This is the first population based controlled SDR long-term outcome study. By selecting all individuals with a medical background and clinical expression that matched the selection criteria for SDR at baseline (1), an SDR-operated group and a control group from the same geographically defined total population, of which 98% were included in the registry, were created retrospectively.
Prospectively collected longitudinal follow-up data are presented for scoliosis and spinal pain from the population of children with spastic diplegic CP, where a group of individuals had undergone SDR at a young age. Neither scoliosis nor spinal pain was more prevalent during 20 years of follow-up in the SDR group, after the cauda equina multilevel surgery, compared to the control group representing the natural history in children with about the same base-line prerequisites, and with same standard of care before and during follow up. In children at GMFCS-level IV at baseline, without functional walking ability, scoliosis developed later and less often in the SDR group during the following 20 years than in the control group.
Population, registry and standard of care issues
The CPUP registry data provided information from standardized and regular assessments performed and recorded by the person’s own physiotherapist at certain ages, same procedures for all individuals, regardless of whether they had undergone SDR surgery or not (16).
All persons in the study were treated at the same public health care units; orthopedic and pediatric hospital health care departments, and the habilitation services in cooperation. Physiotherapy, occupational therapy, social and psychological support, orthoses, braces, orthopedic surgery, ITB, SDR and from 1998 botulinum toxin injections were part of standard care, and with no or very low economic costs for the patients.
Almost all children with CP spastic diplegia in the area were included. Ten children enrolled in CPUP after SDR; their preoperative GMFCS level and muscle tone was assessed and recorded in the medical records by the spasticity-team physiotherapist. All other assessments were performed and recorded in CPUP by the person’s local (re)habilitation personnel, which made it possible to study effects of SDR in this population, without any selection bias or bias regarding expectations on SDR-results.
Natural history control group
When SDR was introduced in Lund 1993, three North American randomized controlled trials (RCTs) were underway and preliminary results were forthcoming (32). At the time, an RCT in the Lund university hospital uptake region was considered both unethical and non-feasible due to the small population eligible. Even if the available RCTs showed promising short-term results, monitoring of long-term effects of SDR was needed. In addition to practice-based follow up (33, 34), the CPUP program/registry was planned at SDR-start, and among the aims were to follow the natural history and relation to long-term results of treatments (17). The program was started in Skåne and Blekinge 1994 and included persons with CP born in 1990 and later, followed regularly since that time.
The CPUP registry data indicated that only few of the children who could have benefited from an SDR were referred to the spasticity clinic during early childhood, especially after treatment with botulinum toxin was introduced in 1998. For this study, we therefore could create a control group with clinical background and physical expression to match the selection criteria for SDR (35). Some may have had features not visible in the registry data that differed from those who actually underwent SDR, such as dependence on spasticity for walking and standing, or other barriers to reach the desired functional goals with the intervention. There were also some children included in the control group who were recommended SDR by the spasticity team, but their parents did not choose the intervention.
The pediatric spasticity team members at Skåne University Hospital have had the same selection criteria and follow-up procedures since the start in 1993 (20). Contraindications to SDR were exclusion criteria in the present study, such as mild spasticity, malformation syndromes, postneonatally acquired CP, CP due to prenatal/congenital infections, severe birth asphyxia, and dyskinetic, ataxic, unilateral spastic, or mixed CP subtypes.
Periventricular leukomalacia or hemorrhages, often in combination with premature birth, are associated with the CP subtype spastic diplegia, often suited for the SDR-intervention (1). Such white matter brain lesions were present in the majority of both the SDR group (17/20, 85%) and the control group (74/87, 85%) who had had brain imaging (Table 1). Less CNS-imaging in the SDR group than among controls was due to the higher proportion SDR-surgery in the oldest age cohorts, before brain imaging was recommended in CP diagnostic work-up.
Spasticity
Even if the MAS have shown weak psychometrical properties (36) it has been used by physiotherapists for assessing muscle tone in the CPUP follow-up since the start in 1994. To create study groups at baseline that correspond to the selection criteria for SDR, an estimated spasticity level classification was performed as described. The MAS is an ordinal scale and does not methodologically allow such calculations, however it estimates a clinically significant entity used for classification and not for evaluation of interventions. It makes clinical sense that a child with a high degree of muscle tone in all muscle groups will get a high summation score in contrast to a child with less tone, who may show an increase in just distal muscle groups. In our study, we added clinical signs of spasticity to the MAS summation score quartiles, such as leg scissoring at rest and activity, to classify muscle tone increase into mild, moderate and severe estimated spasticity levels. We found clear cut-offs between the mild, moderate and severe spasticity level groups using the described classification, and they were retrospectively found to fit the overall clinical picture; none of the children in the SDR group ended up in the mild spasticity level group at baseline.
GMFCS
The GMFCS levels were classified after and as close to the fourth birthday as possible, and they were used to stratify the study population at baseline. At four years of age, the GMFCS level, CP diagnosis, and CP subtype can be decided with high or acceptable accuracy (22, 37).
Retrospective, although not psychometrically tested, classification of GMFCS levels based on clinical descriptions in medical records was used in the 2002 metanalysis of the three North American SDR RCTs (32). In the present study, structured data from the CPUP registry on functional performance and capability was available for retrospective classification of GMFCS levels at baseline date before the GMFCS was introduced. The kappa analysis of this classification showed good agreement (κ = 0.732, p < 0.001), as described in Appendix, and the oldest birth year cohorts could be included in the study.
Each GMFCS level carries a meaningful distinction about function, and it may wrongly lead to the collapse of different GMFCS levels in analyses (38). Therefore, participants at GMFCS levels I and V were excluded from part of the analyses, as it showed that only two and no child respectively at these levels had had SDR-surgery. Also, scoliosis development at each GMFCS level was presented separately.
Scoliosis
The multilevel laminoplasty technique used to access the rootlets for the SDR procedure in the present study included reinstatement of laminae and did not increase the occurrence of scoliosis after SDR. For the SDR GMFCS IV-group, scoliosis occurred even to a lesser extent and with later onset than for GMFCS IV-control group (Fig. 3). Development of contractures and asymmetries, especially common in higher GMFCS-levels (15, 39, 40), may be less severe after SDR combined with physiotherapy, as use of orthoses, sitting and supported standing positions with more symmetric spine may be more easy to obtain after tonus reduction.
In SDR, other forms of spinal misalignments, especially spondylolisthesis have been reported more frequent than in the general population (4, 5, 7, 9, 10), even if scoliosis was reported to be the most common deformity following SDR (2). Studies reporting spinal deformities after SDR are not population based and with no or small comparison groups (2). To further explore spinal misalignments after SDR in the present population, results regarding imaging of the spine beyond scoliosis and Cobb angles would be needed. Absence of spinal pain may, however, indicate absence of significant spinal problems.
Pain
Pain in the CP population has previously not been properly noticed (30), even if it is one of the most common co-morbidities (41). Beside no increase in scoliosis development after SDR, the other main finding of the present study was that the frequency of spinal pain did not differ between the SDR group and the control group at 10, 15, 20 and 25 years of age (Table 2).
Limitations
The low proportion of individuals born 1990–1997, available to serve as natural history control group in adult age, is a study limitation (Table 1). The control group thus included a higher proportion of younger persons, who probably received somewhat different care compared to the older cohorts (16, 17). In study participants born 1994 and later, in contrast to those born 1990–1993, some were treated with botulinum toxin with a lowered muscle tone at the baseline assessment.
Assessments and registrations were performed regularly using a standardized methodology by clinicians in their daily practice, and limited information was available, as only the most important items can be included to keep a register acceptably time-consuming. The spinal screening lacked information on other misalignments than scoliosis, and x-ray examinations with Cobb angles were inconsistently registered at the time data was extracted from the register.
The late introduction of pain screening in the registry resulted in low numbers of recorded answers about spinal pain at different ages, which is another limitation. There were slightly more frequent recordings of spinal pain in the SDR than in the control group, although the differences were not statistically significant. Although possible reduction of pain in adults with CP after early SDR is reported (42), the authors are anxious to find out whether SDR at a young age is causing more spinal pain than expected from natural history. Information of pain intensity, duration, effect on daily living or quality of life was available only in the adult age CPUP forms.
Spinal pain several years after surgical correction of scoliosis, as described in the present study, was found also in a population based study with high number of participants (14). Increased awareness among health professionals of the importance of pain assessments in this population led to extended pain questions in the most recent version of the CPUP PT-form, so more and higher quality data will be available in the future.
Generalizability
This study represents the real-life situation in the ordinary health care, in contrast to RCTs, usually conducted at tertial health care level after rigorous selection of participants. The total population with CP in certain age cohorts were included in the present study, without selection bias. Results would be generalizable in populations where the socio-economic and health care standards are comparable to those in Sweden. Also, the surgery technique, multi-level SDR without permanent removal of the spinal laminae/spinous processes, was used for all individuals in the study, and is commonly used internationally.