Screw Augmentation Research Articles

Tips and tricks for using cement augmentation of pedicle screws and vertebral body replacements—A literature review supported by two case reports

BackgroundThe prevalence of osteoporosis is escalating alongside an aging global population, increasing the demand for spinal surgeries, including those necessitating cement augmentation for enhanced construct stability. ObjectiveThis article delves into the nuanced application of cement augmentation techniques for pedicle screws and vertebral body replacements (VBR), aimed at optimizing surgical outcomes in osteoporotic spines. MethodDrawing from a comprehensive literature review according to important clinical and biomechanical studies and the authors’ clinical experiences, we elucidate strategies to mitigate complications and improve surgical efficacy. ResultsCement augmentation has shown promise in managing vertebral fractures and in securing pedicle screws within osteoporotic vertebrae, with the advent of polymethylmethacrylate (PMMA) bone cement marking a pivotal advancement in spinal surgery. We highlight intraoperative measures like the choice between pre-injecting cement and utilizing cannulated or fenestrated screws, emphasizing the importance of controlling cement viscosity to prevent leakage and embolism. Through two case reports, we demonstrate the practical application of endplate cementation following VBR. ConclusionWhile the use of cement augmentation poses certain risks, its judicious application—supported by evidence-based guidelines and surgical expertise—can substantially enhance the stability of spinal constructs in osteoporotic patients. This allows a reduction in instrumentation length by enhancing biomechanical stability concerning pullout, bending, and rotational forces. Furthermore, the incidence of endplate sintering following VBF can be significantly reduced. Future research, particularly on antibiotic-loaded PMMA, may further expand its utility and optimize its safety profile.

Primary stability of multi-hole acetabular cup combined with posterior column plating for the fixation of complex acetabular fractures in elderly patients: a biomechanical analysis.

Acute total hip arthroplasty has gained increasing popularity in the treatment of complex acetabular fractures in elderly patients, but the biomechanical evidence is lacking. Therefore, we measured the primary stability to evaluate whether acute total hip arthroplasty using a multi-hole acetabular cup and posterior column plating through a single K-L approach can safely be used for treating complexed acetabular fractures in the elderly. In 18 composite osteoporotic hemipelves, T-type acetabular fractures were treated in three ways: CSP (Cup with acetabular screws augmentation combined with posterior plate) group, CP (Cup without acetabular screw combined with posterior plate) group and CSPA (Cup with acetabular screws combined with posterior plate and anterior plate) group. Each specimen was dynamically loaded (300 to 1700N, 1Hz). Primary stability of the acetabular cup and fracture gap was evaluated by 3-dimensional (3D) micromotions. No significant differences in the 3D-micromotions were observed among the CSP, CP and CSPA groups except the test point on the anterior column of the acetabulum in the CP scenario (CSP 49.33 ± 21.08μm vs. CP 224.83 ± 52.29μm, p < 0.001; CSPA 45.50 ± 12.16μm vs. CP 224.83 ± 52.29μm, p < 0.001). No significant differences in the fracture gap displacement on the posterior column of acetabulum were observed among the CSP, CP and CSPA groups. Our results show, that acute total hip arthroplasty using a multi-hole cup with acetabular screws and posterior column plating through single a K-L approach offers good primary stability to allow good osseous integration for treating complex acetabular fractures in the elderly. Furthermore, it also provides good fracture gap displacement on the posterior column.

Early Experience With Novel Molded Allograft Anchors for the Management of Screw Loosening in Elderly Patients With Reduced Bone Density in Primary and Revision Lumbar Surgery.

Various strategies have been used to reduce pedicle screw loosening following lumbar instrumented fusion, but all strategies have limitations. In this prospective multicenter cohort study, outcomes of elderly patients with reduced bone density who underwent primary or revision fusion surgery using a novel technique of pedicle screw augmentation with demineralized bone fiber (DBF) anchors were evaluated. This study included elderly patients (aged >65 years) with dual-energy x-ray absorptiometry-confirmed reduced bone density who required lumbar pedicle screw fixation and were treated with supplemental DBF allograft anchors during primary or revision surgery. The need for DBF anchors was determined by evaluating preoperative computed tomography (CT) scans (for revision surgery) and by the surgeons' tactile feedback intraoperatively during pedicle screw insertion and removal. After determining the pedicle screw void diameter with a sizing instrument, DBF anchors and pedicle screws of the same diameter were placed into the void. CT scans were obtained on postoperative day 2 to assess pedicle breach, pedicle fracture, or anchor material extrusion and at 6 and 12 months postoperatively to assess screw loosening. Thereafter, to minimize radiation exposure, CT scans were only performed for recurrence of pain. Twenty-three patients (79% women; mean age, 74 years) received 50 lumbosacral pedicle screws augmented with DBF anchors. Most surgeries (n = 18, 78%) were revisions, and most anchors were inserted into revision pedicle screw trajectories (n = 33, 66%). Day-2 CT scans revealed no pedicle breach/fracture or extrusion of anchor material. During a mean follow-up of 15 months (12-20 months), no screw loosening was detected, and no patient required pedicle screw revision surgery. There were no adverse events attributable to DBF allografts. DBF allograft anchors appear to be safe and effective for augmenting pedicle screws during revision surgeries in female elderly patients with reduced bone density. Clinically, DBF reduced the rate of pedicle screw loosening in patients with reduced bone density. A significant reduction in screw loosening can decrease the need for revision surgeries, which are costly and carry additional risks. Enhanced bone integration from the DBF may promote better healing and long-term stability.

Bone Allograft Pedicle Screw Augmentation: A Biomechanical Study.

We performed a comprehensive cadaveric biomechanical study to compare the fixation strength of primary screws, screws augmented with bone allograft, and screws augmented with polymethylmethacrylate cement. To evaluate a novel technique for screw augmentation using morselized cortico-cancellous bone allograft to fill the widened screw track of failed pedicle screws. To date, there are no known biological methods available for failed pedicle screw augmentation or fixation. Biomechanical tests were performed using 2 different testing modalities to quantify fixation strength including axial screw pullout and progressive cyclic displacement tests. Fifty vertebrae were instrumented with pedicle screws. Our study showed that bone allograft augmentation using the same diameter screw was noninferior to the fixation strength of the initial screw. In the axial pullout test, screws undergoing bone allograft repair failed at 25% lower loads compared with native screws, and screws augmented with cement showed approximately twice as much strength compared with native screws. In the cyclic displacement test, screws fixed with cement resisted loosening the best of all the groups tested. However, screws augmented with bone graft were found to have an equal strength to native screw purchase. our study did not find a correlation with bone mineral density as a predictor for failure in axial pullout or cyclic displacement tests. Bone allograft augmentation for pedicle screw fixation was noninferior to the initial screw purchase in this biomechanical study. This bone allograft technique is a viable option for screw fixation in the revision setting when there is significant bone loss in the screw track.

Total Hip Arthroplasty in Protrusio Acetabuli: A Systematic Review.

Protrusio acetabuli, or abnormal protrusion of the femoral head into the acetabulum, requires performance of a total hip arthroplasty (THA) for which various reconstruction techniques and outcomes have been described. The aim of this systematic review is to provide a comprehensive analysis of the current evidence, evaluate treatment efficacy, compare surgical techniques, and identify topics for future research along with improving evidence-based decision-making, improving patient outcomes in the management of this condition. A thorough systematic review of the PubMed, Embase, Cochrane Library databases, and Scopus library was conducted, and articles describing techniques of THA for treatment of protrusion acetabuli were extracted. The initial search generated 751 results. After exclusion, 18 articles were included. Of these, eight were prospective studies and 10 were retrospective. Surgery was performed on 783 hips with a mean age of 60 years; 80% of females who mostly had inflammatory arthritis were followed up for 8.86 years (range, 2-15.4 years). Good outcomes have been achieved with THA using uncemented cups with bone graft; however, no conclusion could be drawn with regard to the femoral side. It can be concluded that the concept of restoration of the anatomical hip center of rotation is paramount for good outcome and better survival of the implant is important when using uncemented cups with a bone graft. In addition, screw augmentation for fixation is not recommended unless absolutely necessary. The most common complications were aseptic loosening and heterotopic ossification. While the former required revision, conservative management was administered for the latter.

Comparison of cement-augmented pedicle screw and conventional pedicle screw for the treatment of lumbar degenerative patients with osteoporosis.

A retrospective cohort study. To compare the safety and clinical efficacy between using cement-augmented pedicle screws (CAPS) and conventional pedicle screws (CPS) for the treatment of lumbar degenerative patients with osteoporosis. Management of lumbar degenerative patients with osteoporosis undergoing spine surgery is challenging. The clinical efficacy and potential complications of the mid-term performance of the CAPS technique in the treatment of lumbar degenerative patients with osteoporosis remain to be evaluated. The data of 131 lumbar degenerative patients with osteoporosis who were treated with screw fixation from May 2016 to December 2019 were retrospectively analyzed in this study. The patients were divided into the following two groups according to the type of screw used: (I) the CAPS group (n = 85); and (II) the CPS group (n = 46). Relevant data were compared between two groups, including the demographics data, clinical results and complications. The difference in the VAS, ODI and JOA scores at three and 6months after the operation between the two groups was statistically significant (P < 0.05). At 12months after surgery and the final follow-up, a significant difference in the fusion rate was found between the two groups (P < 0.05). Four cemented screws loosening were observed in the CAPS group (loosening rate 4/384, 1.04%) and 15 screws loosening were observed in the CPS group (loosening rate 15/214, 7.01%). In the CAPS group, a total of 384 augmented screws were used, and cement leakage was observed in 25 screws (25/384, 6.51%), but no obvious clinical symptoms or serious complications were observed. Adjacent vertebral fractures occurred in six patients in the CAPS group and one in the CPS group. CAPS technique is an effective strategy for the treatment of lumbar degenerative patients with osteoporosis, with a higher fusion rate and lower screw loosening rate than CPS.

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

BackgroundThe 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. MethodsOur study included all individuals who received PSA for degenerative lumbar stenosis (DLS) in osteoporotic vertebrae from January 2014 to May 2022. Postoperative CT scan will be used to assess cement leakage. Correlation analysis and logistic regression analyses were utilized to establish the associated clinical or radiological factors, which were then used to construct Nomograms and web calculators. ResultsOur study included a total of 181 patients, with 886 screws being inserted into 443 vertebrae. Perivertebral cement leakage was significantly associated with female, decreased BMD, solid screws, and scattered cement distribution. The majority of cement leakage happened through segmental veins (type S, 72.1%), with basivertebral veins (type B, 23.9%) and instrument-related leakage (type I, 13.9%) following suit. Lower BMD 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. The creation and verification of each Nomogram additionally showcased the prognostic capability and medical significance of the corresponding model. ConclusionNomograms and web-based calculators can accurately forecast the probability of cement leakage. We should regularly perform the procedure using cannulated and fenestrated screws, along with a moderate amount of high-viscosity cement, while continuously monitoring with fluoroscopy during PSA.

Short segment posterior fixation of unstable thoracolumbar vertebral fractures with fractured vertebra augmentation with intermediate pedicle screw - a clinicoradiological analysis.

Unstable thoracolumbar burst fractures are routinely encountered in orthopedic practice. Recently, short-segment fixation with pedicle screw augmentation of the fractured vertebra for unstable thoracolumbar burst fractures has gained popularity. Nonetheless, the maintenance of the kyphotic correction during the follow-up period remains controversial. This study aimed to examine the clinical-radiological outcomes, complications, and functional outcomes of fractured vertebrae augmentation with intermediate pedicle screws in short-segment instrumentation in acute thoracolumbar spine fractures. This retrospective study was conducted in the Department of Orthopedics, All India Institute of Medical Sciences, Jodhpur, using medical records from January 2021 to October 2022. Parameters such as local kyphosis correction, loss of kyphotic correction at final follow-up, anterior body height correction (%), and loss of correction (%) at final follow-up were measured as primary outcomes. Various other parameters such as operative time, blood loss, length of hospital stay, and visual analog scale were measured as secondary outcomes. The mean correction obtained via surgery in the immediate postoperative period was 13.7±2.3 degrees. The mean loss of correction at the final follow-up was 4.1±2.0 degrees, and the mean final local kyphotic angle was 7.2±2.4 degrees (P<0.05). The mean correction obtained via surgery in the immediate postoperative period was 37.2%±9.0%. The mean loss of correction at the final follow-up was 10.5%±5.3%, and the mean final anterior vertebral body height maintained was 72%±11.0% (P<0.05). Short-segment posterior fixation with pedicle screw augmentation achieves good correction of local kyphotic angle and anterior vertebral height in the immediate postoperative period, but some loss of correction at final follow-up is common. In our study, the loss of correction corresponded directly to the load-sharing score.

Cement-Augmented Screw Fixation with PHILOS Plating for Osteoporotic Proximal Humeral Fractures: An Observation of Mid- and Long-Term Curative Efficacy.

The mid- and long-term clinical outcomes of cement-augmented screws in the treatment of osteoporotic proximal humeral fractures have rarely been reported. The aim of this study was to observe the mid- and long-term efficacy of combined cement-augmented screw fixation and PHILOS plating in the treatment of osteoporotic fractures of the proximal humerus. This study retrospectively analyzed data from 19 patients with osteoporotic fractures of the proximal humerus who had undergone internal fixation at the Guizhou Provincial People's Hospital from February 2017 to May 2021. The cohort was comprised of six males and 13 females, aged 75-87 (mean age: 82.52 ± 1.24) years. According to the Neer classification, three, 12, and four patients had two-part, three-part, and four-part fractures, respectively. All patients were treated with open reduction internal fixation with cement-augmented screws and PHILOS plating. Time until fracture healing was recorded postoperatively. Patients were observed for postoperative complications, including humeral head necrosis, loosening or breaking of the augmented screws, screw perforation of the humeral head, and varus fracture displacement. Visual analog scale and Constant scores of the shoulder joint were compared 1, 3, 6, and 12 months after surgery. Scores at the most recent follow-up were used to evaluate shoulder joint function. Measured data conforming to a normal distribution were expressed as mean ± SD. Analysis of variance or rank sum tests were used for intergroup comparisons. A value of p < 0.05 was considered significant. All 19 patients followed up for 1-4 (average: 2.13 ± 0.61) years. Fractures united in all cases, with a healing time of 8-14 (average: 10.25 ± 1.72) weeks. There were no cases of humeral head necrosis, screw loosening, fractures, or perforation of the humeral head. One patient had mild varus fracture displacement with a reduced neck-shaft angle. There were significant differences in visual analog scale and Constant scores 1, 3, and 6 months after surgery (p < 0.05). The visual analog scale score was 0 at final follow-up in all cases. The Constant score of the shoulder joint was excellent, good, fair, and poor in two, 12, four, and one case, respectively, yielding an excellent and good rate of 73.68%. Cement-augmented screw fixation combined with PHILOS plating of osteoporotic proximal humeral fractures had good mid- and long-term clinical efficacy. It should be considered a new option for fracture treatment in such patients.

Osteoplasty of vertebral bone defects caused by pedicle screw loosening using orthobiological approaches: a pilot study of case series

Objective. To analyze the effectiveness and safety of using an orthobiological product in osteoplasty of bone defects of the vertebrae with simultaneous reosteosynthesis.Material and Methods. The results of screw augmentation technology using thrombogel-enriched allogeneic bone were studied in a retrospective, single-center, non-randomized study, which included 17 patients (10 women, 7 men) with instability of the hardware in the form of screw loosening and osteolysis around screws. Results within 12 months were followed up in 17 patients (100 %). We compared preoperative and postoperative instrumental data, clinical parameters in dynamics.Results. The mean age of the patients was 59 (43–75) years. The distribution of patients, according to the primary pathology, was as follows: 11 patients (64.7 %) had a degenerative-dystrophic pathology of the spine, 4 patients (23.5 %) had a traumatic injury, and 2 patients had a kyphotic deformity on the background of Bechterew’s disease (11.8 %). The mean time from primary to revision surgery was 7.06 months (3.1–12.1), mean CRP was 4.48 (0.5–15.0). When observing patients for 12 months, all patients showed a positive trend in the form of a statistically significant regression of back pain according to VAS from 7.0 (6.0; 7.3) to 1.0 (0.0; 1.0) points (χ2 = 47.9, df 3, р &lt; 0.0001). A positive trend was also noted in the form of a decrease in ODI indicators and an improvement in the quality of life of patients from 63.8 (57.1; 69.1) to 3.0 (2.0; 7.5) at 12 months. When comparing the parameters (VAS and ODI), the obtained differences before/after the operation were statistically significant, while these changes have a pronounced correlation. Postoperative CT studies (3, 6, 12 months) showed no instability of the screws.Conclusion. Osteoplasty of vertebral bone defects and screw augmentation using orthobiological approaches have demonstrated their primary efficacy and safety. Further studies with a large sample size are needed to confirm the obtained results.

Anterior column acetabulum fracture fixation with a screw-augmented acetabular cup—a biomechanical feasibility study

BackroundThe beneficial effects of unrestricted postoperative full weight bearing for elderly patients suffering hip fractures have been demonstrated. However, there is still existing disagreement regarding acetabular fractures.The aim of this biomechanical study was to evaluate the initial load bearing capabilities of different fixation constructs of anterior column fractures (ACFs) in osteoporotic bone. MethodsArtificial pelvises with ACFs were assigned to three groups (n = 8) and fixed with either a 7.3 mm partially threaded antegrade cannulated screw (group AASS), an anteriorly placed 3.5 mm plate (group AAPF), or a press-fit acetabular cup with screw augmentation (group AACF). All specimens underwent ramped loading from 20 N preload to 200 N at a rate of 18 N/s, followed by progressively increasing cyclic testing at 2 Hz until failure performed at a rate of 0.05 N/cycle. Relative displacements of the bone fragments were monitored by motion tracking. FindingsInitial stiffness (N/mm) was 118.5 ± 34.3 in group AASS, 100.4 ± 57.5 in group AAPF, and 92.9 ± 44.0 in group AACF, with no significant differences between the groups, p = 0.544. Cycles to failure were significantly higher in groups AACF (8364 ± 2243) and AAPF (7827 ± 2881) compared to group AASS (4440 ± 2063), p ≤ 0.041. InterpretationFrom a biomechanical perspective, the minimally invasive cup fixation with screw augmentation demonstrated comparable stability to plate osteosynthesis of ACFs in osteoporotic bone. The results of the present study do not allow to conclusively answer whether immediate full weight bearing following cup fixation shall be allowed. Given its similar performance to plate osteosynthesis, this remains rather an utopic wish and a more conservative approach deems more reasonable.

Comparative finite element analysis of posterior short segment fixation constructs with or without intermediate screws in the fractured vertebrae for the treatment of type a thoracolumbar fracture

Six-screw short-segment posterior fixation for thoracolumbar fractures, which involves intermediate screws at the fractured vertebrae has been proposed to reduce the rates of kyphosis recurrence and implant failure. Yet, little is known about the mechanisms and biomechanical responses by which intermediate screws at the fracture vertebrae enhance fixation strength. The objective of this study was to investigate the biomechanical properties that are associated with the augmentation of intermediate screws in relation to the severity of type A thoracolumbar fracture using finite element analysis. Short-segment stabilization models with or without augmentation screws at fractured vertebrae were established based on finite element model of moderate compressive fractures, severe compressive fractures and burst fractures. The spinal stiffness, stresses at the implanted hardware, and axial displacement of the bony defect were measured and compared under mechanical loading conditions. All six-screw stabilization showed a decreased range of motion in extension, lateral bending, and axial rotation compared to the traditional four-screw fixation models. Burst thoracolumbar fracture benefited more from augmentation of intermediate screws at the fracture vertebrae. The stress of the rod in six-screw models increased while decreased that of pedicle screws. Our results suggested that patients with more unstable fractures might achieve greater benefits from augmentation of intermediate screws at the fracture vertebrae. Augmentation of intermediate screws at the fracture vertebrae is recommended for patients with higher wedge-shaped or burst fractures to reduce the risk of hardware failure and postoperative re-collapse of injured vertebrae.

Optimal additional support screw position for prevention of hinge fracture in biplanar closed wedge distal femoral osteotomy

BackgroundThe purpose of this study was to examine the biomechanical significance of supplemental fixation using a positional screw in prevention of the hinge fracture in lateral closed-wedge distal femoral osteotomy (LCW-DFO) by means of a three-dimensional finite element analysis. MethodsThe three-dimensional numerical knee models with LCW-DFO were developed. To assess the mechanical efficacy of the positional screw and determine its optimal position and orientation, in total, 13 screwing methods were analyzed. In the first four methods, the screw was supported by the cortical bone only on the medial surface (mono-cortical). In the other 9 models, the screw was supported by both medial and lateral cortical bones (bi-cortical). Under 1000 N of vertical force and 5 Nm of rotational torques, the highest shear stress value around the medial hinge area was adopted as an analytical parameter. ResultsIn mono-cortical methods, with the cancellous bone support, all methods were able to reduce the highest stress value compared to the value without the screw, while the efficacy was rather inferior when the screw was in horizontal direction. Without the cancellous bone support, however, all methods were not able to reduce the stress value. In bi-cortical methods, with the cancellous bone support, almost all screw augmentation methods were able to reduce the stress value. When screwing from the medial to the lateral, it only gets worse when going extremely posterior. Without the cancellous bone support, all methods were able to reduce the stress value. ConclusionThe mechanical efficacy of the bi-cortical method was proven regardless of the quality of the local cancellous bone.

Prediction of Lumbar Pedicle Screw Loosening Using Hounsfield Units in Computed Tomography

One of the most common issues following pedicle screw fixation is pedicle screw loosening. There are, however, few trustworthy methods for predicting screw loosening. The goal of the current study was to identify an efficient technique for using preoperative CT scanning to predict screw loosening in older patients and to offer recommendations for preoperative surgical planning. The current analysis included retrospectively all patients who underwent lumbar pedicle screw fixation for degenerative lumbar diseases in our department between January 2015 and January 2022. Hounsfield units were used to assess each vertebra's attenuation in a CT scan (HU). Postoperative X-ray testing identified screw loosening. Using IBMSPSS 24.00 software, one-way analysis of variance (ANOVA) and receiver operating characteristic (ROC) curve analysis were performed. Over a mean follow-up period of 28.4±11.5 (range 12-44 months) months, screw loosening was noted in 53 of 242 patients (136 male and 106 female, average age 58.7±7.3 years). Gender, BMI, smoking habits, and whether or not a patient had diabetes or spondylolisthesis were not shown to be significantly different among the patients (P>0.05). The difference between the average lumbar vertebral HU values in the screw-loosening group and the control group was significant (P<0.01) at 120.3±31.5HU and 138.6±37.6HU, respectively. The average HU value of L1-L4 exhibited an area under the curve (AUC) of 0.691 (95% CI: 0.614-0.784), according to ROC curve analysis. A HU cut-off value of 122 HU is a likely cut-off point to predict screw loosening with a sensitivity of 70% and a specificity of 58%. The use of screw augmentation techniques can be decided using a prospective CT scan HU value-based prediction. An independent risk factor for screw loosening in an instrumented lumbar vertebra is a cutoff L1-L5 average HU value of 122 HU.

Pedicle screw augmentation in posterior constructs of the thoracolumbar spine: How many pedicle screws should be augmented?

BackgroundsTo evaluate the effects of different pedicle screw augmentation strategies on screw loosening and adjacent segment collapse at the proximal end of long-segment instrumentation. MethodsEighteen osteoporotic (9 male, 9 female donors; mean age: 74.7 ± 10.9 [SD] years) thoracolumbar multi-segmental motion segments (Th11 – L1) were assigned as follows: control, one-level augmented screws (marginally), and two-level augmented screws (fully augmented) groups (3 × 6). Pedicle screw placement was performed in Th12 and L1. Cyclic loading in flexion started with 100–500 N (4 Hz) and was increased by 5 N every 500 cycles. Standardized lateral fluoroscopy images with 7.5 Nm loading were obtained periodically during loading. The global alignment angle was measured to evaluate the overall alignment and proximal junctional kyphosis. The intra-instrumental angle was used to evaluate screw fixation. FindingsConsidering screw fixation as a failure criterion, the failure loads of the control (683 N), and marginally (858 N) and fully augmented (1050 N) constructs were significantly different (ANOVA p = 0.032).Taking the overall specimen alignment as failure criteria, failure loads of the three groups (control 933 ± 271.4 N, marginally 858 N ± 196 N, and full 933 ± 246.3 N were in the same range and did not show any significance (p = 0.825). InterpretationGlobal failure loads were comparable among the three groups and unchanged with augmentation because the adjacent segment and not the instrumentation failed first. Augmentation of all screws showed significant improved in screw anchorage.

Surgical Site Infection After Polymethyl Methacrylate Pedicle Screw Augmentation in Osteoporotic Spinal Vertebrae: A Series of 537 Cases.

Retrospective observational study of prospectively collected outcomes. The use of transpedicular screws augmented with polymethyl methacrylate (PMMA) is an alternative for patients with osteoporotic vertebrae. To investigate whether using PMMA-augmented screws in patients undergoing elective instrumented spinal fusion (ISF) is correlated with an increased risk of infection and the long-term survival of these spinal implants after surgical site infection (SSI). We studied 537 consecutive patients who underwent ISF at some point within a 9-year period, involving a total of 2930 PMMA-augmented screws. Patients were classified into groups: (1) those whose infection was cured with irrigation, surgical debridement, and antibiotic treatment; (2) those whose infection was cured by hardware removal or replacement; and (3) those in whom treatment failed. Twenty eight of the 537 patients (5.2%) developed SSI after ISF. An SSI developed after primary surgery in 19 patients (4.6%) and after revision surgery in 9 (7.25%). Eleven patients (39.3%) were infected with gram-positive bacteria, 7 (25%) with gram-negative bacteria, and 10 (35.7%) with multiple pathogens. By 2 years after surgery, infection had been cured in 23 patients (82.15%). Although there were no statistically significant differences in infection incidence between preoperative diagnoses (P = 0.178), the need to remove hardware for infection control was almost 80% lower in patients with degenerative disease. All screws were safely explanted while vertebral integrity was maintained. PMMA was not removed, and no recementing was done for new screws. The success rate for treatment of deep infection after cemented spinal arthrodesis is high. Infection rate findings and the most commonly found pathogens do not differ between cemented and noncemented fusion. It does not appear that the use of PMMA in cementing vertebrae plays a pivotal role in the development of SSIs.

A Retrospective Evaluation and Review of Radiographic Outcomes for Anterior Cervical Discectomy and Fusion (ACDF) Procedures: Northern Ireland's Experience.

Introduction Anterior Cervical Discectomy and Fusion (ACDF) is the gold standard treatment for symptomatic cervical spondylosis refractory to analgesic medical management. Currently, there are numerous approaches and devices used; however, there is no single implant that is preferred for this procedure. The aim of this study is to evaluate the radiological outcomes of ACDF procedures performed in the regional spinal surgery centre in Northern Ireland. The results of this study will aid surgical decision-making, specifically with regard to the choice of implant. The implants that will be assessed in this study are the stand-alonepolyetheretherketone (PEEK)cage (Cage) and the Zero-profile augmented screw implant (Z-P). Methods A total of 420 ACDF cases were reviewed retrospectively. Following exclusion and inclusion criteria, 233 cases were reviewed. In the Z-P group, there were 117 patients, with 116 in the Cage group. Radiographic assessment was carried out at the pre-operative stage, day one post-operation, and follow-up (> three months). Measured parameters included segmental disc height, segmental Cobb angle, and spondylolisthesis displacement distance. Results Patient characteristic features showed no significant difference between the two groups (p>0.05) and no significant difference in mean follow-up time (p=0.146). The Z-P implant was superior in increasing and maintaining disc height post-operatively (+0.4±0.94mm, 5.20±0.66mm) compared to the Cage (+0.1±1.00mm, 4.40±0.95mm) (p<0.001). Z-P was also more successful in restoring and maintaining cervical lordosis in comparison to the Cage group, as it had a significantly smaller kyphosis incidence (0.85% vs. 34.5%) at follow-up (p<0.001). Conclusions Results of this study show a more advantageous outcome in the Zero-profile group as it restores and maintains both disc height and cervical lordosis; it is also more successful in treating spondylolisthesis. This study advocates cautious endorsement of the use of the Zero-profile implant in ACDF procedures for symptomatic cervical disc disease.

Is implant choice associated with fixation strength for displaced radial neck fracture: a network meta-analysis of biomechanical studies

The multitude of fixation options for radial neck fractures, such as pins, screws, biodegradable pins and screws, locking plates, and blade plates, has led to a lack of consensus on the optimal implant choice and associated biomechanical properties. This study aims to evaluate the biomechanical strength of various fixation constructs in axial, sagittal, and torsional loading directions. We included biomechanical studies comparing different interventions, such as cross/parallel screws, nonlocking plates with or without augmented screws, fixed angle devices (T or anatomic locking plates or blade plates), and cross pins. A systematic search of MEDLINE (Ovid), Embase, Scopus, and CINAHL EBSCO databases was conducted on September 26th, 2022. Data extraction was carried out by one author and verified by another. A network meta-analysis (NMA) was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Primary outcomes encompassed axial, bending, and torsional stiffness, while the secondary outcome was bending load to failure. Effect sizes were calculated for continuous outcomes, and relative treatment ranking was measured using the surface under the cumulative ranking curve (SUCRA). Our analysis encompassed eight studies, incorporating 172 specimens. The findings indicated that fixed angle constructs, specifically the anatomic locking plate, demonstrated superior axial stiffness (mean difference [MD]: 23.59 N/mm; 95% CI 8.12–39.06) in comparison to the cross screw. Additionally, the blade plate construct excelled in bending stiffness (MD: 32.37 N/mm; 95% CI − 47.37 to 112.11) relative to the cross screw construct, while the cross-screw construct proved to be the most robust in terms of bending load failure. The parallel screw construct performed optimally in torsional stiffness (MD: 139.39 Nm/degree; 95% CI 0.79–277.98) when compared to the cross screw construct. Lastly, the nonlocking plate, locking T plate, and cross-pin constructs were found to be inferior in most respects to alternative interventions. The NMA indicated that fixed angle devices (blade plate and anatomic locking plate) and screw fixations may exhibit enhanced biomechanical strength in axial and bending directions, whereas cross screws demonstrated reduced torsional stability in comparison to parallel screws. It is imperative for clinicians to consider the application of these findings in constraining forces across various directions during early range of motion exercises, taking into account the distinct biomechanical properties of the respective implants.

PMMA Teeth-Pedicle Screw Spacers in Revision Spinal Surgery: A Technical Note

BACKGROUND Pedicle screw instrumentation was first described by Boucher in 1959 and subsequently popularised by Camille et al. in 1963. It has since become the most prevalent spinal fixation technique with indications for pedicle screw and rod constructs including congenital disease, trauma, infection, and spinal deformity including scoliosis. Initially used in lumbar spine surgery, the use of pedicle screws has since been extended to the thoracic spine where, because of the narrow pedicle corridor and proximity of critical structures, there is less margin for error in screw placement.1 Pedicle screw misplacement has been described in up to 40% of lumbar spine cases and up to 55% in thoracic spine cases.2 Complications associated with pedicle screw placement include damage to spinal cord, neural elements, nerve roots, pedicle fractures, wall cut out, and difficulty fitting instrumentation to the pedicle. Pedicle screw placement techniques can be grossly divided into freehand and image-guided techniques, with freehand techniques including drill assisted and pedicle gearshift (probe) methods while image-guided techniques incorporate fluoroscopic assisted, navigation assisted and robotic-assisted means. Pedicle screw placement into previously fused spines can be challenging with vital anatomic landmarks altered or obscured by the fusion mass.3 PMMA (Polymethyl methacrylate) was first introduced by Charnley in 1960 for cemented total hip arthroplasty. In spine surgery, PMMA has been used in numerous forms including kyphoplasty, disk substitution, and pedicle screw augmentation. In 1972 Bucholz and colleagues began combining PMMA with antibiotics to achieve high local antibiotic concentration in the setting of osteomyelitis; as such PMMA antibiotic loaded spacers have been well described in revision arthroplasty. Staged revision spinal surgery has been advocated by some authors in the setting of deep infection.4 Our senior author has noted that identification of pedicle screw tracts during second stage surgery can be challenging. Rationale We describe a novel surgical technique for the use of PMMA Teeth in the setting of staged revision spinal surgery to maintain the patency of pedicle screw tracts, permitting prompt identification on proceeding surgery stages and achieving local antibiotic delivery when necessary. Surgical Technique A standard posterior approach to the spine is performed identifying the in situ instrumentation. After removal of the in situ spinal rods and pedicle screws, the pedicle screw tracts are examined evaluating the medial, lateral, superior, and inferior walls of the tract. Residual fibrous tissue is debrided. A standard mix of Palacos R cement (Heraeus Medical, Newbury, UK) with the addition of 2 g vancomycin is performed. The PMMA teeth are subsequently fashioned from the Palacos R cement (Fig. 1). Similar to the technique described by Tsung et al.5 in revision hip arthroplasty, the principle for fixation is that of macroscopic fit as opposed to microscopic interlock of the cement; therefore, the PMMA teeth are inserted once the cement has cured.FIGURE 1: PMMA Teeth.PMMA indicates Polymethyl methacrylate.Expected Outcomes The PMMA teeth technique can assist the spinal surgeon in identifying the pedicle screw tract promptly and safely in staged revision spinal surgery with the added benefit of local antibiotic delivery. Complications Potential complications include PMMA Teeth fracture in situ, however, given the PMMA Teeth are inserted once the cement has cured, removal should be uncomplicated. DISCUSSION & CONCLUSION The incidence of revision spinal fusion has a reported range of 8 to 45%, with the revision rate increasing with follow-up; 21% of patients undergoing revision spinal surgery will require further spinal surgery.6 The rate of pedicle screw perforation has been reported to be as high as 28%, and 19% with a perforation greater than 2mm. This poses a significant challenge with considerable potential for pedicle screws to be misplaced in the revision spinal surgery setting.

Is human bone matrix a sufficient augmentation method revising loosened pedicle screws in osteoporotic bone? – A biomechanical evaluation of primary stability

IntroductionDespite good screw anchorage and safe screw trajectory, screw loosening occurs in several cases, especially in osteoporotic individuals. The aim of this biomechanical analysis was to evaluate the primary stability of revision screw placement in individuals with reduced bone quality. Therefore, revision via enlarged diameter screws was compared to the use of human bone matrix as augmentation to improve the bone stock and screw coverage. Methods11 lumbar vertebral bodies from cadaveric specimens with a mean age of 85.7 years (± 12.0 years) at death were used. 6.5 mm diameter pedicle screws were inserted in both pedicles and hereafter loosened using a fatigue protocol. Screws were revised inserting a larger diameter screw (8.5 mm) in one pedicle and a same diameter screw with human bone matrix augmentation in the other pedicle. The previous loosening protocol was then reapplied, comparing maximum load and cycles to failure between both revision techniques. Insertional torque was continuously measured during insertion of both revision screws. FindingsThe number of cycles and the maximum load until failure were significantly greater in enlarged diameter screws than in augmented screws. The enlarged screws' insertional torque was also significantly higher than of the augmented screws. InterpretationHuman bone matrix augmentation does not reach the same ad-hoc fixation strength as enlarging the screw's diameter by 2 mm and is therefore biomechanically inferior. Regarding the immediate stability, a thicker screw should therefore be prioritised.