Posteromedial Translation Research Articles

Posteromedial Translation for Correction of Severe Hypokyphosis in Adolescent Idiopathic Scoliosis: Outcome Analysis with 2-year Follow-ups

Background: The deformity in the coronal plane is over-emphasized in the surgical management of adolescent idiopathic scoliosis (AIS), whereas the importance of the patient’s sagittal profile is generally neglected. Gold standard treatment in AIS consists of posterior instrumentation, deformity correction - through a reduction maneuver - and arthrodesis. The main focus in most reduction techniques is placed on the correction of deformity in the coronal and/or axial plane, worsening the patient’s sagittal profile. Objectives: This outcome analysis study aimed to investigate the surgical treatment of AIS patients with severe thoracic hypokyphosis (< 10) by adopting the posteromedial translation technique (PMT). Methods: In this retrospective study, the data and records of the patients with minimum 2-year follow-ups were analyzed. Correction of the deformity was radiologically assessed based on Cobb’s angle, thoracic kyphosis, and apex translation. The Scoliosis Research Society 22-item questionnaire (SRS-22r) was used for clinical evaluation before and after the surgery. Results: A total of 11 AIS patients (8 females and 3 males) with hypokyphosis underwent operations by the PMT at Imam Khomeini Hospital Complex between 2000 and 2020. According to the results, 78% correction in the coronal plane and an average correction of 56° (P < 0.001) were obtained. As for the sagittal plane, 18.8° correction was recorded (75%) (P < 0.001). Scoliosis Research Society 22-item questionnaire subscale analysis showed a significant improvement in patients' self-image (P = 0.035) and satisfaction (P = 0.043). Conclusions: The management of hypokyphosis in AIS was challenging. The PMT facilitated the tri-planar deformity correction, including a restoration of the thoracic kyphosis in all patients. A significant improvement was observed in both the coronal and sagittal profiles of the patients.

Correction to: Is posteromedial translation with sublaminar bands effective in correcting axial rotation in adolescent idiopathic scoliosis surgery? A 3D reconstruction study

Correction to: Is posteromedial translation with sublaminar bands effective in correcting axial rotation in adolescent idiopathic scoliosis surgery? A 3D reconstruction study

Is posteromedial translation with sublaminar bands effective in correcting axial rotation in adolescent idiopathic scoliosis surgery? A 3D reconstruction study.

Hybrid constructs with sublaminar bands have recently regained popularity as an alternative to all-screw construct for correction of adolescent idiopathic scoliosis (AIS). The aim of this study is to evaluate the ability of hybrid constructs with sublaminar bands to achieve a tridimensional correction of the scoliotic deformity. Our hypothesis is that hybrid construct with sublaminar bands are able to achieve a substantial derotation of the apical vertebrae, while preserving the thoracic kyphosis. A prospective evaluation of 50 consecutive cases (41 F, 9M, mean age 14.7 ± 2years) of AIS correction with hybrid construct was performed. In all cases, sublaminar bands were used at the apex of the main curve on concave side. All patients underwent pre and postoperative X-rays with EOS System, with full 3D reconstruction. Spinopelvic parameters and axial rotation of the vertebrae were measured pre and postoperatively. 2.7 ± 0.9 mean sublaminar bands were used per patient. Mean correction of deformity was 50 ± 9.5%. on the coronal plane. The mean axial rotation of the apical vertebra went from 18° ± 11.5° preoperatively to 9.4° ± 7.2° postoperatively (p < 0.001) with a mean derotation of 47.7%. Thoracic kyphosis went from 32.1° ± 18° preoperatively to 37.3° ± 13.1° postoperatively (p < 0.05). No intraoperative complications due to sublaminar bands were recorded. Hybrid construct with sublaminar band have been showed to be safe and effective in deformity correction and in maintaining or restoring thoracic kyphosis. This study showed that with sublaminar bands applied at the curve apex a substantial derotation of the apical vertebrae can be achieved.

Benefit-risks analysis of thoracoplasty in adolescent idiopathic scoliosis treated by sublaminar bands

IntroductionCosmetic concerns are one of the main complaints of patients with adolescent idiopathic scoliosis (AIS). Several studies have shown a significant improvement in self-image scores after thoracoplasty. However, the effects of thoracoplasty on pulmonary function and clinical outcomes remain debated. The objective was to analyze the benefits and risks of thoracoplasty during AIS surgery using a hybrid construct with sublaminar bands. Material and methodsIn this monocentric prospective cohort study, 68 patients with thoracic AIS were consecutively included between 2016 and 2017. All patients had low-dose 3D radiographs. Surgical correction was performed via the posterior approach, using the posteromedial translation technique with a hybrid construct (thoracic sublaminar band and lumbar pedicle screws). A thoracoplasty was proposed in cases of severe rib hump (more than 3cm). Pulmonary function was assessed by pulmonary function tests (PFT) with forced vital capacity, forced expiratory volume in 1 second and total lung capacity). Radiographic parameters and PFT were compared between patients who had or had not had a thoracoplasty preoperatively and 2 years postoperatively. The SRS-22 score was collected at follow-up. ResultsThe average age was 15±3 years. Nineteen patients (27%) had a thoracoplasty. The demographic, radiographic and respiratory data of the 2 groups were comparable preoperatively. The correction was similar between the groups on sagittal and coronal views. At 2 years, the PFTs were comparable to those performed preoperatively and no difference was found between the groups. None of the 12 patients who had a pleural effusion had it drained. The total SRS-22 score and the cosmetic subscore were higher in the thoracoplasty group (p<0.03). DiscussionThe association of a thoracoplasty with AIS surgery improves the self-image of patients without altering the PFTs at 2 years postoperatively. Given the low morbidity of thoracoplasty, it seems reasonable to offer it to patients with severe rib hump and high cosmetic demands. Level of evidenceIII.

Comparison of four correction techniques for posterior spinal fusion in adolescent idiopathic scoliosis.

When performing posterior spinal fusion for adolescent idiopathic scoliosis (AIS), it is of major importance to address both coronal and sagittal deformities. Although several techniques have been described, few data exist comparing them. Our objective was to compare four techniques (in situ bending (ISB), rod derotation (RD), cantilever (C) and posteromedial translation (PMT)) for the correction of spinal deformity in AIS including thoracic deformity. We conducted a multicenter retrospective study including 562 AIS patients with thoracic deformity with at least 24-month follow-up. Radiographic analysis was performed preoperatively, postoperatively and at last follow-up. The main outcomes were main curve correction and thoracic kyphosis restoration (TK). Coronal correction rate was significantly different among the four treatment groups (ISB 64% vs C 57% vs RD 55% vs PMT 67%, p < 0.001). Multivariate regression revealed that correction technique did not influence correction rate, whereas implant density, convex side compression and use of derotation connectors did. TK increase was significantly higher in the PMT group (average + 13°) than in DR (+ 3°), while ISB (-3°) and cantilever (-13°) resulted in TK decrease (p < 0.001). Multivariate analysis revealed that TK increase was only influenced by the reduction technique (p < 0.001) and preoperative TK (p < 0.001). The four techniques had the same ability to correct spinal deformity in the coronal plane. Three factors were identified to improve correction rate: implant density, convex compression and use of derotation connectors. On the other hand, PMT was more effective in restoring TK, particularly in hypokyphotic patients.

Development of a framework to assess the biomechanical impact of reverse shoulder arthroplasty placement modifications.

Reverse shoulder arthroplasty biomechanics can be improved by modifying the placement of prosthesis. Biomechanical studies have quantified the impact of placement modifications on the mobility and stability of the reverse shoulder. While these studies have provided detailed insights, direct comparisons between their finding are obfuscated by their use of differing methodologies. The aim of our study was to develop an assessment framework which used musculoskeletal simulations to consistently evaluate the biomechanics of various placement modifications. We conducted musculoskeletal simulations of humeral elevations and rotations using 15 reverse shoulder models. For each model, these simulations were conducted for a reference configuration of the prosthesis, established using surgical guidelines, and 34 modified configurations, which were based on commonplace adaptations to the placement of the glenosphere and humeral tray. The effect of each modified configuration on deltoid elongation, deltoid moment arm (DMA), joint stability, and impingement-free range of motion (IFROM) was determined relative to the reference configuration. We found that 16 of the 34 modified placements had an overall beneficial impact on reverse shoulder biomechanics. Within this subset, we identified two biomechanical trade-offs. First, there is an antagonistic relationship between IFROM and both the DMA and joint stability. Second, functional requirements differ between humeral elevations and rotations. Furthermore, we found that posteromedial translation of the humeral tray had the most beneficial impact on joint stability and inferior translation of the glenosphere had the most beneficial impact on IFROM and DMA.

Proximal Fixation in Adolescent Scoliosis Lenke 1 and 3 Treated by Posteromedial Translation Using Sublaminar Bands: Transverse-pedicular Hook Claw Versus Transverse Hook-pedicular Screw Claw.

This is retrospective comparative study. Numerous studies have focused on the efficacy, safety, and restoration of thoracic kyphosis in adolescent idiopathic scoliosis surgery using posteromedial translation method with sublaminar bands and hook claws at the top. The relevance of exchanging the penultimate anchor, that is, the pedicle hook with a pedicle screw in a hybrid construction has not yet been assessed. Our objective was to assess, in adolescent scoliosis Lenke 1 and 3 operated by posteromedial translation using sublaminar bands, the proximal fixation claw influence (transverse-pedicular hook vs. transverse hook-pedicular screw) for postoperative correction and the proximal junctional kyphosis (PJK) at 2 years follow-up. A comparative monocentric retrospective study included adolescent idiopathic scoliosis thoracic requiring surgery, between 2015 and 2017, with 2 years follow-up. Clinical (complications, revision surgery, and scoliosis research society-30) and radiographic (coronal and sagittal parameters) assessment were reported. Radiologic PJK was defined by a proximal junctional angle increase of 10 degrees or more between postoperative period and the last follow-up. Sixty patients (age at surgery=16±2 y; mean Cobb angle=58.2±12 degrees) were divided into 2 similar groups according to upper fixation: transverse-pedicular hook (H-H) and transverse hook-pedicle screw (S-H). No statistical differences were found for correction parameters (P>0.05). We reported 2 cases of PJK in H-H group (N=2/30=6.6%) and none in S-H group (N=0/30) (P=0.1) none requiring revision. No infectious or neurological events were reported. Mean scoliosis research society-30 was 126±12.7 in H-H group whereas 129.3±10 in S-H group (P=0.4). No differences in postoperative correction and clinical results at 2 years follow-up were found. A claw with transverse-pedicular hook increase proximal junctional angle without significant increase on radiographic PJK incidence compared with a claw with transverse hook and pedicle screws.

The Medial structures of the knee have a significant contribution to posteromedial rotational laxity control in the PCL-deficient knee.

Various reconstruction techniques have been employed to restore normal kinematics to PCL-deficient knees; however, studies show that failure rates are still high. Damage to secondary ligamentous stabilizers of the joint, which commonly occurs concurrently with PCL injuries, may contribute to these failures. The main objective of this study was to quantify the biomechanical contributions of the deep medial collateral ligament (dMCL) and posterior oblique ligament (POL) in stabilizing the PCL-deficient knee, using a joint motion simulator. Eight cadaveric knees underwent biomechanical analysis of posteromedial stability and rotatory laxity using an AMTI VIVO joint motion simulator. Combined posterior force (100N) and internal torque (5Nm) loads, followed by pure internal/external torques (± 5Nm), were applied at 0, 30, 60 and 90° of flexion. The specimens were tested in the intact state, followed by sequential sectioning of the PCL, dMCL, POL and sMCL. The order of sectioning of the dMCL and POL was randomized, providing n = 4 for each cutting sequence. Changes in posteromedial displacements and rotatory laxities were measured, as were the biomechanical contributions of the dMCL, POL and sMCL in resisting these loads in a PCL-deficient knee. Overall, it was observed that POL transection caused increased posteromedial displacements and internal rotations in extension, whereas dMCL transection had less of an effect in extension and more of an effect in flexion. Although statistically significant differences were identified during most loading scenarios, the increases in posteromedial displacements and rotatory laxity due to transection of the POL or dMCL were usually small. However, when internal torque was applied to the PCL-deficient knee, the combined torque contributions of the dMCL and POL towards resisting rotation was similar to that of the sMCL. The dMCL and POL are both important secondary stabilizers to posteromedial translation in the PCL-deficient knee, with alternating roles depending on flexion angle. Thus, in a PCL-deficient knee, concomitant injuries to either the POL or dMCL should be addressed with the aim of reducing the risk of PCL reconstruction failure.

Comparison of different strategies on three-dimensional correction of AIS: which plane will suffer?

PurposeThere are distinct differences in strategy amongst experienced surgeons from different ‘scoliosis schools’ around the world. This study aims to test the hypothesis that, due to the 3-D nature of AIS, different strategies can lead to different coronal, axial and sagittal curve correction.MethodsConsecutive patients who underwent posterior scoliosis surgery for primary thoracic AIS were compared between three major scoliosis centres (n = 193). Patients were treated according to the local surgical expertise: Two centres perform primarily an axial apical derotation manoeuvre (centre 1: high implant density, convex rod first, centre 2: low implant density, concave rod first), whereas centre 3 performs posteromedial apical translation without active derotation. Pre- and postoperative shape of the main thoracic curve was analyzed using coronal curve angle, apical rotation and sagittal alignment parameters (pelvic incidence and tilt, T1–T12, T4-T12 and T10-L2 regional kyphosis angles, C7 slope and the level of the inflection point). In addition, the proximal junctional angle at follow-up was compared.ResultsPre-operative coronal curve magnitudes were similar between the 3 cohorts and improved 75%, 70% and 59%, from pre- to postoperative, respectively (P < 0.001). The strategy of centres 1 and 2 leads to significantly more apical derotation. Despite similar postoperative T4-T12 kyphosis, the strategy in centre 1 led to more thoracolumbar lordosis and in centre 2 to a higher inflection point as compared to centre 3. Proximal junctional angle was higher in centres 1 and 2 (P < 0.001) at final follow-up.ConclusionCurve correction by derotation may lead to thoracolumbar lordosis and therefore higher risk for proximal junctional kyphosis. Focus on sagittal plane by posteromedial translation, however, results in more residual coronal and axial deformity.

Three-dimensional analysis of spinal deformity correction in adolescent idiopathic scoliosis: comparison of two distinct techniques

To compare 3D postoperative deformity correction using two distinct commonly utilized techniques for the treatment of adolescent idiopathic scoliosis (AIS). AIS patients with major thoracic (Lenke 1-2) curves at two sites who underwent deformity correction via posterior spinal instrumented fusion using one of two distinct techniques were retrospectively reviewed. Patients were matched 1:1 between sites for Lenke type (95% Lenke 1) and follow-up time. The "band site" performed posteromedial translation using thoracic sublaminar bands and 5.5-mm rods. The "screw site" performed spine derotation using differential rod contouring with pedicle screws and 5.5-mm rods. 3D measures of deformity from spinal reconstructions were compared between sites. Preoperatively, the groups had similar thoracic curve magnitudes (band, 55 ± 12° vs. screw, 52 ± 10°; p > 0.05); the "screw site" had less T5-T12 kyphosis (2 ± 14° vs. 7 ± 12°, p = 0.05) and greater thoracic apical rotation (- 19 ± 7° vs. - 14 ± 8°, p = 0.007). Postoperatively, the "screw site" had greater percent correction (61% vs. 76%, p < 0.001) and kyphosis restoration (p = 0.002). The groups achieved a similar amount of apical derotation (p = 0.9). The "band site" used cobalt chromium rods exclusively; the "screw site" used cobalt chromium (3%) and stainless steel (97%; p < 0.001). The "band site" performed significantly longer fusions. Significant variations were found between two commonly utilized techniques in AIS surgery, including rod material, correction mechanisms, and fusion levels. Significantly, a greater 3D deformity correction of the coronal and sagittal planes was observed at the "screw site" compared to the "band site", but with no difference in axial plane correction.

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

ABSTRACT 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.

Pulmonary Function After Convex Thoracoplasty in Adolescent Idiopathic Scoliosis Patients Treated by Posteromedial Translation

Study designRetrospective cohort study. ObjectiveTo analyze the morbidity of thoracoplasty, and more specifically its effect on pulmonary function, after surgery with hybrid constructs using sublaminar bands in adolescent idiopathic scoliosis (AIS). BackgroundCosmetic concern is one of the main reasons to consider surgery in adolescent idiopathic scoliosis. Several studies have demonstrated significant improvement of self-image scores after thoracoplasty. However, consequences of thoracoplasty on pulmonary function (ie, pulmonary function tests [PFTs]) remain controversial. MethodsAfter institutional review board approval, 96 consecutive AIS patients with thoracic curves (Lenke 1 and 2) were included between January 2014 and November 2015. All patients underwent low-dose stereoradiography with 3D reconstructions. Surgical procedure was the same in all patients: posterior correction using posteromedial translation technique with hybrid constructs (thoracic sublaminar bands and lumbar pedicle screws). Pulmonary function was explored with PFTs (forced vital capacity, forced expiratory volume in 1 second, and total lung capacity). Radiographic parameters and PFT results were compared between patients with and without thoracoplasty preoperatively and at two years postoperation. ResultsMean age was 15 ± 2 years, and body mass index averaged 18.8 ± 2.6. Thirty-six patients (37.5%) underwent thoracoplasty. Both groups were comparable preoperatively regarding demographic data, radiographic parameters, and PFT results. No significant difference was found between groups regarding postoperative correction rates. At the two-year follow-up, PFT results were similar to the preoperative ones and no difference was observed between groups. However, pleural effusions were reported in 26 patients (72%) on chest radiographs. Only one pleural effusion due to thoracoplasty required drainage. ConclusionResults of the current study demonstrated that thoracoplasty associated with posteromedial translation technique did not alter PFT results at two years postoperation. The morbidity of the procedure is limited, and it can therefore be considered in patients with high cosmetic demand and significant residual rib hump after main curve correction. However, hump height and pain evaluation would be interesting data in a prospective study. Level of EvidenceLevel IV.

How to Optimize Axial Correction Without Altering Thoracic Sagittal Alignment in Hybrid Constructs With Sublaminar Bands: Description of the “Frame” Technique

Study DesignRetrospective monocentric database study. ObjectivesTo describe the “frame” reduction technique and report the 3D quantitative analysis of postoperative corrections in a consecutive series of thoracic adolescent idiopathic scoliosis (AIS) patients. Summary of Background DataPosteromedial translation technique using sublaminar bands have been proved to be efficient and safe for 3D correction of the deformity and overall cosmetic aspect of the trunk. However, the ability to correct the axial plane may tend to rotate the vertebra clockwise instead of counterclockwise, thus increasing apical vertebra axial rotation (AVR) and the rib hump. A technical improvement was developed to emphasize axial correction. Methods60 thoracic AIS patients consecutively operated by posteromedial translation using the “frame” reduction technique were included with a minimum 2-year follow-up. Precontoured rods were connected with fixed transverse connectors according to a personalized preoperative planning. Rods were first inserted distally in the pedicle screws to achieve lumbar correction, and then in the upper anchors, and finally sublaminar bands were connected to their corresponding rods to progressively bring the concave lamina to the concave rod to correct the thoracic deformity. Sagittal and coronal 3D measures were performed preoperatively and at the latest follow-up using SterEOS (EOS Imaging, Paris, France) to assess the efficiency of the technique. ResultsThe distance from the center of the apical vertebra to the reference axis in the frontal plane was reduced from 4.7 to 1.1 cm, traducing the efficient medial translation of the spine during correction. T1–T12 kyphosis significantly increased after surgery (28°–35°). 3D location of the upper instrumented vertebra (UIV) was not affected. The apical rotation was significantly reduced after surgery (19°–11°), and the AVR correction rate averaged 42.2%. ConclusionThe “frame” technique is an innovative way of using polyester bands, optimizing axial correction while respecting sagittal alignment. Level of EvidenceLevel IV.

Cobalt-chrome and titanium alloy rods provide similar coronal and sagittal correction in adolescent idiopathic scoliosis

BackgroundCobalt-chrome (CoCr) and the titanium alloy TA6V (Ti) are the materials most widely used for spinal instrumentations in patients with adolescent idiopathic scoliosis (AIS). The objective of this work was to compare the effectiveness of CoCr and Ti rods in terms of coronal and sagittal correction by pedicle screw constructs in patients with AIS. HypothesisCorrection is similar with CoCr and Ti rods in patients with AIS. Material and methodA retrospective single surgeon study was conducted in patients with AIS managed using pedicle screw posterior spinal fusion with high implant density and reduction by postero-medial translation. Follow-up was more than 2 years in all patients. Patients were divided into two groups based on whether the rods used were made of CoCr (n=30) or Ti (n=33). The groups were identical for age, Risser classification, follow-up duration, type of curve, and implant density. Coronal and sagittal parameters on standing full-spine radiographs were analysed using graphics software before surgery then 1 month after surgery and at last follow-up. Quantitative data were compared by applying Student's t test. ResultsThe percentage of main curve correction at last follow-up was the same in the two groups (76%/75%) (p=0.7). Gains in thoracic kyphosis (12°/13°) and lumbar lordosis (8°/10°) were not significantly different between groups. At last follow-up, 3 patients had proximal junctional kyphosis, 1 in the CoCr group and 2 in the Ti group (p=0.6). ConclusionFor posterior spinal fusion to treat AIS, with a high density of pedicle screws, correction by translation, and 6 mm rods, CoCr rods and Ti rods produce the same amount of coronal and sagittal correction. Level of evidenceIV, comparative retrospective study with no control group.

Preliminary experience with SpineEOS, a new software for 3D planning in AIS surgery.

Preoperative planning of scoliosis surgery is essential in the effective treatment of spine pathology. Thus, precontoured rods have been recently developed to avoid iatrogenic sagittal misalignment and rod breakage. Some specific issues exist in adolescent idiopathic scoliosis (AIS), such as a less distal lower instrumented level, a great variability in the location of inflection point (transition from lumbar lordosis to thoracic kyphosis), and sagittal correction is limited by both bone-implant interface. Since 2007, stereoradiographic imaging system is used and allows for 3D reconstructions. Therefore, a software was developed to perform preoperative 3D surgical planning and to provide rod's shape and length. The goal of this preliminary study was to assess the feasibility, reliability, and the clinical relevance of this new software. Retrospective study on 47 AIS patients operated with the same surgical technique: posteromedial translation through posterior approach with lumbar screws and thoracic sublaminar bands. Pre- and postoperatively, 3D reconstructions were performed on stereoradiographic images (EOS system, Paris, France) and compared. Then, the software was used to plan the surgical correction and determine rod's shape and length. Simulated spine and rods were compared to postoperative real 3D reconstructions. 3D reconstructions and planning were performed by an independent observer. 3D simulations were performed on the 47 patients. No difference was found between the simulated model and the postoperative 3D reconstructions in terms of sagittal parameters. Postoperatively, 21% of LL were not within reference values. Postoperative SVA was 20mm anterior in 2/3 of the cases. Postoperative rods were significantly longer than precontoured rods planned with the software (mean 10mm). Inflection points were different on the rods used and the planned rods (2.3 levels on average). In this preliminary study, the software based on 3D stereoradiography low-dose system used to plan AIS surgery seems reliable for preoperative planning and precontoured rods. It is an interesting tool to improve surgeons' practice, since 3D planning is expected to reduce complications such as iatrogenic malalignment and to help for a better understanding of the complications, choosing the location of the transitional vertebra. However, further work is needed to improve thoracic kyphosis planning. These slides can be retrieved under Electronic Supplementary Material.

45 - Does Thoracoplasty Affect Pulmonary Function in Thoracic AIS Surgery Treated by Posteromedial Translation?

45 - Does Thoracoplasty Affect Pulmonary Function in Thoracic AIS Surgery Treated by Posteromedial Translation?

Correction of hypokyphosis in thoracic adolescent idiopathic scoliosis using sublaminar bands: a 3D multicenter study.

The comparison of implants and correction methods remain controversial in AIS. Excellent frontal and axial correction rates have been reported with all-screw constructs, but at the expense of sagittal alignment, which has a tendency to flatten postoperatively. Posteromedial translation using hybrid constructs seems to preserve and improve thoracic kyphosis (TK), but no series exist to date with a significant number of hypokyphotic patients. In addition, the measures of TK in 2D are often wrong in severe AIS due to axial rotation. The goals of this study were therefore to analyze the 3D radiological outcomes of a group of hypokyphotic AIS patients operated with sublaminar bands. 35 consecutive AIS hypokyphotic patients (T4T12 <15°) operated in three centers were included, with a minimum 2-year follow-up. The surgical technique was similar in all centers, associating lumbar pedicle screws and thoracic sublaminar bands. Posteromedial translation was the main correction technique, and no patient underwent prior anterior release. 3D spinal reconstructions were performed preoperatively, postoperatively and at the latest follow-up by an independent observer using SterEOS (EOS imaging, Paris, France), and 2D and 3D measurements were compared. In addition, a new 3D parameter [sagittal shift of the apical vertebra (SSAV)], reflecting the translation of the apical vertebra of the main curve in the patient sagittal plane, was described and reported. The age of the cohort was 16years and the number of sublaminar bands used for correction averaged 6 (±1.5). T1T12 and T4T12 sagittal Cobb angles appeared to be overestimated on 2D postoperatively (3°, p=0.002 and 4°, p<0.001, respectively). Hence, only 3D measurements were kept for the quantitative analysis of the postoperative correction. T4T12 TK significantly increased after surgery (average 8°±7°, p<0.001), but 11 patients (31.4%) remained hypokyphotic. Seven out of the eight patients (87.5%) who presented a thoracic lordosis (i.e., T4T12 <0°) preoperatively were corrected after surgery (mean gain 16°±4°). A posterior shift (positive SSAV) of the apical vertebra was reported in 24 patients (68.6%). In this subgroup, the mean SSAV was +2cm (±1). Good correlation was found between the SSAV and the postoperative change in 3D T4T12 kyphosis (r=0.62). Measures in 2D tend to overestimate sagittal alignment and are not sufficient to evaluate postoperative correction. SSAV is a new 3D parameter reflecting the TK change that needs to be further investigated and used in the future. This series confirms that sublaminar bands should be considered in hypokyphotic patients, since thoracic sagittal alignment was restored in 68.6% of the cases.

Adolescent idiopathic scoliosis correction achieved by posteromedial translation using polyester bands: A comparative study of subtransverse process versus sublaminar fixation

PurposeSublaminar polyester bands have been used in hybrid construct to achieve correction of adolescent idiopathic scoliosis since 2003. Despite the reported safety of the bands, some surgeons remain reluctant at the idea of approaching the canal because of the potential neurological complications reported with the Luque wiring. Sub transverse bands might be an alternative. The present study is the first to compare sublaminar polyester band fixation to fixation of polyester bands around the transverse processes in hybrid constructs used to treat AIS. MethodsTwo cohorts of consecutive patients treated for thoracic AIS were retrospectively reviewed, with a minimum 2-year follow-up. Posteromedial translation was used for main curve correction in all cases. Sublaminar polyester bands were used in group 1 (20 patients). In group 2 (20 patients), the same implant was used, but the bands were passed around the transverse process instead of the lamina. Radiographic analysis included frontal Cobb angle measurements for each curve, thoracic kyphosis and rotation of the apical vertebra (RVA). ResultsMean operative time was similar in groups 1 and 2 (235±35 and 240±30minutes, respectively). Mean frontal correction achieved for the main curve was similar in both groups, 62.5±17.4% in group 1 and 54.1±19.4% in group 2. Sagittal correction was similar, with a final mean thoracic kyphosis of 30.9°±9.7° and 27.8°± 6.8° in group 1 and 2, respectively. Correction of RVA was similar in both groups postoperatively, 65.8% (±29.1) and 54.4% (±42.7) in group 1 and 2 respectively. No transverse process or lamina fracture was observed during insertion of the bands or curve correction in any of the groups. ConclusionThis study confirms that anchorage of Universal clamps (UCs) around transverse processes is a safe and efficacious technique in both the frontal and sagittal planes, providing a useful alternative for the correction of moderate AIS. UCs attached to transverse processes can achieve correction of moderate AIS similar to that obtained with sublaminar UCs while further reducing risks of vertebral canal complications. Level of evidenceLevel IV.

Role of thoracoscopy for the sagittal correction of hypokyphotic adolescent idiopathic scoliosis patients.

Thoracic adolescent idiopathic scoliosis (AIS) curves (Lenke 1-4) are often characterized by hypokyphosis. Sagittal alignment remains challenging to correct, even with recent posterior segmental instrumentation. Some authors recommend anterior endoscopic release (AER) to reduce anterior column height, and facilitate thoracic kyphosis correction. The aim of this study was to assess the contribution of AER to sagittal correction in hypokyphotic AIS. Fifty-six hypokyphotic (T4T12<20°) AIS patients were included. In group 1 (28 patients), patients first underwent AER, followed by posterior instrumentation and correction 5-7 days later. In group 2 (28 patients), patients underwent the same posterior procedure without AER. Posterior correction was performed in all cases using posteromedial translation and hybrid constructs consisting of lumbar pedicle screws and thoracic sublaminar bands. From radiological measurements performed using low-dose EOS radiographs, the correction of thoracic kyphosis was compared between the two groups. Groups 1 and 2 were comparable regarding demographic data and preoperative thoracic kyphosis (group 1: 11.7° ± 6.9° vs group 2: 12.1° ± 6.3°, p = 0.89). Postoperative thoracic kyphosis increase averaged 18.3° ± 13.6° in group 1 and 15.2° ± 9.0° in group 2. The benefit of anterior release was not statistically significant (p = 0.35). Although previous studies have suggested that thoracoscopic release improved correction compared to posterior surgery alone, the current study did not confirm this finding. Moreover, results of the current series showed that no significant benefit can be expected from AER in terms of sagittal plane improvement when the posteromedial translation technique is used, even in challenging hypokyphotic patients.

Adolescent idiopathic scoliosis treated with posteromedial translation: radiologic evaluation with a 3D low-dose system

Computed tomography can be used for three-dimensional (3D) evaluation of adolescent idiopathic scoliosis (AIS) patients, but at the expense of high radiation exposure, and with the limitation of being performed in the supine position. These drawbacks can now be avoided with low-dose stereoradiography, even in routine clinical use. The purpose of this study was to determine the 3D postoperative correction of AIS patients treated by posteromedial translation. Forty-nine consecutive patients operated for AIS (Lenke 1-4) using posteromedial translation were included. Corrections were evaluated preoperatively, postoperatively and after at least 2 years using the EOS imaging system. 3D angles were measured in the plane of maximum deformity. Mean number of levels fused and operative time were 13.5 ± 1 and 215 ± 25 min, respectively. Main thoracic, proximal thoracic, and lumbar curves corrections averaged 64.4 ± 18, 31 ± 10 and 69 ± 20 %, respectively. Mean T4-T12 kyphosis increased 18.8° ± 9° in the subgroup of hypokyphotic patients. Mean apical vertebral rotation reduction was 48.3 ± 20 %. Trunk height gain averaged 27.8 ± 14 mm. There was no pseudarthrosis or significant loss of correction in any plane during follow-up. Two patients (4 %) developed asymptomatic proximal junctional kyphosis, despite having normal thoracic kyphosis. Their sagittal balance was shifted posteriorly by 36 and 47 mm, respectively, by the operation, but revision surgery was not performed. Low-dose stereoradiography provided 3D reconstructions of the fused and unfused spine in routine clinical use. Postoperative 3D analysis showed that posteromedial translation enhanced sagittal balance correction, without sacrificing frontal or axial correction of the deformity.