All Pedicle Screw versus Hybrid Hook-Screw Instrumentation in the Treatment of Thoracic Adolescent Idiopathic Scoliosis (AIS): A Prospective Comparative Cohort Study.

Background: Posterior spinal correction and fusion remains the most common surgical treatment in AIS. Surgeons currently favour all pedicle screw (AS) correction techniques with alternative implants being less utilised. The purpose of this study was to assess whether a hybrid hook−screw (HS) construct could achieve similar outcomes. Methods: A single centre, prospective cohort study was conducted. Patients with moderate and severe thoracic AIS (Lenke 1) were included. Clinical and radiological results of a standardised hybrid HS technique were compared with those obtained with an AS construct. All patients had a minimum 2-year follow-up. Results: 160 patients were included in this series (80 patients/group). The HS group had significantly reduced surgical time, blood loss and implant density. Both techniques achieved ≥75% scoliosis correction. The HS group was superior in restoring thoracic kyphosis and global sagittal balance with an average 31% increase in kyphosis compared to 10% with the AS group (p < 0.001). There was significant improvement in SRS-22 scores at 2 years postoperative (p < 0.001) in both groups. There were no neurological or visceral complications related to instrumentation, no detected non-union and no reoperations. The HS implant cost was significantly lower than that of AS, with a mean instrumentation saving of almost £2000/patient. Conclusion: A standardised hybrid HS technique achieved excellent correction of thoracic scoliosis, high patient satisfaction and low complication rates in patients with thoracic AIS. These results were comparable to the AS group. The HS technique achieved better correction of thoracic kyphosis and sagittal balance than the AS technique, together with reduced surgical time, blood loss and implant cost.

Early dynamic changes within the spine following posterior fusion using hybrid instrumentation in adolescents with idiopathic scoliosis: a gait analysis study.

INTRODUCTION: In adolescent idiopathic scoliosis (AIS) patients, mechanical consequences of posterior spinal fusion within the spine remain unclear. Through dynamic assessment, gait analysis could help elucidating this particular point. The aim of this study was to describe early changes within the spine following fusion with hybrid instrumentation in adolescents with idiopathic scoliosis, using gait analysis MATERIALS AND METHODS: We conducted a single-centre prospective study including AIS patients scheduled for posterior spinal fusion (PSF) using hybrid instrumentation with sublaminar bands. Patients underwent radiographic and gait analyses preoperatively and during early postoperative period. Among gait parameters, motion of cervicothoracic, thoracolumbar and lumbosacral junctions was measured in the three planes. RESULTS: We included 55 patients (mean age 15 years, 84% girls). Fusion was performed on 12 levels and mean follow-up was 8 months. There was a moderately strong correlation between thoracolumbar sagittal motion and lumbosacral junction pre- and postoperatively (R = - 0.6413 and R = - 0.7040, respectively, all p < 0.001), meaning that the more thoracolumbar junction was in extension, the more lumbosacral extension movements decreased. There was a trend to significance between postoperative SVA change and thoracolumbar sagittal motion change (R = - 0.2550, p = 0.059). DISCUSSION: This is the first series reporting dynamic changes within the spine following PSF using hybrid instrumentation in AIS patients. PSF led to symmetrization of gait pattern. In the sagittal plane, we found that thoracolumbar extension within the fused area led to decreased extension at cervicothoracic and lumbosacral junctions. Even though consequences of such phenomenon are unclear, attention must be paid not to give a too posterior alignment when performing PSF for AIS patients.

Deformity correction in thoracic adolescent idiopathic scoliosis.

AIMS: To compare the rates of sagittal and coronal correction for all-pedicle screw instrumentation and hybrid instrumentation using sublaminar bands in the treatment of thoracic adolescent idiopathic scoliosis (AIS). METHODS: We retrospectively reviewed the medical records of 124 patients who had undergone surgery in two centres for the correction of Lenke 1 or 2 AIS. Radiological evaluation was carried out preoperatively, in the early postoperative phase, and at two-year follow-up. Parameters measured included coronal Cobb angles and thoracic kyphosis. Postoperative alignment was compared after matching the cohorts by preoperative coronal Cobb angle, thoracic kyphosis, lumbar lordosis, and pelvic incidence. RESULTS: A total of 179 patients were available for analysis. After matching, 124 patients remained (62 in each cohort). Restoration of thoracic kyphosis was significantly better in the sublaminar band group than in the pedicle screw group (from 23.7° to 27.5° to 34.0° versus 23.9° to 18.7° to 21.5°; all p < 0.001). When the preoperative thoracic kyphosis was less than 20°, sublaminar bands achieved a normal postoperative thoracic kyphosis, whereas pedicle screws did not. In the coronal plane, pedicle screws resulted in a significantly better correction than sublaminar bands at final follow-up (73.0% versus 59.7%; p < 0.001). CONCLUSION: This is the first study to compare sublaminar bands and pedicle screws for the correction of a thoracic AIS. We have shown that pedicle screws give a good coronal correction which is maintained at two-year follow-up. Conversely, sublaminar bands restore the thoracic kyphosis better while pedicle screws are associated with a flattening of the thoracic spine. In patients with preoperative hypokyphosis, sublaminar bands should be used to restore a proper sagittal profile. Cite this article: Bone Joint J 2020;102-B(3):376-382.

Influence of the sublaminar band density in the treatment of Lenke 1 adolescent idiopathic scoliosis.

INTRODUCTION: Optimal pedicle screw density for the treatment of adolescent idiopathic scoliosis (AIS) remains unknown. It is not clear whether higher implant density results in better clinical outcomes. Large variability in implant density exists among hybrid or all screw constructs. Significant heterogeneity exists with respect to the number of sublaminar bands (SB) used, and the influence of SB density on curve correction in the treatment of AIS. HYPOTHESIS: We hypothesize that increased SB density does not improve sagittal or coronal plane curve correction. METHODS: A single-center, retrospective study of 131 consecutive patients (118 females) with Lenke 1 adolescent idiopathic scoliosis, all operated between 2012 and 2015 by two surgeons using identical surgical technique and type of instrumentation (SB hybrid instrumentation treatment). SB density was measured using the number of SB reported as well as the number of vertebrae instrumented. Radiographic measurements included preoperative thoracic curve flexibility, Cincinnati reduction index (CRI), and postoperative thoracic Cobb (POCC) and kyphosis (POKC) angle correction measured on immediate postoperative radiographs and at 2 years postoperatively. RESULTS: Median patient age was 15.6 years (IQR, 12-18). The median SB density was 0.4 (IQR 0.4-0.5). No statistically significant correlation was identified between SB density and CRI (p=0.71), POCC (p=0.55), or POKC (p=0.61) at 2-years postoperatively. Preoperative curve flexibility was found to have significant effect both on immediate (r=-3.02, p<0.001) and 2-year (r=-2.69, p<0.001). DISCUSSION: SB utilized as a part of a hybrid construct for patients with flexible Lenke I AIS achieve satisfactory deformity correction regardless of SBd. The use of low SB density is appropriate for a subset of patients with flexible Lenke 1 adolescent idiopathic scoliosis.

Adjacent segment degeneration and topping off. Never stop at the apex!

We investigated if applying the Transition system (Globus Medical Inc., Audubon, PA, USA) as topping off can prevent Adjacent Segment Degeneration (ASD) and if rate of ASD is increased if instrumentation stopped at the apex of the Lumbar Lordosis (LL). We enrolled 99 consecutive patients in a retrospective study who have been operated by instrumented fusion of the lumbar spine. Thirty patients were treated by topping of (Group 1), 69 patients received the standard procedure (Group 2). 18 patients of group 1 (60%) and 38 patients of group 2 (55%) developed ASD. The difference was not significant (P>0.05). In 17 patients (17%) instrumentation stopped at apex of LL. 14/17 patients (82%) developed an ASD. This influence was significant (P<0.05). Instrumented fusion of the lumbar spine should not stop at the apex of the lumbar curve. Topping off by hybrid dynamic fixation does not reduce the rate of ASD.

Posterior Lumbar Interbody Fusion versus Dynamic Hybrid Instrumentation: A Prospective Randomized Clinical Trial.

OBJECTIVE: The purpose of this study was to assess the radiologic and clinical outcomes after lumbar fusion intervention and to compare the established posterior lumbar interbody fusion (PLIF) technique and dynamic hybrid instrumentation (topping off). METHODS: In this prospective randomized trial, all patients who presented with degenerative changes to the lumbar spine (L2-S1) were included and randomized in 2 groups: patients who underwent the 360°-fusion procedure in PLIF (group 1: control group) and those patients who underwent fusion surgery with additional hybrid instrumentation (Dynesys-Transition-Optima [Zimmer Spine Inc., Denver, Colorado, USA]) cranial to the rigid fixed segment (group 2: intervention group). Patients' demographics were documented and follow-up visits were conducted after 6 weeks and then stepwise after 6 up to 36 months. Each follow-up visit included assessment of quality of life and pain using specific questionnaires (Core Outcome Measurements Index, Short-Form 36, and Oswestry Disability Index) as well as radiologic evaluation with the focus on the adjacent level alteration. RESULTS: Fifteen patients per group met the inclusion criteria, and after 36 months, the loss to follow-up was 20%. At the maximum follow-up time, the overall risk for adjacent segment degeneration was substantial (i.e., 24.14%), independent of the surgical procedure. Material failure was observed in 17.24%. Although no significant difference was observed between both groups, all patients presented with postoperative improvement regarding the clinical scores. CONCLUSIONS: The present study cannot support the safety of dynamic hybrid devices in those cases if the reduction of adjacent segment degeneration is the main target, especially regarding the reported implant failure rates and the similar clinical outcomes between the both groups.

Anterior release may not be necessary for idiopathic scoliosis with a large curve of more than 75° and a flexibility of less than 25.

BACKGROUND CONTEXT: To improve correction and fusion rates, an anterior release is often needed for the treatment of idiopathic scoliosis with a curve of more than 75° before posterior correction, instrumentation, and fusion. However, there are disadvantages to anterior release, and we are concerned about whether it is necessary for anterior-posterior spinal fusion in these patients. PURPOSE: The objective of this study was to compare the surgical results for idiopathic scoliosis with a curve of more than 75° and a flexibility of less than 25% between using posterior-only approach and combined anterior release followed by posterior correction with a hybrid construct (hooks and pedicle screws) and spinal fusion. STUDY DESIGN/SETTING: This was a retrospective cohort study. PATIENT SAMPLE: From 2000 to 2014, 388 consecutive patients with idiopathic scoliosis were treated surgically at our hospital. Of these patients, 53 whose primary curves were more than 75° with a flexibility of less than 25%, at an incidence of 13.6%, were included and divided into two groups. Thirty-one patients (mean age: 16.3 years old) who underwent anterior release followed by posterior correction, instrumentation, and fusion were included in the A+P group, and the remaining 22 patients (mean age: 17.3 years old) were designated as the P group for posterior procedure alone. OUTCOME MEASURES: The clinical outcomes were analyzed in terms of correction and loss of correction and by the Scoliosis Patient Questionnaire: Version 30 functional questionnaire. MATERIALS AND METHODS: In the A+P group, halo-femoral traction was applied for 1 week between the anterior release and the posterior procedure. Posterior instrumentation with a hybrid construct with hooks and pedicle screws was used for both groups. The radiological and functional outcomes were compared between the two groups. RESULTS: The average preoperative Cobb angle was 85.3° for the A+P group, with an average 17.4% flexibility, and 80° for the P group, with 15.3% flexibility. The postoperative Cobb angle was 53.1° for the A+P group and 45.6° for the P group. The Cobb angle at the final follow-up for the A+P group was 55.2° and that for the P group was 48°. The average correction rates of the A+P and P groups were 37% and 43.4%, respectively. There were no statistically significant differences between the groups in gender, age, number of levels fused, and flexibility of coronal curve. With a minimum 2-year follow-up, similar results were found between these two groups in terms of correction rate, loss of correction, and functional outcome. CONCLUSIONS: In this study, we found that a posterior-only approach with hybrid construct (hooks and pedicle screws) could provide a correction similar to that of an anterior-posterior approach. Also, the disadvantages of anterior release could be avoided by the posterior-only approach.

Hybrid Instrumentation in Lumbar Spinal Fusion: A Biomechanical Evaluation of Three Different Instrumentation Techniques.

STUDY DESIGN: Ex vivo human cadaveric study. OBJECTIVE: The development or progression of adjacent segment disease (ASD) after spine stabilization and fusion is a major problem in spine surgery. Apart from optimal balancing of the sagittal profile, dynamic instrumentation is often suggested to prevent or impede ASD. Hybrid instrumentation is used to gain stabilization while allowing motion to avoid hypermobility in the adjacent segment. In this biomechanical study, the effects of two different hybrid instrumentations on human cadaver spines were evaluated and compared with a rigid instrumentation. METHODS: Eighteen human cadaver spines (T11-L5) were subdivided into three groups: rigid, dynamic, and hook comprising six spines each. Clinical parameters and initial mechanical characteristics were consistent among groups. All specimens received rigid fixation from L3-L5 followed by application of a free bending load of extension and flexion. The range of motion (ROM) for every segment was evaluated. For the rigid group, further rigid fixation from L1-L5 was applied. A dynamic Elaspine system (Spinelab AG, Winterthur, Switzerland) was applied from L1 to L3 for the dynamic group, and the hook group was instrumented with additional laminar hooks at L1-L3. ROM was then evaluated again. RESULTS: There was no significant difference in ROM among the three instrumentation techniques. CONCLUSION: Based on this data, the intended advantage of a hybrid or dynamic instrumentation might not be achieved.

Biomechanical testing of a PEEK-based dynamic instrumentation device in a lumbar spine model.

BACKGROUND: The purpose of this study was to investigate the range-of-motion after posterior polyetheretherketone-based rod stabilisation combined with a dynamic silicone hinge in order to compare it with titanium rigid stabilisation. METHODS: Five human cadaveric lumbar spines with four vertebra each (L2 to L5) were tested in a temperature adjustable spine-testing set-up in four trials: (1) native measurement; (2) kinematics after rigid monosegmental titanium rod instrumentation with anterior intervertebral bracing of the segment L4/5; (3) kinematics after hybrid posterior polyetheretherketone rod instrumentation combined with a silicone hinge within the adjacent level (L3/4) and (4) kinematics after additional decompression with laminectomy of L4 and bilateral resection of the inferior articular processes (L3). During all steps, the specimens were loaded quasi-statically with 1°/s with pure moment up to 7.5Nm in flexion/extension, lateral bending and axial rotation. FINDINGS: In comparison to the native cadaveric spine, both the titanium device and polyetheretherketone-based device reduce the range-of-motion within the level L4/5 significantly (flexion/extension: reduction of 77%, p<0.001; lateral bending: reduction of 62%, p<0.001; axial rotation: reduction of 71%, p<0.001). There was a clear stabilisation effect after hybrid-instrumentation within the level L3/4, especially in flexion/extension (64%, p<0.001) and lateral bending (62%, p<0.001) but without any effect on the axial rotation. Any temperature dependency has not been observed. INTERPRETATION: Surprisingly, the hybrid device compensates for laminectomy L4 and destabilising procedure within the level L3/4 in comparison to other implants. Further studies must be performed to show its effectiveness regarding the adjacent segment instability.

Comparative analysis of pedicle screw versus hybrid instrumentation in adolescent idiopathic scoliosis surgery.

INTRODUCTION: Adolescent idiopathic scoliosis is the most common type of scoliosis. A Cobb angle of 50° will progress beyond the age of spinal maturity. Surgery over bracing is advised at a Cobb angle above or equal to 50°. The aim of surgery is to bring the Cobb angle down below 50° to prevent reprogression as well as improve the quality of life. The objective of the study is to analyze the efficacy and significance in lifestyle improvement of pedicle screw-only fixation system versus the more common hybrid instrumentation system used for the surgical treatment of adolescent idiopathic scoliosis. MATERIALS AND METHODS: A prospective cohort study was conducted involving two groups of patients were included in the study. One group was operated with pedicle screw-only method while the other with hybrid instrumentation system. The pre- and post-operative Cobb's angles were taken across a follow-up of 4 years. An SRS-30 questionnaire was given in a yearly follow-up to assess the lifestyle improvement of the patient. RESULTS: Pedicle screw-only method was significantly more effective in reducing Cobb's angle (P = 0.0487). It was showed less loss of correction (P = 0.009) pedicle screw-only surgery was also better at reducing thoracic curves (P = 0.001). There seemed a better recovery time with pedicle screw surgery (P = 0.003). CONCLUSION: Pedicle screws are more effective and durable than hybrid systems at when treating adolescent idiopathic scoliosis.

[Severe idiopathic scoliosis. Does the approach and the instruments used modify the results?]. / Escoliosis idiopáticas graves. ¿El abordaje y la instrumentación modifican los resultados?

OBJECTIVE: The aim of this work is to evaluate and compare the radiographic results and complications of the surgical treatment of adolescents with idiopathic scoliosis greater than 75 degrees, using a double approach (DA) or an isolated posterior approach with hybrid instruments (posterior hybrid [PH]), or with «all-pedicle screws¼ (posterior screws [PS]). MATERIAL AND METHOD: A retrospective review was performed on 69 patients with idiopathic scoliosis greater than 75°, with a follow-up of more than 2 years, to analyze the flexibility of the curves, the correction obtained, and the complications depending on the type of surgery. The Kruskal-Wallis test for non-parametric variables was used for the statistical analysis. RESULTS: There were no statistically significant differences between the 3 patient groups in the pre-surgical Cobb angle values (DA=89°, PH=83°, PS=83°), in the immediate post-surgical (DA=34°, PH=33°, PS=30°), nor at the end of follow-up (DA=36°, PH=36°, PS=33°) (P>.05). The percentage correction (DA=60%, PH=57%, PS=60%) was similar between groups (P>.05). The percentage of complications associated with the procedure was 20.8% in DA, 10% in PH and 20% in PS. Two patients in the PS group showed changes, with no neurological lesions, in the spinal cord monitoring, and one patient in the same group suffered a delayed and transient incomplete lesion. DISCUSSION AND CONCLUSIONS: No significant differences were observed in the correction of severe idiopathic scoliosis between patients operated using the double or isolated posterior approach, regardless of the type of instrumentation used.