What is orthopedic bone cement?

Bone cement is often made of acrylic and is used to hold implants in joint replacement surgery. Acrylic cement was used only for dental purposes in the past, but it was first used in joint replacement surgery in England in 1960. Bone cement is actually a stimulating substance called polymethyl-methacrylate. This polymer consists of the repetition of small and identical monomer molecules. Bone cement or orthopedic cement is a chemical compound that is used to connect bones or join joints together. These compounds are used in many orthopedic surgeries and are very useful in connecting new joints and bones to the relevant area.

Advantages of orthopedic bone cement

• These materials fill the empty spaces, so using them may cause a slight deviation during the operation, which is negligible.

• These orthopedic cements give more strength to the operated joint which makes it easier and faster for the healing of the patient.

• These materials provide lateral protection of the joint.

Disadvantages of orthopedic bone cement

• Sudden pressure drop for the patient
• Possible infections
• joint inflammation
• Needless to say, after joint surgeries, antibiotics are prescribed by the orthopedic surgeon.

Does bone cement show up on X-rays in case of a fracture?

In radiographic examinations of patients with hip prostheses, a radiolucent line may be identified in the main part of the cement, which indicates the place of fracture.

How many antibiotics are in bone cement?

In prophylactic situations, bone cement can be loaded with low doses of antibiotics (between 0.5 and 2 g of antibiotics and 40 g of PMMA) to prevent the effect on the mechanical properties of the cement.

How long does bone cement last?

This technique has been used for several years, and research has shown that, according to statistics, surgeries using implants containing orthopedic cement last ten to twenty years longer than other methods.

Types of bone cement

In general, there are four types of bone cement, two of which are polymer-based and the other two are ceramic-based:

– Acrylic cement based on polymethyl methacrylate (PMMA)

– Polypropylene Femorate (PPF) based cements

-Calcium phosphate cement (CPBCS)

– Glass ionomer cements (GIC)

Each of these four types of cement has different compositions and properties.

1- Acrylic cement or cement based on polymethyl methacrylate (PMMA)

PMMA bone cement is used for clinical applications and in order to ensure the stabilization of the implant used in the joint, in the replacement of hip and knee prostheses. Bone cements are generally made of polymethyl methacrylate (PMMA), which is called acrylic bone cement. This material self-polymerizes and consists of solid PMMA powder and liquid MMA monomer. After mixing, this cement hardens like building cement. The most important factor determining the properties of acrylic bone cement is the amount and size of pores. Large pores with a size of more than a few millimeters weaken the mechanical properties. In general, acrylic cements are used for non-metallic implants in orthopedics bone surgeries.

2- Polypropylene Femorate (PPF) based cements

Polypropylene Femorate is a non-linear, saturated polyester manufactured for different applications of orthopedic bone applications. Studies have shown that by crosslinking PPF, a cement is produced that has the ability to form bone and is degradable, biocompatible, and has sufficient compressive strength for orthopedic applications. Nowadays, these cements are mostly chosen for the treatment of skeletal defects in the body.

3- Calcium phosphate cements (CPBCS)

Calcium phosphate bone cement includes two liquid and solid phases, which are often a mixture of tetra calcium phosphate (TTCP) and anhydrous dicalcium phosphate (DCPA) or calcium phosphate dihydrate (DCPD) as the solid phase. As a result of mixing these compounds with water, hydroxyapatite is formed. One of the characteristics of this cement is the formation of hydroxyapatite during hardening, which increases the strength of the cement. Calcium phosphate cement has a pH close to 7 and contains only calcium phosphate, hence, it has high biocompatibility and bone formation ability. Calcium phosphate cements can be molded after mixing or while setting, or simply injected into bone defects.

4- Glass ionomer cement (GIC)

Glass ionomer cements are based on ceramics, which are often used in dentistry, but they also have applications in orthopedics. These cements are obtained by combining a concentrated polymer acid (polyacrylic acid) with degradable fluorine aluminosilicate. These cements create very good adhesion between metal and bone.

The operation of injecting bone cement into the lumbar vertebra

In this treatment method, at first, the patient should lie on his back in the specified place, then with the help of special imaging devices, the desired vertebra with damage is determined.

When the injury site is precisely determined, a spine specialist inserts a needle into the skin and goes inside the vertebrae. It may be necessary to take a sample at this time, in this case, a part of the vertebral bones is pulled towards the needle to remove the sample.

Then, if it is necessary specialist can open the body of the vertebra the balloon will be inserted into the body of the vertebra with great strength and a liquid will be injected into it (Kyphoplasty). The balloon inside the vertebra is inflated and leads to the opening of the fracture, doing this will provide the space needed for the cement.

After that, the balloon is deflated and a special needle is inserted. Here it is time to inject bone cement, of course, special cement is used and it is injected into the bead through the needle.

A few minutes after the injection, the cement inside the vertebra dries and strengthens the damaged vertebra. Sometimes it is necessary to use a prosthesis to repair the vertebra; In this case, it is necessary to perform open surgery.

When is vertebroplasty performed?

Vertebroplasty is considered:

For a painful osteoporotic fracture when the pain is not adequately controlled after 3 weeks with other treatment (analgesics, etc.).

For a painful benign vertebral tumor such as a hemangioma or giant cell tumor

Painful vertebrae caused by a malignant tumor, of course, this method is only for the treatment of pain, and other tumor-specific treatments should be considered.

To strengthen the vertebral body or pedicle along with a surgical procedure to treat the posterior (back) part of the vertebra

The main goal of this method is pain control. It may also prevent further collapse of the vertebra. Sometimes, kyphoplasty is used to increase the height of collapsed vertebrae.

Complications of cement injection in the spine

• Although the complication rate of lumbar cement injection is low, with most surgical procedures, serious side effects, some of which can be fatal, can occur, including:
• Heart attack, cardiac arrest (heart stops)
• Stroke and embolism (blood, fat).
• Other risks include infection; Leakage of bone cement into the muscle and tissue around the spinal cord and nerve damage, which in rare cases can cause paralysis. Leakage of bone cement into blood vessels leads to damage to blood vessels, lungs, or heart.
• Of course, don’t worry, we considered the worst-case scenario, the complications mentioned above may occur to 2% of people, if you do this procedure with an experienced doctor, you don’t have any kind of health problems, there will definitely be no complications.