Augmented PMMA distribution: improvement of mechanical property and reduction of leakage rate of a fenestrated pedicle screw with diameter-tapered perforations

Establishment and Validation of Nomograms and Web Calculators for Different Cement Leakage Risk Types in Pedicle Screw Augmentation for Degenerative Lumbar Stenosis in Osteoporotic Vertebrae

BACKGROUND

The use of cement in pedicle screw augmentation (PSA) enhances the pullout force of pedicle screws in vertebrae affected by osteoporosis. Risks involved in the use of cement for PSA include nerve injury and vascular damage caused by cement leakage.

METHODS

This study included all patients who received PSA for degenerative lumbar stenosis in osteoporotic vertebrae from January 2014 to May 2022. Postoperative computed tomography was used to assess cement leakage. Correlation analysis and logistic regression analyses were used to establish the associated clinical or radiological factors, which were then used to construct nomograms and web calculators.

RESULTS

The study comprised 181 patients including 886 screws inserted into 443 vertebrae. Perivertebral cement leakage was significantly associated with female sex, decreased bone mineral density, solid screws, and scattered cement distribution. Cement leakage through segmental veins (type S, 72.1%), leakage through basivertebral veins (type B, 23.9%), and instrument-related leakage (type I, 13.9%) accounted for most cement leakage. Patients with lower bone mineral density and scattered cement distribution were more likely to experience type S or type B leakage. Our analysis data showed that cement augmentation with cannulated and fenestrated screws tended toward concentrated cement distribution. Creation and verification of each nomogram additionally showcased the prognostic capability and medical significance of the corresponding model.

CONCLUSIONS

Nomograms and web-based calculators can accurately forecast the probability of cement leakage. PSA should be routinely performed using cannulated and fenestrated screws, along with a moderate amount of high-viscosity cement, with continuous monitoring using fluoroscopy.

Pedicle screw pull-out testing in polyurethane foam blocks: Effect of block orientation and density

Synthetic bone models such as polyurethane (PU) foam are a well-established substitute to cadaveric bone for screw pull-out testing; however, little attention has been given to the effect of PU foam anisotropy on orthopaedic implant testing. Compressive and screw pull-out performance in three PU foam densities; 0.16 g/cm3 (PCF 10), 0.32 g/cm3 (PCF 20) and 0.64 g/cm3 (PCF 40) were performed in each of the X, Y or Z orientations. The maximum compressive force, stiffness in the linear region, maximum stress and modulus were determined for all compression tests. Pedicle screws were inserted and pulled out axially to determine maximum pull-out force, energy to failure and stiffness. One-way ANOVA and post hoc tests were used to compare outcome variables between PU foam densities and orientations, respectively. Compression tests demonstrated the maximum force was significantly different between all orientations for PCF 20 (X, Y and Z) while stiffness and maximum stress were different between X versus Y and X versus Z. Maximum pull-out force was significantly different between all orientations for PCF 10 foam. No significant differences were noted for other foam densities. There is potential for screw pull-out testing results to be significantly affected by orientation in lower density PU foams. It is recommended that a single, known orientation of the PU foam block be used for experimental testing.

The incidence and risk factors for extensive epidural cement leakage in cement-augmented pedicle screw fixation: a multicenter retrospective study

INTRODUCTION

In cement-augmented pedicle screw fixation (CAPSF), epidural cement leakage (CL) is a frequently reported complication with the potential for neural injury, especially when it is extensive. To date, there has been no reports discussing basivertebral foramen morphology and pedicle screw placement, which is critical in the analysis of the risk of extensive epidural CL. Thus, this study aimed to identify the incidence and risk factors for extensive epidural CL in osteoporotic patients with CAPSF.

MATERIALS AND METHODS

371 osteoporotic patients using 1898 cement-augmented screws were included. Preoperative computed tomography (CT) was utilized to characterize basivertebral foramen morphology. Following CAPSF, the severity of epidural CL, the implantation position of pedicle screw and cement extension within the vertebral body were determined by postoperative CT. In this study, significant risk factors for extensive epidural CL were identified through logistic regression analysis.

RESULTS

There were 19 patients (5.1%) and 32 screws (1.7%) with extensive epidural CL. Nine patients (involving 19 screws) had neurological symptoms. The independent risk factors for patients with extensive epidural CL were decreased BMD and increased number of augmented screws. Significant predictors for extensive epidural CL were a magistral type of basivertebral foramen, more volume of cement injected, solid screw, a shallower screw implantation, and the smaller distance between the tip of the screw and the midline of vertebral body.

CONCLUSION

Extensive epidural CL risk was significant in CAPSF when a magistral basivertebral foramen was present; solid screws and more volume of cement were used; and screw tip was implanted shallower or closer to the midline.

Anatomic distribution of basivertebral foramen with a magistral form in vertebral bodies of T10~L5 and its clinical significance for extensive epidural cement leakage in cement-augmented pedicle screw fixation: a multicenter case-control study

BACKGROUND

There are no reports discussing anatomic distribution of basivertebral foramen (BVF) in the osteoporotic vertebral body, which is critical in the analysis of the risk of epidural cement leakage (ECL) after cement-augmented pedicle screw fixation (CAPSF).

METHODS

371 osteoporotic patients using 1898 cement-augmented screws were included. Preoperative computed tomography (CT) was used to determine the frequency, width, height, and depth of magistral BVF in T10~L5. Additionally, we measured the distance between BVF and the left/right borders of vertebral body as well as the distance between BVF and upper/lower endplates. Following CAPSF, the severity of ECL and the position of pedicle screws were determined by postoperative CT. Finally, significant risk factors for extensive ECL were identified through binary logistic regression analysis.

RESULTS

Of 2968 vertebral bodies ranging from T10 to L5, 801 (42.2%) had a magistral BVF. From T10 to L5, the frequency of magistral BVF appeared to gradually increase. The magistral BVF was much closer to the upper endplate and the depth accounted for about a quarter of anteroposterior diameter of vertebral body. Overall, there were 19 patients (5.1%) and 32 screws (1.7%) with extensive ECL, nine of whom had neurological symptoms. The independent risk factors for extensive ECL were the magistral BVF (OR = 8.62, P < 0.001), more volume of cement injected (OR = 1.57, P = 0.031), reduced distance from screw tip to vertebral midline (OR = 0.76, P = 0.003) and vertebral posterior wall (OR = 0.77, P < 0.001) respectively.

CONCLUSION

When planning a CAPSF procedure, it is important to consider anatomical distribution of BVF and improve screw implantation methods.

The Potential Impact of Basivertebral Foramen Morphology and Pedicle Screw Placement on Epidural Cement Leakage With Cement-Augmented Fenestrated Pedicle Screw Fixation: A Multicenter Retrospective Study of 282 Patients and 1404 Augmented Screws

BACKGROUND

Epidural cement leakage (CL) is a common complication in cement-augmented fenestrated pedicle screw fixation (CAFPSF) with the potential for neural injury. However, there are no reports discussing basivertebral vein morphology and pedicle screw placement, which are critical in the analysis of the risk of epidural CL after CAFPSF.

OBJECTIVE

To identify the incidence and risk factors of epidural CL in osteoporotic patients during CAFPSF.

METHODS

Two hundred and eighty-two osteoporotic patients using 1404 cement-augmented fenestrated screws were included. Preoperative computed tomography (CT) was used to characterize the morphology of posterior cortical basivertebral foramen. After CAFPSF, the severity of epidural CL, the implantation position of the screw tip, and cement extension within the vertebral body were determined by postoperative CT scans. In this study, significant risk factors for epidural CL were identified through logistic regression analysis.

RESULTS

In total, 28 patients (18.8%) and 108 screws (7.7%) had epidural CL and 7 patients (13 screws) experienced neurological symptoms. Although local epidural CL was generally not clinically significant, extensive epidural leakage posed a higher risk of neurological symptoms. Significant predictors for extensive epidural CL were a magistral type of basivertebral foramen and the smaller distance between the tip of the screw and the posterior wall of the vertebral body.

CONCLUSION

In osteoporotic patients receiving CAFPSF, epidural CL is relatively common. The morphology of basivertebral foramen should be taken into account when planning a CAFPSF procedure. It is important to try and achieve a deeper screw implantation, especially when a magistral type of basivertebral foramen is present.

[Cement augmentation in spinal surgery]

Bone cement has been used in spinal surgery for as long as 50 years. In contemporary spinal surgery, cement augmentation of fractured osteoporotic vertebrae in the form of vertebroplasty/kyphoplasty as well as cement augmentation of pedicle screws in instrumented procedures of any etiology are established as standard procedures. Both procedures are very effective, although the benefits of vertebroplasty/kyphoplasty procedures have been controversially discussed in the past. Overall, complications rarely occur. The most relevant complication is cement leakage, which is asymptomatic in the majority of cases but in the worst case might lead to neurological deficits, embolic events and even circulatory collapse. Prevention of cement leakage is therefore crucial. Risk factors for cement leakage and preventive measures are presented in a comprehensive review based on the available literature.

The Biomechanical Properties of Cement-Augmented Pedicle Screws for Osteoporotic Spines

STUDY DESIGN

This is a broad, narrative review of the literature.

OBJECTIVE

In this review, we describe recent biomechanics studies on cement-augmented pedicle screws for osteoporotic spines to determine which factors influence the effect of cement augmentation.

METHODS

A search of Medline was performed, combining the search terms "pedicle screw" and ("augmentation" OR "cement"). Articles published in the past 5 years dealing with biomechanical testing were included.

RESULTS

Several factors have been identified to impact the effect of cement augmentation in osteoporotic spines. These include the type of augmentation material, the volume of injected cement, the timing of augmentation, the severity of osteoporosis, the design of the pedicle screw, and the specific augmenting technique, among others.

CONCLUSIONS

This review elaborates the biomechanics of cement-augmented pedicle screws, determines which factors influence the augmentation effect, and identifies the risk factors of cement leakage in osteoporotic bone, which might offer some guidance when using this technique in clinical practice. Further, we provide information about newly designed screws and recently developed augmentation materials that provide higher screw stability as well as fewer cement-related complications.

Clinical Observations of Kümmell Disease Treatment Through Percutaneous Fixation Combined with Vertebroplasty

OBJECTIVE

To explore the safety and efficacy of percutaneous pedicle screw fixation combined with vertebroplasty for the treatment of stage III Kümmell disease.

METHODS

The clinical data and follow-up results of 22 patients with Kümmell disease who were admitted to our department from 2014 to 2018 were analyzed. There were 14 females and eight males, and the Age range was 58-81 years. All patients were followed up for 24 months. The treatment method was percutaneous pedicle screw fixation combined with vertebroplasty. The patient general information such as age, gender, bedrest time and location of fracture vertebrae were recorded. The clinical symptoms and imaging data of visual analogue scale (VAS), bone cement leakage, Oswestry Disability Index (ODI), Cobb angle, anterior, middle and posterior height of the diseased vertebral body, and complications were recorded before operation and during follow-up.

RESULTS

For patients enrolled, no bone cement leakage was observed during the operation; no patients developed infections after operation. The operation was safe and resulted in a short bedrest time. The VAS score and ODI index at 3 and 24 months postoperative (2.86 ± 0.83, 31.68% ± 6.21%; 3.0 ± 0.82, 32.78% ± 6.05%) were significantly lower than that recoded preoperatively (7.59 ± 0.59, 71.5% ± 8.84%) (P < 0.05). Additionally, there was no significant difference between the records at 3 and 24 months after operation (P > 0.05). Imaging data showed that the bone cement and screws were in good position and did not move during postoperative and follow-up. The anterior, middle and posterior height of the diseased vertebral body measured 2 days after surgery (23.46 ± 4.72, 23.12 ± 3.05, 25.81 ± 2.22) and at last follow-up (20.83 ± 4.48, 21.78 ± 2.74, 24.74 ± 1.93) were higher than that recorded preoperatively (13.08 ± 4.49, 12.93 ± 3.53, 19.32 ± 2.73) (P < 0.05), and the Cobb angle measured 2 days and 24 months after operation (9.57 ± 4.63, 10.68 ± 3.97) were lower than that recorded preoperatively (28.24 ± 8.95) (P < 0.05), and no significant difference was found between the values recorded at 2 days and 24 months after operation (P > 0.05). Follow-up for 24 months, there was no re-fracture of the diseased vertebrae and internal fixation loosening, but two cases of adjacent vertebral refracture complications occurred, and the effect was good after PVP treatment.

CONCLUSION

Short-segment percutaneous pedicle screw fixation combined with vertebroplasty in the treatment of stage III Kümmel disease can effectively restore the height of the diseased vertebrae, kyphosis correction, reduce trauma, prevent the diseased vertebral body from collapsing again, and effectively improves clinical symptoms.

Implant Preservation versus Implant Replacement in Revision Surgery for Adjacent Segment Disease After Thoracolumbar Instrumentation: A Retrospective Study of 43 Patients

OBJECTIVE

To evaluate the mechanical properties of a new connector rod aiming to preserve implants in revision surgery (RS) for adjacent segment disease, a problematic complication of instrumented spinal fusion, and to assess its clinical applicability.

METHODS

The mechanical properties of the connector-rod construct (implant preservation) and traditional rod construct (implant replacement) were evaluated and compared. Forty-three patients underwent RS for adjacent segment disease in the thoracolumbar spine with implant preservation or replacement, and radiological and clinical outcomes were assessed.

RESULTS

Mechanical properties in group A were comparable to those in group B. Total mean time from prior surgery to RS was 6.86 ± 1.08 years. Surgical time and blood loss values of group A were 40.14% and 29.29% statistically significantly smaller than values of group B. In group B, 12% (3/25) of patients developed surgical site infections. In both groups, the visual analog scale leg score decreased significantly after RS. Early postoperative (at 1-month and 3-month follow-up) Oswestry Disability Index and visual analog scale back scores of group A were significantly lower than those of group B; the difference in the visual analog scale back score between groups was significant until the 6-month follow-up. No implant failures occurred, and spinal fusion was achieved in all cases.

CONCLUSIONS

The connector rod is considered safe and can reduce the surgical time, blood loss, risk of complications, and medical costs. Better early postoperative clinical outcomes can be achieved with the rod owing to less surgical trauma.

[Polymethylmethacrylate-augmented screw fixation in treatment of senile thoracolumbar tuberculosis combined with severe osteoporosis]

OBJECTIVE

To explore the safety and effectiveness of polymethylmethacrylate-augmented screw fixation (PASF) in the treatment of elderly thoracolumbar tuberculosis combined with severe osteoporosis.

METHODS

The clinical data of 20 elderly patients with thoracolumbar tuberculosis and severe osteoporosis who underwent PASF after anterior or posterior debridement and bone grafting and met the selection criteria between December 2012 and December 2014 were retrospectively analyzed. There were 8 males and 12 females with an average age of 68.5 years (range, 65-72 years). T value of bone mineral density was -4.2 to -3.6, with an average of -3.9. There were 12 cases of thoracic tuberculosis, 3 cases of thoracolumbar tuberculosis, and 5 cases of lumbar tuberculosis. The diseased segments involved T 3-L 4, including 11 cases of single-segment disease, 6 cases of double-segment disease, and 3 cases of multi-segment disease. The disease duration was 3-9 months, with an average of 6 months. The preoperative spinal nerve function of the patients was evaluated by the American Spinal Injury Association (ASIA) grading. There were 2 cases of grade A, 5 cases of grade B, 6 cases of grade C, 4 cases of grade D, and 3 cases of grade E. Postoperative imaging examination was used to evaluate the bone graft fusion and paravertebral abscess absorption, and to measure the Cobb angle of the segment to evaluate the improvement of kyphosis. The levels of erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were tested. The visual analogue scale (VAS) score, Oswestry disability index (ODI), and ASIA grading were used to evaluate the effectivreness before operation, at 1 month after operation, and at last follow-up. The clinical cure of tuberculosis was also evaluated.

RESULTS

All operation successfully completed. The operation time was 154-250 minutes, with an average of 202 minutes; the intraoperative blood loss was 368-656 mL, with an average of 512 mL. All 20 patients were followed up 18-42 months, with an average of 26.8 months. The postoperative pain and symptoms of tuberculosis in all patients relieved, and the paravertebral abscess was absorbed, reaching the cure standard for spinal tuberculosis. All bone grafts fusion achieved within 1 year after operation. Only 1 case had asymptomatic bone cement leakage into the paravertebral veins, and the remaining patients had no serious complications such as bone cement leakage in the spinal canal, pulmonary embolism, and neurovascular injury. At last follow-up, spinal cord nerve function significantly improved when compared with preoperative one. Among them, ASIA grading were 7 cases of grade C, 8 cases of grade D, and 5 cases of grade E, showing significant difference when compared with preoperative one ( Z=2.139, P=0.000). VAS score, ODI score, segmental Cobb angle, ESR, and CRP at 1 month after operation and at last follow-up were significantly improved when compared with preoperative ones ( P<0.05); there was no significant difference between 1 month after operation and last follow-up ( P>0.05). During the follow-up, no complications such as failure of internal fixation, proximal junctional kyphosis, or tuberculosis recurrence occurred.

CONCLUSION

For elderly patients with thoracolumbar tuberculosis and severe osteoporosis, PASF treatment is safe and effective.

Comparison of unilateral and bilateral polymethylmethacrylate-augmented cannulated pedicle screw fixation for the management of lumbar spondylolisthesis with osteoporosis

Background

Cannulated pedicle screw (CPS) augmented by polymethylmethacrylate (PMMA) can achieve satisfactory clinical efficacy in the treatment of lumbar spondylolisthesis with osteoporosis. However, accurate application of CPSs will help to avoid the difficulty of screw revision and reduce the incidence of PMMA-related complications. This study aimed to investigate the mid-term efficacy of CPS compared to unilateral and bilateral applications in this common lumbar degenerative disease.

Methods

May 2011 and May 2018, 50 patients with lumbar spondylolisthesis with osteoporosis who underwent posterior fixation and fusion using traditional pedicle screws or CPSs were included in the study. Patients were divided into two groups based on the application: the unilateral PMMA-augmented CPS group (UC, n = 29) and the bilateral PMMA-augmented CPS group (BC, n = 21). Operation time, blood loss, average hospitalization time, PMMA leakage, and other complications were recorded. The visual analog scale (VAS) and Oswestry disability index (ODI) scores were used to evaluate symptom recovery. Radiographic results were compared for intervertebral fusion and screw loosening.

Results

There were no significant differences in the baseline data of the two groups.

The VAS and ODI scores improved significantly after surgery (P < 0.05), with no significant differences between the groups (P > 0.05). The operation time and blood loss in the UC group were significantly lower than those in the BC group (P < 0.05). However, the loss of intervertebral disk height and Taillard index did not differ significantly between the groups. The rates of PMMA leakage in the UC and BC groups were 7.0% and 11.9%, respectively (P < 0.05). Bony fusion was achieved in all groups without screw loosening at the last follow-up. Only one patient experienced superficial infection in both groups, while cerebrospinal fluid leakage was observed in two patients in the BC group.

Conclusions

Unilateral application of PMMA-augmented CPS may provide adequate clinical safety and effectiveness in the surgical treatment of lumbar spondylolisthesis with osteoporosis.

Effect of Fenestrated Pedicle Screws with Cement Augmentation in Osteoporotic Patients Undergoing Spinal Fusion

OBJECTIVE

Osteoporosis is a well-known risk factor for instrumentation failure and subsequent pseudoarthrosis after spinal fusion. In the present systematic review, we analyzed the biomechanical properties, clinical efficacy, and complications of cement augmentation via fenestrated pedicle screws in spinal fusion.

METHODS

We conducted a systematic review in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Reports appearing in the PubMed database up to March 31, 2020 were queried using the key words "cement," "pedicle screw," and "osteoporosis." We excluded non-English language studies, studies reported before 2000, studies that had involved use of cement without fenestrated pedicle screws, nonhuman studies, technical reports, and individual case reports.

RESULTS

Twenty-five studies met the inclusion criteria. Eleven studies had tested the biomechanics of cement-augmented fenestrated pedicle screws. The magnitude of improvement achieved by cement augmentation of pedicle screws increased with the degree of osteoporosis. The cement-augmented fenestrated pedicle screw was superior biomechanically to the alternative "solid-fill" technique. Fourteen studies had evaluated complications. Cement extravasation with fenestrated screw usage was highly variable, ranging from 0% to 79.7%. However, cement extravasation was largely asymptomatic. Thirteen studies had assessed the outcomes. The use of cement-augmented fenestrated pedicles decreased screw pull out and improved fusion rates; however, the clinical outcomes were similar to those with traditional pedicle screw placement.

CONCLUSIONS

The use of cement-augmented fenestrated pedicle screws can be an effective strategy for achieving improved pedicle screw fixation in patients with osteoporosis. A potential risk is cement extravasation; however, this complication will typically be asymptomatic. Larger comparative studies are needed to better delineate the clinical efficacy.

A minimally invasive, 3D-fluoroscopy-navigation-guided, 3D-controlled pedicle approach in spine surgery: first reliable results and impact on patient safety

PURPOSE

Safe pedicle screw placement is a daily challenge to every spine surgeon. Introduction of minimally invasive approaches in spinal surgery led to an impaired facility of inspection of the surgical field increasing the importance of intraoperative imaging and navigation. During the past years, we established a minimally invasive, navigated approach in our clinical setting.

METHODS

We retrospectively reviewed the accuracy of pedicle approaches in patients treated due to traumatic or osteoporotic fractures, spondylitis/discitis, and tumoral lesions. Guide wires for pedicle screws or kyphoplasty cannulas were inserted in a 3D-navigation-guided, minimally invasive technique. Positioning of the guide wires was verified via 3D-scan, and pedicle screws/kyphoplasty cannulas were then visualized via a.p./lateral radiographs. Accuracy data were compared to a standard navigated open approach control group with indications similar to the MIS-group.

RESULTS

23 MIS patients were included in this study (25-84 years, mean 70 years) with a total of 154 placed guide wires. Handling of the navigated Jamshidi needle was easy and secure. The guide wires showed correct placement in 151/154 cases. Three wires (1.9%) needed correction of placement after control scan. There were no vascular or neurologic complications due to wire misplacement. In the open-surgery control group, 7/181 screws (3.9%) needed intraoperative correction presenting no significant difference compared to the correction rate of the MIS-group (p = 0.35).

CONCLUSION

Our study shows the feasibility and reliability of a navigation-guided, minimally invasive pedicle approach in the clinical setting. Therefore, reduced morbidity due to minimized approaches can be combined with higher accuracy of navigated pedicle screw/kyphoplasty cannula placement improving patient safety.

An innovative technique for osteoporotic vertebral compression fractures - vertebral osteotome with side-opening cannula

Objective

This study is to assess an innovative technique - a vertebral osteotome (VO) combined with side-opening injection cannula for percutaneous vertebroplasty (PVP).

Methods

A retrospective study by propensity score matching. From January 2016 to April 2016, 63 patients who were diagnosed with monosegmental osteoporotic vertebral compression fracture received the innovative technique. The epidemiologic data, surgical indexes, and recovery outcomes were collected in the follow-up period. Propensity score matching identified 63 pairs form historical controls by traditional unilateral PVP approach in 2015 using six independent variables: age, sex, preoperative visual analog score (VAS), Oswestry Disability Index (ODI), body mass index, and bone mineral density.

Results

The surgical duration and cement distribution were longer and larger in patients by VO method. Besides, postoperative VAS and ODI in the VO group were lower than those in the control group. However, there were no differences in radiation exposure times, improvement of Cobb angle, cement leakage, or adjacent vertebral fracture between two groups. Cement volume in the VO group was less than that in the control group.

Conclusion

This new innovative technique makes PVP safe and effective. Although it lasts longer, the restoration rate of vertebral height and cement distribution can be improved, which contributes to a better pain relief.

Pedicle screw augmentation in osteoporotic spine: indications, limitations and technical aspects

PURPOSE

The need for spinal instrumented fusion in osteoporotic patients is rising. In this review, we try to give an overview of the current spectrum of pedicle screw augmentation techniques, safety aspects and indications.

METHODS

Review of literature and discussion of indications, limitations and technical aspects.

RESULTS

Various studies have shown higher failure rates in osteoporotic patients, most probably due to reduced bone quality and a poor bone-screw interface. Augmentation of pedicle screws with bone cement, such as polymethylmethacrylate or calcium based cements, is one valid option to enhance fixation if required.

CONCLUSIONS

Crucial factors for success in the use of augmented screws are careful patient selection, a proper technique and choice of the ideal cement augmentation option.