Compressive fatigue properties of commercially available standard and low-modulus acrylic bone cements intended for vertebroplasty

Advancements in poly(methyl Methacrylate) bone cement for enhanced osteoconductivity and mechanical properties in vertebroplasty: A comprehensive review

The evolution of polymethyl methacrylate (PMMA) based bone cement (BC) from plexiglass to a biomaterial has revolutionized the joint and vertebral arthroplasties field. This widely used grouting material possesses exceptional properties for medical applications, including excellent biocompatibility, impressive mechanical strength, and favorable handling characteristics. PMMA-based BC is preferred in challenging conditions such as osteoporotic vertebral compression fractures, scoliosis, vertebral hemangiomas, spinal metastases, and myelomas, where it is crucial in withstanding stress. This review aims to comprehensively analyze the available reports and guide further research toward enhanced formulations of vertebral BC, focusing on its osteoconductive and mechanical properties. Furthermore, the review emphasizes the significant impact of BC's mechanical properties and osteoconductivity on the success and longevity of vertebroplasty procedures.

Implantable drug delivery systems for the treatment of osteomyelitis

Osteomyelitis is an infection of the bone tissue and bone marrow which is becoming increasingly difficult to treat due to the infection causing pathogens associated. Staphylococcus aureus is one of the main bacteria that causes this infection, which has a broad spectrum of antibiotic resistance making it extremely difficult to treat. Conventional metal implants used in orthopaedic applications often have the drawback of implant induced osteomyelitis as well as the requirement of a second surgery to remove the implant once it is no longer required. Recently, attention has been focused on the design and fabrication of biodegradable implants for the treatment of bone infection. The main benefit of biodegradable implants over polymethylmethacrylate (PMMA) based non-degradable systems is that they do not require a second surgery for removal and so making degradable implants safer and easier to use. The main purpose of a biodegradable implant is to provide the necessary support and conductivity to allow the bone to regenerate whilst themselves degrading at a rate that is compatible with the rate of formation of new bone. They must be highly biocompatible to ensure there is no inflammation or irritation within the surrounding tissue. During this review, the latest research into antibiotic loaded biodegradable implants will be explored. Their benefits and drawbacks will be compared with those non-degradable PMMA beads, which is the stable material used within antibiotic loaded implants. Biodegradable implants most frequently used are based on biodegradable natural and synthetic polymers. Implants can take the form of many different structures; the most commonly fabricated structure is a scaffold. Other structures that will be explored within this review are hydrogels, nanoparticles and surface coatings, all with their own benefits/drawbacks.

A Three-Dimensional Cement Quantification Method for Decision Prediction of Vertebral Recompression after Vertebroplasty

Objective

Proposing parameters to quantify cement distribution and increasing accuracy for decision prediction of vertebroplasty postoperative complication.

Methods

Finite element analysis was used to biomechanically assess vertebral mechanics (n = 51) after percutaneous vertebroplasty (PVP) or kyphoplasty (PKP). The vertebral space was divided into 27 portions. The numbers of cement occupied portions and numbers of cement-endplate contact portions were defined as overall distribution number (oDN) and overall endplate contact number (oEP), respectively. And cement distribution was parametrized by oDN and oEP. The determination coefficients of vertebral mechanics and parameters (R 2) can validate the correlation of proposed parameters with vertebral mechanics.

Results

oDN and oEP were mainly correlated with failure load (R 2 = 0.729) and stiffness (R 2 = 0.684), respectively. oDN, oEP, failure load, and stiffness had obvious difference between the PVP group and the PKP group (P < 0.05). The regional endplate contact number in the front column is most correlated with vertebral stiffness (R 2 = 0.59) among all regional parameters. Cement volume and volume fraction are not dominant factors of vertebral augmentation, and they are not suitable for postoperative fracture risk prediction.

Conclusions

Proposed parameters with high correlation on vertebral mechanics are promising for clinical utility. The oDN and oEP can strongly affect augmented vertebral mechanics thus is suitable for postoperative fracture risk prediction. The parameters are beneficial for decision-making process of revision surgery necessity. Parametrized methods are also favorable for surgeon's preoperative planning. The methods can be inspirational for clinical image recognition development and auxiliary diagnosis.

[Biomechanical study of polymethyl methacrylate bone cement and allogeneic bone for strengthening sheep vertebrae]

Objective

To investigate the feasibility and mechanical properties of polymethyl methacrylate (PMMA) bone cement and allogeneic bone mixture to strengthen sheep vertebrae with osteoporotic compression fracture.

Methods

A total of 75 lumbar vertebrae (L ₁-L ₅) of adult goats was harvested to prepare the osteoporotic vertebral body model by decalcification. The volume of vertebral body and the weight and bone density before and after decalcification were measured. And the failure strength, failure displacement, and stiffness were tested by using a mechanical tester. Then the vertebral compression fracture models were prepared and divided into 3 groups ( n=25). The vertebral bodies were injected with allogeneic bone in group A, PMMA bone cement in group B, and mixture of allogeneic bone and PMMA bone cement in a ratio of 1∶1 in group C. After CT observation of the implant distribution in the vertebral body, the failure strength, failure displacement, and stiffness of the vertebral body were measured again.

Results

There was no significant difference in weight, bone density, and volume of vertebral bodies before decalcification between groups ( P>0.05). After decalcification, there was no significant difference in bone density, decreasing rate, and weight between groups ( P>0.05). There were significant differences in vertebral body weight and bone mineral density between pre- and post-decalcification in 3 groups ( P<0.05). CT showed that the implants in each group were evenly distributed in the vertebral body with no leakage. Before fracture, the differences in vertebral body failure strength, failure displacement, and stiffness between groups were not significant ( P>0.05). After augmentation, the failure displacement of group A was significantly greater than that of groups B and C, and the failure strength and stiffness were less than those of groups B and C, the failure displacement of group C was greater than that of group B, and the failure strength and stiffness were less than those of group B, the differences between groups were significant ( P<0.05). Except for the failure strength of group A ( P>0.05), the differences in the failure strength, failure displacement, and stiffness before fracture and after augmentation in the other groups were significant ( P<0.05).

Conclusion

The mixture of allogeneic bone and PMMA bone cement in a ratio of 1∶1 can improve the strength of the vertebral body of sheep osteoporotic compression fractures and restore the initial stiffness of the vertebral body. It has good mechanical properties and can be used as one of the filling materials in percutaneous vertebroplasty.

Long-term mechanical properties of a novel low-modulus bone cement for the treatment of osteoporotic vertebral compression fractures

In spite of the success of vertebroplasty (VP) and balloon kyphoplasty (BKP), which are widely used for stabilizing painful vertebral compression fractures, concerns have been raised about use of poly(methyl methacrylate) (PMMA) bone cements for these procedures since the high compressive modulus of elasticity (E) of the cement is thought to be one of the causes of the higher number of adjacent-level vertebral fractures. Therefore, bone cements with E comparable to that of cancellous bone have been proposed. While the quasi-static compressive properties of these so-called "low-modulus" cements have been widely studied, their fatigue performance remains underassessed. The purpose of the present study was to critically compare a commercial bone cement (control cement) and its low-modulus counterpart on the basis of quasi-static compressive strength (CS), E, fatigue limit under compression-compression loading, and release of methyl methacrylate (MMA). At 24 h, mean CS and E of the low-modulus material were 72% and 77% lower than those of the control cement, whereas, at 4 weeks, mean CS and E were 60% and 54% lower, respectively. The fatigue limit of the control cement was estimated to be 43-45 MPa compared to 3-5 MPa for the low-modulus cement. The low-modulus cement showed an initial burst release of MMA after 24 h followed by a plateau, similar to many other commercially available cements, whereas the control cement showed a much lower, stable release from day 1 and up to 1 week. The low-modulus cement may be a promising alternative to currently available PMMA bone cements, with the potential for reducing the incidence of adjacent fractures following VP/BKP.