.02 (N = 32) | 70.87 ± 27.99 (N = 70) |
Secondary scoliotic curve, Cobb | 52.34 ± 25.81 (N = 5) | 39.94 ± 28.49 (N = 5) | 32.30 ± 10.59 (N = 4) | 62.40 ± 11.74 (N = 2) | 44.71 ± 23.14 (N = 16) |
Pelvic obliquity, Cobb | 10.28 ± 10.50 (N = 13) | 18.46 ± 8.25 (N = 12) | 17.99 ± 7.76 (N = 14) | 13.87 ± 10.98 (N = 32) | 14.79 ± 10.13 (N = 71) |
Thoracic kyphosis Th5-12, Cobb | 28.39 ± 24.50 (N = 13) | 41.44 ± 27.46 (N = 12) | 5.99 ± 22.42 (N = 14) | 30.97 ± 21.12 (N = 32) | 27.34 ± 25.37 (N = 71) |
Lumbar lordosis L1-S1, Cobb | 58.97 ± 19.97 (N = 13) | 46.58 ± 22.64 (N = 12) | 30.69 ± 39.82 (N = 14) | 65.81 ± 39.10 (N = 32) | 54.38 ± 36.15 (N = 71) |
CP - cerebral palsy, DMD - Duchenne muscular dystrophy, MD – muscular dystrophy, N - number of patients, NMS – neuromuscular scoliosis, SD - standard deviation, SMA - spinal muscular atrophy |
Mean FIM score in the whole NMS group before surgery was 49.7 ± 32.02, with a predominance of non-ambulatory patients (89% vs 11%). Among patients with CP were 6 ambulatory and 26 non-ambulatory cases (GMFCS IV-V).
CT of the chest demonstrated significant deviation in four patients: atelectasis, hypoectasis and lung fibrosis. MRI of the spine did not reveal any significant pathology. Spirometry was done in 45 patients and showed variable results from absence of lung function violations (13 patients) to extremely severe dysfunction (five patients). The rest of the patents (17 patients) had mild decreasing of respiratory function. Spirometry could not be done in 26 patients due to peculiarities of mental and physical development (the patients could not execute instructions, or procedure was not effective).
In group DMD there were slightly more mild scoliosis than other groups (DMD 53.41 ± 24.66⁰Cobb vs MD 69.67 ± 24.29⁰Cobb, SMA 78.20 ± 26.47⁰Cobb, CP 76.20 ± 29.02⁰Cobb, p = 0.076).
S-shaped scoliosis with a secondary scoliotic curve were relatively common in patients with MD (38%), SMA (42%) and DMD (29%), and less often in patients with cerebral palsy (2 patients, 6%), everyone else had a C-shaped scoliosis (Table 2).
Pelvic obliquity was significantly less in MD patients (10.28 ± 10.50⁰Cobb, p = 0.047), with a relatively uniform distribution among the other nosological groups (Table 2, Fig. 1a).
The tendency to thoracic hypokyphosis, and sometimes even thoracic lordosis, was more pronounced in the DMD group (p = 0.004) (Fig. 1b and Fig. 2).
More pronounced lumbar hyperlordosis with extremely pronounced rotation occurred in CP patients (p = 0.003) (Fig. 1c and Fig. 3).
Growth-friendly instrumentation without pelvic screws was implanted for 14 patients (growing rod system), and the final correction with pelvic fixation produced for 57 patients. The main types of pelvic fixation were sacral (S1, S2 bilateral pedicle screws) and iliac screws (iliac or S2 alar iliac screws). Osteotomies, excluding facetectomy, were not performed in any patient. Allobone grafts were usually used for additional fusion. Operating time were longest in patients with CP (217.69 ± 68.05 min, p = 0.035), with relatively little blood loss (342.81 ± 197.34 ml) (Table 3). The greatest blood loss was observed in patients with SMA (438.17 ± 262.96 ml, p = 0.177) (Table 3). Intraoperative neurophysiological neuromonitoring (IONM) was done in 21 patients (spontaneous electromyography and motor evoked potentials recording) and in most cases it was unstable basally or not called up, most likely due to muscle dystrophy, pathology of the spinal cord path or cortical atrophy.
NMS group | MD (N = 13) | SМА (N = 12) | DMD (N = 14) | CP (N = 32) | Total (N = 71) |
---|---|---|---|---|---|
Measurements | Mean ± SD | Mean ± SD | Mean ± SD | Mean ± SD | Mean ± SD |
Blood loss (mL) | 378.46 ± 250.53 | 438.17 ± 262.96 | 340.00 ± 165.34 | 342.81 ± 197.34 | 364.90 ± 212.72 |
Surgery duration (min) | 177.31 ± 43.10 | 181.67 ± 49.14 | 190.71 ± 51.06 | 217.69 ± 68.05 | 198.89 ± 59.54 |
Length of hospital stay (days) | 29.00 ± 10.85 | 25.08 ± 4.44 | 23.31 ± 7.60 | 19.59 ± 6.59 | 22.97 ± 8.13 |
CP - cerebral palsy, DMD - Duchenne muscular dystrophy, MD – muscular dystrophy, N - number of patients, NMS – neuromuscular scoliosis, SD - standard deviation, SMA - spinal muscular atrophy |
Severe post-hemorrhagic anemia and the need for blood transfusion occurred in 38 patients (53.5%). All patients after surgery performed CT of the spine, significant screws malposition was not found.
Average time of in-patient treatment was 22.97 ± 8.1 days (from 9 to 55 days), which is 2-2.5 times more than most patients after spinal deformity correction in our hospital. The longest hospital stay was in patients with MD (29.00 ± 10.85 days, p = 0.189), then in SMA (25.08 ± 4.44 days) and DMD (23.31 ± 7.60 days), and the shortest in patients with CP (19.59 ± 6.59 days) (Table 3).
Moderate scoliosis correction was seen in all groups measuring 45% in MD, 47% in SMA, 61% in DMD and 63% in CP (Table 2 vs Table 4). Correction of the pelvic obliquity was 62%, 50%, 65% and 67% in the groups, respectively (Table 2 vs Table 4). DMD thoracic hypokyphosis (p = 0.001) and CP lumbar hyperlordosis (p = 0.001) was more rigid to surgical correction.
NMS group | MD (N = 13) | SМА (N = 12) | DMD (N = 14) | CP (N = 32) | Total (N = 71) |
---|---|---|---|---|---|
Measurements | Mean ± SD | Mean ± SD | Mean ± SD | Mean ± SD | Mean ± SD |
Major scoliotic curve, Cobb | 38.78 ± 14.53 (N = 12) | 42.07 ± 21.88 (N = 12) | 21.16 ± 16.89 (N = 14) | 28.21 ± 17.57 (N = 32) | 30.99 ± 18.91 (N = 70) |
Secondary scoliotic curve, Cobb | 34.62 ± 18.35 (N = 5) | 33.90 ± 17.45 (N = 5) | 18.90 ± 7.71 (N = 4) | 19.80 ± 11.17 (N = 2) | 28.26 ± 15.55 (N = 16) |
Pelvic obliquity, Cobb | 3.88 ± 3.41 (N = 13) | 9.24 ± 5.75 (N = 12) | 6.30 ± 6.57 (N = 14) | 6.18 ± 6.12 (N = 32) | 6.30 ± 5.86 (N = 71) |
Thoracic kyphosis Th5-12, Cobb | 25.95 ± 12.70 (N = 13) | 16.24 ± 8.86 (N = 12) | 9.72 ± 12.29 (N = 14) | 27.00 ± 14.00 (N = 32) | 21.58 ± 14.31 (N = 71) |
Lumbar lordosis L1-S1, Cobb | 48.48 ± 13.07 (N = 13) | 39.02 ± 7.67 (N = 12) | 47.21 ± 16.10 (N = 14) | 57.03 ± 20.80 (N = 32) | 50.48 ± 17.98 (N = 71) |
CP - cerebral palsy, DMD - Duchenne muscular dystrophy, MD – muscular dystrophy, N - number of patients, NMS – neuromuscular scoliosis, SD - standard deviation, SMA - spinal muscular atrophy |
Unfortunately, X-rays evaluation one year after surgery could not be performed in all patients, which is due to the large territory of the country, the difficulties of transporting such patients, which often takes 2–3 days, COVID-19 trip restrictions, as well as the poor quality of X-ray at the living place (impossibility to perform vertical X-ray images of the entire spine). In addition, some of these patients (1 with DMD and 1 with CP) did not take lateral X-ray on out-patient clinic at the living place for unclear reasons. Only 45 cases came up for analysis. Evaluation of the results one year after surgery showed average loss of scoliosis correction of 0.57 ± 8.96° Cobb, 0.56 ± 17.09°Cobb, 1.72 ± 6.48°Cobb and 6.92 ± 9.24°Cobb during a year, respectively for MD, SMA, DMD and CP (Table 4 vs Table 5). FIM score was also measured only in 45 patients, among them 33 patients (46%) had improving and patients (27%) had deterioration in functional independents. The average postoperative FIM score 1 year after surgery was 47.30 ± 30.43 (vs preoperative 49.7 ± 32.02). In addition, one patient with CP died 6 month after surgery because of acute cardiorespiratory insufficiency of an unknown cause.
NMS group | MD (N = 7) | SМА (N = 9) | DMD (N = 7) | CP (N = 22) | Total (N = 45) |
---|---|---|---|---|---|
Measurements | Mean ± SD | Mean ± SD | Mean ± SD | Mean ± SD | Mean ± SD |
Major scoliotic curve, Cobb | 36.64 ± 24.54 (N = 7) | 45.22 ± 23.30 (N = 9) | 20.54 ± 16.12 (N = 7) | 30.72 ± 12.51 (N = 22) | 32.96 ± 18.73 (N = 45) |
Secondary scoliotic curve, Cobb | 40.23 ± 34.74 (N = 3) | 17.27 ± 4.05 (N = 3) | 21.20 (N = 1) | 27.65 ± 23.26 (N = 2) | 27.67 ± 21.87 (N = 9) |
Pelvic obliquity, Cobb | 3,41 ± 5.4 (N = 7) | 12.61 ± 6.7 (N = 9) | 6.20 ± 4.76 (N = 7) | 5.45 ± 5.26 (N = 22) | 6.68 ± 6.17 (N = 45) |
Thoracic kyphosis Th5-12, Cobb | 28.14 ± 7.99 (N = 7) | 25.57 ± 23.03 (N = 9) | 10.62 ± 9.10 (N = 6) | 23.70 ± 13.91 (N = 21) | 22.99 ± 15.49 (N = 43) |
Lumbar lordosis L1-S1, Cobb | 56.60 ± 6.01 (N = 7) | 45.27 ± 13.89 (N = 9) | 38.63 ± 12.77 (N = 6) | 56.58 ± 15.29 (N = 21) | 51.71 ± 14.89 (N = 43) |
CP - cerebral palsy, DMD - Duchenne muscular dystrophy, MD – muscular dystrophy, N - number of patients, NMS – neuromuscular scoliosis, SD - standard deviation, SMA - spinal muscular atrophy |
A large number of neuromuscular diseases could provoke the occurrence of spinal deformity 4. The most common pathologies leading to NMS are CP, DMD and another MD, SMA, myelomeningocele, traumatic myelopathy and tumors of spinal cord 4. The occurrence of spinal deformity depends on the nosology and level of nervous system damage, so the prevalence of spinal deformities in neuromuscular disease is extremely variable 4.There are a large number of works, which is concentrated on prediction model for the NMS development in different pathology, conservative and operative methods of treatment, reporting the results of surgical deformity correction, advantages and disadvantages of surgery 4.
The risks of scoliosis development and natural course of disease depend on pathology, its severity, functional status of the patient and timely started treatment. For example, scoliosis development predictable in non-ambulatory patients with CP and SMA 4. In our study, most of the patients were non-ambulatory (89%).
Features of spinal deformity also vary depending on pathology. If in cases of myelomeningocele and posttraumatic myelopathy difference is obvious and depends on the level of pathology, and is often accompanied by lumbar kyphosis 5, then in other diseases difference is poorly written.
In our study group CP patients were characterized by hyperrotational lordoscoliosis that was associated with hip contractures and/or dislocation. Our data are confirmed by the findings reported by Yazici and Senaran who demonstrated a high incidence of such sagittal disorders in CP. Another question, what were the firs: hip dislocation and pelvic obliquity or scoliosis? Hip dislocation may lead to pelvis rotation and scoliosis; on the contrary deformity may cause pelvic obliquity and initiate hip dislocation. It still remains unclear6.
SMA patients showed moderately mobile kyphoscoliosis in our group. Merlini et al one of the first to notice that when children with SMA begin to sit, their backs become kyphotic and then scoliotic curve develops, pelvic obliquity as a rule commensurate to scoliosis. Most studies indicate that thoracolumbar C-shaped scoliosis develops in most SMA patients, less often - S-shaped or local lumbar 7.Sagittal (kyphosis and lordosis)and axial (vertebrae rotation) features rarely considered for analysis. It is noted that the greater the degree of scoliosis, the greater the amount of vertebrae rotation .
For patients with DMD some authors described follow types of scoliotic deformity : progressive collapsing kyphoscoliosis with significant rotation, progressive hyperlordotic scoliosis and straight sagittal profile and non-progressive curves up to 30°Cobb.At the same time, it was noted that in sitting position, the kyphotic and scoliotic components increases. The general trend for DMD scoliosis is the occurrence of thoracolumbar C-scoliosis with pelvic tilt, as with other types of NMS. In our study, we noted the predominance of thoracic hypokyphosis and back straightening, which is also found in some other studies .
It is necessary to start with conservative treatment8. Steroids in DMD patient results in a substantial decreased need for spinal deformity surgery.Development of NMS in CP can prevent or slow down timely by special exercises, bracing, custom sitting system, passive stretching, postural management and botulinum toxin injection 9–11. The use of intrathecal baclofen pumps and selective dorsal rhizotomy, in contrary, can cause progression of a scoliosis 12, 13. In SMA cases early medical treatment by gene therapy with adeno-associated viral vector or intrathecal injections of an antisense oligonucleotide medication can prevent disease progression and deformity development 14, 15.
In general, studies of the natural course of scoliosis in patients with SMA and DMD (without specific medicament treatment) have shown had substantial progression of spinopelvic deformities 7.
Bracing can be useful when deformity mobile 10, 16, 17. The role of bracing in a part of patients with NMS (for example in non-ambulatory CP, in all SMA and DMD cases) is limited due to because of the effect on respiratory movements of chest, risk of bedsore and even more movement restriction. Custom-sitting system with multiply support can slow down deformity progression in non-ambulatory patients 4, 10.
Surgery can be considered in patients with scoliosis angle > 40–50°Cobb, which cause difficulties in daily care and positioning, lead to significant pain, alterations in skin integrity and bed sores, worsening pulmonary and cardiac function 4.The aims of deformity correction: achieving a balanced spine, prevention of curve progression, decreased pain, restoration of skin integrity, reduction of chest and abdominal cavity deformity, improving urine passage, daily care facilitation, improvement in functionality and quality of life,. The timing of surgery should be considered on an individual case basis5, 18. Inpatients with NMS, skeletal immaturity and rigid curves > 30°Cobb early surgical treatment can be considered, they have risk of deformity progression almost 100% 18. They usually performed growth-friendly surgical treatment: growing rods or anterior growth modulating procedures.
It’s clear now than pedicle screw system gives an advantage in deformity correction, their main disadvantage is that there are restrictions on spine movement18. On the one hand, scoliosis straightens better, but the other hand patents have more limited movement freedom, what can lead to a decrease in functional independence and quality of life. There are still heated debates now 19.Most patients will have spinopelvic fixation 1.The exception is ambulatory patients with NMS with adequate head control, without hip subluxation or dislocation and small degree pelvic obliquity (< 15°), they may not need pelvis fixation 20.
Anterior release and fusion procedure also provide a good correction, especially in cases with rigid lordoscoliosis and large rigid thoracic curves (> 70°Cobb) .
Different types of osteotomies (facetectomy, Ponte vertebrectomy, Smith-Peterson osteotomy, pedicle subtraction osteotomy, vertebral column resection) in rigid large scoliotic curves can help provide better intraoperative curve correction18. An increased number of complications described in more of these techniques, in addition they definitely increase amount of blood loss and surgery time. Therefore, the use of osteotomies in patients with neuromuscular diseases is controversial and needs to choose carefully. As a rule, in patients with SMA, CP and MD, especially in non-ambulatory cases, we generally avoid osteotomy or performed only multilevel facetectomy.
Correction and posterior instrumentation of the thoracic and lumbar spine and pelvic fixation can be recommended for cases with initial pelvic obliquity exceeding 15° .Scoliosis with thoracic hypokyphosis and even fully lordotic spine were common for DMD cases and were surgically addressed for realignment and sagittal balance of the spine.
In our group, IONM turned out to be useless in most patients, and recent studies have explored the frequent unreliability of IONM in NMS patients also 21. In our opinion, in this direction it would be useful to conduct additional studies and find the optimal way of IONM 22.
The reported overall complication rate in NMS is variate from 6–40%12. In CP complication after surgery developed in 17–68%5.
The general tendency for complication in NMS is as follow: the lower functional status accompanied by a higher risk of complication 16, pulmonary complications are most common, implant-related complications and infection meet a little bit less often 16. Younger age of surgery associated with higher risk of pseudoarthrosis and neurological deterioration .
There are studies showing that the respiratory function of NMS patients can be improved by proper periodical management, such us training program in which they used noninvasive positive pressure ventilation and mechanical insufflation-exsufflation before and after surgery21.
It should be remembered that the functional status of patients with NMS varies greatly, so in some cases researchers cannot assess directly a quality of life or functional status of patient, in such cases evaluation of quality of life and satisfaction of theirs caregivers will help 4.
Most studies show improvement in quality of patients and caregivers life and caregivers satisfaction 23–26.They did find that the majority of the patient caregivers felt that those patients treated surgically was more comfortable than those who were not. Not all research results demonstrated significant changes in quality of life of the patients or improvement in vital signs 27.
Spinal deformity in NMS patients is characterized by specific manifestations with prevailing deformity components depending on the nosology. The findings showed that lordosis was the key problem of spinal deformities in neuromuscular patients and was often rigid to surgical correction. Lumbar hyperlordosis with significant rotation were common for CP patients whereas the thoracic hypokyphosis often occurred in DMD patients. Scoliosis and pelvic obliquity can be well corrected in NMS by pedicle screw construction with standard maneuvers and pelvic screw fixation. The data obtained can be practical for planning of surgical corrections of spinal deformities and identifying correction maneuvers.
A small group of patients has weak strength and sampling power and imposes limitations on the conclusions made. Recognizing the specific nosological spectrum with the need for accurate verification of the underlying pathology multicenter prospective studies with databases of high-volume spinal centers including neuromuscular scoliosis patients can be used to prove or disprove our assumptions.
Conflicts of Interest and Source of Funding: This study was sponsored by Medtronic Limited Liability Company (123112, Moscow, Presnenskaya nab., 10, floor 9, office III, room 41) and all researchers benefited financially. This publication is based on "Children with neuromuscular diseases – efficacy evaluation of spinal deformity surgery via different pedicle screw fixation systems study – CHIVALRY study", Study ID: NCT03863496. All participants provided informed written informed consent (consent was provided by the patient(s) or a legally authorized representative).
Ethical approval: We conducted this study in compliance with the principles of the Declaration of Helsinki. The study’s protocol was reviewed and approved by the Institutional Review Board of Ilizarov Center (IRB No. 2 (62) 05.03.2019).