Our results support the treatment of EOS by serial Risser casting. The benefits for children with NIS of syndromic-associated origin are clear. A highly significant reduction in CA was achieved. The RVAD has proven as a reliable parameter to measure the complex apical three-dimensional spinal morphology on a plane radiograph [11]. Significant reduction in RVAD was only observed in IS patients. Whether the reduced RVAD through serial casting is as beneficial for the long-term course of scoliosis as it was observed for idiopathic “benign” EOS remains to be proven [12]. Due to prior serial casting, corrective spinal surgery can be delayed [13]. Poorer results from the treatment of NIS compared to IS can be explained by the more severe deformity at the onset of treatment (larger CA and RVAD).
An additional functional benefit is conferred by this treatment as well. Trunk elongation is accompanied by better trunk balance and reduction in falls [14]. The functional aspect needs to be emphasized for children with NIS. Because of the primary disease, these patients have fewer resources to compensate for pulmonary malfunction.
In our study, patients with syndromic curves responded to serial casting with an average correction of 24° (44%) in CA, which is significantly better than previously observed. We hypothesize that this can be explained by the more rapid changes in the casts with our treatment protocol (every 4 weeks). Sanders et al. performed serial casting for longer than 1 year [15]. Their approach involved changing the casts every 2 months in a 2-year-old and every 3 months in a 3-year-old child is not based on evidence and is not supported by any clinical observations. In our opinion, the prolonged cast treatment provides no advantages to the patient and may disproportionately increase complication rates in terms of skin breakage.
However, our practice as well as Sanders’ practice necessitate that young children receive multiple rounds of general anesthesia. The risks of multiple rounds of general anesthesia for the immature brain are not fully investigated, yet [16, 17]. From our point of view, correction and derotation at maximum can only be received with the help of a muscle relaxant agent. Unfortunately, Sanders did not give details regarding the anesthesia used in his study. But since he recommended intubation, the usage of a muscle relaxant agent is presumable.
But in general, the necessity of general anesthesia is under ongoing discussion. Similarities between serial castings and the Ponseti method for clubfoot treatment can be seen. Both methods base on redressing castings to correct a deformity. Comparable data with or without general anesthesia only exists for clubfoot treatment and revealed no difference in overall outcome [18]. The influence of general anesthesia and especially the influence of muscle relaxant agents on the outcome of correction in patients with serial casting should be further investigated.
Spontaneous resolution of IS has been observed in cases with the “benign” form [19]. In contrast, the natural history of non-idiopathic early onset scoliosis is usually progressive. As non-idiopathic EOS are curves referred to of a neuromuscular, congenital or syndromic origin. To take all these distinctively different pathologies together and put them into one clinical picture, is an obsolete idea. Therefore, we selected only patients with syndromic-associated EOS for comparison.
Because of the deteriorating nature of non-idiopathic EOS, most of the patients will develop curves over 80°, if left untreated. This results in significant thoracic deformity and extrinsic pulmonary restriction measured by diminished vital capacity [20]. Therefore, early treatment is mandatory. After the introduction of “growth-friendly” implants, surgical treatment with a non-fusion method has become the method of choice for patients with severe, progressive curves. However, higher complication rates after surgical treatment were observed in younger patients and in patients with NIS compared to those of idiopathic cases [21, 22]. Serial casting has been used as a safe and effective method for treatment of IS in order to correct a spinal curve or postpone surgical treatment [23]. Clinical experience with serial casting for the treatment of NIS is still lacking. Only recently, Baulesh et al. [24] and Gussous et al. [25] reported good results for serial casting in NIS patients. In contrast to our treatment protocol, the wear time and number of the casts were individually adapted for every patient [24] or the patients received five serial casts [25].
Baulesh observed a correction of only 5° in CA in patients with EOS of non-idiopathic origin, compared to 13° in IS patients treated by casting. Identical results have been published by Gussous with a correction of 5° in CA in patients with NIS, compared to 20° in IS patients.
Our results demonstrate an even greater reduction in scoliosis in syndromic-associated NIS patients compared to patients with IS by means of only three serial casts followed by consecutive implementation of a Chêneau brace.
The study has the following limitations: retrospective design and the short follow up. Many different protocols for serial casting in EOS patients exist and the very best has yet to be discovered. Therefore, prospective randomized studies are desirable.