Bone Cement Ppt Oluyor Galiba±u

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Transcript of Bone Cement Ppt Oluyor Galiba±u

Ersin KRAT December

Contents

History Fields of applications Components Polymerisations Clinical case Antibiotics Clinical studies Surgical procedurs

HISTORY

The story of modern cements began with Otto Rhms invention in the early 20th century of polymethyl methacrylate (PMMA), a solid material with good biocompatibility.

In the 1960s Sir John Charnley began using bone cement on numerous patients for the fixation of both the femur and acetabulum. Before the end of the decade, Buchholz came up with the idea of adding an antibiotic to the cement to decrease the incidence of infection.

The evolution of bone cement1902 1936 Animal studies on skull defects 1939 Human studies on skull defects 1940 1943 1949 1955 1959 1970 ~1990 2000 Buchholz used PMMA bone cement with gentamicin; E. Merck starts marketing bone cement. Focus on cementing technique in trade publications Polymerisation of PMMA becomes possible at room temperature Judet brothers developed hip implant with PMMA Filling of spinal defects (Idelberger) Sir John Charnley uses PMMA cement in hip replacement; femur and acetabulum implant is fixed by bone cement First synthesis of PMMA by O. Rhm First industrial production of PMMA

Bone Cement

Bone cements consist of two primary components: a powder consisting of copolymers based on the substance polymethyl methacrylate (PMMA), and a liquid monomer, methylmethacrylate (MMA). These two components are mixed at an approximate ratio of 2:1 to form a polymethyl methacrylate cement.

When the polymer powder and monomer liquid meet, the polymerization process starts. During polymerization of the monomer, the original polymer beads of the powder are bonded into a dough-like mass. The mass hardens approximately 715 minutes after the start of mixing, depending on temperature The polymerisation process can be divided into four different phases:

Processing times of bone cement

Polymerization depends on a.Room temperature b.Temperature of the bone cement components c.Prothesis temperature 1. Mixing phase Complete wetting of the powder with liquid ! This produces a homogeneous

2. Waiting phase Swelling of the paste material Slow polymerisation Increased viscosity, but paste still sticky

3. Working phase completion of the waiting phase essential!(ideal working viscosity) application into the femur(for manual application non-sticky,viscosity not too high))

4.Hardening phase Strength of the cement increases Polymerisation comes to a halt Duration of poymerisation dependent on .Room temperature, .Component temperature, .Prothesis temperature .Air humidity

Properties

During polymerization, cement properties critical for operating procedures, such as viscosity change, setting time, cement temperature, mechanical strength, shrinkage and residual monomer, are determined. These properties will influence cement handling, penetration and interaction with the prosthesis.

Viscosity

Mixing together the powder and the liquid components marks the start of the polymerization process. During the reaction, the cement viscosity increases, slowly at first, then later more rapidly. Clinical experience has shown that high viscosity cements produce better clinical results, as compared to low viscosity cements.

Viscosity affects the following:

Mixing behaviour Penetration into cancellous bone Resistance against bleeding Insertion of the implant *Bone cements may be divided into two kinds: low viscosity and high viscosity.

Low viscosity: These cements have a long-lasting liquid, or mixing phase, which makes for a short working phase.4 As a consequence, application of low viscosity cements requires strict adherence to application times.

High viscosity: These cements have a short mixing phase and loose their stickiness quickly. This makes for a longer working phase, giving the surgeon more time for application

Revision due to stem loosening

The Norwegian Arthroplasty Register shows that high viscosity bone cements yield better long-term results than low

Temperatures

Temperature affects mixing time, delivery of the cement, prosthesis insertion, and other aspects of the cementing process. It is therefore very important to control the temperature of the bone cement and the OR. To achieve optimal cement properties, it is important to adhere to the time schedules indicating the correlation of temperature to handling time. These time schedules are usually included in the instructions for the bone cement. High viscosity cements are sometimes prechilled for use with mixing systems for easier mixing and prolonged working

Mechanical properties

The bonecement is subjected to high mechanical stress in the body. In vivo, the biomechanical situation is rather complex, involving different types of loading (bending, compression, shear), which must be tested. The international standard ISO 5833 describes the methods for determining compressive strength, bending strength and bending modulus.7 As the cemented implant is subjected to not only static load but also dynamically

Antibiotic-loaded bone cement

Periprosthetic infection is the most feared complication in total hip and knee replacement. The infection usually leads to a complete failure of the joint replacement, resulting in a long series of operative procedures, great discomfort for the patient and heavy costs.1 Infections occur because of the high affinity of many germs to the surface of implants. Once settled, germs are less sensitive to antibiotics, as they are covered with a slime preventing them

A solution to the problem is preventing the settlement of germs. The use of antibioticloaded bone cements allows for high local concentrations of antibiotics to be administered to the areas surrounding the implant, protecting the implant from the settling of germs. Moreover, antibiotic levels in the serum are sufficiently low so as to avoid causing side effects.

The addition of antibiotics to bone cement was undertaken at the beginning of the 1970s by Buchholz,2 from the Endo-Klinik in Hamburg. His idea was to add antibiotics to the cement in order to reduce the incidence of infection, which was high at that time. Using gentamicin in combination withPMMA cement, it was found that the combination with gentamicin was

Attention must be given to reducing the incidence of infection in joint replacement surgery and to fighting infection once it has occurred. Orthopaedic infections There are numerous reports in the literature about the incidence of postoperative wound sepsis and the organisms causing this complication. Almost 75% of all bacteria that can be isolated during hip operations are Grampositive, with staphylococci representing the majority. Among Gram-negative

Antibiotic therapy, although usually not adequate alone, is a critical element in the treatment of infected total hip arthroplasty. Consultation with an infectious disease specialist can help the surgeon select the appropriate antibiotic, determine the duration of therapy, and evaluate

Antibiotic therapy, although usually not adequate alone, is a critical element in the treatment of infected total hip arthroplasty. Consultation with an infectious disease specialist can help the surgeon select the appropriate antibiotic, determine the duration of therapy, and evaluate the response to the treatment

Antibiotic-loaded bone cement

Gentamicin is an aminoglycoside antibiotic . It is bactericidal, has a dose-dependent killing curve, remains stable when exposed to heat and is soluble in water. These four characteristics make it especially suited for use in bone cement.

Gentamicin loaded bone cement

Gentamicin is mixed in bone cement for prophylaxis against infections after arthroplasties. The substance is slowly eluted in the surrounding tissue

Clindamycin belongs to the group of lincosamide antibiotics. It is additionally active against some anaerobic germs, such as peptostreptococci, anaerobic germs. This activity makes it a suitable antibiotic in combination with gentamicin, covering most of the germs typically occuring in periprosthetic infection Gentamicin and clindamycin is a combination known to have a bacterical effect on more than 90% of the bacteria common to infected arthroplasty cases.8

Vacuum mixing, which was adapted from the dental field, was developed for bone cement in the early 1980s. Vacuum mixing has several important purposes: to enhance cement properties to reduce bone cement porosity and to improve the working environment in the operating room.

Vacuum Mixing and Delivery

Numerous studies have shown that, compared to hand mixing, vacuum mixing prevents air entrapment in cement, reduces cement porosity, decreases the number of unbounded particles in cement and increases cements mechanical strength. Vacuum mixing furthermore reduces monomer evaporation and exposure in the operating room

Mixing as well as collecting cement under vacuum yields a homogenous mix without affecting viscosity or any cement additives such as antibiotics or radio-contrast media. Delivering cement with a syringe,under

Bone bed preparation and Pressurization in Total Hip Replacement

Careful preparation of the bone cavity and bone bed with high-pressure pulse lavage and brushing is essential for achieving an effective microinterlock between the bone and the cement. Clinical studies have shown that the use of highpressure pulse lavage reduces the risk of revision due to aseptic loosening. In the early days syringes and knives were used to clean the bone bed. These tools had the disadvantage of removing healthy tissue along with unhealthy and not sufficiently cleaning the bone bed.

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