Bone cement and the implications

for anaesthesia
Matrix reference 2A06, 3A08
Gautam Khanna FCARCSI, EDRA
Jan Cernovsky FRCA

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Key points Poly(methyl methacrylate) (PMMA) was devel- hollows on uneven surfaces. This means that
Bone cement is a radio-opaque oped in 1928 and was first marketed under the bone cement can be strongly adherent to the
compound composed of name of ‘Plexiglas’. Since then, PMMA has surface of the THR prosthesis (Table 1).
poly(methyl methacrylate) (90%) been used in a huge number of applications, in-
and a small quantity of
radio-opaque crystals. cluding transparent glass substitutes in
Antibiotic-loaded bone cement
windows, semiconductor research, and for the
combined with systemic antibiotics bodies of electric guitars. PMMA has a good The role of antibiotics in bone cement
provides the best prophylaxis degree of biocompatibility, which has made it Data from the Scandinavian Joint Registries
against postoperative infection.
an important component of replacement intra- showed that antibiotic-loaded bone cement was
Bone cement implantation
ocular lenses, dentures, and dental filling com- used in 95% of revision hip or knee arthroplas-
syndrome (BCIS) is poorly
understood, and clinical features posite materials. In orthopaedic surgery, ties. In Norway, 48% of surgeons, compared
include hypoxia, hypotension, PMMA bone cement is used to affix implants with 85% of those in Sweden, used
cardiac arrhythmias, and cardiac
and to remodel lost bone. antibiotic-loaded bone cement for primary joint
arrest.
The medical orthopaedic use of PMMA is replacements. In the National Hip Replacement
The effects of BCIS can be
moderated by the recognition of universally credited to Sir John Charnley, who Outcome Project in Great Britain,1 69% of the
high-risk patients and modifications was inspired by his dentist to use dental acrylic surgeons who responded stated that they used
of surgical technique to reduce for prosthetic fixation in total hip replacement
cardiopulmonary compromise.
antibiotic-loaded bone cement in their primary
(THR) procedures in 1957. In 1965, he began THR procedures.
Management of BCIS is mainly
focused towards treating pulmonary
to use bone cement (CMW Bone CementTM ) Antibiotic-loaded bone cement is a well-
arterial hypertension and right that was developed specifically for THRs rather accepted adjunct for the treatment of an estab-
ventricular failure. than dental acrylic. Bone cement is now rou- lished infection. However, its role in the
tinely used in a variety of orthopaedic prevention of infection remains controversial.
procedures. Many different antibiotics, including gentami-
The microscopic structure of bone cement cin, cefuroxime, vancomycin, and tobramycin,2
comprises two substances glued together. The have been loaded into bone cement. In contrast
so-called ‘pearls’ in bone cement consist of to the treatment of infection, prophylaxis
small particles of pre-polymerized PMMA, requires low doses of antibiotics in the bone
which are present as white powder. The second cement. The use of low doses also avoids the
substance is a liquid monomer of methyl adverse mechanical effects of the antibiotics
methacrylate (MMA). Both substances are on the cement. In general, low-dose antibiotic-
mixed together in theatre after the addition of a loaded bone cement is defined as 1 g of pow-
catalyst that initiates the polymerization of the dered antibiotic per 40 g of bone cement.
Gautam Khanna FCARCSI, EDRA monomer fluid. When the bone cement Antibiotic-loaded bone cements have also
Specialist Registrar Anaesthetics hardens, the individual pearls are entrapped and been implicated as a cause of postoperative
Royal National Orthopaedic Hospital glued within the net of the polymerized
Stanmore, UK
renal failure. This is a rare cause of post-
monomer, but no chemical binding occurs operative renal failure as serum antibiotic
Specialist Registrar Anaesthetics between the pearls and the polymerized levels after the placement of antibiotic laden
Royal London Hospital monomer.
Whitechapel
bone cement remain below toxic levels;
London E1 1RB, UK Antibiotics can be incorporated within the however, there have been recent case reports3
Tel: þ44 7960205145 polymerized matrix in the form of a soluble describing patients who developed acute renal
E-mail: drgautamkhanna@yahoo.co.uk powder that is subsequently released into the
(for correspondence)
failure after placement of aminoglycoside laden
joint cavity. bone cement. The development of renal failure
Jan Cernovsky FRCA Bone cement is used to fill all small open- in these case reports was associated with pre-
Consultant Anaesthetist ings in the spongy skeleton and to fill all of the existing co-morbidities (which placed them at
Royal National Orthopaedic Hospital
Stanmore, UK
doi:10.1093/bjaceaccp/mks011 Advance Access publication 23 February, 2012
213 Continuing Education in Anaesthesia, Critical Care & Pain | Volume 12 Number 4 2012
& The Author [2012]. Published by Oxford University Press on behalf of the British Journal of Anaesthesia.
All rights reserved. For Permissions, please email: journals.permissions@oup.com
Bone cement and the implications for anaesthesia

Table 1 Composition of bone cement Table 3 Risk factors for the development of BCIS

Poly(methyl methacrylate) (PMMA) (90%) Powder polymer: pre-polymerized PMMA Patient factors ASA III –IV
Initiator: dibenzoylperoxide Pre-existing pulmonary hypertension
Liquid monomer (MMA) Significant cardiac disease
Activator: N,N-dimethyl-p-toluidine Osteoporosis
Antibiotics Gentamicin, tobramycin, clindamycin Surgical factors Pathological fracture
Radiographic contrast material (10%) Zirconium dioxide or barium sulphate Intertrochanteric fracture
Long-stem arthroplasty

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Table 2 Potential disadvantages of antibiotic-loaded bone cement
These changes cause an immediate decrease in left ventricular
Alteration in the mechanical and structural properties of the bone cement
Antibiotic resistance compliance, reduced ventricular filling, and cardiac output (CO).
Allergic reactions Studies in humans have demonstrated the presence of emboli in
Systemic toxicity the cerebral circulation in patients undergoing cemented hip arthro-
Cost implications
plasty using transcranial Doppler imaging.5 This may occur as a
result of the transpulmonary passage of the emboli or emboli
high risk of renal failure) and with the dose of the antibiotics used passing through a patent foramen ovale, but none of the patients in
in the cement. these studies developed any neurological deficit. However, these
Thus, the use of antibiotic-loaded bone cement should follow emboli may be a contributory factor for postoperative delirium that
national guidelines with careful monitoring of patients at high risk commonly occurs in elderly patients (Table 3).
of developing renal failure (Table 2).
Aetiology and pathophysiology of BCIS
Bone cement implantation syndrome
While the aetiology and pathophysiology of BCIS is poorly under-
Bone cement implantation syndrome (BCIS) is a poorly understood stood, several models have been proposed. First, the monomer-
phenomenon and currently has no agreed definition. It is an im- mediated model arose after it was demonstrated that circulating
portant cause of intraoperative mortality and morbidity and is most MMA monomers cause vasodilatation in vitro.6 However, this
commonly, but not restricted to, being associated with cemented hypothesis is not supported in vivo, where the plasma MMA con-
hip arthroplasty. The clinical features of BCIS typically occur at centration after cemented hip arthroplasty is considerably lower
the time of cementation, prosthesis insertion, reduction in the joint, than the concentration required to cause adverse pulmonary or car-
or deflation of a limb tourniquet. A classification system for BCIS diovascular effects.
has been proposed according to its severity4 as follows: The embolus-mediated model proposes two possible aetiolo-
gies: mechanical and mediator effects. According to the former,
† Grade 1: moderate hypoxia (SpO2 ,94%) or a decrease in
debris, including marrow, fat, cement particles, air, bone particles,
systolic arterial pressure (SAP) .20%.
and aggregates of platelets and fibrin, embolize to the right atrium,
† Grade 2: severe hypoxia (SpO2 ,88%) or hypotension
right ventricle, and pulmonary artery intraoperatively. High intra-
(decrease in SAP .40%) or unexpected loss of consciousness.
medullary pressure is the main causative factor for the release of
† Grade 3: cardiovascular collapse requiring cardiopulmonary
these deposits into the circulation, and this has been confirmed in
resuscitation.
both in vitro and in vivo studies.
BCIS has a wide spectrum of clinical features that range from tran- Furthermore, one study compared the incidence of embolic
sient desaturation and hypotension to cardiac arrhythmias and events using conventional vs modified cementing techniques in
cardiac arrest at the time of cement deployment. Clinical reports 120 patients undergoing THR procedures.7 The modification con-
and studies all demonstrate the presence of right ventricular failure sisted of a suction catheter placed in the proximal femur to reduce
secondary to increased pulmonary artery pressure (PAP) as the the increase in intramedullary pressure during the insertion of the
underlying cause of systemic hypotension and sudden cardiac prosthesis. Embolic events were imaged during the insertion of the
arrest. The cause of the acute increase in pulmonary vascular re- prosthetic stem in 93.4% of the patients with the use of the con-
sistance (PVR) remains uncertain. It may be due to deposition of ventional cementing technique and 13.4% of the patients with the
cement or fat emboli or may be a result of systemic absorption of modified technique. It should be noted that the degree of cardio-
the volatile monomer. Regardless of the cause, the thin-walled and vascular compromise is not necessarily proportional to the degree
compliant right ventricle rapidly dilates and shifts of the interven- of the embolic load.
tricular septum to the left thereby reducing the volume of the left In terms of the mediator effects, vasoactive or pro-inflammatory
ventricular cavity. This occurs because the total volume of the substances are released as a result of systemic embolization of the
heart cannot expand within such a rapid time frame, as it is con- bone cement. These can directly increase PVR by raising the
strained by the pericardium. blood levels of thrombin and tissue thromboplastin. Other

214 Continuing Education in Anaesthesia, Critical Care & Pain j Volume 12 Number 4 2012
 Bone cement and the implications for anaesthesia

mechanisms that cause mediator release include mechanical stimu- The use of intraoperative CO monitoring has been recommended
lation or endothelial damage by the cement emboli, which induce in patients with one or more risk factors for BCIS. This can be in
reflex vasoconstriction through the release of endothelial the form of semi-invasive transoesophageal Doppler monitor or in-
mediators. vasive CO monitor (pulmonary artery flotation catheter). The use of
These mechanisms result in increased PVR, which is respon- intraoperative transoesophageal Doppler has been shown to aid the
sible for V/Q mismatch resulting in hypoxaemia. C3a and C5a are early detection of cardiovascular changes around the time of
potent mediators of vasoconstriction and bronchoconstriction. An cementing, improve fluid management, and reduce postoperative
increase in C3a and C5a levels has been demonstrated in cemented cardiopulmonary complications in hip surgery. A transoesophageal

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hemiarthroplasty in some studies; this may play a role in pulmon- Doppler study11 involving patients undergoing hip arthroplasty
ary vasoconstriction and the desaturation seen during cement im- demonstrated the superiority in detecting cardiovascular changes
plantation. Raised levels of histamine have also been found in during cementing compared with standard haemodynamic monitor-
patients8 who were hypotensive after cemented hip arthroplasties, ing, recommending its use in high-risk patients. Pulmonary artery
which could be either the result of a hypersensitivity reaction or a flotation catheter and transoesophageal echocardiography should
direct effect of the cement. also be considered in high-risk patients. But their use is limited by
In vitro studies found that the quantity of emboli and the sever- their availability and expertise required to use them.
ity of cardiorespiratory changes observed during total hip arthro-
plasty with the use of bone cement were greater than those seen
when cement was not used. A study that involved the use of trans- Role of surgery in prevention of bone
oesophageal echocardiography in humans showed that the insertion cement-associated complications
of the femoral component with cement caused more severe and
The use of a cementless hip prosthesis can reduce the morbidity
more prolonged embolic cascades than the insertion of the compo-
associated with cement embolization and must be considered on an
nent without cement.9 Intraoperative pulmonary shunt values
individual basis. Surgical measures that can reduce the incidence of
increased significantly when the femoral component was inserted
complications associated with bone cement, especially BCIS,
with cement, but the shunt values did not change when the compo-
include thorough lavage of the intramedullary canal of the femoral
nent was inserted without cement.10 These findings suggest that
shaft in order to remove debris, good haemostasis, the use of non-
patients who require a total hip arthroplasty, especially those who
cemented prostheses, and drilling a venting hole in the distal
have underlying cardiorespiratory disease, may have less morbidity
femoral shaft.10 The latter technique reduces air trapping during the
if the femoral component is inserted without cement than if it is
cementing process and acts as a pressure-relieving opening during
inserted with cement.
the intramedullary reaming of the femoral canal. However, drilling a
venting hole increases the risk of fracture and prosthetic instability.
Prevention of BCIS The bone-vacuum cementing technique has been shown to reduce
the embolic load during total hip arthroplasty. In this technique, a
The anaesthetist should be fully involved in the preoperative as-
suction pressure of 2800 mbar (280 kPa) is applied to a proximal
sessment of patients. This involves the identification of high-risk
drainage cannula placed along the linea aspera and a distal drainage
surgical patients before operation, the assessment and optimization
cannula is placed in the diaphysis to produce a vacuum in the medul-
of their cardiovascular reserve before surgery, and the appropriate
lary cavity of the femur during the application of cement and the in-
use of this information to select the type of prosthesis, surgical
sertion of the stem. The reduction in embolic load using this
procedure, and techniques in order to minimize the risk of cardio-
technique was evident in intraoperative transoesophageal imaging.12
vascular complications.
The retrograde insertion of cement (from distal to proximal) by
Patient risk factors that have been implicated in genesis of
a cement gun causes the compartmentalization of the bone marrow
BCIS after cemented THRs include grade III and IV ASA levels,
contents. This can lead to a more uniform increase in intramedullary
old age, poor pre-existing physical reserve, impaired cardiopul-
pressure and less physiological disturbance. Furthermore, mixing
monary function, pre-existing pulmonary hypertension, osteopor-
bone cement in a specific cement-mixing set, which is in a vacuum,
osis, bony metastases, and concomitant hip fractures, particularly
reduces the load of volatile vasoactive compounds. This, and the use
pathological or intertrochanteric fractures.
of low-viscosity cement, can reduce the incidence of BCIS.
There is no clear evidence with regards to the effect of anaes-
thetic technique on the severity of BCIS. The general principles of
management include the maintenance of normovolaemia to avoid
Management of BCIS
the cardiovascular consequences of cementing and the mainten-
ance of high inspired concentrations of oxygen. The use of high Human and animal studies have shown that BCIS is a reversible,
anaesthetic vapour concentrations should be avoided as it is asso- time-limited phenomenon. The PAPs can normalize within 24 h
ciated with greater haemodynamic compromise with the same and non-diseased hearts can recover within minutes to hours. This
embolic load. means that aggressive resuscitation and supportive treatment is

Continuing Education in Anaesthesia, Critical Care & Pain j Volume 12 Number 4 2012 215
Bone cement and the implications for anaesthesia

essential to reduce the morbidity and mortality of this potentially References

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Declaration of interest
None declared. Please see multiple choice questions 37 –40.

216 Continuing Education in Anaesthesia, Critical Care & Pain j Volume 12 Number 4 2012