USE OF SUBLAMINAR BANDS FOR ADOLESCENT IDIOPATHIC SCOLIOSIS - A SYSTEMATIC REVIEW

Objective: In 2003, Mazda et al. introduced a new device for surgical correction of Adolescent Idiopathic Scoliosis (AIS) called sublaminar bands (SB). The reduction principle that SBs use is posteromedial spinal translation, similar to Luque’s wiring, but using polyester bands. Methods: We performed a systematic review of the literature on this subject, evaluating the technique in terms of coronal correction, sagittal correction, bleeding, mean surgical time, loss of correction, infection, pseudoarthrosis, and neurological and other complications. The total search resulted in 14 articles published over the last 10 years. We found that the use of SBs in hybrid AIS correction instrumentations provides an average correction of 69% in the frontal plane, a 5° increase in thoracic kyphosis (average increase of 55%), overall complications of 4.5%, and no neurological complications were reported in any of the studies analyzed.. The mean blood loss was 682.5 mL and the mean surgical time was 228.6 minutes. Conclusions: We conclude that the literature suggests that this instrumentation is safe, allows good correction in the frontal plane and great correction in the sagittal plane. As for complications, mean surgical time, and blood loss, their averages are lower than those of other constructions used for AIS. Level of evidence IIA; Systematic review. de la literatura sobre el tema evaluando la técnica con relación a la corrección coronal, corrección sagital, sangrado, tiempo operatorio promedio, pérdida de corrección, infec-ción, pseudoartrosis, complicaciones neurológicas y otras complicaciones. La búsqueda result ó en 14 artículos publicados en los últimos 10 años. Resultados: Observamos que el uso de las BS en instrumentaciones híbridas para la corrección de la EIA proporciona una reducción promedio de 69% en el plano frontal y aumento de la cifosis torácica del 5º (aumento promedio de 55%); 4,5% de complicaciones en general y ninguna complicación neurológica fueron presentadas en todos los estudios analizados. El promedio de sangrado fue 682,5 mL y el tiempo quirúrgico promedio de 228,6 minutos. Conclusiones: Se concluye que la literatura sugiere que esta instrumentación es segura, permite buena corrección en el plano frontal y gran corrección en el plano sagital. Con relación a las complicaciones, tiempo quirúrgico promedio y sangrado, todas estas variables en promedio son inferiores si comparadas con las demás construcciones usadas para EIA. Nivel de evidencia IIA; Revisión sistemática. Descriptores : Curvaturas de la Columna Vertebral; Cirugía; Prótesis e Implantes; Dispositivos de Fijación Ortopédica.


INTRODUCTION
Surgical strategies for the treatment of adolescent idiopathic scoliosis (AIS) continue to be developed and improvement in correction power is notable. 1 Pedicle screws have become the standard, but they are already being associated with a decrease in thoracic kyphosis and a risk of junctional kyphosis. 2,3 In 2003, Mazda et al. introduced the use of a new device: sublaminar bands (SB). The reduction principle that SBs use is the posteromedial translation of the spine, similar to that of Luque wires, but using malleable polyester bands instead of metallic wires. 4 Recent literature suggests that using this type of instrumentation allows good curve correction in the frontal plane and it has been shown to be particularly effective in the sagittal plane with improved restoration of thoracic kyphosis. 5,6 SBs consist of polymeric strips made of polyester, whose curved rigid edges are introduced under the vertebral lamina. The sublaminar insertion of polyester bands is simple and because of their greater contact surface they offer advantages over steel wires, permitting greater traction with a lower risk of fracture of the lamina. 7 The bands are tensioned level by level with a special tool, pulling the vertebra by the lamina and guiding them to the rods. 8 The strength of the rod to band connection is equivalent to the connections using screws or hooks, allowing conventional deformity correction maneuvers such as compression and distraction. They can also be used in combination with pedicle screws, especially in the lumbar region. 4 Studies about SBs, although scarce, emphasize the safety of the method and the efficiency of its posteromedial translation in the restoration of sagittal alignment, possibly superior in this respect to the use of screws. In this sense, we sought to conduct a systematic review of the current literature to evaluate the correction power in the coronal and sagittal planes, as well as safety and complications, in order to include SBs in the surgical therapeutic arsenal available for the treatment of AIS.

METHODS
A systematic review of the literature on the subject was conducted according to the Cochrane Handbook for Systematic Reviews. We reviewed studies reporting cases of surgical treatment for AIS using hybrid constructions that used SB. Data analysis focused on the descriptive evaluation of the extracted information. The search for articles was conducted in the PubMed, Scopus, and Google Scholar electronic databases. The keywords and the search strategy used were: ("adolescent idiopathic scoliosis") AND ("sublaminar band" OR "sublaminar bands" OR "posteromedial translation" OR "universal clamp" OR "sagittal correction" OR "sagittal balance") AND ("pedicle screw" OR "hybrid construction" OR "hybrid instrumentation").
We limited the search to works published in English from 2010 forward. The last search was conducted by the authors at the end of February 2019. The searches were conducted independently by two researchers who collected the abstracts. We identified additional works from the references of the included studies. Unpublished works and those not reviewed by peers were not considered.
The exclusion criteria were articles written in a language other than English, animal and cadaver studies, in vitro studies, technical notes, letters to the editor, and articles that did not specifically contain results reports. The three-level selection system was used for the final analysis of the full articles.
Two authors independently extracted the data using an extraction form. Disagreements were resolved through discussion or consensus with a third author. The corresponding author of the study was contacted to collect any missing information. The information was extracted using special tables designed for the review-based study. The tables contained the following variables: coronal correction, sagittal correction, cervical alignment, bleeding, mean surgical time, loss of correction, infection, pseudoarthrosis, neurological complications, and other complications.

RESULTS
We found a total of 158 articles with the search strategy. After applying the inclusion and exclusion criteria, 14 articles remained for analysis. (Figure 1) Two of them were produced in Italy, one in Iran, one in Japan, and ten in France. The selected articles are described in Table 1.
Except for in one study, all the patients studied in the other articles participated in a minimum follow-up of two years to evaluate complications and loss of correction. (Table 1) The patients in twelve of the studies were submitted to the same hybrid construction surgical technique combining pedicle screws below the inflection point and thoracic sublaminar bands above the inflection point with posteromedial translation for thoracic correction. Two studies differed from this technique, using pedicle screws together with SBs in the thoracic region above the inflection point. ( De Gauzy, J. S. et al. 12 Ilharreborde, B. et al. 7 Mazda, K. et al. 4 Palmisani, M. et al. 13 Ilharreborde, B. et al. 14 Hassankhani, E.G. et al. 15 Angelliaume, A. et al. 16 Issa, S.P. et al. 17 Pesenti, S. et al. 18 Ilharreborde,B. et al. 19 Authors    and Ilharreborde B. et al.,7 used the same cohort of 75 patients. Thus, the total number of patients who underwent surgery using the thoracic SB technique in the 14 articles was 1030. For purposes of calculating means and parameter results, these two studies were considered a single study, but for the purpose of quantifying articles that address any of the parameters analyzed here, they were considered distinct articles. When considering the 12 studies that used only thoracic SBs, the total number of patients was 981. (Table 1) Four studies compared the outcomes of the groups submitted to the technique using SBs to another group that underwent a different surgical technique: one compared them to those of a technique using subtransverse bands, another to the use of thoracic hooks, another to a technique with thoracic screws, and the last compared them to those of a technique using thoracic hooks and screws. One study used SBs in two groups, differentiated only by the material used for the longitudinal rods (titanium or cobalt chromium). (Table 1) All 14 studies analyzed the surgical technique according to at least one of the following parameters: coronal correction power, sagittal correction power, loss of coronal correction, mean bleeding volume, mean surgical time, occurrence of complications, occurrence of infection, and occurrence of pseudoarthrosis and 2 studies analyzed cervical alignment. A single study was focused only on an analysis of the occurrence of infection and pseudoarthrosis. (Table 2) None of the 11 studies that analyzed the occurrence of neurological complications reported any complications of this nature. Similarly, none of the 6 studies that analyzed the occurrence of pseudoarthrosis reported the occurrence of this condition during follow-up. (Table 2) Ten studies analyzed the occurrence of complications from the surgical technique. There was a total of 20 complications obtained among the 423 patients evaluated in these studies, for a complication rate of 4.73%. When we considered those 9 studies that used the same thoracic SB-only technique separately, there was a total of 16 cases of complications or 4.1%. (Table 2) These same 10 studies also analyzed the occurrence of other types of postoperative complications, observing a total of 19 different complications for an overall rate of 4.5%. When we considered only the 9 out of these 10 studies that used the same thoracic SB-only technique, the total of different complications was 17 or 4.33%. ( Table 2) The natures of these 17 complications were pleural effusion (3), intestinal disorder (2), superior mesenteric artery syndrome (2), debilitating pain (5), and proximal junctional kyphosis (5).

France
Seven studies, totaling 266 patients, analyzed the volume of intraoperative bleeding, reporting a mean overall blood loss of 682.5 mL. When we considered only the 5 out of these 7 studies that used the same thoracic SB-only technique, the mean value was 645 mL (Table 2). Nine studies, totaling 315 patients, analyzed the mean surgical time, but one of them did not report the value obtained and was excluded from the calculation of the overall mean surgical time, which was 228.6 minutes. When we considered only the 7 out of these 8 studies that used the same thoracic SB-only technique, the overall mean was 220.4 minutes. (Table 2) Seven studies, totaling 777 patients, analyzed the occurrence of postoperative infections, observing a total of 32 cases for an overall infection rate of 4.12%. (Table 2)

Coronal correction
Eleven studies analyzed the power of coronal correction for the technique used in the immediate postoperative period, with a mean coronal correction of 70.3%. (Figure 2) When we considered only the 9 out of these 11 studies that used only thoracic SBs, the overall mean was 69.22%. (Table 3)

Sagittal correction
Thirteen studies analyzed the power of sagittal correction. However, only 10 studies in the sample provided data about the power of sagittal correction in the immediate postoperative period. (Table 4) All of these 10 studies used the same technique of only thoracic SBs. The overall mean sagittal correction power of these 10 studies in the immediate postoperative period was 5.95°. (Figure 3)

Cervical alignment
Two studies, totaling 78 patients, analyzed the effect of the surgical technique on the cervical spine. Correction of cervical lordosis in the immediate postoperative period was 10.9° and 10.3° in these two studies for mean immediate correction of 10.6°. 5,14 Hirsch, C. et al. 8 La Rosa, G. et al. 9 Ilharreborde, B. et al. 10 Imagama, S. et al. 11 De Gauzy, J. S. et al. 12 Ilharreborde, B. et al. 7 Mazda, K. et al. 4 Palmisani, M. et al. 13 Ilharreborde, B. et al. 14 Hassankhani, E.G. et al. 15 Angelliaume, A. et al. 16 Issa, S.P. et al. 17 Pesenti, S. et al. 18 Ilharreborde , B. et al. 19 Authors 2014    Loss of correction Eleven studies analyzed postoperative loss of correction after a minimum follow-up period for an overall mean loss of correction of 1.49° (Figure 4). When we considered only the 9 out of these 11 studies that used only thoracic SBs, the overall mean was 1.33°. (Table 5)

DISCUSSION
The advantage of sublaminar instrumentation, initially developed by Luque in the 1970s, was its being a truly segmental instrumentation with a high power of correction, thanks to the superiority of apical translation. This allowed the elimination of orthotic use, a great advance at that time. 20 SBs are evolved from the wires developed by Luque. They allow the integration of the advantages of sublaminar wiring without any of its disadvantages. The polyester bands can be inserted with less invasion of the spinal canal than the wires and less risk of spinal cord injury and they have a greater contact surface, permitting greater traction with a lower risk of laminar failure. 21 This review showed us that the use of SBs in hybrid instrumentations to correct AIS is safe, with a mean overall complication rate of 4.5% and no neurological complications were observed in all the studies analyzed. It is also noteworthy that no cases of pseudoarthrosis were reported during two years of follow-up. 9 We found a mean postoperative infection rate of 4% in the studies. This mean postoperative infection rate is lower than that of the largest study on the subject, which retrospectively involved 524 patients with AIS who had undergone surgery using SBs and had an overall infection rate of 5.3%. 17 Coronal correction was like that obtained using pedicle screws, which is the standard used today. The technique achieved a mean reduction of 69% (ranging from 41-95%) in the frontal plane, which is equivalent to the best results published in the literature on AIS corrections. 4 Loss of correction in the first 2 years of follow-up was minimal with a mean of 1.5º.
Restoring sagittal spinal balance continues to be one of the most challenging goals of scoliosis surgery. The reduction of deformity using SBs presented a mean 5º increase in thoracic kyphosis in normokyphotic and hypokyphotic patients. These results are superior to those previously reported in the literature for thoracic correction using screws. 4 The results are matched in the literature, which shows that hybrid constructions increase sagittal correction, which may also reduce the risk of junctional kyphosis. 22,23 Mean bleeding also was less than the means presented by the other most-used hybrid instrumentations, at around 682.5 mL, compared to instrumentation using hooks, which average 1090 mL. Similarly, the mean surgical time of 228.6 minutes is less than the mean surgical time of the other hybrid constructions, especially the hook at an average of 295 minutes. 7

CONCLUSIONS
In conclusion, the results of this review confirm that hybrid constructions using SBs to correct spinal curvature in patients with AIS are safe. It is effective in correcting deformities in the coronal plane. Today, SBs seem to provide better correction in the sagittal plane than other devices, especially in constructions using screws and they reduce mean surgical time and blood loss.