Types of Bone Cement in Orthopedics - A Comprehensive Overview

What Is Bone Cement?

Bone cement is largely utilized in orthopedic and trauma surgery to secure an implant to the bone. To create a little space between the bone and the implant, it acts as a space filler. Despite being called "cement," bone cement lacks adhesive qualities and instead relies on the interlocking mechanism between the prosthesis and the uneven surfaces of the bone. Additionally, it is employed to patch up holes and fractures in bone.

Bone cement is frequently used in orthopedic surgery to fill bone gaps brought on by fractures or other diseases, as well as to secure prosthetic implants such as joint replacements. Bone cement can be categorized into three types, low, medium, and high viscosity.

• Low Viscosity: Because these cements have a lengthy liquid or mixing phase, the working phase is also very brief. Low-viscosity cement application hence necessitates rigorous adherence to application times.

• High Viscosity: This cement has a quick mixing time and quickly loses its stickiness. This lengthens the working phase and gives the surgeon more time to apply.

• The Ideal Viscosity: This will be high enough to prevent cement from combining with any blood, fat, or bony from the implantation location, yet low enough to penetrate the bone adequately.

What Is the Main Function and Quality of Bone Cement?

Bone cement's primary purpose is to efficiently transfer forces from the bone to the implant and vice versa for a sufficient period. It must be able to act as a cushion against the stresses affecting the bone since it fills the space between the bone and the prosthesis. If the tension placed on the bone and cement is too great, fatigue, breaks, or fractures may result. The following characteristics are some of the ones optimal bone cement should have:

• Handling simplicity and injectability.

• A lack of disintegration following contact with biological fluids, an almost neutral pH, and a mechanical strength that is suitable.

• Greater radiopacity.

• Non-toxicity.

• Biocompatible.

However, there are several restrictions on the bone cement that are routinely utilized today.

Polymethyl methacrylate (PMMA), an acrylic polymer, is one of the most frequently occurring substances in bone cement. Calcium phosphate (CPC), which is known to be biocompatible and bioresorbable, is present in other types of commercially available bone cement. As a result of its lesser mechanical strength than PMMA, it is more frequently used in surgery involving the jaw, face, and mouth. Glass polyalkenoate (ionomer) cement (GPC) is another type. Application areas for all three forms of bone cement include orthopedic and dentistry procedures.

What Are the Types of Bone Cements?

In orthopedics, there are two primary forms of bone cement:

Cement Made of Polymethyl Methacrylate (PMMA):

• The most used bone cement in orthopedics is PMMA cement.

• It is a two-part system made up of a liquid (monomer) and a powder (polymer).

• They can be injected into the bone after being combined to create a product that resembles dough.

• PMMA cement hardens quickly, giving implants almost instant fixation.

• It is renowned for its durability and mechanical strength.

• Long-term stability is dependent on mechanical interlock and the biological reaction of the bone because it does not directly connect with bone.

• If the heat generated during the curing of PMMA cement is not effectively controlled, it could potentially harm nearby tissues.

Cement Made With Calcium Phosphate:

• Calcium phosphate cements are bioactive and biocompatible materials and are used as an alternative to PMMA cement.

• They may be made of different calcium phosphate substances, such as tricalcium phosphate or hydroxyapatite.

• These cements have the benefit of being resorbable, which means that as time passes, natural bone tissue will progressively replace them.

• Cement made of calcium phosphate may encourage the incorporation of newly formed bone with the surrounding bone.

• They are frequently utilized in cases where long-term stability and prospective bone ingrowth are crucial, such as in specific types of fractures, treatments involving young patients, or in patients whose bone quality has deteriorated.

• In contrast to PMMA cement, they typically have lesser initial mechanical strength.

What Are the Adverse Effects of Bone Cement?

During cement insertion, hypotensive episodes and cardiac arrest have been documented. Pulmonary embolisms have been linked to the thorough cleaning of the bone and evacuation of bone marrow, and this risk is higher in patients with extremely osteoporotic bone and those who have been given a femoral neck fracture diagnosis. The insertion of bone cement and reaming of the marrow cavity may have comparable effects on mean arterial pressure. The cement should be digitally introduced after the marrow cavities have been evacuated. However, a paper claims that the early postoperative and perioperative phase is the only time when using cemented implants may provide a risk of death. If the patient has hypovolemia, the hypotensive effects of methyl methacrylate are amplified.

The following are the most typical side effects associated with acrylic bone cement:

• A transitory drop in blood pressure.

• Increased serum gamma-glutamyl-transpeptidase (GGTP) for up to 10 days following surgery.

• Thrombophlebitis (blood clots and inflammation in the veins).

• Loss of stability or movement of the prosthesis.

• Infection of a superficial or deep wound.

• Abnormalities in the short-term cardiac conduction.

• Heterotrophic production of new bone.

• Separation of the trochanters.

• Clinical manifestations of BCIS (bone cement implantation syndrome) include hypoxia, hypotension, cardiac arrhythmias, elevated pulmonary vascular resistance (PVR), and cardiac arrest. Although not exclusively, it is most frequently connected to hip arthroplasty.

• Hypoxemia (low oxygen level in blood).

• Cardiac erratic rhythm.

• Bronchitis.

• Negative tissue response.

• Hematuria.

• Dysuria.

• Fistula in the bladder.

• Neuropathy localized.

• Localized vascular occlusion and erosion.

• Temporary pain worsening brought on by the heat generated during polymerization.

• Delayed sciatic nerve entrapment as a result of bone cement being applied outside of its designated area of use.

• Ileal stricture and intestinal blockage that occur due to adhesions and the heat produced during cement polymerization.

Conclusion

As bone cement dries, shrinks, and then expands as a result of absorbing water, heat is produced. It does not remodel, and neither is osteoinductive nor osteoconductive. There is a chance of allergic reactions to cement components, and the monomer is hazardous. For all orthopedic surgeons, understanding bone cement is of utmost importance. The introduction of press-fit implants, which promote bone ingrowth, has somewhat reduced the usage of bone cement, even though it had previously been the gold standard in the field of joint replacement surgery. Recent research has focused on the toxicity, drawbacks, and inadequacies of bone cement. To enhance the quality of bone cement and eliminate or reduce any undesirable side effects, more research is required and is being done in the areas of nanoparticle additions, enhanced bone cement interface, and other developments.