Bone cement

Bone cement refers to a non-biological material used in various orthopedic and dental surgeries to anchor implants to bone. The most common type of bone cement is polymethyl methacrylate (PMMA), which has been widely used in clinical settings for decades. Bone cement acts as a grout, not as an adhesive, to fill the space between the bone and the implant, providing immediate fixation of the implant.

Composition

Bone cement primarily consists of a powder and a liquid. The powder is predominantly polymethyl methacrylate (PMMA), and may also contain a radio-opaque agent to allow the surgeon to visualize the cement during and after surgery using X-ray imaging. The liquid is mainly methyl methacrylate (MMA) monomer. When mixed, the powder and liquid undergo a polymerization reaction, transforming into a solid material.

Types

There are two main types of bone cement:

• Antibiotic-loaded bone cement, which is used to prevent or treat infections in the surgical site. Antibiotics such as gentamicin or vancomycin are commonly mixed with the PMMA powder.
• Non-antibiotic bone cement, which does not contain any antibiotics.

Applications

Bone cement is used in various orthopedic procedures, including:

• Total hip arthroplasty (THA)
• Total knee arthroplasty (TKA)
• Vertebroplasty and Kyphoplasty
• Fixation of certain types of dental implants

Mechanism of Action

The primary function of bone cement is to distribute loads from the implant to the bone, reducing stress on the bone and preventing implant loosening. The cement fills the irregular space between the bone and the implant, creating a tight fit. Bone cement does not chemically bond to bone or implants; rather, it relies on mechanical interlocking.

Complications

While bone cement is widely used and generally safe, there are potential complications, including:

• Bone cement implantation syndrome (BCIS), a rare but serious condition that can occur during cemented orthopedic surgeries, leading to cardiovascular instability.
• Allergic reactions to the components of bone cement.
• Infection, particularly if antibiotic-loaded cement is not used in cases where there is a high risk of infection.

Recent Developments

Research into bone cement has focused on improving its mechanical properties, reducing the risk of complications, and enhancing its antibiotic delivery capabilities. New formulations and additives are being explored to address these challenges.

See Also

• Orthopedic surgery
• Dental surgery
• Polymethyl methacrylate (PMMA)
• Implant (medicine)