Cement-augmented Pedicle Screw Research Articles

Asymptomatic Pulmonary Cement Embolism after Cement-Augmented Pedicle Screw Instrumentation: A Case Report

Asymptomatic Pulmonary Cement Embolism after Cement-Augmented Pedicle Screw Instrumentation: A Case Report

Cardiac Perforation Caused by Cement Embolus after Cement-Augmented Pedicle Screw Instrumentation: A Case of Report

Cardiac Perforation Caused by Cement Embolus after Cement-Augmented Pedicle Screw Instrumentation: A Case of Report

Effect and potential risks of using multilevel cement-augmented pedicle screw fixation in osteoporotic spine with lumbar degenerative disease

BackgroundThe increase of augmented level and bone cement dose are accompanied by the rising incidence of cement leakage (CL) of cement-augmented pedicle screw instrumentation (CAPSI). But the effect and potential risks of the application of CAPSI to osteoporotic lumbar degenerative disease (LDD) have not been studied in the case of multilevel fixation. This study aimed to investigate the effectiveness and potential complications of using multilevel CAPSI for patients with osteoporotic LDD.MethodsA total of 93 patients with multilevel LDD were divided into the CAPSI group (46 subjects) and the conventional pedicle screw (CPS) group (47 subjects), including 75 cases for three levels and 18 cases for four levels. Relevant data were compared between two groups, including baseline data, clinical results, and complications.ResultsIn the CAPSI group, a total of 336 augmented screws was placed bilaterally. The CL was observed in 116 screws (34.52%). Three cemented screws (0.89%) were found loosened during the follow-up and the overall fusion rate was 93.47%. For perioperative complications, two patients (4.35%) experienced pulmonary cement embolism (PCE), one patient augmented vertebral fracture, and three patients (6.52%) wound infection. And in the CPS group, thirty-three screws (8.46%) suffered loosening in cranial and caudal vertebra with a fusion rate of 91.49%. The operation time and hospital stay of CAPSI group were longer than the CPS group, but CAPSI group has a lower screw loosening percentage (P<0. 05). And in terms of blood loss, perioperative complications, fusion rate, and VAS and ODI scores at the follow-up times, there were no significant differences between the two groups.ConclusionsPatients with osteoporotic LDD underwent multilevel CPS fixation have a higher rate of screw loosening in the cranial and caudal vertebra. The application of cemented pedicle screws for multilevel LDD can achieve better stability and less screw loosening, but it also accompanied by longer operating time, higher incidence of CL, PCE and wound infections. Selective cement augmentation of cranial and caudal pedicle screws may be a worthy strategy to decrease the complications.

Influence of cement-augmented pedicle screw instrumentation in an osteoporotic lumbosacral spine over the adjacent segments: a 3D finite element study

PurposeTo compare the effect of conventional pedicle screw (CPS) and cement-augmented pedicle screw instrumentation (CAPSI) on adjacent segment degeneration (ASD).MethodsA normal male volunteer without a history of spinal disease was selected, lumbar CT data was collected, an intact L3-S1 three-dimensional finite element model was created by software including Mimics, Geomagic, and SolidWorks, and the fixation methods were performed accordingly. A common pedicle screw model and a cement-augmented pedicle screw model of L4–L5 with fusion and internal fixation were constructed. With ANSYS Workbench 17.0, a 500 N load was applied to the upper surface of L3 to simulate the weight of a human body, and a 7.5 N m moment was applied at the neutral point to simulate flexion, extension, left/right bending, left/right rotation of the spine. The peak von Mises stress of intervertebral disc and the range of motion (ROM) on the adjacent segments (L3–4 and L5–S1) were compared.ResultsThe validity of the intact model shows that the ROM of the model is similar to that of a cadaveric study. Compared with the intact model, CPS model and CAPSI model in all motion patterns increased the ROM of adjacent segments. The intervertebral disc stress and the ROM of adjacent segments were found to be higher in the CAPSI model than in the CPS model, especially in L3–4.ConclusionIn general, the biomechanical analysis of an osteoporotic lumbar spine showed that both CPS and CAPSI can increase the ROM and disc stresses of osteoporotic lumbar models, and compared with CPS, CAPSI is more likely to increase the potential risk of adjacent segment degeneration.

Clinical efficacy of Bone Cement-injectable Cannulated Pedicle Screw Short Segment Fixation for Lumbar Spondylolisthesis with Osteoporosise

Many clinical studies have shown a satisfactory clinical efficacy using bone cement-augmented pedicle screw in osteoporotic spine, however, few studies have involved the application of this type of screw in lumbar spondylolisthesis. This study aims to investigate the mid-term clinical outcome of bone cement-injectable cannulated pedicle screw (CICPS) in lumbar spondylolisthesis with osteoporosis. From 2011 to 2015, twenty-three patients with transforminal lumbar interbody fusion (TLIF) using CICPS for lumbar spondylolisthesis were enrolled in the study. Oswestry Disability Index (ODI) and Visual Analogue Scale (VAS) were used to evaluate faunctional recovery and physical pain; and operation time, blood loss and hospitalization time were recorded, respectively. Radiograph and computed tomography of lumbar spine was performed to assess loss of the intervertebral disc space height, fixation loosening, and the rate of bony fusion. The average follow-up time of 23 patients was 22.5 ± 10.2 months (range, 6–36 months). According to VAS and ODI scores, postoperative pain sensation and activity function were significantly improved (p < 0.05). The height of the intervertebral disc space was reduced by 0.4 ± 1.1 mm, and the bone graft fusion rate was 100%. No cases of internal fixation loosening or screw pullout was observed. CICPS using cement augmentation may suggest as a feasible surgical technique in osteoporotic patients with lumbar spondylolisthesis.

Effect of surgical factors on the augmentation of cement-injectable cannulated pedicle screw fixation by a novel calcium phosphate-based nanocomposite.

Bone cement-augmented pedicle screw system demonstrates great efficacy in spinal disease treatments. However, the intrinsic drawbacks associated with clinically used polymethylmethacrylate (PMMA) cement demands for new bone cement formulations. On the basis of our previous studies, a novel injectable and biodegradable calcium phosphate-based nanocomposite (CPN) for the augmentation of pedicle screw fixation was systematically evaluated for its surgical feasibility and biomechanical performance by simulated and animal osteoporotic bone models, and the results were compared with those of clinical PMMA cement. ASTM-standard solid foam and open-cell foam models and decalcified sheep vertebra models were employed to evaluate the augmentation effects of CPN on bone tissue and on the cement-injected cannulated pedicle screws (CICPs) placed in osteoporotic bone. Surgical factors in CICPs application, such as injection force, tapping technique, screw diameter, and pedicle screw loosening scenarios, were studied in comparison with those in PMMA. When directly injected to the solid foam model, CPN revealed an identical augmentation effect to that of PMMA, as shown by the similar compressive strengths (0.73 ± 0.04 MPa for CPN group vs. 0.79 ± 0.02 MPa for PMMA group). The average injection force of CPN at approximately 40-50 N was higher than that of PMMA at approximately 20 N. Although both values are acceptable to surgeons, CPN revealed a more consistent injection force pattern than did PMMA. The dispersing and anti-pullout ability of CPN were not affected by the surgical factors of tapping technique and screw diameter. The axial pullout strength of CPN evaluated by the decalcified sheep vertebra model revealed a similar augmentation level as that of PMMA (1351.6 ± 324.2 N for CPN vs. 1459.7 ± 304.4 N for PMMA). The promising results of CPN clearly suggest its potential for replacing PMMA in CICPs augmentation application and the benefits of further study and development for clinical uses.

P151. Two-year experience with fenestrated pedicle screw cement augmentation in spine surgery: a safety and efficacy study

P151. Two-year experience with fenestrated pedicle screw cement augmentation in spine surgery: a safety and efficacy study

Augmented pedicle trajectory applied on the osteoporotic spine with lumbar degenerative disease: mid-term outcome

PurposeTo compare the safety and efficiency of cement-augmented pedicle screw with traditional pedicle screw technique applied on the patients in the osteoporotic spine with lumbar degenerative diseases.MethodsFifty-six patients followed up at least 2 years were enrolled in our institute with retrospectively reviewed from January 2009 to June 2014, diagnosed as lumbar spondylolisthesis, or lumbar stenosis, with T score ≤− 2.5 SD of BMD, and received less than three-segment PLIF or TLIF. All patients were divided into 2 groups: 28 (2 males, 26 females) in polymethylmethacrylate-augmented pedicle screw group (PSA) group, the other 28 (3 males, 25 females) in traditional pedicle screw group (TPS). Surgical data including the operation time, intra-operative blood loss, hospitalization day and surgical complications were recorded, as well as the radiological parameters measured from the postoperative X-rays and CT scans containing the rates of fusion, screw loosening, and cage subsidence incidence. In addition, the visual analog scores (VAS) and Oswestry Disability Index (ODI) were evaluated preoperatively and postoperatively.ResultsThe average follow-up period was 34.32 months (ranging from 24 months to 51 months). Compared with PSA group, operation time and average hospital stay in the TPS group decreased significantly (P < 0.05). While no statistical difference for blood loss between 2 groups (P > 0.05). At 2 years postoperation, from CT-scans, 2/172 screws loosening and 1/56 segment non-union occurred in PSA group, with significantly lower incidence than those in TPS group (8/152 screws loosening and 6/50 segments non-union occurred, P < 0.05). Regarding the cage subsidence, 24 segments found height loss (5.30 ± 1.92 mm) in PSA group without difference compared with that of 19 segments (4.78 ± 1.37 mm) in TPS group (P > 0.05). Besides, the number and the location of cages and the leakage of the cement were found out little related with the subsidence in the PSA group (P > 0.05). After surgeries, VAS and ODI at 1 month, 6 months, 12 months, and last follow-up improved significantly in two groups (P < 0.05). There were no significant differences in VAS and ODI preoperatively and postoperatively between 2 groups (P > 0.05). In addition, eight patients with asymptomatic trajectory PMMA leakages were detected.ConclusionCement-augmented pedicle screw technique is effective and safe in the osteoporotic spine with lumbar degenerative diseases, with better fusion rates and less screw loosening incidence. There is no difference in the fusion rate and loosening rate between the two groups in the single segment patients; however, there are better fusion rate and lower pedicle screw loosening rate of the PSA group in the double or multiple group patients.

Early Complications and Cement Leakage in Elderly Patients Who Have Undergone Intraoperative Computed Tomography (CT)-Guided Cement Augmented Pedicle Screw Placement: Eight-Year Single-Center Experience

To assess early complications, mortality rate, and cement leakage in elderly patients who had undergone navigation-based pedicle screw placement of the thoracic and lumbar spine. Eighty-six patients older than 65 years of age who had received cement-augmented pedicle screws for various conditions were retrospectively included between May 2008 and December 2016. Complications, mortality, and cement leakage were determined. All patients had a radiograph as a control. In patients with cement leakage seen on radiographs, a computed tomography scan of the surgical area was also obtained. Average age was 73.4 years (range 65-86 years). A total of 319 vertebral bodies with 637 screws were inserted, of which 458 screws were cement-augmented; 348 (76%) of the augmented screws were placed in the lumbar spine and 110 (24%) in the thoracic spine. Cement leakage occurred in 55 of 86 patients, of whom 52 (60%) were asymptomatic. In all cases with cement leakage (asymptomatic or symptomatic), cement could be found in the perivertebral veins: in the inferior vena cava in 25%, in the epidural space in 7%, in the azygos vein in 5%, and in pulmonary arteries in 7%. Our study confirms that the use of cement correlates with a high risk of cement leakage in elderly patients. Using computed tomography navigation for screw placement did not reduce the risk of venous cement leakage, but leakage into the epidural space or through a cortical defect seems to be low.

Utility of Cement Augmentation via Percutaneous Fenestrated Pedicle Screws for Stabilization of Cancer-Related Spinal Instability.

Cancer patients experience pathological fractures and the typical poor bone quality frequently complicates stabilization. Methods for overcoming screw failure include utilization of fenestrated screws that permit the injection of bone cement into the vertebral body to augment fixation. To evaluate the safety and efficacy of cement augmentation via fenestrated screws. A retrospective chart review of patients with neoplastic spinal instability who underwent percutaneous instrumented stabilization with cement augmentation using fenestrated pedicle screws. Patient demographic and treatment data and intraoperative and postoperative complications were evaluated by chart review and radiographic evaluation. Prospectively collected patient reported outcomes (PRO) were evaluated at short (2-<6 mo) and long term (6-12 mo). Cement augmentation was performed in 216 fenestrated pedicle screws in 53 patients. Three patients required reoperation. One patient had an asymptomatic screw fracture at 6 mo postoperatively that did not require intervention. No cases of lucency around the pedicle screws, rod fractures, or cement extravasation into the spinal canal were observed. Eight cases of asymptomatic, radiographically-detected venous extravasation were found. Systemic complications included a pulmonary cement embolism, a lower extremity deep vein thrombosis, and a postoperative mortality secondary to pulmonary failure from widespread metastatic pulmonary infiltration. Significant improvement in PRO measures was found in short- and long-term analysis. Cement augmentation of pedicle screws is an effective method to enhance the durability of spinal constructs in the cancer population. Risks include cement extravasation into draining blood vessels, but risk of clinically significant extravasation appears to be exceedingly low.

The cement leakage in cement-augmented pedicle screw instrumentation in degenerative lumbosacral diseases: a retrospective analysis of 202 cases and 950 augmented pedicle screws.

To evaluate the incidence, type and risk factors of cement leakage (CL) with cement-augmented pedicle screw instrumentation (CAPSI) in degenerative lumbosacral disease. Two hundred and two patients using a total of 950 cement-augmented screws were enrolled. CL was classified into three types: type S: leakage via segmental veins; type B: leakage via basivertebral veins; and type I: leakage via pedicle screw instrumentation to paravertebral soft tissue. The age, gender, operation stage (primary or later stage), body mass index, bone mineral density, the number and type of augmented screw, the position of the tip of screw (lateral or internal part of vertebral body), the position of screw (left or right side), the volume of bone cement, location of the augmented vertebra (lumbar or sacrum), the type of CL and complications were recorded. Binary logistic regression correlation was used to analyze risk factors of veins leakage (type S and type B). The CL was observed in 165 patients (81.68%) and 335 screws (35.26%), leakage types of S, B and I were seen in 255 (76.12%), 77 (22.99%), and 30 (8.96%) of screws, respectively. Besides, double or multiple routes of leakage were seen in 27 screws. Number of augmented screw was a risk factor for vein leakage (OR 0.58; 95% CI 0.44-0.77; P = 0.000). Furthermore, the doses of cement (OR 0.79; 95% CI 0.61-0.99; P = 0.038) and the position of screw (OR 0.39; 95% CI 0.29-0.53; P = 0.000) were identified as risk factors for type S, and the doses of bone cement (OR 0.37; 95% CI 0.25-0.54; P = 0.000) and the position of the tip of screw (OR 0.07; 95% CI 0.04-0.13; P = 0.000) were risk factors for type B. CAPSI bears a high risk of asymptomatic CL, with a higher rate of leakage into segmental veins and basivertebral veins. As is known, more augmented screws and larger doses of cement are risk factors for veins leakage (type S and type B), while the tip of screw approaching to the midline of the vertebral body is another risk factor to type B. Thus, the CL could be reduced by the amelioration of operative techniques and procedures. These slides can be retrieved under Electronic Supplementary Material.

Risk Factors for Adjacent Fractures After Cement-Augmented Thoracolumbar Pedicle Screw Instrumentation.

The aim of our study was to identify factors that influence the occurrence of adjacent fractures in patients with cement-augmented pedicle screw instrumentation. Data were retrospectively collected from medical charts and operative reports for every surgery in which cement-augmented instrumentation was used in our hospital of 4 consecutive years. A total of 93 operations were included and examined for gender, age, T-score, number of fused segments, number of implanted screws, broken screws, loosening of screws, leakage and distribution pattern of cement, pre- and postoperative kyphosis angle, revision surgery and adjacent fractures in follow-up. Categorical data were compared using the χ2 test or by Fisher's exact test, as appropriate. Continuous variables conforming to a normal distribution were compared using Student's t test. Otherwise the Mann-Whitney U test was applied. A P-value of <.05 was considered statistically significant. A trend was defined as a P < .2. The mean age was 68.1 years with a mean T-score of -3.12. Nineteen adjacent fractures occurred during follow-up and the median follow-up was 12 months (range, 1-27). Patients showed a higher risk for adjacent fractures following revision surgery (P = .016). Most fractures occurred superior to the instrumented level (P = .013) and in the first 12 months. Difference of T-score between the group "no adjacent fracture" and the group "adjacent fracture" was 0.7 (P = .138). Another trends were found in greater age (P = .119) and long instrumentations (P = .199). Revision surgeries are associated with a higher risk of adjacent fractures. In these cases, prophylactic kyphoplasty of the superior vertebra should be considered. This study is a retrospective, nonrandomized cohort/follow-up study. 3.

Surgical Trend Analysis for Use of Cement Augmented Pedicle Screws in Osteoporosis of Spine: A Systematic Review (2000-2017).

Study Design:Systematic review.Objectives:(1) Study indications for cement-augmented pedicle screws (CAPS) in patients with osteoporosis. Have they changed over the years (2000-2017)? Are there any differences in usage of CAPS based on the geographical region? (2) What were the outcome of the studies? (3) What are the complications associated with this technique?Methods:Electronic database and reference list of desired articles were searched from the database (2000-2017). Articles were selected discussing indications, clinical and radiological outcomes, and complications in cases of preexistent osteoporosis treated surgically using CAPS.Results:Seventeen studies were identified; 3 were comparative studies and had a control arm (cemented vs noncemented screws). Most studies originated from Europe (10) or Asia (7). Painful vertebral fracture with or without neurological deficit, Kummell’s lesion, deformity and failure to respond to conservative treatment are the common indications for cement augmentation. Visual analogue scale score was the most commonly used to assess pain and average improvement after surgery was 6.1. Average improvement in kyphosis was 13.21° and average loss of correction at the end of the study was 3°. Cement leak was the most common complication observed and pulmonary cement embolism was the most dreaded complication. Nevertheless, majority of cement leaks discussed in studies were asymptomatic.Conclusion:CAPS are being increasingly used in osteoporotic spine. Pain scores, functional quality of life, and neurological function indices were studied. CAPS improved anchorage in osteoporotic vertebra and helped improve/maintain clinical and radiological improvement. Common risks of cement leak were observed.

The Effect and Safety of Polymethylmethacrylate-Augmented Sacral Pedicle Screws Applied in Osteoporotic Spine with Lumbosacral Degenerative Disease: A 2-Year Follow-up of 25 Patients

A high rate of instrumentation failure is frequently seen in osteoporotic spines, especially at the sacral segment because of the great shear stress. Several techniques of sacral pedicle screw placement, such as bicortical and tricortical fixation, have been developed; however, the problems of loosening and pulling out of the screws are still a concern. Recently, the polymethylmethacrylate (PMMA)-augmented pedicle screws have been shown to strengthen the purchase in osteoporotic spine, but there are few reports on the effect of S1 pedicle screw with PMMA augmentation. Seventy-five patients receiving cement-augmented pedicle screws at lumbosacral vertebra were enrolled and divided into 3 groups by different patterns of S1 pedicle screw placement: S1 pedicle screw with PMMA augmentation (group A, 25 patients), S1 bicortical pedicle screw fixation (group B, 25 patients), and S1 tricortical pedicle screw fixation (group C, 25 patients). The Visual Analogue Scale (VAS) and Oswestry Disability Index (ODI) scores were assessed preoperatively and at the last follow-up. Besides, the complications, loosening rate, and fusion rate were recorded. The VAS and ODI scores at the last follow-up were significantly improved in the 3 groups compared with preoperative results. Better pain relief and functional improvement at the last follow-up was seen in group A compared with the other 2 groups; however, no significant difference was detected between groups B and C. Although the lowest screws loosening rates and the highest fusion rate were found in group A, no significant difference among these 3 groups. Furthermore, longer fusion segments and larger postoperative pelvic incidence-lumbar lordosis (PL-LL) were found as risks related to S1 screw loosening without cement augmentation. The S1 pedicle screws with PMMA augmentation achieved better stability with less screw loosening in the osteoporotic spine with lumbosacral degenerative diseases compared with bicortical/tricortical fixation at S1. This procedure is especially recommended for patients with long segment fixation and large postoperative PI-LL, but there is also a risk of bone cement leakage and a learning curve.

Thursday, September 27, 2018 1:05 PM–2:05 PM Lumbar Spine Surgery: What You Need to Know: 111. Fibular allograft as a salvage option in revision pedicle screw fixation

BACKGROUND CONTEXT In the setting of revision spine surgery for pseudoarthrosis, a variable amount of pedicle bone loss may be present. This is a result of screw loosening and subsequent screw track widening. Often the bone quality may be poor secondary to aging, malnutrition, previous infection and smoking. In these difficult cases, multiple techniques have been utilized to enhance the construct strength. Current options for revision pedicle screw fixation include cement augmented screw fixation and custom-made large diameter screws. PURPOSE The purpose of this study was to present the authors’ experience using fibular allograft in the setting of bone loss with loose pedicle screw revision. STUDY DESIGN/SETTING Retrospective. PATIENT SAMPLE A total of 10 patients. OUTCOME MEASURES CT scan lumbar spine ODI. METHODS In patients with extensive screw track dilation, fibular allograft was obtained and cut into small, longitudinal strips—approximately 3 mm in thickness. The length of each fibular allograft strut was trimmed to coincide with the length of the former screw, allowing for overhang. Allograft strut was inserted into the screw track along the wall. The screw was then advanced between the allograft, and after full insertion of the screw, the fibular allografts were then trimmed. RESULTS This technique was successfully used in 10 consecutive patients during revision lumbar spine surgeries for pseudoarthrosis. All patients had loose pedicle screws with significant bone loss around the screw tracks. Excellent purchase was achieved in all patients. CT scan at the last follow up showed incorporation of the fibular allograft and sound fusion in all patients except one. CONCLUSIONS Fibular allograft is a viable option in the setting of revision pedicle screw fixation and has several advantages when compared to currently available methods. It avoids the complications associated with cement augmented pedicle screws. In addition, it can be used impromptu, when other options are not immediately available. This technique can be employed without specialized instrumentation at significant cost savings when compared to custom made screws. Finally, this technique allows for biologic fixation at the screw-bone interface. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Time to augment?! Impact of cement augmentation on pedicle screw fixation strength depending on bone mineral density.

Cement augmentation of pedicle screws is known to increase their mechanical strength. Aim was to evaluate the impact of cement augmentation on pedicle screw fatigue strength in dependence of the bone mineral density (BMD). Twenty-one human L2 vertebral bodies from donors between 19 and 96years of age were used for in vitro experiments. BMD was measured using quantitative computed tomography (QCT). Two pedicle screws were inserted in each specimen and unilaterally augmented with bone cement. Fatigue testing was performed using a cranio-caudal sinusoidal, cyclic load (0.5Hz) with increasing compression force (100N + 0.1N/cycles). Results were evaluated for the BMD groups: normal: BMD > 120mg/cm3, osteopenic: BMD 80-120mg/cm3, and osteoporotic: BMD < 80mg/cm3 bone mass. There was a significant correlation between fatigue force and BMD for the non-augmented and augmented screws (non-augmented R2 = 0.839, p < 0.001; augmented R2 = 0.551, p < 0.001). There was a significantly increased fatigue strength of the augmented screws over the non-augmented screws in the osteoporotic group (p = 0.001), while the differences in the other groups were not significant (normal p = 0.818/osteopenic p = 0.132). The benefit of pedicle screw cement augmentation significantly depends on the bone mineral density and has the greatest extent of increased fatigue strength in osteoporotic vertebrae. Preoperative measurement of the BMD is strongly recommended to predict the benefit of augmentation and reinforce the decision for cement augmentation. These slides can be retrieved under Electronic Supplementary Material.

Development and optimization of biodegradable calcium phosphate-based nanocomposite for the application of spinal fixation

ABSTRACTClinical practices in spinal surgery have shown that pedicle screw fixation augmented by polymethyl methacrylate (PMMA) bone cement has improved outcomes for osteoporotic patients, Here, a biodegradable calcium phosphate-based nanocomposite (CPN) exhibiting better anti-pullout ability but similar fluidity and dispersing ability compared to clinically-used polymethyl methacrylate (PMMA) was developed. The present study showed that the axial pullout strength of cement-augmented pedicle screws was increased as the liquid/solid ratio (L/S) of CPN decreased. Mechanical evaluation using ASTM-standard Sawbones showed that the axial pullout force of CPN could reach ∼720 N at the L/S ratio of 0.4 mL/g, while PMMA cannot be injected through the screw. In vitro evaluation in decalcified sheep vertebral models showed that the axial pullout forces of CPN and PMMA were similar, both reaching ∼800 N. The excellent anti-pullout property of CPN clearly suggests its potential for replacing PMMA in the application of cannulated pedicle-screw fixation, worth further study and development for clinical uses.

Minimally invasive transforaminal lumbar interbody fusion using bone cement-augmented pedicle screws for lumbar spondylolisthesis in patients with osteoporosis. Case series and review of literature.

Instrumentation in patients with osteoporosis is challenging. Bone cement-augmented fenestrated pedicle screw fixation is a new procedure for fixation in the osteoporotic bone; and, applying minimally invasive techniques to the above is a challenging and novel concept. To evaluate the clinical and radiological outcome of minimally invasive spine surgery transforaminal lumbar interbody fusion (MIS-TLIF) in patients with spondylolisthesis and poor bone quality, performed with rigid instrumentation using bone cement [poly(methylmethacrylate)]-augmented fenestrated pedicle screws. Prospective, observational, single-center study. Wilcoxon nonparametric test for paired samples with a level of significance of 0.05. A clinical series of 25 patients with lumbar spondylolisthesis and osteoporosis who underwent minimally invasive TLIF with bone cement-augmented pedicle screws were included in the study. Clinical outcome and the function were assessed using the visual analog scale (VAS) score for pain and the Oswestry Disability Index (ODI). Perioperative, postoperative, and long-term complications were monitored with a mean follow-up of 18 months. A total of 25 (20 female and 5 male) patients were included in the study with an average age of 61.05 years. The major symptom was low back pain with radiating pain to lower limbs. The average T-score was -3.0. All the patients were followed clinically and radiologically. There was a statistically significant improvement in the VAS scores and ODI scores postoperatively. No events of cement extravasation, radiological loosening, or pulling out of screws were observed. Fenestrated pedicle screw fixation with bone cement augmentation in patients with osteoporosis is a well-established alternative to increase the pullout strength of screws placed in the osteoporotic bone. Applying the concept of minimally invasive surgery to this procedure makes it a more complete solution for instrumentation in osteoporotic spine. Our series is the largest in literature on spondylolisthesis and confirms the feasibility and safety of this procedure in treating spondylolisthesis in the aging population.

Clinical outcome of bone cement-augmented pedicle screw fixation for thoracolumbar refractures after percutaneous kyphoplasty

Objective To investigate the clinical therapeutic effects of bone cement-augmented pedicle screw fixation for cement vertebrae refractures with lower limb neurological symptoms after percutaneous kyphoplasty (PKP) in elderly patients with osteoporotic thoracolumbar compression fractures. Methods A total of 123 elderly patients with osteoporotic thoracolumbar compression fractures underwent PKP from December 2013 to December 2016 were retrospectively analyzed by case series study. Twelve patients had vertebral refracture with compression of the spinal cord or cauda equina which resulted in lumbosacral and leg pain, numbness and disability of ambulation and there were five males and seven females, with age of (69.2±7.1)years. Injured vertebrae was located at T12in five cases, at L1 in five and at L2 in two. Bone cement-augmented pedicle screw fixation through a standard posterior approach was utilized to treat all the 12 patients. Visual analogue scale (VAS), Oswestry disability index (ODI), anterior vertebral height compression ratio, and kyphotic angle at the preoperative time, one week postoperatively and last follow-up were recorded and compared. Intraoperative and postope-rative complications were also recorded. Results The mean duration of follow-up in all the patients was 26.7 months (range, 12-36 months). Intraoperative nerve injury, dural tear, leakage of bone cement, bone cement toxicity reaction, and pulmonary embolism were not observed during the surgery. The postoperative radiographs for all the 12 patients showed that the bone cement was distributed in cancellous bone and around the screw appropriately where there was no cement leakage out of the vertebral body or pedicle. Compared with preoperative scores, the average low back pain VAS, leg pain VAS and ODI at postoperative one week were improved by (2.2±0.7)points, (2.2±0.4)points and (33.2±8.9)points, respectively (P 0.05). Conclusion For elderly patients with spinal cord or cauda equina nerve compression symptoms after PKP for osteoporotic thoracolumbar compression fractures, the usage of posterior approach bone cement-augmented pedicle screw fixation can effectively correct kyphosis, relieve neurological symptoms and restore spinal stability. Key words: Spinal fractures; Thoracic vertebrae; Lumbar vertebrae; Internal fixators; Vertebral refracture

Surgical Treatment With Pedicle Screws of Scoliosis Associated With Osteogenesis Imperfecta in Children

Study DesignRetrospective study. ObjectiveTo assess results of posterior instrumented fusion using pedicle screws in 12 children with osteogenesis imperfecta (OI) with spinal deformity at a single institution from 2001 to 2012. Summary of Background DataThis is the first case series of OI patients who underwent non–cement augmented screw-rod instrumented fusion published in the literature. MethodsOf a total of 54 children with spinal deformity associated with OI, 12 (22.2%) were submitted to posterior spinal fusion with pedicle screws (80% density) because of severe spinal deformity. Here we reported the results in seven females and five males. ResultsFive thoracic (41.7%), five double (thoracic and lumbar 41.7%), and two lumbar (16.7%) curves were considered. The mean number of fused levels was 11.8 (range: 5 to 16). Mean age at surgery was 13 years 8 months. Mean follow-up was 7 years 11 months (range: 3 years 7 months to 16 years 1 month). The mean preoperative scoliosis angle was 75.6°, whereas the postoperative angle was 31.4° (58.5% correction rate). The mean preoperative kyphosis angle was 57.4° and the postoperative angle was 42.3°. We observed one superficial infection, one dural tear, and three cases of proximal junctional kyphosis; two patients required one revision surgery each (2 years and 4 months postoperatively on average). ConclusionsTo our knowledge, this is the first case series published in the literature regarding OI with instrumented fusion with non–cement augmented pedicle screws exclusively in children with spinal deformity. We found that posterior spinal fusion with the screw-rod system in OI deformity in children is feasible and reliable, and has acceptable clinical and imaging results in the long-term follow-up. Level of EvidenceLevel IV