Risk Factors for Pulmonary Cement Embolism (PCE) After Polymethylmethacrylate Augmentation: Analysis of 32 PCE Cases

Objective: Pulmonary cement embolism (PCE) is an underestimated but potentially fatal complication after cement augmentation. Although the treatment and follow-up of PCE have been reported in the literature, the risk factors for PCE are so far less investigated. This study aims to identify the preoperative and intraoperative risk factors for the development of PCE.Methods: A total of 1,373 patients treated with the polymethylmethacrylate (PMMA) augmentation technique were retrospectively included. Patients with PCE were divided into vertebral augmentation group and screw augmentation group. Possible risk factors were collected as follows: age, sex, bone mineral density, body mass index, diagnosis, comorbidity, surgical procedure, type of screw, augmented level, number of augmented vertebrae, fracture severity, presence of intravertebral cleft, cement volume, marked leakage in the paravertebral venous plexus, and periods of surgery. Binary logistic regression analyses were used to analyze independent risk factors for PCE.Results: PCE was identified in 32 patients, with an incidence rate of 2.33% (32 of 1,373). For patients who had undergone vertebral augmentation, marked leakage in the paravertebral venous plexus (odds ratio [OR], 0.012; 95% confidence interval [CI], 0.001–0.103; p = 0.000) and previous surgery (OR, 0.161; 95% CI, 0.042–0.610; p = 0.007) were independent risk factors for PCE. Regarding patients who had undergone screw augmentation, the marked leakage in the paravertebral venous plexus (OR, 0.042; 95% CI, 0.005–0.373; p = 0.004) was the main risk factor.Conclusion: Marked leakage in the paravertebral venous plexus and previous surgery were significant risk factors related to PCE. Paravertebral leakage and operator experience should be concerned when performing PMMA augmentation.

Novel Biodegradable Composite of Calcium Phosphate Cement and the Collagen I Mimetic P-15 for Pedicle Screw Augmentation in Osteoporotic Bone

Osteoporotic vertebral fractures often necessitate fusion surgery, with high rates of implant failure. We present a novel bioactive composite of calcium phosphate cement (CPC) and the collagen I mimetic P-15 for pedicle screw augmentation in osteoporotic bone. Methods involved expression analysis of osteogenesis-related genes during osteoblastic differentiation by RT-PCR and immunostaining of osteopontin and Ca2+ deposits. Untreated and decalcified sheep vertebrae were utilized for linear pullout testing of pedicle screws. Bone mineral density (BMD) was measured using dual-energy X-ray absorptiometry (DEXA). Expression of ALPI II (p < 0.0001), osteopontin (p < 0.0001), RUNX2 (p < 0.0001), and osteocalcin (p < 0.0001) was upregulated after co-culture of MSC with CPC-P-15. BMD was decreased by 28.75% ± 2.6%. Pullout loads in untreated vertebrae were 1405 ± 6 N (p < 0.001) without augmentation, 2010 ± 168 N (p < 0.0001) after augmentation with CPC-P-15, and 2112 ± 98 N (p < 0.0001) with PMMA. In decalcified vertebrae, pullout loads were 828 ± 66 N (p < 0.0001) without augmentation, 1324 ± 712 N (p = 0.04) with PMMA, and 1252 ± 131 N (p < 0.0078) with CPC-P-15. CPC-P-15 induces osteoblastic differentiation of human MES and improves pullout resistance of pedicle screws in osteoporotic and non-osteoporotic bone.

Treatment of Severe Rigid Posttraumatic Equinus Deformity With Gradual Deformity Correction and Arthroscopic Ankle Arthrodesis

Background: Posttraumatic ankle equinus is associated with rigid deformity, poor skin condition, and multiple prior surgeries. Open acute correction has been described using osteotomies, talectomy, and arthrodesis, but concerns exist about skin complications, neurologic alterations, secondary limb discrepancy, and bone loss. Gradual correction using a multiplanar ring fixator and arthroscopic ankle arthrodesis (AAA) may decrease these complications. Methods: We retrospectively reviewed patients undergoing correction of posttraumatic rigid equinus with at least 1 year of follow-up after frame removal. The procedure consisted of percutaneous Achilles lengthening, gradual equinus correction using a multiplanar ring fixator, and AAA retaining the fixator in compression with screw augmentation. Frame removal depended on signs of union on the computed tomography scan. Visual analog scale (VAS) and Foot Function Index (FFI) scores were assessed as well as preoperative and postoperative x-rays. Complications were noted throughout the follow-up period. Results: Five patients were treated with a mean age of 35 years and mean follow-up of 31 months. Deformities were gradually corrected into a plantigrade foot over an average duration of 6 weeks. Union was achieved in all patients with a mean time of an additional 25 weeks, for a mean total frame time of 31 weeks. The mean preoperative tibiotalar angle was 151 degrees and was corrected to 115 degrees. FFI score improved from a mean of 87 to 24 and VAS from 8 to 2. Conclusion: Posttraumatic rigid equinus can be treated effectively using gradual correction followed by integrated AAA in a safe and reproducible manner. Patients in this series had excellent functional, radiological, and satisfaction results. Level of Evidence: Level IV, retrospective case series.

Removal of cement-augmented screws in distal femoral fractures and the effect of retained screws and cement on total knee arthroplasty: a biomechanical investigation

Background Given the increasing number of osteoporotic fractures of the distal femur, screw augmentation with bone cement is an option to enhance implant anchorage. However, in implant removal or revision surgeries, the cement cannot be removed from the distal femur without an extended surgical procedure. Therefore, the aims of this study were to investigate (1) whether cement augmentation has any influence on screw removal and removal torque, and (2) whether the implantation of a femoral component of a knee arthroplasty and its initial interface stability are affected by the remaining screws/cement. Material and methods Eight pairs of fresh-frozen human female cadaveric distal femurs (mean age, 86 years) with a simulated AO/OTA 33 A3 fracture were randomized in paired fashion to two groups and fixed with a distal femoral locking plate using cannulated perforated locking screws. Screw augmentation with bone cement was performed in one of the groups, while the other group received no screw augmentation. Following biomechanical testing until failure (results published separately), the screws were removed and the removal torque was measured. A femoral component of a knee arthroplasty was then implanted, and pull-out tests were performed after cement curing. Interference from broken screws/cement was assessed, and the maximum pull-out force was measured. Results The mean screw removal torque was not significantly different between the augmented (4.9 Nm, SD 0.9) and nonaugmented (4.6 Nm, SD 1.3, p = 0.65) screw groups. However, there were significantly more broken screws in in the augmented screw group (17 versus 9; p < 0.001). There was no significant difference in the pull-out force of the femoral component between the augmented (2625 N, SD 603) and nonaugmented (2653 N, SD 542, p = 0.94) screw groups. Conclusion The screw removal torque during implant removal surgery does not significantly differ between augmented and nonaugmented screws. In the augmented screw group, significantly more screws failed. To overcome this, the use of solid screws in holes B, C, and G can be considered. Additionally, it is possible to implant a femoral component for knee arthroplasty that retains the initial anchorage and does not suffer from interference with broken screws and/or residual cement. Level of Evidence 5

Primary Tritanium acetabular components have increased rates of radiolucency associated with inferior clinical outcomes at short-term follow-up

Introduction: Cementless fixation is the standard for acetabular fixation in primary total hip arthroplasty (THA). There are various surface finishes thought to improve osteointegration, although literature regarding the long-term survival of some of these surfaces is limited. Regardless of design, primary stability is essential to allow for osteointegration. Previous studies have suggested an increased rate of radiolucency and compromised short-term functional outcomes using the Tritanium primary acetabular component (Stryker, Mahwah, NJ). The purpose of this study was to compare the primary Tritanium acetabular component to another contemporary acetabular component as a control group with an established clinical record. Methods: 444 consecutive, primary THAs performed by a single surgeon from 2008 to 2012 were reviewed. Patients were included if they had a minimum 1-year follow-up. Implant survivorship and modified Harris Hip Scores (mHHS) were recorded for all patients at final follow-up. Radiographs were evaluated by 2 surgeons at 6 weeks, 1 year, and the most recent follow-up for evidence of radiolucency and migration. Components were considered to have evidence of radiographic lucency if they had radiolucency in 2 or more DeLee zones. Results: 198 patients met criteria for inclusion (96 Pinnacle, 102 Tritanium). Average follow-up was 28 (12–72) months. At final follow-up 6.2% of the Pinnacle cups and 29.4% of the Tritanium cups had radiographic evidence of loosening ( p < 0.01). The average mHHS for the Tritanium group was 83.1, and 88.4 for the Pinnacle group ( p < 0.01). Radiographic evidence of loosening also correlated with a lower mHHS: 75.5 versus 86.4 ( p < 0.01). In patients that received Tritanium cups without screw fixation 44.6% showed radiographic evidence of loosening versus 8% that received screw fixation ( p < 0.01). In total, 6 patients in the Tritanium group required revision for aseptic loosening of the acetabular component. Conclusions: The 30% rate of radiographic loosening in the Tritanium group was significantly higher than the Pinnacle group and correlated with an inferior clinical outcome. Interestingly the use of screw augmentation was protective against radiographic evidence of loosening. This suggests that the Tritanium component may be prone to fibrous in-growth because of inadequate primary stability.

Comparable results using 2.0-mm vs. 3.5-mm screw augmentation in midshaft clavicle fractures: a 10-year experience

Purpose Absence of cortical alignment in wedge-shaped and multifragmentary fractures (Fx) results in decreased fixation stability. The aim of this study was to compare the outcome using 2.0- vs. 3.5-mm screws for open reduction and internal fixation (ORIF) in dislocated, wedge-shaped or fragmentary midshaft clavicle fractures. Materials and methods Patients suffering from AO/OTA 15 2.A-C midshaft clavicle fractures were operatively treated between 2008 and 2018. 2.0- or 3.5-mm cortical screws were used to restore anatomic alignment in dislocated, wedge-shaped and fragmentary clavicle fractures. Data of radiologic outcome were collected until fracture consolidation was identified. Results 80 consecutive patients with a mean age of 44.5 ± 16.3 years, who were operatively treated for dislocated midshaft clavicle fractures were enrolled. 40 patients were treated using 2.0-mm and 40 patients using routine 3.5-mm cortical screws, respectively. Time to fracture consolidation was 12.8 ± 7.8 months. No mal- or non-unions occurred during routine follow-up until 18 months postoperatively. Conclusion Restoring anatomic alignment in wedge or fragmentary clavicle fractures can ultimately be addressed using cortical screw augmentation. Both groups showed comparable results with respect to fracture reduction, fixation and stability as well as time to consolidation of the fracture, while the 2.0-mm screw diameter was associated with easier handling of small Fx fragments.

Functional Properties of Low-Modulus PMMA Bone Cements Containing Linoleic Acid

Acrylic bone cements modified with linoleic acid are a promising low-modulus alternative to traditional high-modulus bone cements. However, several key properties remain unexplored, including the effect of autoclave sterilization and the potential use of low-modulus cements in other applications than vertebral augmentation. In this work, we evaluate the effect of sterilization on the structure and stability of linoleic acid, as well as in the handling properties, glass transition temperature, mechanical properties, and screw augmentation potential of low-modulus cement containing the fatty acid. Neither 1H NMR nor SFC-MS/MS analysis showed any detectable differences in autoclaved linoleic acid compared to fresh one. The peak polymerization temperature of the low-modulus cement was much lower (28–30 °C) than that of the high-modulus cement (67 °C), whereas the setting time remained comparable (20–25 min). The Tg of the low-modulus cement was lower (75–78 °C) than that of the high-stiffness cement (103 °C). It was shown that sterilization of linoleic acid by autoclaving did not significantly affect the functional properties of low-modulus PMMA bone cement, making the component suitable for sterile production. Ultimately, the low-modulus cement exhibited handling and mechanical properties that more closely match those of osteoporotic vertebral bone with a screw holding capacity of under 2000 N, making it a promising alternative for use in combination with orthopedic hardware in applications where high-stiffness augmentation materials can result in undesired effects.