تفنگ سیمان استخوانی
تفنگ سیمان استخوانی ( Bone cement gun – cement gun ) :
انتهای پروگزیمال آن دارای یک دیسک پیستونی شکل است که در هنگام فشردن دسته وسیله ، به سمت جلو حرکت خواهد کرد . این نیرو سبب حرکت سیمان در درون محفظه و نهایتا خروج آن از نوک وسیله می باشد .
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مورد استفاده :
جهت تزریق سیمان استخوانی پلی متیل متاکریلات ( PMMA ) درطول جراحی های آرتوپلاستی کامل مفاصل کار برد دارد .
توضیحات بیشتر : زمان سفت شدن PMMA حدود 8-16 دقیقه بعد از گذاشتن پروتز است . جراح باید با نحوه ی سفت شدن آن ها آشنا باشد ، جهت اطمینان ، باید میزان کمی ازسیمان را از لحاظ گرما و سفت شدن ، تست نمود .زمان گداشتن سیمان بر روی تفنگ را باید ثبت کرد .
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Bone cement
Rajesh Kumar Ranjan, Manish Kumar, Rakesh Kumar and Md Farman
Ali
Abstract
Polymethyl methacrylate (PMMA) bone–cement was introduced in the 1960s for fixation of total hip
arthroplasty replacement components.
The use of PMMA bone cement has been a key factor in the
advent of joint replacement as a surgical option.
Long-term results of cement fixation for hip and knee
arthroplasty have been extremely good.
Although the use of PMMA bone–cement has enabled long-term
survival of joint arthroplasty implants, there has been concern about aseptic loosening.
Despite
revolutionary changes in joint replacement technology for the treatment of hip and knee arthritis, the use
of PMMA bone cement in its intraoperative application has not significantly changed.
Bone cement
implantation syndrome (BCIS), It is an important cause of intraoperative mortality and morbidity in
patients undergoing cemented hip arthroplasty and may also be seen in the postoperative period in a
milder form causing hypoxia and confusion.
It is possible to identify high risk groups of patients in which
avoidable morbidity and mortality may be minimized by surgical selection for uncemented arthroplasty.
Invasive anaesthetic monitoring should be considered during cemented arthroplasty in high risk patients.
Keywords:
Bone cement, Joint replacement, Arthroplasty, Antibiotic, Viscosity, Bone cement
implantation syndrome
Introduction تفنگ سیمان استخوانی
Polymethylmethacrylate (PMMA) bone cement is an essential component in many total joint
arthroplasty procedures.
In a cemented arthroplasty, the main functions of the cement are to
immobilize the implant, transfer body weight and service loads from the prosthesis to the
bone, and increase the load-carrying capacity of the prosthesis-bone cement-bone system.
The
term “cement,” however, is misleading since bone cement acts more like a grout, filling in
space in order to create a tight space to hold the implant against bone.
Good quality cement is
essential for long-term implant survival.
Accurate bone cement mixing and precise application
techniques are critical to ensuring the stability and longevity of the prosthesis.
Since bone
cement is prepared and used in the operating room environment, it is importa nt that all
perioperative personnel recognize the unique safety considerations that are related to its
preparation and its use.
Components of Bone Cement
PMMA bone cements are usually supplied as two-component systems made up of a powder
and a liquid. These two components are mixed at an approximate ratio of 2:1 to start a
chemical reaction called polymerization, which forms the polymethylmethacrylate (PMMA)
cement.
Bone cement gun
Powder components
Copolymers beads based on the substance polymethylmethacrylate (PMMA)
Initiator, such as benzoyl peroxide (BPO), which encourages the polymer and monomer to
Polymerize at room temperature
Contrast agents such as zirconium dioxide (ZrO2) or barium sulphate (BaSO4) to make
the bone cements radiopaque and
Antibiotics (eg, gentamicin, tobramycin).
Liquid components
A monomer, methylmethacrylate (MMA)
Accelerator (N,N-Dimethyl para-toluidine) (DMPT)
Stabilizers (or inhibitors) to prevent premature
polymerization from exposure to light or high
temperature during storage
Chlorophyll or artificial pigment sometimes added to cements
for easier visualization in case of revision.
There is a difference between PMMA bone cement and
PMMA; however, many healthcare personnel use the terms
interchangeably and PMMA has become shorthand for “bone
cement”.
However, PMMA is the substance from which
copolymers are derived for the powder component. When the
copolymer powder is mixed with the MMA monomer liquid,
polymerization occurs and PMMA bone cement is created.
Bone cement gun
Types of Bone Cement
There are several types of bone cement in regards to its
viscosity.
Viscosity affects the bone cement’s handling
characteristics, handling time, and its penetration into the
cancellous bone and therefore, the quality and longevity of the
fixation achieved.
Optimum viscosity helps cement penetrate
the bone for good attachment, i.e., the cement must be liquid
enough to be delivered and then to penetrate the interstices of
cancellous bone.
تفنگ سیمان استخوانی
Bone cement gun
There are two requirements for bone cement
viscosity during the working phase:
first, viscosity must be
sufficiently low to facilitate the delivery of the cement dough
from the syringe to the bone site; secondly, it must penetrate
into the interstices of the trabecular bone.
On the other hand,
the viscosity of the bone cement should be sufficiently high to
withstand the back bleeding pressure, thereby avoiding the
risk of the inclusion of blood into the cement.
Different type
of bone cement according to viscosity describe below.
Low viscosity cements:
These cements remain in a runny
state for a much longer period of time as compared to medium
or high viscosity cements.
Typically they have a long waiting
phase. The true working time in which the cement can be
picked up with a gloved hand usually is short, and the setting
time can vary.
Bone cement gun
تفنگ سیمان استخوانی
Medium viscosity cements:
These types of cements can offer
versatility for various types of procedures.
Medium viscosity
cements are both low and high in viscosity, depending on the
time at which the cement is delivered.
Medium viscosity
cements are considered to be dual phase cements.
They begin
in a low viscosity state while being mixed, which allows for
the easy and homogenous mixing of the powder and the
liquid.
High viscosity cements:
These types of cements primarily
are comprised of PMMA with no methylmethacrylatestyrene-copolymer content; they have no runny state at all.
Immediately after mixing, the cement is doughy and ready to
apply by hand to the implant surface.
The working time for
high viscosity cements needs to be closely monitored; it is not
always easy to determine the end of the working time before
it is too stiff to interdigitate with the bone.
Bone cement gun
Antibiotic Cements
Not all antibiotics are suitable for use in bone cements. The
following bacteriologic and physical and chemical factors
should be considered in the choice of an antibiotic
Preparation must be thermally stable and able to
withstand the exothermic temperature of polymerization.
Must have broad antimicrobial coverage.
Must be available as a powder.
Must have a low incidence of allergy.
Must not significantly compromise mechanical integrity.
Must elute from the cement over an appropriate period of
time.
Gentamicin and tobramycin are the only antibiotics available
in U.S. commercial antibiotic bone cement products;
tobramycin is the most often used and studied antibiotic
added to cement worldwide, but gentamicin is more common
in the United States.
Other antibiotics (singly or in
combination with other antibiotics) that have been studied
include vancomycin, cephalothin, clindamycin, meropenem,
teicoplanin, ceftazidime, imipenem, piperacillin, and
ciprofloxacin.
Polymerization
Polymerization is a chemical reaction in which two or more
small molecules combine to form larger molecules that
contain repeating structural units of the original molecules.
In
the case of bone cement, the polymerization process starts
when the copolymer powder and monomer liquid meet,
reacting together to produce an initiation reaction creating
free radicals that cause the polymerization of the monomer
molecules.
The original polymer beads of the powder are
bonded into a dough-like mass, which eventually hardens into
hard cement.
The polymerization process is an exothermic reaction, which
means it produces heat. With a maximum in vivo temperature
of 40 °C to 47 °C, this thermal energy is dissipated into the
circulating blood, the prosthesis, and the surrounding tissue.
Once polymerization ends, the temperature decreases and the
cement starts to shrink.
Phases And Times
The polymerization process can be divided into four different
phases:
Mixing, waiting, working, and setting Time. Dough Time and
Setting Time are measured from the beginning of mixing;
Working Time is the interval between Dough Time and
Setting Time.
تفنگ سیمان استخوانی
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