MINI-SYMPOSIUM: THE KNEE
fracture.1e4 In this article we will discuss the important factors to
consider in careful pre-operative planning in order to obtain
successful surgical outcomes. We will then go on to discuss the
principles of patient consent and describe how to obtain
informed consent for TKA surgery.
Knee joint arthroplasty is performed to reduce knee pain,
improve function and to improve quality of life.5 In order to
obtain the best surgical results the surgeon must perform an
adequate pre-operative work up including appropriate patient
selection, pre-operative medical assessment, clinical and radiological examination of the limb, selection of an appropriate
prosthesis and adequate patient counselling about the operation.
(i) Planning and consent for
primary total knee
replacement
Donald J Davidson
Susannah G Clarke
Chinmay M Gupte
Abstract
Pre-operative clinical evaluation and assessment
The aim of primary total knee replacement is to decrease pain, restore
function and reduce disability. This is achieved by correct patient selection and adequate planning so that the appropriate prosthesis can be
implanted in the appropriate manner. The technical goal of total knee
arthroplasty is to implant a well-aligned prosthesis in a well-balanced
knee, with linear patellar tracking and achieve infection-free healing.
Weight bearing anteroposterior, lateral and patellofemoral joint radiographs are mandatory and standing long leg views help determine alignment. CT and MRI scans may be of value in assessing bone stock and
ligamentous deficiency. If there is a lack of bone stock a stemmed prosthesis or augmentation wedges may be required, whilst a ligamentous
deficiency may necessitate a stabilized or constrained prosthesis.
The consent process for TKR commences at the outpatient consultation
and must consider the reason for operation, alternative treatments, all
common and serious risks and the rehabilitation protocol. There is an
increasing use of multimedia tools (e.g. www.orthoconsent.com) in the
consent process.
History
An adequate history is the key to patient selection. This
should include a thorough assessment of pain (including rest
pain and night pain) and disability (including walking distance,
stair disability and leisure/occupational restriction). Previous
treatments should be established including steroid injections
(which increase the risk of infection), physiotherapy and operations such as arthroscopy or osteotomy.
A past medical history of concomitant conditions such as
diabetes, hypothyroidism, and immunosuppression may necessitate blood investigations prior to the procedure.6
A drug history should determine whether the patient is on
warfarin, immunosuppressant therapy or diabetic medication.
An allergy to nickel or metal may necessitate allergy testing as a
non-cobalt chrome prosthesis (e.g. zirconium) may be required.
The patient’s social history may determine post-operative
rehabilitation and length of hospital stay, especially if they
have little social support or live in a property with many stairs.
With the growing volume of TKA surgery there has been a rise
in multidisciplinary integrated peri-operative care pathways;
these pathways aim to enhance the recovery of patients undergoing elective primary TKA by identifying and anticipating
challenges likely to hamper the successful outcome of the operation.7 These pathways include thorough medical, nutritional
and social circumstance assessment which, coupled with patient
education, has been demonstrated to reduce pre-operative patient
anxiety and improve post-operative outcome including shortened
hospital stays, reduced morbidity and reduced mortality.7e9
These peri-operative clinics also permit patient information capture for joint registries and functional assessment scoring.
Keywords consent; planning; pre-operative; primary total knee
replacement; TKA
Introduction
With over 72 000 primary total knee replacements performed
every year in the UK, primary total knee arthroplasty (TKA) is a
common, but technically demanding surgical procedure that requires careful pre-, intra- and post-operative consideration. TKA
surgery generally has excellent results with long prosthesis survival rates of 15e20 years and improved quality of life, but
serious complications do occur in approximately 5% of cases due
primarily to loosening, infection, instability, dislocation and
Contraindications to primary total knee replacement
The absolute contraindications to TKA include local or systemic
infection, extensor mechanism discontinuity or severe dysfunction, recurvatum deformity secondary to muscular weakness
and the presence of well-functioning knee arthrodesis.10 Relative
contraindications include significant peripheral vascular disease,
a Charcot joint and dermatitis within the operative field.10
Patients with pre-existing obesity and diabetes require special
consideration prior to TKA. The prevalence of obesity is
increasing and is linked to osteoarthritis, especially affecting the
knee joint. Evidence shows that the outcome for morbidly obese
(BMI >40) patients post primary TKA can be successful, but they
suffer from higher rates of peri-operative complications and do
Donald J Davidson MA (Cantab) MBBS MRCS Specialist Registrar, Trauma
and Orthopaedics, Imperial College NHS Trust, St Mary’s Hospital,
Paddington, London, UK. Conflict of interest: none.
Susannah G Clarke MA (Cantab) MEng PhD Research Doctor, MSK Laboratory, Charing Cross Hospital Campus, Imperial College London, UK.
Conflict of interest: none.
Chinmay M Gupte MA (Oxon) BMBCh PhD FRCS (Tr&Orth) Consultant Orthopaedic Surgeon and Senior Lecturer, Imperial College NHS Trust, St
Mary’s Hospital, Paddington, London, UK. Conflict of interest: none.
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MINI-SYMPOSIUM: THE KNEE
not go on to lose weight after knee arthroplasty.11,12 Patients
with Diabetes Mellitus have an increased risk of postoperative
deep infection due to immune dysfunction and there is evidence
to support the use of antibiotic impregnated bone cement in
primary TKA to reduce this risk.13
may subsequently require the consideration of using a constrained TKA system.
Inspection: joint angular deformity (especially varus or valgus)
should be identified and then assessed clinically to determine if it
is correctable. If it is not passively correctable, plans for soft
tissue release during surgery should be made, or in severe cases,
a constrained prosthesis should be available. It would also
exclude a unicompartmental knee replacement even if only one
knee compartment is affected.21 Femoral or tibial bowing should
be noted and warrants further radiological assessment (a full
length leg AP).
Surgical scars should be noted and are evidence of previous
surgery (e.g. high tibial osteotomy or trauma) which can impact
upon the operative plan. The location of existing surgical scars
affects where a new incision can be sited (the vascular supply to
the skin anterior to the knee joint runs from medial to lateral).
Ideally, a 7 cm skin bridge between incisions is advisable or the
most lateral pre-existing vertical scar should be re-incised. If a
transverse scar is evident the incision should be made perpendicular to this. If unsure, plastic surgical input is vital and
consideration should be made to performing a sham incision
prior to the definitive arthroplasty surgery.
Clinical and radiological examination of the limb
Thorough pre-operative planning permits the anticipation of
many intra-operative challenges necessary to achieve accurate
prosthetic seating, thus improving surgical technique. Suboptimal technique is a known risk factor for early prosthetic failure.14,15 The technical goals necessary to achieve a successful
outcome in primary TKA surgery are16:
Restoration of the neutral mechanical alignment of the
limb
The objective is to achieve a neutral mechanical alignment
where the forces pass through the centre of the hip, knee and
ankle joints. This permits equal load sharing across the prosthesis thus preventing excessive stress on either side leading to
accelerated wear and early failure.17
Preservation (or restoration) of the joint line
By the end of the procedure the joint line must be recreated at
its original position taking into account any cartilaginous or bony
erosion secondary to the arthritic process. Restoration of the joint
line is important as it means peri-articular knee ligaments are
correctly tensioned which is essential for prosthetic knee
kinematics.18
Balancing of the peri-articular ligaments
Over the course of the disease progression ligaments may
become scarred and contracted or lax owing to a progressive
articular angular deformity. It is long established that correct
ligamentous balance is necessary to provide optimum function
and wear of the prosthesis.19 Simplistically, ligaments on the
concave side of the joint need releasing and those on the convex
side tightening. Balancing must be achieved in both the coronal
and sagittal planes. The goal in sagittal balancing is to achieve an
equal flexion and extension gap, taking into account the two radii
of curvature in the knee; the first at the patellofemoral articulation and the second at the weight bearing portion of the knee.
Maintenance (or restoration) of linear patellar tracking and
a normal Q angle
Abnormal patellar tracking is the most common complication of
TKA.20 The Q angle, the angle between the axis of extensor
mechanism and the axis of the patellar tendon, is normally 11 þ/
7 .20 An increased Q angle leads to lateral subluxation forces on the
patella relative to the trochlear grove, which can lead to pain,
mechanical symptoms, accelerated wear and even dislocation.
Common intra-operative errors include internal rotation of the
femoral or tibial prosthesis, medialization of the femoral component and placing the patellar prosthesis lateral on the patella.
Joint range of motion: the pre-operative range of motion of the
knee should be assessed and recorded, as there is a positive
correlation between pre and post-operative movement range.22
Identification of a fixed flexion deformity will impact upon the
surgical strategy possibly necessitating, depending on severity:
the excision of the posterior osteophytes, posterior capsular
release, posterior cruciate ligament (PCL) release and distal
femoral resection (cadaveric studies demonstrate that a 2 mm
distal femoral resection can give 10 of further extension).23,24
Assessment of ligaments: the integrity of the ligamentous
structures of the knee must be assessed and further knee imaging
may be warranted. An incompetent PCL is a contraindication to a
cruciate retaining prosthesis and a competent anterior cruciate
ligament (ACL) is essential if a unicompartmental knee replacement is to be considered. The integrity of the collateral ligaments
is also essential for a non-constrained TKA design to be utilized
and if there is any concern a constrained system should be
available at the time of surgery.
Radiological evaluation
A detailed pre-operative radiographic assessment of the knee
joint is essential to confirm the diagnosis, the severity of disease
and to adequately plan TKA. The standard radiographic views
include a standing anteroposterior (AP) of both knees, extension
and flexion lateral of the affected knee and a tangential axial of
the patellofemoral joint (typically a Merchant view but other
alternatives include a skyline patellar view). Whilst a standing
AP radiograph of the lower extremity (hip to ankle joint) is
preferred, this is not routine in many orthopaedic centres, but is
obligatory if there is:
Obvious clinical deformity of the femoral or tibial shaft,
Altered ipsilateral hip/femoral neck/shaft anatomy (e.g.
from dysplasia, trauma, infection, previous operation),
Extremes of height.
Clinical assessment of the knee joint
Crucial information necessary to pre-operatively plan TKA can be
gathered in the clinic room. The affected knee, the ipsilateral hip
and ankle, as well as the contralateral knee, should all be thoroughly examined.
Gait assessment: evidence of a thrust gait is indicative of ligamentous laxity and warrants careful radiological assessment and
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The AP, lateral and Merchant radiographs will also demonstrate the presence of osteophytes, bony defects, loose bodies or
deformities, which may require intervention during surgery. The
position of osteophytes should be noted, as osteophyte excision
is the first step in achieving ligamentous balance both in the
coronal and sagittal planes. Pre-operative identification of the
nature of the deformity allows the formulation of a sequential
surgical plan to tighten the convex side and release the concave
side of the joint until equilibrium is restored. The joint line can
also be determined in the AP view which is important for
balancing the flexion and extension gaps and the ligaments.
If a varus thrust gait is evident and varus deformity is also
present on weight bearing AP radiographs then a standing single
leg AP radiograph is recommended to identify the presence of
lateral ligament laxity. In this instance a constrained system
should be made available at the time of surgery as instability
problems are likely to be encountered during balancing and
trialling.25
Radiographic evidence of previous surgery (e.g. high tibial
osteotomy) will be apparent and intra-operative management
must be considered pre-operatively.
Supplementary radiographic views may be also indicated,
including tunnel or Rosenberg views, which are useful to detect
early joint space narrowing of the posterior weight bearing surfaces, osteochondritis dissecans in young patients, intra articular
loose bodies and osteophytes projecting into the intercondylar
notch. Additional imaging modalities can be indicated, including
a CT and MRI, in the context of complex primary TKA post
trauma or dysplasia, altered bone stock (Figure 1) and also for
patient-matched instrumentation.
The analysis of this radiographic survey gives valuable information for the formulation of an operative plan, namely the25:
Determination of the femoral and tibial end cuts and cut
angle,
Position of the femoral canal entry point,
Anticipation of ligamentous release,
Identification of bone defects, joint subluxation or ligamentous laxity,
Templating of prosthetic components.
AP radiograph, to confirm and assess severity of knee pathology: the weight bearing AP radiograph (Figure 2) is used to
confirm the involvement and severity of the arthritic process in
the medial and lateral tibiofemoral joint compartments. When
weight bearing, the radiographic joint space represents the
thickness of the articular cartilage and is pathological if less than
3 mm.26
On review of the AP, in conjunction with the lateral and
Merchant views, it is possible to confirm which of the joint
compartments are affected and the decision to opt for either a
primary TKA, unicompartmental arthroplasty, isolated patellofemoral arthroplasty or high tibial osteotomy can be considered.
Lateral flexion and extension radiograph: the lateral radiographic (Figure 3) views have a role in disease confirmation and
severity assessment. Additionally, in this view the suprapatellar
region can also be evaluated for the presence of a joint effusion
or loose bodies.
Evidence of anterior tibial subluxation and/or posteromedial
tibial wear on the lateral radiograph is indicative of an ACL
injury and would be a contraindication to unicompartmental
arthroplasty. If PCL insufficiency is suspected, a lateral kneeling
Figure 1 This radiographic case study highlights the role of CT scanning in planning a left complex primary TKA (post gunshot wound). Images: (a), (b) and
(d) are the pre-operative radiographs of the left knee; (c) is a sagittal image from the pre-operative planning CT scan demonstrating marked bone loss,
leading to preoperative planning of a stemmed prosthesis and wedges if required at the time of surgery. However, after trialling, a standard prosthesis
was implanted (e).
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intra-operatively, can cause loss of flexion and impingement
pain. The patellar height can be described using the ratio of
patellar tendon length to the greatest diagonal patellar length; a
ratio greater than 1.2 is considered patella alta and less than 0.8
is considered patella baja.27
Tangential axial view of the patellofemoral joint: the Merchant
view (Figure 4) is the most commonly used tangential axial view
of the patellofemoral joint and, as already described, allows
evaluation of the patellofemoral joint arthritis.28 The alignment
of the patellofemoral joint can be assessed allowing the presence
of pre-operative patellar subluxation to be identified and intraoperative lateral release to be considered.14
The role of the full length leg radiograph in achieving mechanical alignment: with the standing full length leg AP radiograph (Figure 5) it is possible to determine the anatomical and
mechanical axes of the tibia and femur and determine where the
bone cuts should be made to correct any malalignment.
The femoral anatomic axis (Figure 6) is the line that bisects the
intramedullary canal of the femur and typically exits the femur
inferiorly through the intercondylar notch. The exit point determines the entry point for the intramedullary rod of the femoral
jig used to prepare the femur during TKA. With femoral deformity
the exit point of the axis can migrate away from the intercondylar
notch in the coronal plane and this must be established preoperatively. The mechanical axis of the femur is the line connecting the centre of the femoral head to the point where the femoral
anatomical axis intersects the intercondylar notch. The difference
between these two axes determines the valgus cut angle (VCA) for
the preparation of the distal femur. By setting the VCA on the
femoral guide it is possible to make the distal femoral cut
perpendicular to the femoral mechanical axis. The VCA is typically
between 5 and 7 , decreasing with patient height.
The anatomic axis of the tibia (the line bisecting the medullary
canal) is, in the majority of patients, coincident with the tibial
mechanical axis (the line from the centre of the proximal tibia to
the centre of the ankle). Therefore, when the proximal tibial cut is
made perpendicular to the anatomical axis it is also perpendicular
to the mechanical axis thus permitting even loading through the
tibial component. The proximal tibial cut can be made with
reference to either an intramedullary or extramedullary tibial guide
and they are equally efficacious.29 In the presence of a tibial
bowing deformity (e.g. congenital or post trauma) the bowed tibia
may not permit placement of the intramedullary guide; this must
be established pre-operatively. Note that with tibial bowing the
anatomical and mechanical axes can be disparate.
The tibial joint line is typically 3 of varus compared with a
perpendicular subtended from the mechanical axis (i.e. 87 )
(Figure 7). If not addressed, after the tibial cut there would be an
unequal (unbalanced) trapezoidal flexion gap created due to the
unparallel tibial and posterior femoral cut surfaces causing an
increased lateral joint space. In order to equalize the flexion gap,
the femoral component is placed in 3 of external rotation, thus
compensating for the increase in lateral joint space. This has the
additional benefit of improving patellar tracking by reducing the Q
angle.
The standing full length leg radiograph will also determine if
there is varus or valgus alignment of the knees; this allows the
Figure 2 AP radiographs of the knee joint (weight bearing and non-weight
bearing). Note the partial loss of joint space in the medial tibiofemoral
joint compartment which is complete in the weight bearing radiograph
(on the right).
stress radiograph will demonstrate this. Excessive fixed flexion
both clinically and in the lateral view is evident in PCL tightness
and prompts consideration of a PCL sacrificing prosthesis.
The patellar height can be ascertained on the lateral radiograph. The presence of a patella baja which, if not addressed
Figure 3 Lateral radiograph of the knee demonstrating reduced joint
space, fixed flexion, osteophytes and subchondral sclerosis.
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surgery so that intra-operatively the correct implant sizes are
available.31 It has been shown to be cost effective and presumed
to shorten the surgical time.32 Various acetate and digital templating techniques have been investigated and the results are
similar; the accuracy of predicting actual component size to
within one size above or below is 90e95%.31 Templating based
solely on patient characteristics (age, gender, height, weight and
body mass index) has been shown to be more efficacious
compared to all other radiographic templating techniques.31
Figure 4 Tangential axial view of the patellofemoral joint demonstrating
bilateral loss of joint space and subchondral sclerosis.
anticipation of the intra-operative ligament release for coronal
balancing as described previously. Significant valgus deformity is
associated with lateral femoral condyle hypoplasia which should
be anticipated as, in this instance, posterior axis referencing
would result in the placement of the femoral component in an
internally rotated position.
If severe extra-articular angular deformity (>10 in the coronal plane and >20 in the sagittal plane) is evident, simultaneous
osteotomy and TKA should be planned, as in this instance
attempted joint line restoration can result in complex imbalance
of the collateral ligaments.30
Patient-matched technology: the advent of 3D printing as a cost
effective method of manufacture has allowed the introduction of
customized instrumentation for TKA. All major orthopaedic
companies now offer a customized pre-operative planning and
instrumentation service.
Pre-operative planning is undertaken on CT or MRI scans; 3D
models are constructed from the imaging data. The scan must
include the ankle, knee and hip. To reduce radiation dose, specific
protocols may be set up-to include only the required areas. From
the 3D models, bony landmarks at the ankle, knee and hip are
located and used to provide the mechanical axis reference frame for
the lower leg. Default sizing and positioning of the total knee implants in accordance with manufacturer recommendations can be
made with reference to the mechanical axes of the femur and tibia.
Interactive planning software allows variation of implant position
and orientation to accommodate each patient’s specific needs.
The pre-operative plan is used to create custom instrumentation for the patient. The custom instrumentation is manufactured using one of a number of methods of rapid manufacture
and will generally be made out of Nylon or a similar polymer.
Depending on the manufacturer, the custom instrumentation will
guide the initial tibial and femoral saw cuts, or will allow pin
placement for use with re-usable metal cutting guides. The
custom instrumentation is designed to provide a positive fit onto
the patient’s exposed bone. A CT-based system will fit onto bone;
an MRI-based system will fit onto the articular cartilage. Once
designed, the custom instrumentation is manufactured, sterilized
and sent to the operating theatre.
This type of patient-matched technology is still in its infancy and
there is not a wealth of supporting evidence to demonstrate superiority to conventional techniques. In contrast to planar radiographs, the use of 3D imaging allows a greater understanding of the
case prior to surgery. Accurate placement of the instrumentation is
essential to ensure correct implementation of the plan.
Templating: pre-operative templating attempts to accurately
determine the size of the femoral and tibial components prior to
Choice of TKA prosthesis
There are different designs of prostheses that can be used for primary TKA and they are categorized depending upon the level of
mechanical constraint in the prosthesis. The most common primary TKA designs are divided into those which retain or sacrifice
the PCL; the merits of one system over the other have been much
debated.33 Beyond this are the constrained systems, either hinged
(highly constrained) or non-hinged, which tend to be used for
revision surgery but can also be used in the context of a complex
primary TKA with ligamentous insufficiency or marked deformity.
Figure 5 A standing full length leg AP radiograph the bilateral lower limbs.
In this radiograph the mechanical axis of the limb (from the centre of the
femoral head to the centre of the ankle joint; marked with a blue line)
passes more medially through the knee joint in the left leg compared to
the right. This patient had undergone a left medial meniscectomy 30 yrs
earlier, leading to medial OA and varus malalignment.
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Cruciate retaining TKA: in the native knee, posterior glide and roll
back of the tibiofemoral contact point during flexion is influenced
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MINI-SYMPOSIUM: THE KNEE
demonstrated paradoxical forward sliding with knee flexion.35 The
advantages are that it is a bone preserving prosthesis, the joint line
is consistently restored and post-operative proprioception is better
as the PCL remains. The disadvantages are that it is harder to
balance with severe deformities (Varus >10 and Valgus >15 ).
PCL balance is critical for long-term wear but PCL recession is
technically demanding and excessive recession can result in late
PCL rupture which can cause instability of the knee.36
Cruciate sacrificing TKA: there are two types of cruciate sacrificing (CS) TKA; posterior stabilized (post and cam mechanism)
and the anterior stabilized (extended anterior polyethylene lip).
The posterior stabilized TKA is the most commonly used CS TKA
and there are specific indications for its use including pre-existing
patellectomy, inflammatory arthritis (as risk of subsequent PCL
rupture) or pre-existing PCL rupture.37 The advantages of CS TKA
include that it is technically easier to balance in the presence of
severe deformities, as excision of the PCL increases the flexion gap
by 5 mm which permits surgical access.34,38 Evidence suggests that
using CS design increases post-operative knee flexion, although the
difference is small (8 ) and not associated with improved function.34 There is less sliding wear debris created compared to the CR
system, although wear analysis of retrieved posterior stabilized
TKAs demonstrate the cam-post interface is an additional source of
polyethylene debris.39 The disadvantages specific to the posterior
stabilized system are that the femoral cam can jump over the tibial
post if the flexion gap is too loose, scar tissue can form superior to
the patella which can get caught in the cam mechanism as the knee
moves into extension causing a patellar clunk. It also requires
additional bone stock removal compared to the CR prosthesis to
accommodate the post and cam mechanism.
Figure 6 Diagram demonstrating the anatomical axis of the femur (solid
red line), mechanical axis of the femur (solid blue line) and the coincident
tibial mechanical and anatomical axes (dashed red and blue line).
Additional TKA design decisions
There are other decisions to be made pre-operatively in choosing
the prosthetic design for the patient’s primary TKA. Mobile
bearing TKA were developed in an attempt to decrease wear at
by the PCL and is essential for deep flexion as it prevents posterior
impingement.34 The advantage of the cruciate retaining (CR) TKA
is that the PCL helps regulate flexion stability and PCL tension also
regulates femoral roll back, although some studies have
Figure 7 Left; native balanced knee with joint line in slight varus. Middle; proximal tibia is cut perpendicular to mechanical axis leaving wide lateral joint
space. Right; flexion gap balanced by externally rotating femoral component 3 .
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dictated in the clinic letter), confirmed at pre-assessment and reconfirmed on admission for surgery.47
There is no UK statute setting out the general principles for
consent, however case law has established that if a health professional intentionally or recklessly touches a patient without
valid consent they are committing a crime of battery or a tort of
trespass to the person or negligence.43,46
There is no set method established to obtain valid informed
consent prior to any surgery. There are, however, generic guidance documents produced by the Department of Health and the
GMC which aid clinicians who are seeking consent for medical
procedures and operations. More specifically the British Orthopaedic Association (BOA) has endorsed a freely accessible website (www.orthoconsent.com) which gives orthopaedic surgeons
access to a bank of pre-written procedure specific consent forms,
including primary TKA, covering the procedure description,
alternative procedures and the specific risks of surgery.45e47
the tibiofemoral articulation, the aim being to reduce wear by
permitting the insert to slide on a smooth tibial base plate. Slight
improvements in knee scores and pain have been noted, but no
long-term differences have been observed and there is a dislocation rate (spin out) of the insert of 2.5%.40,41
The decision whether or not to resurface the patella during
primary TKA has been debated. The results from the Knee
Arthroplasty Trial, a multicentre randomized control trial,
demonstrated at 5 years no benefit in resurfacing with regard to
functional status, treatment cost, or quality of life, although there
was a non-significantly higher re-operation rate in the nonresurfaced group compared to the resurfaced group over that
time frame.42 The senior author (CG) prefers to resurface the
patella in most patients. However, in the presence of patellofemoral joint wear of grade two or less, in a patient with no systemic disease (rheumatoid, hypothyroidism or diabetes) and
with a well-tracking patella on trialling of the prostheses, the
patella is left unresurfaced.
The potential role of computer navigated surgery (CAS)
should also be considered pre-operatively to aid the placement of
prosthetic components. There are advantages to CAS including
the calculation of soft tissue tension to perfectly balance the
knee, the accurate restoration of the mechanical alignment,
reducing blood loss and fat embolism, but there are also disadvantages including prolonged operation time, higher costs and
lack of long-term evidence of benefit.2 A recent review of CAS
demonstrates that it improves the alignment of the components,
but there is no demonstrable improvement in outcomes; its role
may be in complex primary and revision TKA.2
Specifics of consent
Who should take consent?
The responsibility for the taking of consent for TKA surgery falls
on the operating surgeon. If it is not practical for the operating
surgeon to take the consent, they can delegate this role to a
suitably trained and qualified person with sufficient knowledge
of the proposed operation and who understands the risks
involved and the principles of consenting patients as outlined in
the GMC guidance.45 If this role is delegated the operating surgeon is still responsible for ensuring that the patient has had
sufficient time and information to make an informed decision
and that the patient has given their informed consent before
commencing the operation.
Consent for primary TKA
Principles and legal background
The consenting process for a TKA, as for any procedure, is a
dialogue between the patient and the surgeon culminating in the
patient giving permission for the operation to be performed. In
order to give consent the patient must have intellectual capacity,
be acting voluntarily and be broadly aware of the nature and
purpose of the treatment.43 The process of obtaining informed
consent involves explaining the salient features of the procedure,
describing any alternative therapies (including any conservative
management), describing the risks of the procedure, answering
any relevant questions and asking for the patient’s written
permission to proceed to surgery.44,45 The decision to consent is
not binding and the patient still has the autonomy to withdraw
that consent at any point.46
Guidance from the General Medical Council (GMC) encourages orthopaedic surgeons to work in partnership with their
patients and discuss with them, in a way they understand, their
medical condition and the intended operation. Patient autonomy
must be respected allowing the patient to make their own
informed decision regarding their care.45
Consent can be written, verbal or implied, but for a significant
operation, such as a TKA, written informed consent should be
obtained.45,46 It is, however, worth bearing in mind that signed
written consent can be invalid if the consenting process is
inadequate.43 Obtaining informed consent is a continuous process; it is recommended that consent should be taken in clinic at
the point the patient is placed on the operating list (preferably
ORTHOPAEDICS AND TRAUMA 27:6
What should be discussed?
In the process of obtaining informed consent for a primary TKA
the surgeon must do the following: introduce themselves and
describe their role in the management of the patient, inform the
patient of their knee pathology and the likely disease progression,
the management options including non-operative treatments, the
potential risks and benefits of the procedure, explain to the patient
their right to refuse the operation or seek a second opinion.45 If the
procedure is being performed in the private medical sector, the
cost of any procedure must also be discussed as should any potential conflict of interest which may impact patient care.45 This
conversation should be tailored depending on the specific needs
and concerns of each individual patient. The surgeon can
augment this discussion with written or any other up-to-date
multimedia material. Patients should also be consented for their
data to be collected for the National Joint Registry database.
Risks of surgery
The risks of TKA surgery must be clearly and accurately
explained in a way the patient understands in order to make an
informed decision.45 The risks should be presented in a balanced
fashion and include the side effects of having a TKA, the potential complications of surgery and the potential failure of the
TKA to achieve the desired outcome.45 When assessing the risk
of surgery the patient’s specific co-morbidities must be considered and the patient specific surgical risks should be explained.45
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MINI-SYMPOSIUM: THE KNEE
Complication rates (BOA consent form, literature and joint registries)
Complication
BOA consent form rate (%)
Joint registry/literature rate (%)
Pain
2e5%
Dissatisfaction
Bleeding necessitating transfusion
Blood vessel damage
Revision
Knee stiffness
e
2e5
<1
e
2e5
Prosthesis wear
Infection
Deep vein thrombosis
Pulmonary embolism
Myocardial infarction
Death
Nerve damage
Bone damage (fracture)
2e5
1e2
2e5
<1
e
<1
<1
<1
Altered wound healing
Joint dislocation
Leg length discrepancy
<1
<1
<1
1 month: 44.4; 3 months: 22.6; 6 months:
18.4; 12 months: 13.1
14e19
15.1
0.08e0.17
6.6
1.3e5.3; necessitating manipulation under
anaesthesia: 2
Necessitating revision: 7e15
1.6
Symptomatic 1.8; asymptomatic 38.1
0.7e0.81; fatal 0.15
0.4
0.5
Peroneal 0.3; overall 1.3
Supracondylar fracture: 0.3e2.5; patellar
fracture: 0.05e21; tibial fracture: rare
e
0.5
e
Table 1
Conclusion
Contrary to the widely held belief that the patient should only be
informed of risks of >1%, patients must be informed of any serious
adverse outcome from the operation, even if they occur infrequently, and they should also be informed of less serious
frequently occurring risks. The GMC describe a serious adverse
outcome as, “an outcome resulting in death, permanent or longterm physical disability or disfigurement, medium or long-term
pain, or admission to hospital; or other outcomes with a longterm or permanent effect on a patient’s employment, social or
personal life.” The table above lists the clinically significant complications of primary TKA surgery and compares the complication
rates listed on the BOA validated consent forms with those published in the literature and from joint registry data.44 (Table 1)
Primary TKA is a successful operation but one which requires
careful pre-operative planning to achieve the best outcome.
Adequate pre-operative planning for primary TKA includes
appropriate patient selection for the operation, clinical and radiological evaluation of the limb, pre-operative medical assessment,
selection of an appropriate TKA prosthesis and adequate patient
counselling about the operation, which culminates in the patient
providing written informed consent for surgery.
A
REFERENCES
1 National joint registry of England and Wales. 9th annual report, 2012.
http://www.njrcentre.org.uk/NjrCentre/Portals/0/Documents/England/
Reports/9th_annual_report/NJR%209th%20Annual%20Report%
202012.pdf. Accessed August 27, 2013.
2 Desai AS, Dramis A, Kendoff D, Board TN. Critical review of the current practice for computer-assisted navigation in total knee
replacement surgery: cost-effectiveness and clinical outcome. Curr
Rev Musculoskelet Med 2011; 4: 11e5.
3 Ethgen O, Bruyere O, Richy F, Dardennes C, Reginster J-Y. Healthrelated quality of life in total hip and total knee arthroplasty. A
qualitative and systematic review of the literature. J Bone Joint Surg
Am 2004; 86-A: 963e74.
4 Harris WH, Sledge CB. Total hip and total knee replacement (2).
N Engl J Med 1990; 323: 801e7.
5 Singh JA. Epidemiology of knee and hip arthroplasty: a systematic
review. Open Orthop J 2011; 5: 80e5.
6 National Institute for Health and Care Excellence. Preoperative tests
the use of routine preoperative tests for elective surgery, CG3.
London: National Institute for Health and Care Excellence, 2003.
Litigation relating to primary TKA
With the growing litigious culture in orthopaedic surgery, especially lower limb arthroplasty, insufficiency in the consenting
process is a common source of legal complaint.48 The volume
and cost of litigation claims relating to TKA is rising significantly.49 By reviewing the National Health Service Litigation
Authority database of claims made relating to TKA, it is clear that
the litigation success rates are higher when involving technical
errors, but a large number of claims brought (39%) related to
poor patient reported outcome.50,51 The mismatch between patient expectation, informed consent and outcome is at the core of
many claims and often centres on the fact that the patient feels
they were not properly counselled regarding the risks and potential complications of the procedure.48,49 Errors, insufficiencies
and omissions in the provision of information relating to forthcoming TKA surgery leads to confused patients and puts orthopaedic surgeons and health trusts at risk of litigation and must be
remedied prior to surgery.47
ORTHOPAEDICS AND TRAUMA 27:6
352
Ó 2013 Elsevier Ltd. All rights reserved.
MINI-SYMPOSIUM: THE KNEE
7 Ibrahim MS, Khan MA, Nizam I, Haddad FS. Peri-operative interventions producing better functional outcomes and enhanced recovery following total hip and knee arthroplasty: an evidence-based
review. BMC Med 2013; 11: 37.
8 Cook JR, Warren M, Ganley KJ, Prefontaine P, Wylie JW.
A comprehensive joint replacement program for total knee arthroplasty: a descriptive study. BMC Musculoskelet Disord 2008; 9: 154.
9 Kamal T, Conway RM, Littlejohn I, Ricketts D. The role of a multidisciplinary pre-assessment clinic in reducing mortality after complex
orthopaedic surgery. Ann R Coll Surg Engl 2011; 93: 149e51.
10 Crockarell JR, Guyton JL. Part III e arthroplasty of ankle and knee. In:
Canale, ed. Campbell’s operative orthopaedics. 10th edn. Mosb.,
2003.
11 Winiarsky R, Barth P, Lotke P. Total knee arthroplasty in morbidly
obese patients. J Bone Joint Surg Am 1998; 80: 1770e4.
12 Samson AJ, Mercer GE, Campbell DG. Total knee replacement in the
morbidly obese: a literature review. ANZ J Surg 2010; 80: 595e9.
13 Chiu FY, Lin CF, Chen CM, Lo WH, Chaung TY. Cefuroxime-impregnated cement at primary total knee arthroplasty in diabetes mellitus. A prospective, randomised study. J Bone Joint Surg Br 2001;
83: 691e5.
14 Erdogan AO, Gokay NS, Gokce A. In: Kinov Plamen, ed. Preoperative
planning of total knee replacement, arthroplasty e update. InTech,
2013 ISBN 978-953-51-0995-2. http://dx.doi.org/10.5772/55023.
Available from: http://www.intechopen.com/books/arthroplastyupdate/preoperative-planning-of-total-knee-replacement. Accessed
August 27, 2013.
15 Fitzgerald SJ, Trousdale RT. Why knees fail in 2011: patient, surgeon,
or device? Orthopedics 2011; 34: e513e5.
16 Lotke PA, Ecker ML. Influence of positioning of prosthesis in total
knee replacement. J Bone Joint Surg Am 1977; 59: 77e9.
17 Fang DM, Ritter MA, Davis KE. Coronal alignment in total knee
arthroplasty: just how important is it? J Arthroplasty 2009; 24(Suppl
6): 39e43.
18 Ee G, Pang HN, Chong HC, Tan MH, Lo NN, Yeo SJ. Computer navigation is a useful intra-operative tool for joint line measurement in
total knee arthroplasty. Knee 2013; 20: 256e62.
19 Insall JN, Binazzi R, Soudry M, Mestriner LA. Total knee arthroplasty.
Clin Orthop Relat Res 1985; 192: 13e22.
20 Malo M, Vince KG. The unstable patella after total knee arthroplasty:
etiology, prevention, and management. J Am Acad Orthop Surg 2003;
11: 364e71.
21 Kozinn SC, Scott R. Unicondylar knee arthroplasty. J Bone Joint Surg
Am 1989; 71: 145e50.
22 Menke W, Schmitz B, Salm S. Range of motion after total condylar
knee arthroplasty. Arch Orthop Trauma Surg 1992; 111: 280e1.
23 Mihalko WM, Whiteside LA. Bone resection and ligament treatment
for flexion contracture in knee arthroplasty. Clin Orthop Relat Res
2003; 406: 141e7.
24 Cross MB, Nam D, Plaskos C, et al. Recutting the distal femur to increase maximal knee extension during TKA causes coronal plane
laxity in mid-flexion. Knee 2012; 19: 875e9.
25 McPherson EJ. Adult Reconstruction. In: Miller M, Thompson S, Hart J,
eds. Review of orthopaedics. 6th edn. Elsevier Saunders, 2012.
26 Ahlb€
ack S. Osteoarthrosis of the knee. A radiographic investigation.
Acta Radiol Diagn 1968;(suppl 277); 7e72.
27 Insall J, Salvati E. Patella position in the normal knee joint. Radiology
1971; 101: 101e4.
ORTHOPAEDICS AND TRAUMA 27:6
28 Merchant AC, Mercer RL, Jacobsen RH, Cool CR. Roentgenographic
analysis of patellofemoral congruence. J Bone Joint Surg Am 1974;
56: 1391e6.
29 Blakeney WG, Khan RJK, Wall SJ. Computer-assisted techniques
versus conventional guides for component alignment in total knee
arthroplasty: a randomized controlled trial. J Bone Joint Surg Am
2011; 93: 1377e84.
30 Lonner JH, Siliski JM, Lotke PA. Simultaneous femoral osteotomy
and total knee arthroplasty for treatment of osteoarthritis associated with severe extra-articular deformity. J Bone Joint Surg Am
2000; 82: 342e8.
31 Miller AG, Purtill JJ. Total knee arthroplasty component templating: a
predictive model. J Arthroplasty 2012; 27: 1707e9.
32 Hsu AR, Gross CE, Bhatia S, Levine BR. Template-directed instrumentation in total knee arthroplasty: cost savings analysis. Orthopedics 2012; 35: e1596e600.
33 Wright G, Chitnavis J. Which design of TKR e does it matter? J Bone
Joint Surg Br 2011. Available at: http://www.boneandjoint.org.uk/
sites/default/files/FocusOn_TKRdesign.pdf. Accessed 27 Aug 2013.
34 Jacobs WCH, Clement DJ, Wymenga AB. Retention versus removal of
the posterior cruciate ligament in total knee replacement: a systematic literature review within the Cochrane framework. Acta Orthop
2005; 76: 757e68.
35 Delport HP, Banks SA, De Schepper J, Bellemans J. A kinematic
comparison of fixed- and mobile-bearing knee replacements. J Bone
Joint Surg Br 2006; 88: 1016e21.
36 Worland RL, Jessup DE, Johnson J. Posterior cruciate recession in total
knee arthroplasty. J Arthroplasty 1997; 12: 70e3.
37 Paletta GA, Laskin RS. Total knee arthroplasty after a previous
patellectomy. J Bone Joint Surg Am 1995; 77: 1708e12.
38 Mihalko WM, Krackow KA. Posterior cruciate ligament effects on the
flexion space in total knee arthroplasty. Clin Orthop Relat Res 1999;
360: 243e50.
39 Puloski SK, McCalden RW, MacDonald SJ, Rorabeck CH, Bourne RB.
Tibial post wear in posterior stabilized total knee arthroplasty. An
unrecognized source of polyethylene debris. J Bone Joint Surg Br
2001; 83-A: 390e7.
40 Kim Y-H, Yoon S-H, Kim J-S. The long-term results of simultaneous fixed-bearing and mobile-bearing total knee replacements
performed in the same patient. Acta Radiol Diagn 2007; 89:
1317e23.
41 Price AJ, Rees JL, Beard D, et al. A mobile-bearing total knee prosthesis compared with a fixed-bearing prosthesis. A multicentre
single-blind randomised controlled trial. J Bone Joint Surg Br 2003;
85: 62e7.
42 Breeman S, Campbell M, Dakin H, et al. Patellar resurfacing in
total knee replacement: five-year clinical and economic results of a
large randomized controlled trial. J Bone Joint Surg Am 2011; 93:
1473e81.
43 Pattinson SD. Medical law and ethics. 3rd edn. Thompson Reuters
(Professional) UK Limited, 2011.
44 Beresford-Cleary NJ, Beresford-Cleary N, Halliday J, et al. Consent
process for elective total hip and knee arthroplasty. J Orthopaedic
Surg (Hong Kong) 2011; 19: 274e8.
45 General Medical Council. Consent: patients and doctors making decisions together. London: General Medical Council, 2008.
46 Department of Health. Reference guide to consent for examination or
treatment. 2nd edn. London: Department of Health, 2009.
353
Ó 2013 Elsevier Ltd. All rights reserved.
MINI-SYMPOSIUM: THE KNEE
47 Atrey A, Leslie I, Carvell J, et al. Standardised consent forms on the
website of the British Orthopaedic Association. J Bone Joint Surg Br
2008; 90: 422e3.
48 Khan IH, Jamil W, Lynn SM, Khan OH, Markland K, Giddins G. Analysis of
NHSLA claims in orthopedic surgery. Orthopedics 2012; 35: e726e31.
49 McWilliams AB, Douglas SL, Redmond AC, et al. Litigation after hip
and knee replacement in the National Health Service. Bone Jt J 2013;
95-B: 122e6.
ORTHOPAEDICS AND TRAUMA 27:6
50 Atrey A, Gupte CM, Corbett SA. Review of successful litigation against
English health trusts in the treatment of adults with orthopaedic
pathology: clinical governance lessons learned. J Bone Joint Surg Am
2010; 92: e36.
51 Chen A, Khan Y, Akhtar K, Cobb JP, Gupte CM. Cost of adverse events
in knee arthroplasty e a review of the National Health Service Litigation Authority database. In: Bask spring meeting March 2013;
12e13 [Leeds, UK].
354
Ó 2013 Elsevier Ltd. All rights reserved.