In the preceding section, it was established that the true benefits of scoliosis correction should be measured in terms of outcomes of interest to the patient and/or caregiver. In a general sense, taking neuromuscular diagnoses as a whole, there are several studies that met the inclusion criteria for this evidence-based review and used a QOL measure to assess patient-centered benefits.

In a prospective study utilizing the Swedish spine registry, Ersberg and colleagues used the EQ-5D (a validated instrument with sections that evaluate self-care, mobility, usual activities, pain, and anxiety) and the SRS-22 questionnaire to compare QOL between idiopathic, neuromuscular, and congenital scoliosis groups [15]. From a surgical risk perspective, patients with neuromuscular scoliosis experienced statistically significant increases in intra-operative blood loss, duration of surgery, and length of hospital stay as compared to the idiopathic group. With respect to QOL measures, there were significant increases in the post-operative EQ-5D total score and in particular the reduction of post-operative pain. When assessed via the SRS-22 instrument, neuromuscular patients experienced significantly improved function and better self-image. Interestingly, despite the significant number in complications in the neuromuscular group, when stratified into groups with and without complications, there were no significant differences in QOL scores. The conclusion of this study was that QOL was improved after scoliosis surgery even despite the high risk of complications.

In another prospective Swedish study, the impact of scoliosis surgery in neuromuscular patients was assessed in terms of outcomes pertaining to QOL, using a questionnaire that assessed sitting, care-giving, reaching, pain, rest time, seating supports, and activities of daily living (ADL), Cobb angle correction, and respiratory function as measured by vital capacity (VC) at a mean follow-up of 7 years [7]. This landmark study stratified patients who underwent scoliosis surgery into 4 subgroups including those that: (1) understood verbal instructions, (2) did not understand verbal instructions, (3) had progressive disease (e.g. DMD), and (4) had non-progressive disease (e.g. CP). Overall, surgical patients had significant QOL improvements in sitting balance, weight distribution, ADL, time used for resting, number of seating supports in addition to improvements in Cobb angle (~50 %) and respiratory function. When analyzed by subgroups, both the non-progressive and verbal instructions subgroups maintained improvements in outcomes as per the study results overall, but those that did not understand verbal instructions showed no improvement in ADL, ease of care giving, or respiratory function. Even more telling, scoliosis surgery had no impact on QOL-related outcomes or respiratory function in the progressive disease subgroup in which the only significant improvement was in Cobb angle correction. The sample size in this subgroup however, was quite small (only 14 patients) so this should be interpreted with caution.

In a general sense, the results of these two prospective studies support the surgical treatment of scoliosis in neuromuscular diagnoses, citing significant improvements in QOL-related outcomes, radiographic measures and, in some cases, respiratory function. That said, an objective assessment of the literature with respect to the risks involved with such procedures is required to balance the risk-benefit equation.

In a large retrospective study utilizing the Kids Inpatient Database (US based database of nationwide hospital discharges), 437 children with progressive neurodegenerative disorders (e.g. SMA, myopathies, etc.) who underwent scoliosis surgery were identified and their results were compared to non-progressive patients. In general, the progressive group had significant increases in length of stay (10.3 versus 7.7 days), pulmonary complications, in-hospital mortality (1.6 % versus 0.6 %), and hospital costs [14].

These results were similar to a study from the Scoliosis Research Society Morbidity and Mortality Committee, which analyzed complication rates from a database of 19,360 patients who underwent pediatric scoliosis surgery; 4657 of which had a neuromuscular diagnosis (including non-progressive and progressive diagnoses) [10]. Within this large sample, as compared to idiopathic scoliosis (IS), neuromuscular patients again had the highest risk of complications at 18 % versus 6 %. As with the previous study, mortality rates were significantly higher in the neuromuscular group (0.3 % versus 0.02 % for IS) with respiratory complications being the leading cause of death. Non-fatal complications such as blood loss (NM: 1.2 % versus IS: 0.2 %) and deep wound infection (NM: 3.8 % versus IS: 0.8 %) were also significantly higher in the neuromuscular group.

Continuing the trend, a systematic review analyzing the rate of complications in scoliosis surgery substantiated these results with significantly increased risks of death, infection, and pseudoarthrosis associated with a neuromuscular diagnosis when compared to IS [9].

The results of these studies confirm that the risks associated with scoliosis correction in neuromuscular diagnoses are substantial but, at the same time, the best evidence available also suggests that QOL is improved for these patients despite the risks. These points must be carefully considered and effectively communicated by the treating surgeon so the patient and/or caregiver can make an informed decision as to whether or not they proceed with surgery. Furthermore, any discussion regarding disease-specific risks and benefits needs to take into consideration the differences in outcomes that are beginning to emerge in the recent literature when analyzed by diagnosis.

Though typically associated with high patient/care-giver satisfaction, scoliosis surgery in children with CP is fraught with high complication rates likely related to the increased prevalence of co-morbidities inherent to this patient population including: poor nutritional status, epilepsy, infections of the urinary and respiratory tract, feeding disorders, and relative immunodeficiency [23]. Despite these risks, children with CP seem to be highly tolerant of spinal surgery with a relatively long predicted life expectancy post-operatively [24]. The evidence regarding the risks and benefits of scoliosis correction in CP, as in other diagnoses, is scant but a few studies did meet our inclusion criteria.

In a recent systematic review with an aim to determine the risks, benefits of scoliosis correction in CP, in addition to the pre-operative factors affecting surgical outcome, only 1 prospective and 3 retrospective cohort studies were identified, with the rest being retrospective case series. Unfortunately, none of these studies analyzed included an observational group and the conclusions of the review were that the “overall strength of the evidence was insufficient” to make any firm recommendations for or against surgical intervention [25]. The authors also revealed that outcomes in these studies were “poorly delineated with limited or no use of validated outcome instruments”. They suggested that future studies needed to employ validated outcomes relating to patient satisfaction and function.

Recently, the development of the Caregiver Priorities & Child Health Index of Life with Disabilities (CP CHILD) questionnaire by Narayanan and colleagues has provided a validated disease-specific outcome measure to apply to patients with CP [13]. In a prospective longitudinal cohort multi-center study investigating the utility of the CP CHILD questionnaire for children with severe CP who underwent scoliosis surgery, the authors found that by 12 months post-operatively, significant improvements in positioning/transfers, health, and overall QOL were achieved. The instrument was found to be sensitive to change and suggested as a meaningful outcome measure for evaluating this patient population [26].

These results were corroborated by a recent retrospective case-control study that also used the CP CHILD as its primary outcome measure [27]. In this study, children with severe CP (GMFCS IV and V) and scoliosis greater than 40 degrees were analyzed to determine the impact of scoliosis correction. The operative group demonstrated significant improvements in overall CP CHILD scores, personal care/activities of daily living, positioning/transferring/mobility, comfort/emotions, and communication/social interactions while the observational group deteriorated. In the surgical group, the complications included wound infections (22 %), pneumonia (17 %), reoperations due to post-surgical collections (12 %), pneumothorax (6 %), and recurrent hip dislocation (6 %).

Two other retrospective case-control studies also concurred with the findings of the previous studies, reporting a high level of patient and/or caregiver satisfaction but with a high rate of associated complications [28, 29].

In conclusion, given the best evidence available, it would seem that scoliosis correction improves quality of life in CP albeit with a high rate of complications.

Spina bifida represents a spectrum of disease severity and patho-anatomical variations (including deficiencies of the bony posterior elements in conjunction with congenital abnormalities of the spinal cord, brain stem, and peripheral nerves) that make it a difficult entity to assess from a disease-specific standpoint. To this point, many previous studies that refer to ‘spina bifida’ as the diagnosis in question typically focus on patients with myelomeningocele rather than typically higher functioning forms of spinal dysraphism including meningocele, lipomeningocele and others. As in other neuromuscular disorders, this distinction is relevant since the incidence of scoliosis and risks associated with curve correction vary according to these differing manifestations of the ‘spina bifida’ diagnosis. For example, disease severity in myelomeningocele is commonly related to neurosegmental level, with the risk of scoliosis progression being more prevalent at higher motor levels (e.g. T12 and above (high risk) versus L5 and below (low risk) [18, 30]. Furthermore, QOL and functional scores have also been linked to neurosegmental level, a potential confounder when assessing the impact of interventions without taking disease severity into consideration [31].

Scoliosis is one of the most common musculoskeletal manifestations in spina bifida with up to 50 % prevalence being reported [3]. As curve magnitude increases, a progressive loss in truncal balance and sitting stability can occur which may impact QOL [32]. The indications for scoliosis correction in spina bifida have mirrored that of other neuromuscular diagnoses including a progressive curve greater than 50° and functional concerns such as sitting balance and wheelchair tolerance. However, the operative risks associated with spinal fusion have been reported to be among the highest for scoliosis of any diagnosis which necessitates a comprehensive assessment of the benefits and risks of surgery, and their effective communication to patient and/or caregiver, before embarking on such a procedure.

Until recently, there were no validated outcome measures to evaluate the impact of scoliosis correction of QOL and patient satisfaction in spina bifida despite complication rates approaching 75 % [33]. To rectify this, Wai and colleagues developed the Spina Bifida Spine Questionnaire (SBSQ), a validated tool that evaluated self-perception and overall physical function for these children with associated spinal deformity [34]. Interestingly, in this cross-sectional study, the authors found no relationship between spinal deformity and self-perception or physical function.

In a follow-up retrospective case-control study involving the same institution, the SBSQ and 36-Item Short Form Health Survey (SF-36) were used to assess the impact of scoliosis correction on QOL in patients with spina bifida at a mean 14-year follow-up [35]. Like the previous study, they found no difference in SBSQ and SF-36 scores between the operative and non-operative groups and no relation to curve magnitude. In addition, the study showed that, of the patients that could walk pre-operatively, only 50 % remained ambulatory after scoliosis correction. The authors suggest that this finding, coupled with an increased spinal stiffness after fusion and a lack of improvement in sitting balance between the groups, may have contributed to the lack of impact on QOL.

A prospective study from Poland also investigated the relationship between QOL/functional scores and the presence of spinal deformity in spina bifida in a non-operative cohort [32]. They used the Quality of Life in Spina Bifida Questionnaire (QLSBQ) to assess QOL and the SBSQ to assess physical function in addition to a self-perception outcome measure. They found that very large curve magnitudes did have a negative affect on QOL but no impact on physical function or self-perception was identified. Since there was no surgical arm in the study, no inference can be made as to whether surgery would improve these QOL limitations.

A recent evidence-based review on the subject identified 9 level III studies involving the spine but only two that evaluated physical function within both operative and non-operative groups [36]. The authors concluded that surgery had little effect on physical function and cautioned that the risks may outweigh the benefits when considering scoliosis correction for children with spina bifida. If surgery was to be done, a combined anterior and posterior fusion was reported to have a decreased complication rate over other approaches.

As previously mentioned, complication rates associated with scoliosis correction in spina bifida are very high and are an important consideration. In one retrospective comparative study investigating complication rates associated with different surgical approaches, an overall complication rate of 48–60 % was found with infection (19 %), shunt insufficiency (12 %), pseudoarthrosis (22 %), and hardware-related problems (30 %) being the most notable [33]. They also found that the addition of anterior instrumentation and fusion to a posterior fusion provided the lowest rate of hardware-related complications and loss of correction. Furthermore, one death from shunt insufficiency was identified and as such the authors stressed that shunts should be evaluated pre-operatively to help decrease the rates of peri-operative malfunction.

In summary, unlike CP, current evidence suggests that the risk-benefit ratio for scoliosis correction in spina bifida is not favourable given the lack of significant improvements in QOL or physical function coupled with very high complication rates. As such, unless a substantial functional problem (e.g. severe pain from costo-pelvic impingement; functional sitting imbalance) is identified which is unresponsive to conservative management (e.g. wheelchair modifications), scoliosis surgery should not be recommended for children with spina bifida.

Duchenne Muscular Dystrophy (DMD) is an inherited X-linked myopathic disorder secondary to mutations in the gene coding for dystrophin, a muscle cell membrane stabilizer. The absence, or reduced action, of dystrophin renders muscle cells susceptible to damage that is thought to result in an inflammatory response with eventual replacement of viable muscle with fibro fatty scar tissue [37]. As a result of this process, unlike CP and other non-progressive disorders, the natural history of DMD is typified by progressive deleterious changes in muscle strength, static contractures, and the development of scoliosis. Concomitant to these changes, progressive decreases in respiratory and cardiac function, along with a significantly reduced life span, increase the risks associated with the correction of scoliosis in this population.

Key questions regarding scoliosis correction in DMD center around whether it: (1) improves long-term survival, (2) improves respiratory function, (3) improves QOL and overall physical function, (4) has a positive benefit-to-risk ratio, and (5) is still required given the potential for scoliosis prevention or delay in onset by the use of newer corticosteroids with fewer side effects.

In an attempt to answer some for these questions, a recent Cochrane review was published which investigated the role of scoliosis correction in DMD [38]. Expectedly, no randomized controlled studies were identified and the authors’ conclusions were that the available literature was insufficient to make any direct recommendations regarding the application of scoliosis correction in DMD. However, based on the available literature, some of which was at least level III, a few general statements were offered.

Most of the studies reviewed were in agreement that spinal surgery improved sitting position, patient satisfaction, and overall QOL, in addition to improvements in Cobb angle and pelvic obliquity for children with DMD. However, most failed to show significant improvements in respiratory function or long-term survival despite the many studies investigating this over the past 35 years [39–42]. In fact, one retrospective case-control study cited found no significant differences in respiratory function deterioration between operative and non-operative groups. Furthermore, the addition of surgery did not improve respiratory function despite significant Cobb angle correction (61.7 %) [43].

The published complication rates were significant as in other neuromuscular disorders. In a recent level III study comparing complication rates for scoliosis surgery in DMD and CP, it was suggested that DMD involves even higher perioperative risks with significantly higher complication rates (DMD: 38 % vs CP: 18 %) [44]. A systematic review from Mercado and colleagues supported these statements suggesting that cosmesis, QOL, and overall patient satisfaction are generally improved after scoliosis correction in DMD despite the fact that most patients undergo surgery at a relatively early stage (e.g. 25° Cobb angle) [3]. Given the lack of controlled studies however, the authors stated that the relationship between spinal surgery and improvement in respiratory function is still unclear. They also cautioned that a consistent negative aspect was the adverse impact on self-feeding due to the combination of a stiff, straight spine and upper limb weakness post-operatively.

Recently, it has been suggested that perhaps scoliosis surgery in DMD might be completely avoided. In the absence of effective medical management, it has been reported that over 90 % of patients with DMD will develop scoliosis, most of which will require spinal stabilization [45, 46]. Previous studies have shown that corticosteroid administration can slow the decline in muscle strength, prolong walking in children, and delay the onset of scoliosis with DMD but often at the expense of unacceptable side effects [47]. However, several recent studies have demonstrated that deflazacort (an oxazolone derivative of prednisone) can achieve similar improvements in function with substantially better side effect profile.

In a prospective cohort study investigating the role of deflazacort in the development of scoliosis, the Kaplan-Meier survival rate of not developing scoliosis or needing spinal surgery was 78 % in the treatment group and 8.3 % in the non-treatment group at a mean follow-up of 15 years [48]. Scoliosis measuring 20° or more developed in 20 % of patients for the treatment group and in 92 % for the non-treatment group, all of which required surgery. Of further benefit, patients in the treatment group had significantly improved pulmonary function, prolongation of walking, and ability to climb stairs. Side effects were common with 70 % (21 patients) in the treatment group developing cataracts but only two patients required cataract surgery. Other side effects included decreased height (17 cm shorter), weight gain (55 kg vs 51 kg), and no difference in bone fractures (treatment group was given bisphosphonates). The authors concluded that glucocorticoids have a long-term protective effect against the development of scoliosis in DMD.

Two additional retrospective cohort studies investigating the role of deflazacort in DMD supported the findings above [46, 49]. In each of these studies, the treatment group showed a similar decrease in the need for spinal surgery with an acceptable side effect profile. In one of these cohorts with a mean 8-year follow-up, surgery was completely avoided in the treatment group while 43 % of the non-treatment group underwent surgery [46]. In addition to prolonged walking, this study also reported significant improvements in cardiac function.

Given the studies above, it would seem that the use of deflazacort prevents, or at least delays, the onset of scoliosis in DMD with secondary benefits of preserving respiratory and cardiac function with an acceptable side effect profile. When surgery is required, it can be expected to result in improvements in QOL and patient satisfaction albeit with high perioperative risks. At this time, the available evidence regarding scoliosis correction in DMD does not seem to support improvements in survival and/or respiratory function.

Evidence-based statements and GRADE recommendations for this section are provided in Table 24.2.

Regarding the assessment of spinal fixation methods in neuromuscular scoliosis, our literature search revealed no prospective studies and a small number of retrospective comparative studies. One such study compared hybrid fixation (sublaminar wires/hooks in the thoracic spine, pedicle screws in the lumbosacral spine) to segmental pedicle screw fixation and found significant improvements in curve correction (75 % vs 59 %), operating time (6.0 vs 7.4 h), blood loss (1785 vs 3760 mL), and the need for anterior surgery (12 % vs 40 %) for the pedicle screw group as compared to the hybrid group [53]. As might be expected, the authors reported no change in QOL as measured by the SRS-24 questionnaire and no significant difference in overall complication rate between the two groups. They stressed that, although Cobb correction was greater in the pedicle screw group, the attainment of spinal balance was most important and was achieved by both groups.

In another retrospective comparative study with 44 of 68 patients having a neuromuscular diagnosis, four different types of apical spinal fixation were compared for large curves greater than 100°: sublaminar wires, hooks, anterior vertebral screws, and all pedicle screw constructs [5]. Like the previous study, all pedicle screw constructs demonstrated significant improvements in Cobb correction, a decreased rate of anterior release, and the lowest complication rate between the groups. The all-pedicle screw group was also better at maintaining curve correction by final follow-up as compared to other methods, which tended to be associated with a significant loss of curve correction over time. That said, there were no significant differences in the ability to achieve coronal/sagittal balance or in the neurologic risk profile between the wire and screw groups.