Hook Constructs Research Articles

Range of international surgical strategies for adolescent idiopathic scoliosis: Evaluation of a multi-center survey.

Surgical treatment of adolescent idiopathic scoliosis (AIS) is very complex and modern instrumentation techniques offer multiple possibilities. Despite numerous publications, there is no clear consensus on the optimal strategy for the correction of scoliotic deformities. The goal of this study was to summarize the current surgical strategies for specific AIS cases within various countries. Thirty-two experienced scoliosis surgeons from 15 countries were asked to plan surgeries on 12 representative AIS cases. All AIS cases had an indication for surgery. A questionnaire was provided to document surgical planning. The surgeons were provided with the patients' age and sex, together with radiographs in the lateral and sagittal planes during upright standing and in lateral bending to the left and right, as well as with clinical images. The angles of the main spinal curvatures were specified in the questionnaire. The surgeons were asked to specify their preferred classification system, their surgical approach, the planned fusion length, the type of implants, the rod type, and the resection steps. The data were analyzed with respect to the inter-rater variability, which was quantified using the Fleiss-Kappa Method. There was a good agreement (k = 0.61) between the surgeons in choosing the Lenke curve type, and a moderate agreement for the lumbar (0.41) and sagittal (0.56) modifiers. The most frequently planned resection procedure was complete facetectomy (67%). The posterior approach was the most commonly (91%) selected strategy to treat AIS. Anterior approaches were chosen most for Lenke 5 type with a rate of 20%. The upper instrumented vertebra (UIV) varied most for Lenke 1, 5, and 6 cases, with a vertebral level discrepancy of up to 10 levels at Lenke 6. The lowest instrumented vertebra varied most for Lenke 1 and 4 by up to five levels. Polyaxial screws were chosen most (56%), followed by monoaxial (20%) and uniplanar (19%) screws and hooks (5%). The results highlight the commonalities and discrepancy in the surgical treatment of AIS in between surgeons. The selected LIV and UIV can vary depending on the curve type and surgeon. Hook constructs appear to be generally replaced by transpedicular screws. The survey indicates open questions in the AIS treatment and in the understanding of scoliosis biomechanics.

Let's think beyond the pedicle: A biomechanical study of a new conceptual extra pedicular screw and hook construct

BackgroundTranspedicular screws have proven the test of time, yet they are not devoid of complications. Many newer techniques such as 2 D and 3D fluoroscopy,O arm Navigation assisted surgery, robotic assisted surgery have come into existence to the increase precision in pedicle screw insertion. But, complications do occur in their presence. We propose an Extra pedicular screw and hook system (EPSH) system with similar biomechanical property, better safety profile and short learning curve compared to traditional pedicle screw. PurposeTo Compare the pull out strength of Traditional Pedicle screw Vs Extra pedicular screw and hook system(EPSH). MethodsBiomechanical testing was conducted according ASTM F543 guidelines to compare the pull-out strength of EPSH based construct and traditional pedicle screw construct. Six saw bone samples in each group considered. Screw of 5.5 mm diameter and length of 35 mm was used in both the groups. Pull out strength assessed by giving 5 mm/min axial load. The axial load Vs displacement of the screw were recorded and plotted. The maximum load required for screw failure is noted in both the group. Statistical analysis was done. ResultsThe mean peak load of pedicle screw group was found to be 1670.9 ± 393.2 N with mean displacement at peak load was found to be 13.44 ± 1.7 mm and in EPSH group it was 1416.4 ± 341.4 N and 15.78 ± 3.9 mm respectively. A paired t-test showed no statistical difference(p < 0.05) between 2 groups. ConclusionEPSH has shown to have almost similar biomechanical property as that pedicle screw construct. With Addition of the hook, it provides an extra rotational stability as well. Being an extra-pedicular screw it has high safety profile and needs less expertise for insertion.

Does Construct Type Matter? A Retrospective Review Comparing Outcomes of Distal Radius Fractures Treated with Standard Volar Plating versus Fragment-Specific Fixation.

Background Treatment of intra-articular distal radius fractures (DRFs) rests on anatomic internal fixation. Fragment-specific fixation (FSF) is applied when fracture pattern is too complex for standard volar plating (SVP), oftentimes with potential increased risk of complications. We hypothesized that patients undergoing FSF would achieve less wrist range of motion (ROM) with higher risk of complications compared with SVP. Methods We conducted a retrospective review of 159 consecutive patients undergoing DRF fixation from 2017 to 2020. Patients < 18 years old, < 8 weeks' follow-up, open fractures, ipsilateral trauma, and fractures requiring dorsal spanning plate were excluded. Patient demographics, specific construct type, AO fracture classification, ROM, and complications were assessed. ROM was calculated using average flexion, extension, supination, and pronation. t -Tests were used to determine differences in ROM among construct types. Results Ninety-two patients met all inclusion criteria: 59 underwent SVP and 33 underwent FSF. Average wrist ROM for patients undergoing SVP was 57 degrees/50 degrees flexion-extension and 87 degrees/88 degrees supination-pronation; average ROM for patients undergoing FSF was 55 degrees/49 degrees flexion-extension and 88 degrees/89 degrees supination-pronation. No significant differences were identified when comparing final wrist flexion ( p = 0.08), extension ( p = 0.33), supination ( p = 0.35), or pronation ( p = 0.21). Overall reoperation rate was 5% and higher for FSF (12%) versus SVP (2%). Highest reoperation rate was observed in the double volar hook cohort (80%; N = 4). Conclusion Construct type does not appear to affect final ROM if stable internal fixation is achieved. SVP and FSF had similar complication rates; however, double volar hook constructs resulted in increased reoperations likely from fixation failure and plate prominence. Level of Evidence Level IV, retrospective review.

Lumbar Spondylolysis Reconstruction–Stabilization Using a Motion-Preserving Technique

Conservative methods are the traditional options in the management of lumber spondylolysis whereas surgery is indicated for symptomatic patients not responding to medical treatment and cases with a multilevel pars defect. The aim of this prospective study was to evaluate the clinical, functional, and radiologic results of using bone graft and fixation with pedicular screw-rod-laminar hook construct in treatment of lumber spondylolysis. Between October 2017 and January 2020, 20 patients with symptomatic lumbar spondylolysis not responding to conservative treatment for more than 6 months were treated by defect reconstruction fixation using bone block autografting and pedicular screw laminar hook construct. The mean follow-up time was 12.5 ± 03.5 months. All patients were examined pre- and postoperatively and followed up clinically (pain [visual analog scale]), functionally (Oswestry Disability Index, Modified Prolo Functional Economic Scales, and Macnab criteria), and radiologically (pars defect healing). Perioperative outcomes and complications were documented. Clinical, radiologic, and functional outcomes were significantly improved. Bony union was evident in all patients (100%). Blood loss, operative time, and hospital stay increased in cases with a multilevel pars defect and cases with associated injuries. Two cases reported complications in this study as misplaced pedicular screw and superficial wound infection. Reconstruction fixation of pars defect using this construct is an effective, feasible procedure in the treatment of Lumbar spondylolysis regarding the preservation of lumbar motion and avoidance of adjacent-segment problems after fusion.

Shoulder Balance Following Correction Surgery for Adolescent Idiopathic Scoliosis: When Is It Achieved and Does the Type of Construct Matter?

This is a retrospective study. This study aims to determine (1) when shoulder rebalancing occurs after adolescent idiopathic scoliosis (AIS) correction surgery and (2) whether shoulder asymmetry was influenced by the use of pedicle screws or hooks. Postoperative shoulder imbalance is an important outcome of AIS correction surgery as it may influence a patient's appearance and satisfaction. Seventy AIS patients undergoing AIS correction surgery at a single institution were retrospectively reviewed. Radiographic parameters were measured from anteroposterior x-rays at preoperative, immediate postoperative, 6 months postsurgery, and 12 months postsurgery. Shoulder parameters measured were: radiographic shoulder height (RSH), clavicle angle, coracoid height difference (CHD), and T1 tilt. The Cobb angle of the proximal thoracic curve, major thoracic curve, and thoracolumbar/lumbar curve. The percentage of correction was also calculated. Lateral shoulder asymmetry (RSH and CHD) changed significantly from preoperative to up to 6 months postsurgery. T1 tilt, a measure of medial shoulder asymmetry, did not change significantly. Postoperatively, the hook group attained significantly better shoulder balance than the screw group in terms of RSH and CHD up to 12 months postsurgery. However, the percentage correction of the major thoracic curve was significantly greater in the screw group than the hook group (hook: 62.2±18.4% vs. screw: 76.0±16.0%, P=0.007). Lateral shoulder rebalancing occurs up to 6 months after surgery. While thoracic pedicle screws offer greater correction of major AIS curves, hook constructs offer better postoperative shoulder symmetry. III.

Spinal balance and lumbar curve stability after selective thoracic fusion in idiopathic scoliosis.

Selective thoracic fusion (STF) for double curve patterns in idiopathic scoliosis is an attractive treatment option. However, short-term coronal decompensation and truncal imbalance are known findings. Previous studies with hook constructs showed that eventually balance is achieved via an increase in lumbar curve magnitude, as the lumbosacral obliquity did not change following surgery. Our aim is to investigate patients with idiopathic curves who underwent STF using all-pedicle screw constructs to determine if the uninstrumented lumbar curve and lumbosacral obliquity responded in the same manner as was previously reported with all-hook constructs. 102 consecutive patients with Lenke 1B, 1C or 3C curves who underwent STF using all-screw constructs at a single institution were included in this study. Radiographic assessment was performed, and patient reported outcomes were obtained. Subgroup analyses were performed based on preoperative thoracic: lumbar curve ratio as well as lumbar curve magnitude. Overall, the patients showed statistically significant improvement in both trunk shift and L4-pelvis obliquity at final follow-up. The uninstrumented lumbar curves trended toward improvement over time, but did not reach statistical significance (p = 0.107). SRS-30 scores were statistically significantly improved in multiple domains. Selective thoracic fusion is an excellent treatment option in most double curve patterns. Balance in the coronal plane is predictably achieved at 2-year follow-up. The lumbosacral obliquity improves more with screw technology than was previously found with hook constructs; therefore, the improvement in balance over time does not depend upon an increase in the uninstrumented lumbar curve. IV.

Outcomes of Direct Lumbar Spondylolysis Reconstruction by Bone Graft and Fixation Using Pedicular Screw Rod Laminar Hook Construct

Background Data: Lumbar spondylolysis is often managed by conservative methods in most patients. Operative interference is indicated in symptomatic patients not responding to medical treatment or patients with multilevel pars defect. Purpose: To evaluate the clinical, functional, and radiological results of bone graft and pedicular screw fixation and rod laminar hook construct in treatment of lumbar spondylolysis. Study Design: A prospective clinical case cohort study. Patients and Methods: Between October 2017 and January 2019, fifteen patients with symptomatic lumbar spondylolysis not responding to conservative treatment for more than 6 months were treated by reconstruction of pars defect by bone block autografting and fixation using pedicular screw laminar hook construct. The mean follow-up was 9.47±3.07 months. All patients were examined pre- and postoperatively and they were followed up clinically; for measuring their pain scale, Visual Analogue Scale (VAS); functionally, Oswestry Disability Index (ODI); radiologically (pars defect healing). Perioperative outcomes and complications were documented. Results: Clinical, radiological, and functional outcomes were significantly improved. Bony union was evident in all patients (100%). Blood loss, operative time, and hospital stay were reported. Two cases reported complications in this study: misplaced pedicular screw and superficial wound infection. Conclusion: Direct reconstruction of pars defect by bone graft and fixation using pedicular screw rod laminar hook constructis an effective feasible procedure in treating lumbar spondylosis. It preserves lumbar motion and hence may decrease adjacent segment problems. (2019ESJ194) Background context: Lumber Spondylolysis is often managed by conservative methods or the operative interference which is indicated for symptomatic not responding patients to medical treatment and cases with multilevel pars defect. Purpose: The goal of this study is to evaluate the clinical, functional and radiological results of using bone graft and fixation with pedicular screw rod laminar hook construct in treatment of Lumber Spondylolysis. Study Design: A prospective clinical study. Patients and methods: Between October 2017 and January 2019, fifteen patients with symptomatic lumbar spondylolysis not responding to conservative treatment more than 6 months were treated by reconstruction of pars defect by bone block autografting and fixation using pedicular screw laminar hook construct. The mean follow-up time was 9.47±3.07months. All patients were examined pre, postoperative and followed up clinically {pain (Visual Analogue Scale VAS)}, functionally {Oswestry Disability Index (ODI), Modified Prolo Functional Economic Scales (MPFES) and Macaneb's criteria}, radiologically (pars defect healing). Perioperative outcomes and complications were documented. Results: Clinical, radiological and functional outcomes were significantly improved. Bony union was evident in all patients (100%). Blood loss, operative time and hospital stay increased in case with multilevel pars defect and cases with associated injuries. Two cases reported complications in this study as misplaced pedicular screw and superficial wound infection. Conclusion: Direct reconstruction of pars defect by bone graft and fixation using pedicular screw rod laminar hook construct is an effective feasible procedure in treatment of lumbar spondylosis concerning to preservation of lumbar motion and avoidance of adjacent segment problems after spinal fusion.

Secondary Surgery Rates After Primary Fusion for Adolescent Idiopathic Scoliosis.

Instrumented spinal fusion is the gold standard treatment for surgical magnitude adolescent idiopathic scoliosis (AIS), with the goal being stable fusion without the need for additional procedures. The purpose of this study was to define the surgical return rates of AIS at a single center with respect to various instrumentation constructs used during initial spinal fusion. A retrospective chart review was performed of all patients with AIS who underwent instrumented fusion with a minimum of 2-year follow-up. Demographic information, implant type, and surgical approach for the primary surgery and all subsequent secondary operations were recorded. Four hundred eleven patients who underwent instrumented fusion for AIS during the study period met inclusion criteria. Sixty-six secondary operations were performed in 50 patients (12.2%). Symptomatic hardware, pseudarthrosis, and infection were the most common indications for secondary surgery. Posterior pedicle screw constructs had a lower secondary surgery rate (5.8%) compared with hybrid and combined fusions (P<.05). The all hook, hybrid, anterior only, and combined fusions had secondary surgery rates of 13.0%, 18.5%, 10.0%, and 20.8%, respectively, which were not statistically different. When specifically comparing pedicle screw with hook constructs, there was a statistically lower pseudarthrosis rate (P=.03) favoring pedicle screw instrumentation. Patients undergoing instrumented fusion for AIS are at some risk for subsequent surgery. To lessen that risk, pedicle screw constructs should be considered, as they have shown an overall lower secondary surgery rate and in particular a lower rate of pseudarthrosis. [Orthopedics. 2019; 42(4):235-239.].

Development and current situation of reconstruction methods following total sacrectomy

To review the development of the reconstruction methods following total sacrectomy, and to provide reference for finding a better reconstruction method following total sacrectomy. The case reports and biomechanical and finite element studies of reconstruction following total sacrectomy at home and abroad were searched. Development and current situation were summarized. After developing for nearly 30 years, great progress has been made in the reconstruction concept and fixation techniques. The fixation methods can be summarized as the following three strategies: spinopelvic fixation (SPF), posterior pelvic ring fixation (PPRF), and anterior spinal column fixation (ASCF). SPF has undergone technical progress from intrapelvic rod and hook constructs to pedicle and iliac screw-rod systems. PPRF and ASCF could improve the stability of the reconstruction system. Reconstruction following total sacrectomy remains a challenge. Reconstruction combining SPF, PPRF, and ASCF is the developmental direction to achieve mechanical stability. How to gain biological fixation to improve the long-term stability is an urgent problem to be solved.

Review of Pediatric Spondylolysis and Spondylolisthesis.

Pediatric spondylolysis and spondylolisthesis present with a wide spectrum of pathology and clinical findings, including back pain, leg pain, crouch gait, or neurological deficit. The treatment of spondylolysis alone is typically conservative with bracing, non-steroidal anti-inflammatory drug, and activity restriction, but refractory pain can be successfully surgically managed with intralaminar compression screw, wires, or pedicle screws with rods and laminar hook constructs. The treatment of dysplastic spondylolisthesis is aggressive to prevent neurological deficit, whereas even high-grade isthmic slips can be treated safely with nonoperative measures if no significant neurological deficits are present. However, patients with higher slip angles tend to progress and require fusion. More long-term data are needed to compare the outcomes of operative versus nonoperative treatment of high-grade slips. Although more evidence will be helpful in guiding surgical treatment, fortunately, the vast majority of these patients are successfully managed nonsurgically.

Plate fixation in periprosthetic femur fractures Vancouver type B1—Trochanteric hook plate or subtrochanterical bicortical locking?

IntroductionProximal plate fixation in periprosthetic femur fractures can be improved by plate anchorage in the greater trochanter (lateral tension band principle) or bicortical locking screw placement beside the prosthesis stem in an embracement configuration. Both concepts were compared in a biomechanical test using a femoral hook plate (hook) or a locking attachment plate (LAP). MethodsAfter bone mineral density (BMD) measurement in the greater trochanter, six pairs of fresh frozen human femora were assigned to two groups and instrumented with cemented hip endoprostheses. A transverse osteotomy was set distal to the tip of the prosthesis, simulating a Vancouver B1 fracture. Each pair was instrumented using a plate tensioner with either hook or LAP construct. Cyclic testing (2Hz) with physiologic profile and monotonically increasing load was performed until catastrophic failure. Plate stiffness was compared in a four-point-bending-test. Paired student’s-t-test was used for statistical evaluation (p<0.05). ResultsMean BMD was 250mgHA/ccm±47. The hook construct exhibited a significantly (p=0.015) lower number of cycles and load to failure (26′177cycles±2777; 3′118N±778) correlating significantly with BMD (R2=0.83; p=0.04) compared to the LAP construct (37′423cycles±5′299; 4′242N±1′030) (R2=0.71;p=0.11). BMD was a significant covariate (p=0.01). Plate stiffness was in a comparable range (hook Plate 468N/mm±7; LCP 445N/mm±6). ConclusionSubtrochanterically placed LAP provides an increased fixation strength under repetitive loading compared to hook plate fixation in the greater trochanter. Trochanteric fixation is highly BMD dependent and may be restricted to major greater trochanteric involvement requiring stabilization.

Traumatic Disc Herniation Following Flexion-Distraction Injury of the Thoracolumbar Spine: A Rare Presentation

Objective: To report a rare presentation of Flexion-distraction injuries. Summary of background data: To the best of our knowledge, traumatic disc herniation following non translated flexion distraction injuries of the thoracolumbar spine has not been reported in the English literature. Methods: Description of the clinic and radiological presentation of a 35-year-old male who sustained a flexion distraction injury of the thoracolumbar spine following an assault. Results: The intraoperative findings confirmed the presence of a large herniated disc fragment displacing the thecal sac. This was removed, the canal was decompressed and a hybrid screw-laminar hook construct was used to stabilize the fractured level while preserving uninjured motion segments. Conclusions: MRI provides useful information to help define the pathology and management strategies in patients with discordance between their clinical presentation and imaging. It helped define a rare presentation of disc herniation and alerted us to the need for a formal decompression in this case of a non-translated flexion-distraction injury.

Comparison of fusion rates between rod-based laminar claw hook and posterior cervical screw constructs in Type II odontoid fractures

BackgroundThis study was aimed (i) to compare the fusion rates of rod-based laminar claw hook constructs to that of posterior C1/C2 screw constructs in odontoid fractures, and (ii) to evaluate any complications associated with claw hook/rod constructs. To our knowledge, no study in contemporary literature has presented the effects of using modern rod-based laminar claw hooks for treating odontoid fractures. Unlike laminar clamps from the 1980s, contemporary laminar hook–rod instrumentation systems provide better immobilisation of the cervical spine and allows for building reliable frame-like constructs similar to cervical screw–rod systems. MethodsA retrospective review of a series of 167 consecutive odontoid fractures from a single-institution was conducted. 30 cases from the series were treated using posterior atlantoaxial fusion, 12 using C1/C2 posterior screws (control group), and 18 with rod-based laminar claw hooks (study group). Hooks were mounted bilaterally in a claw manner on each individual lamina and were rigidly fixed to perpendicular rods with a transverse connector whenever feasible. The minimum follow-up period was one year. Bony union was determined using computed tomography (CT) scan, while stability at the fusion site was assessed using dynamic radiograms. ResultsThe study group had an overall fusion rate of 89% (non-geriatric 93% while geriatric subgroup 75%) with a 100% stability rate at the fusion site in all cases. In the control group fusion rate was 100%. There were no major complications in both control and study groups. Four minor complications, three in the control and one in the study group, were noted in 3 patients. ConclusionPreliminary results of this study suggest that laminar claw hook–rod systems are useful alternatives to posterior screw techniques. Moreover, the fusion rate in non-geriatric patients is comparable to that of posterior screws. Importantly, they are devoid of the disadvantages and complications posed by screw constructs. Further studies are necessary to confirm these promising results.

Surgical techniques for spinopelvic reconstruction following total sacrectomy: a systematic review

To identify all available reconstruction methods for a total sacrectomy. Secondarily, we aimed to evaluate outcomes based on different interventions. We searched PubMed to identify sacral resections for tumors requiring internal fixation for stabilization. Demographic information, fixation techniques and postoperative outcomes were abstracted. Twenty-three publications (43 patients) met inclusion criteria from an initial search of 856 (κ 0.93). Mean age was 37years and follow-up was 33months. Fixation methods included a combination of spinopelvic fixation (SPF), posterior pelvic ring fixation (PPRF), and/or anterior spinal column fixation (ASCF). For the purposes of analysis, patients were segregated based on whether they received ASCF. Postoperative complications including wound/instrument infections, GI or vascular complications were reported at a higher rate in the non-ASCF group (1.63 complications/patient vs. 0.7 complications/patient). Instrument failure was seen in 5 (16.1%) out of the 31 patients with reported outcomes. Specifically, 1 out of 8 patients (12.5%) with ASCF compared with 4 out of 23 patients (17.4%) without ASCF had hardware failure. At final follow-up, 35 of 39 patients were ambulating. While surgical treatment of primary sacral tumors remains a challenge, there have been advances in reconstruction techniques following total sacrectomy. SPF has shifted from intrapelvic rod and hook constructs to pedicle and iliac screw-rod systems for improved rigidity. PPRF and ASCF have adapted for deficiencies in the posterior ring and anterior column. A trend toward a lower rate of hardware failure emerged in the group utilizing anterior spinal column support. Despite a more involved reconstruction with ASCF, surgical complications such as infection rates and blood loss were lower compared to the group without ASCF. While we cannot definitively say one system is superior to the other, based on the data gleaned from this systematic review, it is our opinion that incorporation of ASCF in reconstructing the spinopelvic junction may lead to improved outcomes. However, most importantly, we recommend that the treating surgeon operate on patients requiring a total sacrectomy based on his or her level of comfort, as these cases can be extremely challenging even among experts.

Comparative Analysis of Hook, Hybrid, and Pedicle Screw Instrumentation in the Posterior Treatment of Adolescent Idiopathic Scoliosis

Spinal instrumentation in adolescent idiopathic scoliosis (AIS) aims to correct spinal deformity and maintain long-term spinal stability until bony healing is ensured. The purpose of this study was to compare the minimum 2-year postoperative radiographic and clinical results of posterior spine correction and fusion with all-hook instrumentation versus hybrid segmental instrumentation versus pedicle screw instrumentation for AIS from a single institution. A total of 105 patients with AIS who underwent a posterior spinal fusion with segmental pedicle screw (35), hook (35), or hybrid (35) instrumentation were sorted and matched according to the following criteria: similar age at surgery, identical Lenke curve types, curve magnitude, and Risser grade. Patients were evaluated before, immediately after, and at 2 years after surgery for radiographic parameters, complications, and outcome, as well as on the basis of the Scoliosis Research Society (SRS) questionnaire. The age and Risser grade, major curve Cobb angle, apical vertebral rotation (AVR), apical vertebral translation (AVT), lowest instrumented vertebral tilt, global coronal and sagittal balance, lumbar lordosis, and thoracic kyphosis were determined as part of preoperative evaluation. All 3 groups showed significant differences between the preoperative and postoperative major curve Cobb angle, lowest instrumented vertebral tilt, AVT, and AVR. At the latest follow-up, lumbar lordosis, thoracic kyphosis, and global coronal and sagittal balance remained similar among the 3 groups. Major curve Cobb angle, AVT, and AVR were significantly different--the hook group's measurements were significantly higher than the other groups, but there was no difference between the pedicle screw and hybrid groups. Major curve correction rate was significantly different among all groups (screw=71.9%±13.8%, hybrid=61.4%±16.6%, hook=48.1%±19.7%) (P<0.001). The pedicle screw group had the least amount of correction loss but there was no statistically significant difference between groups (screw=2.6±6.7 degrees, hybrid=4.5±7.4 degrees, hook=4.4±6.2 degrees) (P=0.35). The hook group had the least amount of AVT correction, but the screw group and the hybrid groups were similar (pedicle=67.3%±15.5%, hybrid=57.5%±22.4%, hook=39.9%±32.5%) (P<0.001). Surgery time and blood loss were higher in the screw group. No differences in global SRS-22 scores were demonstrated between the patients treated with pedicle screw, hybrid, and hook constructs; however, the satisfaction domain was higher in the screw group at the latest follow-up. Pedicle screw and hybrid instrumentations offer significantly better spinal deformity correction than hook constructs in major curve coronal correction, AVT, and AVR. Patients with pedicle screw instrumentation had the greatest curve correction percentage, maintenance of this correction in the coronal and sagittal planes, and higher patient satisfaction by the SRS outcome scores. Global SRS-22 scores were similar at 2-year follow-up in all groups. Therapeutic level III retrospective comparative study.

Correction of Moderate (&lt;70 Degrees) Lenke 1A and 2A Curve Patterns

Multiple reports have demonstrated the superiority of all-pedicle screw constructs, over hybrid and hook constructs, for severe sagittal and coronal deformities (>70 degrees) and have made anterior spinal releasing unnecessary for almost all spinal deformities. However, for lesser deformities, specifically coronal deformities <70 degrees, published studies have not been able to consistently demonstrate clinical superiority of all-pedicle screw constructs over hook or hybrid constructs. A prospective, multicenter database on AIS identified patients with <70 degrees main thoracic (MT) curves surgically treated with a posterior spinal fusion. Inclusion criteria were: Lenke 1A and 2A curve patterns, neurologically normal, primary surgery only, and at least 13 years of age at surgery or be Risser 3 or greater and a construct consisting of all-pedicle screws (PS) or hybrid instrumentation. Minimum follow-up was 2 years postoperative. Patients were excluded if surgeries included any releases (laminectomies, ligament releases, or osteotomies), which may increase curve flexibility. A total of 101 patients satisfied the criteria for inclusion: PS (n=53) and hybrid (n=48). Preoperative patient data, preoperative curve characteristics, and operative data were similar between the 2 groups. Postoperative thoracic coronal Cobb demonstrated PS had better proximal thoracic (PT) and MT correction, MT Cobb correction % and correction index than hybrid. Interestingly there were no differences in correction index/fixation point between the 2 groups, indicating PS constructs achieved better correction due, at least in part, to the greater number of spine fixation points. Lower instrumented vertebrae tilt and rotational correction was better in the PS group than hybrid. At 2-year follow-up PS had better absolute forced expiratory volume in 1 second values, trunk shift, and total scoliosis appearance questionnaire than hybrids. T5-T12 sagittal alignment was unchanged at 2-year follow-up for PS versus increased kyphosis in hybrids. All-pedicle screw systems had better coronal correction, lower instrumented vertebrae tilt, MT scoliometer measurements and scoliosis appearance questionnaire total measures than hybrid constructs. The improved coronal correction in the PS group is likely due, in part, to the higher number of spine fixation points than used in the hybrid groups.

Pediatric Pedicle Screws: Comparative Effectiveness and Safety

Background: Pedicle screws are widely used in spinal surgery. There is extensive published literature concerning the use of pedicle screw instrumentation for spinal surgery in adults. Now there is a trend to use pedicle screws in pediatric patients, including the very young. A systematic review of the current English-language literature on the use of pedicle screw instrumentation in the pediatric age group was performed to specifically determine (1) the pedicle screw placement accuracy in patients with spine deformity and (2) the effect size of all-pedicle screw constructs compared with other methods of spinal instrumentation in terms of the percentage of scoliosis correction. Methods: English-language studies of pedicle screw use in pediatric patients (defined as those younger than eighteen years of age) were included. Descriptive statistics synthesized the accuracy of pedicle screw placement. Accuracy rates were compared between pediatric and adult patients. The effect of pedicle screw instrumentation on scoliosis correction was calculated with use of Cobb angle measurements. Results: On the basis of the literature search, 1181 articles were screened, 320 abstracts were examined, and ninety full-text articles representing 5761 patients were reviewed in detail. Seventeen studies met the inclusion criteria for the analysis of pedicle screw placement accuracy. A total of 13,536 pedicle screws were placed in 1353 pediatric patients. The overall placement accuracy rate in pediatric patients was 94.9%, which was higher than the rate of 91.5% reported for adults. The weighted, geometric, and 5% trimmed mean accuracy rates of pedicle screw placement were 91.9%, 88.5%, and 89.1%, respectively (standard deviation = 10%; interquartile range = 10%). Sixteen comparative studies met the inclusion criteria for the analysis of the effect of pedicle screw instrumentation on scoliosis correction. Pedicle screw constructs had a significantly larger percentage of Cobb angle correction compared with hooks (Cohen's d = 1.14) and hybrid constructs (Cohen's d = 0.49). Conclusions: The accuracy of pedicle screw placement in the pediatric spine exceeds the accuracy rate reported in adults. Pedicle screw instrumentation constructs are significantly more effective for scoliosis correction, as determined on the basis of Cobb angle measurements, than are hook constructs and hybrid constructs. Level of Evidence: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

Comparative Intermediate and Long-term Results of Pedicle Screw and Hook Instrumentation in Posterior Correction and Fusion of Idiopathic Thoracic Scoliosis

Prospective cohort study. To comprehensively compare the intermediate and long-term results of posterior correction and fusion with segmental pedicle screw instrumentation versus those with hook constructs in idiopathic adolescent thoracic scoliosis. Posterior correction and fusion represent the current standard surgical treatment in progressive idiopathic thoracic scoliosis. The 3-column fixation of pedicle screws has been shown to be superior to all other posterior spinal fixation devices. A total of 168 patients with idiopathic thoracic scoliosis at a single institution who underwent a posterior spinal fusion with segmental pedicle screw (88) or a combination of hooks and pedicle screws (80) instrumentation. Patient's evaluation consisted of clinical and radiographic analysis preoperatively, postoperatively, and at final follow-up. All patients were prospectively evaluated with an average follow-up of 5 years (range 5 to 11 y). The average number of segments in the fusion was 9.1 (range 6 to 15) in the hook group and 8.5 in the screw group (range 5 to 12). At the final follow-up, the amount of loss of correction in thoracic curves averaged 8.4 in the hook group and 5.3 in the screw group. The difference between the mean postoperative Cobb angle and the final Cobb angle of the major curves with a preoperative value was statistically significant in the 2 groups (P<0.01). The frontal and sagittal plane correction can be satisfactorily obtained by the screw group versus the pedicle screw group. There were no cases of pseudarthrosis, deep wound infections, or any neurologic complications. Satisfactory correction and maintenance of scoliotic curves could be obtained by pedicle screw instrumentation compared with hook constructs. Thoracic and thoracolumbar pedicle screw instrumentation is a safe and reliable method for obtaining rigid segmental spinal fixation over the conventional hook and rod.

Junction kinematics between proximal mobile and distal fused lumbar segments: biomechanical analysis of pedicle and hook constructs

Background context Biomechanical studies have demonstrated increased motion in motion segments adjacent to instrumentation or arthrodesis. The effects of different configurations of hook and pedicle screw instrumentation on the biomechanical behaviors of adjacent segments have not been well documented. Purpose To compare the effect of three different fusion constructs on adjacent segment motion proximal to lumbar arthrodesis. Methods Seven human cadaver lumbar spines were tested in the following conditions: 1) intact; 2) L4–L5-simulated circumferential fusion (CF); 3) L4–L5-simulated fusion extended to L3 with pedicle screws; and 4) L4–L5-simulated fusion extended to L3 with sublaminar hooks. Rotation data at L2–L3, L3–L4, and L4–L5 were analyzed using both load limit control (±7.5 N·m) and displacement limit control (truncated to the greatest common angular motion of the segments for each specimen). Results Both the L3–L4 and L2–L3 motion segments above the L4–L5-simulated CF had significantly increased motion in all loading planes compared with the intact spine, but no significant differences were found between L3–L4 and L2–L3 motion. When the L3–L4 segment was stabilized with pedicle screws, its motion was significantly smaller in flexion, lateral bending, and axial rotation than when stabilized with sublaminar hooks. At the same time, L2–L3 motion was significantly larger in flexion, lateral bending, and axial rotation in the pedicle screw model compared with the sublaminar hook construct. Conclusions The use of sublaminar hooks to stabilize the motion segment above a circumferential lumbar fusion reduced motion at the next cephalad segment compared with a similar construct using pedicle screws. The semiconstrained hook enhancement may be considered if a patient is at a risk of adjacent segment disorders.

Preventing Distal Pullout of Posterior Spine Instrumentation in Thoracic Hyperkyphosis

An in vitro biomechanical study. Compare the mechanical behavior of 5 different constructs used to terminate dual-rod posterior spinal instrumentation in resisting forward flexion moment. Failure of the distal fixation construct can be a significant problem for patients undergoing surgical treatment for thoracic hyperkyphosis. We hypothesize that augmenting distal pedicle screws with infralaminar hooks or sublaminar cables significantly increases the strength and stiffness of these constructs. Thirty-seven thoracolumbar (T12 to L2) calf spines were implanted with 5 configurations of distal constructs: (1) infralaminar hooks, (2) sublaminar cables, (3) pedicle screws, (4) pedicle screws+infralaminar hooks, and (5) pedicle screws+sublaminar cables. Progressive bending moment was applied to each construct until failure. The mode of failure was noted and the construct's stiffness and failure load determined from the load-displacement curves. Bone density and vertebral dimensions were equivalent among the groups (F=0.1 to 0.9, P>0.05). One-way analysis of covariance (adjusted for differences in density and vertebral dimension) demonstrated that all of the screw-constructs (screw, screw+hook, and screw+cable) exhibited significantly higher stiffness and ultimate failure loads compared with either sublaminar hook or cable alone (P<0.05). The screw+hook constructs (109+/-11 Nm/mm) were significantly stiffer than either screws alone (88+/-17 Nm/mm) or screw+cable (98+/-13 Nm/mm) constructs, P<0.05. Screw+cable construct exhibited significantly higher failure load (1336+/-328 N) compared with screw constructs (1102+/-256 N, P<0.05), whereas not statistically different from the screw+hook construct (1220+/-75 N). The cable and hook constructs failed by laminar fracture, screw construct failed in uniaxial shear (pullout), whereas the screws+(hooks or wires) failed by fracture of caudal vertebral body. Posterior dual rod constructs fixed distally using pedicle screws were stiffer and stronger in resisting forward flexion compared with cables or hooks alone. Augmenting these screws with either infralaminar hooks or sublaminar cables provided additional resistance to failure.