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In all levels of disc herniations the absolute surgical indications include deteriorating neurological deficits with myelopathy or cauda equina syndrome. However, this review summarized the relative indications for surgery in each level.In cervical disc herniation (CDH), the indications for surgery consist of six months of persisting symptoms, not responding to conservative treatment. However, high-quality studies are lacking, and a randomized controlled trial is now underway to clarify the indications.In thoracic disc herniation (TDH), the indications for surgery comprise failure of conservative measures and/or worsening neurological symptoms. Moreover, giant calcified thoracic disc herniations or myelopathy signs on magnetic resonance imaging, even in the absence of neurological symptoms, may benefit from surgical treatment as a preventive measure.In lumbar disc herniation (LDH), the indications for surgery include imaging confirmation of LDH, consistent with clinical findings, and failure to improve after six weeks of conservative care. Cite this article: EFORT Open Rev 2021;6:526-530. DOI: 10.1302/2058-5241.6.210020.

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AIMS: Significant correction of an adolescent idiopathic scoliosis in the coronal plane through a posterior approach is associated with hypokyphosis. Factors such as the magnitude of the preoperative coronal curve, the use of hooks, number of levels fused, preoperative kyphosis, screw density, and rod type have all been implicated. Maintaining the normal thoracic kyphosis is important as hypokyphosis is associated with proximal junctional failure (PJF) and early onset degeneration of the spine. The aim of this study was to determine if coronal correction per se was the most relevant factor in generating hypokyphosis. METHODS: A total of 95 patients (87% female) with a median age of 14 years were included in our study. Pre- and postoperative radiographs were measured and the operative data including upper instrumented vertebra (UIV), lower instrumented vertebra (LIV), metal density, and thoracic flexibility noted. Further analysis of the post-surgical coronal outcome (group 1 < 60% correction and group 2 ≥ 60%) were studied for their association with the postoperative kyphosis in the sagittal plane using univariate and multivariate logistic regression. RESULTS: Of the 95 patients, 71.6% (68) had a thoracic correction of > 60%. Most (97.8%) had metal density < 80%, while thoracic flexibility > 50% was found in 30.5% (29). Preoperative hypokyphosis (< 20°) was present in 25.3%. A postoperative thoracic hypokyphosis was four times more likely to occur in patients with thoracic correction ≥ 60% (odds ratio (OR) 4.08; p = 0.005), after adjusting for confounding variables. This association was not affected by metal density, thoracic flexibility, LIV, UIV, age, or sex. CONCLUSION: Our study supports the 'essential lordosis' hypothesis of Roaf and Dickson, i.e. with a greater ability to translate the apical vertebra towards the midline, there is a commensurate lengthening of the anterior column due to the vertebral wedging. Cite this article: Bone Joint J 2020;102-B(4):513-518.

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BACKGROUND: Growth guidance sliding treatment devices, such as Shilla (Medtronic, Minneapolis, MN USA) or LSZ-4D (CONMET, Moscow, Russia), used for the treatment of scoliosis in children who have high growth potential have unlocked fixtures that allow rods to slide during growth of the spine, which avoids periodical extensions. However, the probability of clinical complications associated with metallosis after implantation of such devices is poorly understood. The content of metal ions in the blood and tissues of pediatric patients treated for scoliosis using fusionless growth guidance sliding instrumentation has not yet been investigated. PURPOSE: The aim of the present study was to measure the content of metal ions in the blood and tissues surrounding the implanted growth guidance sliding LSZ-4D devices made of titanium alloy (Ti6Al4V), and to identify the incidence of metallosis-associated clinical complications in some patients with these devices. STUDY DESIGN: This is a one-center, case-control retrospective study. PATIENTS SAMPLE: The study group included 25 patients with high growth potential (22 females, 3 males; average age at primary surgery for scoliosis treatment is 11.4±1.2 years old) who had sliding growth guidance instrumentation LSZ-4D (CONMET) implanted on 13 (range: 10-16) spine levels for 6±2 years. The LSZ-4D device was made from titanium alloy Ti6Al4V and consisted of two rectangular section rods and fixture elements. Locked fixtures were used on one spinal level, whereas the others were unlocked (sliding). The control group consisted of 13 patients (12 females and 1 male; 11±1.2 years old) without any implanted devices. OUTCOME MEASURES: The content of Ti, Al, and V metal ions in the whole blood and tissues around the implanted device was measured. The incidences of metallosis-associated complications in the study group were recorded. METHODS: Metal ion content was measured by the inductively coupled mass spectrometry method on quadrupolar NexION 300D (PerkinElmer Inc, Shelton, CT, USA). RESULTS: Five of 25 patients in the study group developed metallosis-associated complications (two sinuses and three seroma in the lumbar part of the spine). Revisions were carried out in two of these patients. Ninety percent of the patients in the study group had increased content of Ti and V ions in the blood (2.8 and 4 times, respectively). Median content of Ti ions in soft tissues adjacentto implanted sliding device was more than 1,500-fold higher than that of the control group. These levels are much higher than previously reported for spinal instrumentation. CONCLUSIONS: Increased content of Ti and V ions in the blood and especially in tissues around the titanium growth guidance sliding device LSZ-4D accompanied by clinical manifestations (seroma and sinuses) indicates the importance of improving wear resistance of such instrumentation with the coatings and the necessity to exchange sliding instrumentation once the child is fully grown.

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Recent regenerative medicine and tissue engineering strategies (using cells, scaffolds, medical devices and gene therapy) have led to fascinating progress of translation of basic research towards clinical applications. In the past decade, great deal of research has focused on developing various three dimensional (3D) organs, such as bone, skin, liver, kidney and ear, using such strategies in order to replace or regenerate damaged organs for the purpose of maintaining or restoring organs' functions that may have been lost due to aging, accident or disease. The surface properties of a material or a device are key aspects in determining the success of the implant in biomedicine, as the majority of biological reactions in human body occur on surfaces or interfaces. Furthermore, it has been established in the literature that cell adhesion and proliferation are, to a great extent, influenced by the micro- and nano-surface characteristics of biomaterials and devices. In addition, it has been shown that the functions of stem cells, mesenchymal stem cells in particular, could be regulated through physical interaction with specific nanotopographical cues. Therefore, guided stem cell proliferation, differentiation and function are of great importance in the regeneration of 3D tissues and organs using tissue engineering strategies. This review will provide an update on the impact of nanotopography on mesenchymal stem cells for the purpose of developing laboratory-based 3D organs and tissues, as well as the most recent research and case studies on this topic.

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PURPOSE: This study investigated whether ultrasound (U/S) is an alternative to radiography when measuring magnetically controlled growth rod (MCGR) length in order to reduce radiation exposure. Distractible spinal growth rods are the gold standard when treating early-onset scoliosis (EOS). METHODS: This was a prospective series. Patients were already undergoing EOS treatment using MCGRs. Forty-eight data points measured using radiography and U/S were compared. Each U/S data point was measured three times by three observers to assess intra- and inter-observer reliability. The radiation dose of the pre-lengthening and post-lengthening radiographs was recorded. RESULTS: The average rod lengths were 1.322 cm with U/S and 1.329 cm with radiography. The ICC (radiography vs. U/S) was 0.992 (95 % confidence interval (CI) 0.976, 1.000). The inter- and intra-rater reliability of U/S had an ICC of 0.987 (95 % CI 0.966, 1.000) and 0.983 (95 % CI 0.956, 1.000), respectively. The mean total effective radiation dose of the pre-lengthening and post-lengthening PA spinal radiographs was 0.26 mSv with a mean attributable lifetime cancer risk of one in 39,686 per lengthening. CONCLUSION: U/S highly agrees with radiography when measuring MCGR length. It has a high inter- and intra-observer reliability and does not require radiation exposure. Although U/S allows accurate MCGR measurement and soft tissue assessment, patients will still need occasional radiographs to assess spine bony elements, overall spinal balance and scoliosis correction. Combining radiography and U/S allows patient monitoring and accurate MCGR measurement whilst decreasing patients' radiation exposure.

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STUDY DESIGN: Analysis of volumetric wear loss of retrieved growth guidance sliding devices LSZ-4D for treatment of early onset scoliosis and laboratory in vitro wear test for comparison of wear resistance of alloys Nitinol, Ti, and cobalt chromium (CoCr). OBJECTIVE: To evaluate quantitatively the amount of wear debris from the sliding LSZ-4D device and to investigate the potential of using Nitinol for replacing Ti alloys in spinal instrumentation. To do that, wear resistance of Nitinol, Ti, and CoCr was compared. SUMMARY OF BACKGROUND DATA: There are little data regarding the amount of wear debris associated with growth guidance sliding devices for patients with early onset scoliosis and the wear resistance of superelastic Nitinol compared with Ti and CoCr. METHODS: Volumetric wear loss was measured on LSZ-4D devices made from titanium alloy Ti6Al4V and each consisted of 2 rectangular section (6 × 4 mm) rods and 40 ± 8 fixture elements (20 ± 4 hooks and 20 ± 4 clips) retrieved from 3 patients (implantation period, 3.5-5.8 yr). Images of wear scars were taken on Bruker interferometer microscope and incorporated into MATLAB software. Wear resistance of Nitinol, Ti, and CoCr was studied using reciprocation pin-on-disk wear test in bovine serum at 37°C ± 1°C. RESULTS: The volume wear rate of LSZ-4D device was found to be 12.5 mm per year from which 5 mm³ per year is the wear debris of the rod and 7.5 mm per year is the contribution of fixtures. Wear resistance of Nitinol is 100 times higher than that of Ti and comparable with that of CoCr. CONCLUSION: Application of wear-resistant coatings on Ti components in growth guidance sliding devices for the treatment of early onset scoliosis will be useful. High wear resistance of Nitinol combined with its superelastic and shape memory properties could make application of Nitinol rods for spinal instrumentation beneficial.

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BACKGROUND: Our aim was to determine whether patients derived benefit from removal of pedicle screw instrumentation for axial pain without other cause using our surgical technique and patient selection. A secondary aim was to investigate factors that were associated with poorer outcomes for this procedure as well as complication rate in this cohort. METHODS: Theater records from a single spinal surgeon's practice were reviewed to identify patients that had undergone lumbar fusion for discogenic back pain with subsequent pedicle screw instrumentation removal (Expedium, DePuy Synthes) in the preceding 3 years with a minimum of 18 months follow-up. Inclusion criteria were persisting midline axial back pain with computed tomography (CT)-confirmed solid fusion with non-radicular symptoms and nil other potential causes found, e.g., infection. Case note review along with pre- and post-operative Oswestry disability index (ODI) questionnaires and visual analog scores (VAS) were assessed for all patients. Surgical technique included re-use of previous midline posterior incision and the Wiltse approach with removal of implants, confirmation of a solid fusion mass, washout and bone grafting of removal sites. RESULTS: From 50 consecutive patients who underwent removal of posterolateral instrumentation for an index elective lumbar fusion for discogenic back pain, 34 patients were identified that met the criteria with a mean follow-up of 25 months (range, 18-36 months). The VAS and ODI improved in 22/34 (65%) of participants. The mean cohort VAS score was 6.6 pre-surgery and 4.3 post-surgery (P=0.04). Preoperative and postoperative mean Oswestry disability scores were 64 and 41, respectively (P=0.05). There was a statistically significant difference in the proportion of patients with poorer compared to satisfactory outcomes with regards to compensable status, preoperative grade II opioid use and shorter time between fusion and removal procedure. Complications were one postoperative hematoma and one superficial wound infection, both of which settled without re-operation. CONCLUSIONS: Approximately two thirds of patients were satisfied with removal of instrumentation for treatment of residual low back pain (LBP) following elective lumbar fusion and recorded reduced VAS and grade II opioid use. A subset of patients remained that did not derive benefit and were associated with compensable status, preoperative grade II opioid use and a shorter time between fusion and removal procedure. A prospective cohort study with preoperative diagnostic injections and standardized imaging and microscopic techniques would strengthen future studies. However, this study suggests that removal of instrumentation is safe and provides modest benefit as a palliative procedure for a subset of patients with significant disability from chronic LBP without an underlying cause following lumbar fusion.

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STUDY DESIGN: Case series. OBJECTIVE: To determine whether there is improvement in pulmonary function in children with early-onset scoliosis (EOS) using magnetic growth rods (MGRs). SUMMARY OF BACKGROUND DATA: EOS deformities have large impacts on lung function and volumes. Deterioration of pulmonary function in scoliosis is multifactorial, including severity, location of apex vertebra, and medical comorbidities. MGR insertion has benefits including reduction in operative procedures with repeated anesthetics, cost-effectiveness, and minimizing surgical and psychological distress. Pulmonary function tests provide objective and quantitative information about functional impairment caused by scoliosis. This is the first study that observes the MGR lengthening and changes in pulmonary function during a minimum period of 2.2 years. METHODS: Six cases of EOS secondary to neuromuscular disease were identified. Mean age at diagnosis was 2.8 year (2.1-4.9 yr), mean age at surgery was 7.5 year (5-10 yr), and mean follow-up was 2.5 year (2.2-2.8 yr). Pulmonary function test (forced vital capacity [FVC] + forced expired volume in 1 second [FEV1] both % predicted) was measured before and after insertion of MGR and at every lengthening clinic subsequently for a minimum 2 years. Coronal and sagittal Cobb angles were measured pre- and postoperatively as were length extension of growth rods. All except 1 patient had dual MGRs inserted (the other had a single rod). Lengthening was commenced and data was collected at 6-month intervals. RESULTS: Average correction was 34° ± 18° and 36° ± 15° for coronal and sagittal Cobb angles, respectively. Mean lengthening achieved was 24.9 mm. Mean improvement in postoperative FVC and FEV1 was 14.1% and 17.2%, respectively. There was significant difference between the median preoperative and postoperative Cobb angle, P = 0.028. CONCLUSION: This study demonstrates early intervention using MGR in patients with EOS is associated with significant improvement in postoperative pulmonary function tests; and significant improvement in deformity correction with use of MGR with added benefits of reduction in repeat anesthesia, reduction in surgical and psychological distress, and cost-effectiveness. LEVEL OF EVIDENCE: 4.

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