Spine Deformity

Small-diameter spinal rods were tested in fatigue loading before and after contouring in pedicle screw constructs using dynamic testing machines. To characterize the change in fatigue performance of spinal rods resulting from contouring. Spine surgeons have a variety of rod materials to choose from, and selecting the best rod depends on patient characteristics and rod material properties, including fatigue performance. Four rod materials were tested, all 4.5 mm in diameter: titanium alloy (Ti), cobalt-chromium alloy (CoCr), and 2 different grades of stainless steel (SS and ultra SS). Three conditions were tested: straight (virgin rods), bent (rods bent to a radius of curvature of 100 mm), and re-bent (rods over-bent to a radius of 50 mm, then partially straightened to a 100-mm radius). Fatigue testing was conducted on unilateral vertebrectomy constructs with polyaxial screws. In all conditions, the endurance limit of the CoCr rods was at least 25% higher than the other materials but could not be determined because screw failure precluded rod failure. In the bent condition, the endurance limits of Ti, standard SS and ultra SS were reduced between 20% and 40%. In the re-bent condition, the endurance limit of Ti, standard SS, and ultra SS increased compared with the bent condition. Changes in fatigue performance are best explained by residual rod stresses induced during contouring. It appears safe to over-bend and then re-bend, for 1 cycle, small-diameter spinal rods made of the materials tested in this study using tube benders, and CoCr rods were clearly superior for all conditions. However, larger rods, multiple cycles of bending and re-bending, and rods bent using other instruments such as French benders were not studied and may result in different performance under the same conditions.

Estimated blood loss (EBL), anesthesia time, operative time, and length of stay decreased over 67 navigated vertebral body tethering (VBT) surgeries performed in a 5-year period, indicating a steep learning curve. Retrospective review of prospectively collected data. There would be a significant improvement in the performance of VBT procedures over time at a single tertiary center in terms of perioperative and postoperative outcomes. Learning a new procedure for surgeons takes time, and previous studies have described improved efficiency as experience grows. VBT procedures are increasingly being performed in the US, but there is limited data regarding the learning curve specifically regarding the use of CT-guided navigation. We sought to assess the learning curve of VBT with respect to estimated blood loss, anesthesia time, operative time, length of stay, percent correction of the major curve at first follow-up. We further sought to characterize change in rates of 90-day complications. Pediatric scoliosis patients who underwent thoracic or lumbar CT-guided navigated VBT with a consistent surgical team at a single tertiary referral center between 2015 and 2020 were included. Student t-test was used to assess change in perioperative parameters over time, and also results between first and latest group of 20 patients were compared. 67 patients met inclusion criteria. Estimated blood loss (EBL), operative time, anesthesia time and length of stay significantly decreased over the 5-year study period. Specifically, on comparison of our first 20 patients with our last 20, the former had greater EBL (282 vs 116 ml, p = 0.0005; 8.5% vs 3.6%, p = 0.0024), operative time (4.8 h vs. 3.3 h, p < 0.001), anesthesia time (7.4 h vs. 5.7 h, p = 0.0001), and length of stay (3.7 days vs. 3.2 days, p = 0.019). We also found significant reduction in EBL, operative time, anesthesia time and LOS in patients who underwent VBT surgery after 2019. There was no significant change in the percent correction of the major Cobb angle at first erect imaging or 90-day complications over the 5-year study period or between the various cohorts. This series has demonstrated improvements in surgical efficiency for VBT including reduced EBL, operative time, anesthesia time and hospital stay over a 5-year period. This indicates improved surgical technique and outlines the significant learning curve for surgeons who wish to perform this procedure. Improved surgeon training programs and newer instrumentation may reduce this learning curve. 67 cases in a 5-year period, VBT procedures performed at a single center had significantly decreased EBL, anesthesia time, operative time, and length of stay, indicating a steep learning curve.

The frequency of disc degeneration (DD) in the distal mobile segments will increase over time following surgery for adolescent idiopathic scoliosis (AIS). Retrospective review of a prospective AIS registry. Durability of surgical outcomes is essential for maintenance of quality of life as well as for family decision making and for assessment of the value of a healthcare intervention. We assessed DD, its risk factors, and association with health-related quality of life 10 years after AIS surgery. Five radiographic indicators of DD, previously validated, were evaluated preoperatively and 1 month, 2, 5, and 10 years postoperatively by a radiologist in operative AIS patients. A composite radiographic score (CRS; range 0-10) was calculated using the sum of each of the DD indicators. The severity of CRS in relation to the time point after surgery and various risk factors were assessed using linear regression or Pearson χ2 test. CRS ≥3 was chosen to indicate significant DD. Association of CRS with SRS-22 outcome was evaluated by linear regression. 193 consecutive patients (mean age at surgery 14.4 years; 86% female) were assessed. Surgical approach included 102 posterior and 91 anterior fusions. Contributors to maximum CRS at 10 years were Schmorl’s nodes (7.3% of patients), osteophytes (40.4%), sclerosis (29%), and irregular endplate (8.3%). CRS ≥3 occurred in 1.6%, 0.54%, 3.7%, 6.8%, and 7.3% of patients at the various time points (r 2=0.83, p=.0313), respectively. More than 50% of DD occurred at the second (35.5%) and third (20%) disc caudal to the LIV. LIV of L4 compared with more cephalad LIV had the highest risk of developing significant DD (27.3%; p=.0267). It was found that disc wedging subjacent to the LIV (≥5°) and LIV translation (≥2 cm) lead to a sixfold increase in significant DD (odds ratio=6.71 and 6.13, respectively). Severity of DD was not associated with the number of levels fused (p=.2131), the surgical approach (p=.8245), or the construct type (p=.2922). No significant association was established between 10-year CRS and SRS-22 scores. In the first study of its kind, we found that only 7.3% of patients had significant DD 10 years after surgical correction of AIS. Rates of DD increased over time. Our data provide evidence to support recommendations to save as many caudal motion segments as possible, to avoid fusing to L4, and maintain the LIV tilt angle below 5° and LIV translation less than 2 cm.

To assess biomechanics of a lumbar PSO stabilized with different multi-rod constructs (4-, 5-, 6-rods) using satellite and accessory rods. A validated spinopelvic finite element model with a L3 PSO was used to evaluate the following constructs: 2 primary rods T10-pelvis (“Control”), two satellite rods (4-rod), two satellite rods + one accessory rod (5-rod), or two satellite rods + two accessory rods (6-rod). Data recorded included: ROM T10-S1 and L2-L4, von Mises stresses on primary, satellite, and accessory rods, factor of safety yield stress, and force across the PSO surfaces. Percent differences relative to Control were calculated. Compared to Control, 4-rods increased PSO flexion and extension. Lower PSO ROMs were observed for 5- and 6-rods compared to 4-rods. However, 4-rod (348.6 N) and 5-rod (343.2 N) showed higher PSO forces than 2-rods (336 N) and 6-rods had lower PSO forces (324.2 N). 5- and 6-rods led to the lowest rod von Mises stresses across the PSO. 6-rod had the maximum factor of safety on the primary rods. In this finite element analysis, 4-rods reduced stresses on primary rods across a lumbar PSO. Although increased rigidity afforded by 5- and 6-rods decreased rod stresses, it resulted in less load transfer to the anterior vertebral column (particularly for 6-rod), which may not be favorable for the healing of the anterior column. A balance between the construct’s rigidity and anterior load sharing is essential.

Retrospective comparative study The goal of this study was to investigate fluoroscopy time and radiation exposure during pediatric spine surgery using a dedicated radiology technologist with extensive experience in spine operating rooms. Repetitive use of intraoperative fluoroscopy during posterior spinal fusion (PSF) exposes the patient, surgeon, and staff to radiation. Retrospective review was conducted on patients with posterior spinal fusion (PSF) of ≥ 7 levels for adolescent idiopathic scoliosis (AIS) at a pediatric hospital from 2015 to 2019. Cases covered by the dedicated radiology technologist (dedicated group) were compared to all other cases (non-dedicated group). Surgical and radiologic variables were compared between groups. 230 patients were included. 112/230 (49%) were in the dedicated group and 118/230 (51%) were in the non-dedicated group. Total fluoroscopy time was significantly reduced in cases with the dedicated technologist (46 s) compared to those without (69 s) (p = 0.001). Radiation dose area product (DAP) and air kerma (AK) were reduced by 43% (p < 0.001) and 42% (p < 0.001) in the dedicated group, respectively. The dedicated group also had reduced total surgical time (4.1 vs. 3.5 h; p < 0.001) and estimated blood loss (447 vs. 378 cc (; p = 0.02). Multivariate regression revealed that using a dedicated radiology technologist was independently associated with decreased fluoroscopy time (p = 0.001), DAP (p < 0.001), AK (p < 0.001), surgical time (p < 0.001), and EBL (p = 0.02). In AIS patients undergoing PSF, using a dedicated radiology technologist was independently associated with significant reductions in fluoroscopy time, radiation exposure, surgical time, and EBL. This adds to the growing body of research demonstrating that the experience level of the team—not just that of the surgeon—is necessary for optimal outcomes. III

Nghiên cứu hồi cứu cắt ngang cấp độ 3. Nghiên cứu nồng độ ion Titanium và Aluminium trong huyết thanh của những bệnh nhân được phẫu thuật bằng hệ thống đinh lớn từ tính (MCGR). 14 bệnh nhân liên tiếp bị scoliosis khởi phát sớm với nhiều nguyên nhân khác nhau được điều trị bằng hệ thống MCGR và có thời gian theo dõi tối thiểu 24 tháng đã được chọn cho nghiên cứu. Nhóm bệnh nhân bao gồm hai bé trai (14,3%) và 12 bé gái (85,7%). Tuổi trung bình của các bệnh nhân tại thời điểm phẫu thuật là 10,4 năm (từ 5 đến 15 tuổi). Thời gian theo dõi trung bình là 43,7 tháng (từ 28 đến 79 tháng). Sau khi có sự đồng ý của các bệnh nhân và người chăm sóc, nồng độ titani và nhôm trong huyết thanh đã được đo lường. Những nồng độ này sau đó được đánh giá liên quan đến số lượng vít sử dụng, số lượng kéo giãn và các biến chứng. Nồng độ ion titani và nhôm trong huyết thanh được đo bằng phương pháp quang phổ khối phổ plasma cảm ứng định hướng với độ phân giải cao. Để thuận tiện trong việc đánh giá, các bệnh nhân được chia thành ba nhóm dựa trên nguyên nhân - nguyên phát (n = 6), thần kinh cơ (n = 2) và hội chứng (n = 6). Nồng độ huyết thanh titanium trung bình là 15,9 μg/L (5,1–28,2 μg/L) trong khi nồng độ aluminium là 0,1 μmol/L (0,1–0,2 μmol/L). Trong số 14 bệnh nhân, 2 (14,2%) có sự cố cơ giới (rối loạn pin tác động), 3 (21,4%) bị gãy thanh yêu cầu phẫu thuật sửa chữa và một bệnh nhân (7,1%) bị nhiễm khuẩn tại vị trí phẫu thuật đã được quản lý bằng kháng sinh phù hợp. Các bệnh nhân phẫu thuật sửa chữa do gãy thanh không cho thấy bất kỳ sự xuất hiện của bệnh kim loại trong mô khi phẫu thuật. Phân tích các bệnh nhân bị scoliosis được phẫu thuật bằng hệ thống đinh lớn từ tính kết luận rằng nó đi kèm với sự hiện diện của titanium trong máu nhưng mức độ có ý nghĩa lâm sàng hay không cần được xác định bằng việc so sánh nồng độ máu preop và postoperative của các ion titanium trong từng bệnh nhân. Nồng độ ion nhôm vẫn nằm trong giới hạn bình thường. Mặc dù sự cố cấy ghép có thể làm gia tăng nồng độ titanium trong máu, nhưng ý nghĩa lâm sàng của điều này cần được xác định. Nồng độ nhôm không bị ảnh hưởng bất kể có hay không có biến chứng. Các hiệu ứng lâu dài của nồng độ titanium tăng trong máu cũng đòi hỏi các nghiên cứu tiềm năng bổ sung được thiết kế cho các phân tích chính xác và sâu sắc hơn.

Retrospective cohort. The aim of this study was to describe the various locations of spinal stenosis (LSS) in lumbar scoliosis and its related clinical symptoms. Adults with lumbar scoliosis often present with pain and disability. Association of scoliosis and stenosis is not rare, but remains sparsely explored. Consequences of scoliosis on stenosis location and treatment remain debatable. Patients operated for symptomatic LSS with lumbar scoliosis (Cobb angle >20°) from 2015 to 2016 were included. All patients completed preoperative clinical and neurologic examination. Coronal and sagittal radiographic parameters, rotatory subluxation (RS), and spondylolisthesis were analyzed on full spine radiographs. Computed tomographic scan multiplanar reconstructions were performed to measure central, foraminal, and lateral recess stenosis, from T10 to the sacrum. A total of 76 patients were included (69 ± 9 years old, 77% female). Sixty percent had neurogenic claudication, and L5 was the most common radicular pain (41%). The mean Cobb angle was 33° ± 16°. Overall, 35 (46%) patients had coronal malalignment; in 69%, side of the coronal tilt corresponded to side of the concavity of the lumbosacral curve. Sixty patients had RS (most frequent level L3–L4). In 50% of the cohort, RS was located at the junction between the lumbar and lumbosacral curves. In 70% (n = 53) of the patients, central stenosis occurred at the junction between the lumbar and lumbosacral curves. Foraminal and lateral stenosis were most frequently observed in the concavity of the distal lumbosacral curve. L5 radicular pain was significantly more frequent in case of lumbosacral contra-curve and right coronal malalignment. LSS is frequent in lumbar scoliosis. Relationships exist between curve characteristics and symptomatic LSS in lumbar scoliosis; especially, concavity of the lumbosacral contra-curve and the junctional level between the lumbar curve and the lumbosacral contra-curve. Therefore, accurate analysis of stenosis in ASD seems mandatory, to at least perform decompression because perfect planned treatment for stenosis and scoliosis correction might not always be possible because of the patient’s general health status. Level 4.