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Nicholas Wei and Paul Banaszkiewicz
Figure 5.16 Normal bone ingrowth acetabular component. This
acetabular component shows signs of osseointegration with no
lucent lines present, developing superolateral sclerosis, medial
osteopenia (stress shielding), and remodelling of trabeculae (arrow).
pattern usually begins to develop. As the abnormal
contact forces associated with an arthritic hip are
replaced by the predominantly direct, compressive
force associated with an osseointegrated cup, the
trabeculae reorient in line with that force and
radial trabeculae are seen radiographically.
Moore MS, McAuley JP, Young AM, Engh Sr
CA. Radiographic signs of osseo integration in
porous-coated acetabular components. Clin
Orthop Relat Res. 2006;444:176–183.
Chang CY, Huang AJ, Palmer WE.
Radiographic evaluation of hip implants. Semin
Musculoskeletal Radiol. 2015;19:12–20.
7. Answer E. Pathogenesis involves a delayed
hypersensitive (type IV) response to Co-Cr
particles
The lesion seen on the MRI scan is highly suggestive of a pseudotumour. A pseudotumour is
a cystic lesion in the periarticular region that
is neither infective no r neoplastic. It develops in
the vicinity of a THA and has a direct communication with the joint. It is best diagnosed using
Metal Artefact Reducing Sequence (MARS) MRI.
Biopsy is generally not performed on a pseudotumour. FNA biopsy may occasionally be indicated if infection or malignancy is suspected.
ALVAL is a histological diagnosis made from
tissue sampling at the time of revision surgery
identifying an abundance of lymphocytes in the
local pericapsular tissue. There is a spectrum of
(a) (b)
84
Figure 5.17 (a) A post-operative
radiograph showing an absence of a
superolateral buttress, and the (b) prerevision radiograph shows a superolateral
buttress (white arrows).
(a) (b)
Hip III Structured SBA
Figure 5.18 (a) A post-operative
radiograph shows the presence of
subchondral sclerosis (black arrows), and
the (b) pre-revision radiograph
demonstrating that the subchondral
sclerosis has resolved and medial stress
shielding has occurred (white arrows).
Figure 5.19 (a) A post-operative
radiograph demonstrating a radial
trabecular pattern. (b) The radial
trabecular pattern is more evident in the
pre-revision radiograph (white arrows).
(a) (b)
necrotic and inflammatory changes in response to
deposition of cobalt chromium wear particles.
A pseudotumour can present in different
ways. Common presentations include gradually
worsening groin pain, hip pain with or without
groin pain, or a palpable swelling. More often, it is
asymptomatic.
The patient’s hip symptoms may be due to a
variety of both intra- and extra-articular reasons
and may not necessarily be specific to an adverse
reaction to metal debris (ARMD).
The pathogenesis of a pseudotumour is uncertain but it may involve both a delayed hypersensitivity (type IV) response to Co-Cr particles and
85
Nicholas Wei and Paul Banaszkiewicz
cytotoxicity. Option E is partially correct but the
best option of the available five to choose.
Mahendra G et al. Necrotic and inflammatory
changes in metal-on-metal resurfacing hip arthroplasties. Acta Orthop. 2009;80:653–659.
8. Answer C. Loose femoral component
Diagnosis of a loose femoral component can be
difficult. It is important to exclude extrinsic and
other causes of intrinsic hip pain.
Whilst thoracolumbar discogenic pain may present in a non-specific manner patients would usually
complain of both low back pain and neurogenic pain.
The giveaway for a loose femoral component is
the antalgic gait with abductor lurch. The antalgic
gait is caused by motion of the stem within the
femoral canal. With significant stem subsidence an
abductor lurch is often seen as the abductors have
shortened and are at a biomechanical disadvantage.
Vastus lateralis muscle herniation through a
defect in the fascia lata is an unusual and rare
cause of thigh pain. This usually presents weeks
to months following surgery as a patient increases
their activity levels.
Abductor muscle atrophy with partial detachment would definitely be in the differential diagnosis but these patients typically have longstanding difficulties and the diagnosis would have
been apparent within a year or so of surgery.
These patients can slowly progress in time until
symptoms become quite disabling but this should
be well documented in the clinic follow-up letters.
Infection following THA must always be ruled
out. At 10 years the cause is most likely to be haematogenous. Patients would typically present with
rest pain and night pain. It is important to try and
identify a source for the infection so ask about any
recent dental procedure, chest or urinary infection.
With persistent hip pain following THA ask about
any history of a leaking wound post-operatively or a
return to theatre for hip washout or DAIR.
Comparison of serial radiographs is the most
useful method for making the diagnosis of a loose
femoral stem. Otherdifferentials for thigh pain include
mismatch in the modulus of elasticity between an
implant and host bone (mostly an issue for uncemented stems), stress fractures and oncological lesions.
Moucha CS. I have a patient with start-up thigh.
In Curbside Consultation in Hip Arthroplasty: 49
Clinical Questions. SLACK Incorporated, 2008:81.
9. Answer A. Aspirate the hip
The use of oral antibiotics is generally discouraged
until a definite diagnosis is made as the indiscriminate use of antibiotics will cloud the clinical
picture.
Early discontinuation of anticoagulation treatment following arthroplasty surgery is a balance
between reducing the risk of thromboembolism
and preventing excessive bleeding. The decision
must be individualised for each patient, weighing
up the risks and benefits of stopping prophylaxis.
Discontinued anticoagulation use at 2 or 3 days due
to a leaky wound is a reasonable option especially if
there is a suggestion of over anticoagulation (low
BMI, reduced renal function, advanced age) but at
10 days the preferrable option is to aspirate the hip.
DAIR would be used for a patient that has a
proven hip infection.
Persistent wound drainage (PWD) following
arthroplasty surgery and appropriate wound management strategies have been shown to reduce the
risk of surgical site infection and development of
deep joint infection. We do not currently have UK
agreed definitions of PWD or an agreed way of
managing wounds that are persistently draining to
prevent development of infection. The UKPJI
group are working to try and develop a UK consensus in the definition, identification and management of PWD and appropriate dressing
selection to reduce development of infection.
10. Answer B. Inspection and palpation abductor
muscle mass
Cobra head plating involves release of the abductors from the iliac crest to accommodate a cobrashaped plate. This invariably causes damage to the
abductors and can be problematic if at a later date
conversion to a THAis needed. Weak or destroyed
abductors are considered by some surgeons to be a
contraindication to conversion to a THA.
Although CT, MRI and US scan may be used
to assess abductor status the most important
information about the state of the abductors is
obtained by clinical examination. Inspection and
palpation of the abductor mass for active contraction, bulk and defects.
Electromyography is thought to be useful to
access the gluteus medius and minimus muscles
for evidence of denervation but this is generally
not performed.
86
Hip III Structured SBA
The patient would be asked to attempt abduction in the arthrodesed hip and the degree of
contraction assessed.
A Trendelenburg test (TT) will give you a false
negative result as the pelvis will not move despite
probable abductor muscle compromise. In general
if a hip is fused a TT should not be performed as
this suggests a candidate doesn’t fully understand
the biomechanical principles behind the test.
An option that we removed was ‘CT scan to
assess abductor status’.
A CT is useful in the assessment of the bone
stock and identifying if a pseudarthrosis is present but not abductor status. Trendelenburg test
(TT) was a much better plausible distractor.
11. Answer E. Refer on to hip surgeon who per-
forms MoM resurfacing
This is a difficult clinical situation. The patient
despite his young age has advanced hip OA and
although continuing on with conservative management is an option, he is unlikely to accept
this. A steroid local anaesthetic injection is best
used if there is any diagnostic uncertainty as to
the source of pain and would be unlikely to
provide any long-term therapeutic value.
A hip fusion remains an option in a young
male patient with advanced osteoarthritis but it is
unlikely that he would agree to it given the excellent outcomes following THA.
THA is likely to result in early failure in a
young active patient and whilst certainly an
option would be ideally managed with a second
opinion from an experienced hip surgeon.
Referral on to a hip surgeon who performs
MoM hips is a good option as the patient can
explore the possi bility of a MoM hip which still
has a role albeit in a very narrow defined group
of patients. Young males either with a heavy
manual job or those still wanting to play sports
such as football. Even if a MoM hip is not performed the patient has a further opinion
regarding his hip arthritis and whether to proceed or not with a more conventional THA.
MoMhipsareagoodoptioninmanual
workers or in an occupation that places the hip at
a risk for dislocation (e.g. carpenter, steel worker).
This is an ideal test SBA as we have not
included a radiograph to better guide a candidate
and also made the clinical situation suitably vague.
It is very similar to a real SBA seen in the exam.
SBA exam questions may have incomplete clinical
information on purpose so that you have to apply
higher order thinking to the situation to come up
with the most appropriate clinical choice.
12. Answer E. Increased transfusion requirements
The literature regarding 2-stage bilateral THA
versus simultaneous bilateral total hip arthroplasty (SBTHA) is controversial and contradictory. Not good terms to come across when
constructing SBAs!
This is a good SBA to test for higher order
thinking and having to make assumptions.
The benefits of SBTHA include patients
needing only one anaesthesia, only one hospital
stay, a reduced overall hospital length of stay
(LOS), cost reduction and similar outcomes.
Some studies advocate SBTHA as they have
demonstrated that the rates of perioperative
complications are similar to staged bilateral
THA (Stavrakis et al. 2015).
Huang et al. (2019) suggested the sa fety
and reliability of simultaneous bilateral THA
(SBTHA) in low-risk patients showing a reduction
of LOS, a shorter anaesthesia and surgery time,
faster rehabilitation and better cost-effectiveness.
Opposing studies have found that SBTHA
poses greater risks to patients, with increased
transfusions, greater adverse events and suboptimal functional outcomes.
A meta-analysis by Shao et al. (2017)
reported SBTHA had a lower risk of major systemic complications, less DVTs, and shorter
operative time compared with 2-stage bilateral
THA. There were no significant differences in
death, pulmonary embolism, cardiovascular
complication, infections, minor complications,
and other surgical complications between procedures. Interestingly this study did not encourage performing simultaneous over 2-stage
bilateral THA as the paper concluded that higher
evidence level studies were needed before firm
recommendations could be given.
Allogenic blood transfusion is a known risk
factor for post-operative infection, venous
thromboembolism and acute lung injury in
TJA. Although there are differences in studies,
the transfusion rate after SBTHA is reported to
be as high as 50%.
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Nicholas Wei and Paul Banaszkiewicz
For the average day one fellowship trained
consultant hip surgeon in a DGH, whilst
SBTHA may have a role in patients with AS or
those with significant bilateral flexion deformities, the surgery would need careful planning.
SBTHA is a demanding procedure and ultimately may best be performed in high volume
centres by more experienced surgeons.
Several studies have been conducted to determine which is the best way to address a patient
requiring bilateral hip surgery. Unfortunately,
there are few definitive conclusions. There is a
lack of control groups with few prospective studies. Most of the literature often compares
SBTHA with unilateral THA.
Recent interest has focused on bilateral DAATHA as it offers an opportunity to consider a
simultaneous bilateral procedure under one
anaesthetic and without repositioning.
Disadvantages include a steep learning curve
and a possible increased risk of intraoperative
femoral fracture.
Ramezani et al. (2022) in a systematic review
and meta-analysis demonstrated that simultaneous and staged THA have similar 90-day mortality, dislocation and PJI rates. A statistically
significant risk reduction was identified in DVT,
pulmonary, systemic and local complications in
the SBTHA group. Reduced length of hospital
stay and total surgery cost are considered essential
advantages of SBTHA compared with 2-stage
THA (Ramezaniet et al. 2022).
In summary SBTHA comprise about 1% of
THA. They are more commonly performed in
males, younger patients, those with private insurance, higher volume hospitals and lower risk
patients (ASA 1, 2). There may be a role for
SBTHA surgery in selected indi viduals especially
considering the cost savings involved.
Shao H et al. Bilateral total hip arthroplasty:
1-stage or 2-stage? A meta-analysis. J
Arthroplasty 2017;32:689–695.
Stavrakis AI, SooHoo NF, Lieberman JR.
Bilateral total hip arthroplasty has similar complication rates to unilateral total hip arthroplasty.
J Arthroplasty 2015;30:1211–1214.
Ramezani A et al. Simultaneous versus
staged bilateral total hip arthroplasty: a systematic review and meta-analysis. J Ort hop Surg Res.
2022;17:392.
Huang L et al. Comparison of mortality and
complications between bilateral simultaneous and
staged total hip arthroplasty: a systematic review
and meta-analysis. Medicine (Balt.) 2019;98:e16774.
13. Answer C. Cemented total hip arthroplasty
This patient is borderline alcoholic with probable
osteoporosis so there is a high chance that
internal fixation with either cannulated screws
or a DHS would fail. The surgery most likely to
get the patient back to walking again as quickly
as possible would be a cemented THA, provided
she met NICE guidelines for this.
An uncemented THA is not a good option in
someone likely to be osteoporotic. In particular,
in this situation an uncemented femoral stem
could sink down into the femur with failure of
osteointegration, LLD and a risk of dislocation.
In general aim to perform a cemented femoral
stem in every fracture patient. Very occasionally a
cementless femoral stem may be indicated but be
confident about the bone quality, young age of
patient, no inflammatory arthritis etc.
In general, it is best to avoid a cemented
monopolar arthroplasty in someone this young.
An Exeter bipolar hemiarthroplasty is a reasonable option if the patient is considered too high
risk for a THA. This patient is relatively young at
51 so she would need to have a number of additional co-morbidity factors before opting for a
bipolar prosthesis over THA.
The fracture pattern is intracapsular and if
undisplaced and she was younger with no significant co-morbidity issues there would be merit
in discussing fixation options with her with the
warning that if ORIF failed a THA would be
required at a later date.
A hybrid THA would be our preferred method
as it is likely a larger femoral head could be
used reducing the dislocation risk. Supplementary
acetabular cup screws should be used to reduce any
excessive cup motion and help with osseointergration. This choice wasn’t given in the options.
14. Answer A. Bipolar cemented hemiarthroplasty
hip
The fractured NOF occurring in various age
groups, with different fracture patterns and different co-morbiditi es is fair game for at least 1 or
2 SBA questions in each Part 1 exam sitting.
88
Hip III Structured SBA
An alcoholic patient with ost eoporosis.
Compared with question 13 the patient is
younger but with a presumed higher alcohol
intake and inference that she is probably alcoholic arising from the concern regarding fitness
for surgery. It is preferable to again avoid
internal fixation as bone quality would be poor
and the fracture unlikely to heal.
The choice lies between a THA or bipolar
hip. A THA is a high-risk procedure with concerns regarding post-operative physiotherapy
compliance (dislocation risk), increased blood
loss, wound healing issues and deep infection.
A bipolar arthroplasty is a safer option, less of a
surgical insult, less operating time, less blood loss, a
more stable prosthesis and can be converted at a
later date to THA if acetabular erosion develops.
The design of the bipolar implant allows for
inter-prosthetic movement between the inner
and outer head. This theoretical mechanical
advantage results in minimal acetabular erosion
without risking dislocation, ideal for younger
and more active patients than a monopolar prosthesis. A monopolar hemiarthroplasty should be
avoided in a 38-year-old female even if alcoholic.
15. Answer D. Dual mobility cup
Many patients with Parkinson’s disease (PD) have
severe hip osteoarthritis that warrants THA.
The muscular rigidity and diminished bone quality
encountered in these patients presents important
challenges to the orthopaedic surgeon. Disease
symptoms, such as tremor, shuffling gait and
instability, can potentially make performing THA
riskier. The unsteadiness in PD patients makes
them more likely to fall, resulting in post-operative
prosthesis dislocation and periprosthetic fracture.
Because of these concerns, PD has historically been
considered a relative contraindication to THA.
All listed options will decrease the risk of
dislocation.
Recent studies indicate that short-term
results of THA using cementless dual mobility
implant in patients with PD reduces the dislocation rate without an increased risk of loosening
(Lazennec et al. 2018). This is a good management option to deal with the increased risks of
dislocation in this population group.
A captive cup is generally viewed as a last ‘get
out of jail’ option for a recurrent hip dislocator. It
is best avoided in a primary arthroplasty setting.
Inserting an uncemented captive cup risks the
shell pulling out of the bony acetabulum in the
early post-operative period before osseointegration has occurred. The use of acetabular screws
reduces but does not eliminate this risk. A lipped
liner will decrease the risk of dislocation but at the
expense of reducing hip range of movement.
Use of a 36mm head reduces dislocation risk
but this is not as effective as using a dual motion
implant. A large femoral head may increase the
risk of trunnionosis.
Many experienced hip surgeons believe that
there is little evidence to support the view that
the Hardinge anterolateral approach reduces the
risk of a dislocation and that there are significant
disadvantages using a Hardinge approach
(abductor muscle damage).
Lazennec JY, Kim Y, Pour AE. Total hip arthroplasty in patients with Parkinson disease: improved
outcomes with dual mobility implants and cementless fixation. J Arthroplasty 2018;33:1455–1461.
Silverberg A, Parvataneni HK, Pulido L,
Prieto H. The current role of dual mobility
articulations in total hip arthroplasty. J Hip
Surgery 2018;2(:194–204.
16. Answer C. Convert to using a cement cup
If the surgeon finds the bone quality to be poor
when reaming the acetabulum and is concerned
about achieving either a good press fit or osteointegration they should consider changing plan and
using a cemented component instead. This may
mean trading off an increased dislocation risk using
a smaller head size against eliminating the concern
of failure to osseointegrate when using an uncemented cup. Partial weight bearing for several weeks
is an option if the initial press fit is suboptimal
but it is unlikely the patient would comply with this.
Theoretically, a press-fit method does not
require additional screw fixation since sufficient
primary fixation can be achieved.
Whilst additional screw fixation can be used in
certain situations if press-fit fixation alone is not
satisfactory the giveaway in the SBA is that the
bone quality is poor. In this situation despite the
use of screws a surgeon may still be unsure about
the chances of successful osteointegration. The
other subtle clue is mild cognitive impairment
with the inference that the risk for revision
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Nicholas Wei and Paul Banaszkiewicz
surgery for this patient should be minimised. The
question does not elaborate on dislocation risk.
Inserting a TM revision shell may provide a
better surface for bone ingrowth but is difficult
to justify on the basis of high cost and its need
in a primary arthroplasty case.
Hydroxyapatite is an adjunct coating and aids
bidirectional closure of gaps and shortens
osseointegration. However, if the cup is loose
and the bone stock also poor, substituting the
cup for one that is HA coated is unlikely to result
in a successful outcome. It is a good distractor
option for the weaker candidate to choose.
Inserting the next sized larger cup into the acetabulum may be successful but with the added concern of poor bone stock is best avoided in this
situation. This would usually require additional
acetabular reaming which in some situations is
undesirable. The acetabulum may end up being
over-reamed predisposing to an acetabular fracture
+/ possible dissociation. Again, the surgeon
should avoid taking any unnecessary risks that
may end up resulting in needing revision surgery.
In order to obtain long-term osseointegration, a press-fit acetabular cup must gain initial
rigid stability with limited micromotion. In addition, the implant surface must promote
ingrowth and maintain contact with viable bone.
17. Answer C. Increased risk of mortality
Some studies report higher perioperative complications, longer hospital stays, poorer wound
healing and more anaesthetic complications in
obese patients undergoing THA. Furthermore,
obesity is associated with poor short-term
outcomes after undergoing THA, with reported
complications of increased rates of periprosthetic
infections, dislocations and instability. Other
studies report no difference in short-term outcomes in obese patients after THA.
A recent systematic study reported a revision
rate of 7.99% in the morbidly obese versus 2.75%
in non-obese patients at medium-term follow up
(Barrett et al. 2018).
It is thought that even though a higher BMI is
associated with increased loading of the hip prostheses, the lack of a large difference in aseptic wear
rates may arise from a more sedentary lifestyle in
morbidly obese patients, resulting in reduced mobility and less prosthetic wear (Halawi et al. 2019).
Data fr om the Swedish Hip Registry reported
an increasing risk of reoperat ion at 2 years and
revision at 5 years mainly due to increased risk of
infection. Uncemented and reversed hybrid fixations and surgical approaches other than posterior were all associated with increased risk.
Obesity class III (40), male sex and increasing
ASA class were associated with increased 90-day
mortality (Sayed-Noor et al. 2019 ).
There appears to be no difference in patientreported outcome measurements.
Barrett M et al. Total hip arthroplasty outcomes in morbidly obese patients: a systematic
review. EFORT Open Rev. 2018;3:507– 512.
Halawi MJ, Gronbeck C, Savoy L, Cote MP.
Effect of morbid obesity on patient-reported outcomes in total joint arthroplasty: a minimum of
1-year follow-up. Arthroplasty Today
2019;5:493–496.
Sayed-Noor AS, Mukka S, Mohaddes M,
Kärrholm J, Rolfson O. Body mass index is
associated with risk of reoperation and revision
after primary total hip arthroplasty: a study
of the Swedish Hip Arthroplasty Register
including 83,1 46 patients. Acta Orthopaedica
2019;90:220–225.
18. Answer C. Mode 4 failure can be recognised early
by radiolucencies developing along the proximal
lateral cortex (convex) surface of the stem
In the original paper by Gruen mode Ib is the
most common cause of failure in 5.1% of cases.
Modes 1a, II and IV were each seen in 3% of
cases (Gruen et al. 1979). Mode III (calcar pivot)
was seen only in 3 hips (0.7%).
The radiograph is showing mode IV failure
bending cantilever (fatigue) with femoral stem
fracture. Bending cantilever failure is by far the
most common cause of femoral stem fracture.
The stem is of the composite beam variety
and is most probably a Charnley type stem.
Distally the stem appears to be well fixed but
proximally it is loose within the cement mantle
with lucent lines particularly in Gruen zones 6
and 7 suggesting mode IV failure bending cantilever fatigue with femoral stem fracture.
The four modes of femoral stem failure are
described in detail:
Mode Ia is stem pistoning within the cement,
occurs secondary to an incomp lete cement
90
Hip III Structured SBA
mantle or loss of proximal medial cement
support.
Mode Ib consists of stem/cement subsidence
within bone. This mode of failure is most
familiar to orthopaedic surgeons evaluating
radiographs of loose total hip replacements.
Mode II is medial midstem pivot,
characterised by medial migration proximal
stem coupled with lateral migration distal
stem tip. It is caused by weak proximal/
medial (calcar) support and lack of distal
cement support.
Mode III failure consists of medial-lateral
toggle distal stem due to lack of distal stem
support. This is the windshield type of
loosening.
Mode IV failure is cantilever fatigue failure
characterised by partial or complete loss of
proximal support with subsequent medial
migration of the proximal stem whilst the
distal end remains rigidly fixed in cement.
This mode of failure can be recognised early
by radiolucencies developing along the
proximal lateral cortex (convex) surface of
the stem.
Comment: We have rewritten and recycled this
SBA a couple of times changing either the correct
answer or a distractor. This is similar to what
occurs in the an exam setting when preparing a
paper. This SBA is important as it tests basic
science knowledge of femoral stem failure which
is core knowledge for surgeons and essential for
hip arthroplasty practice.
Gruen TA, McNeice GM, Amstutz HC.
‘Modes of failure’ of cemented stem-type femoral
components: a radiographic analysis of loosening.
Clin Orthop Relat Res.1979;141:17–27.
19. Answer A. Bending cantilever (fatigue)
When writing SBAs what should be a level 2
SBA sometimes ends up being level 1 and tests
factorial knowledge.
A contributing factor to a femoral stem
fracture could be poor femoral stem design –
sub-optimal stem geometry, manufacture (metallurgic defects) and sub-optimal stem material
as the loosening is not dramatic.
Bending cantilever (fatigue) is Gruen mode
IV: the distal cement holds well, but proximal
cement fixation is lost which can lead to fatigue
fracture of the implant.
The SBA is testing the same core knowledge
as in the previous SBA but the twis t in the question is femoral stem fracture. In the original
paper by Gruen Mode Ib is the most common
cause of failure in 5.1% of cases.
When there is some doubt as to the correct
answer go back to the original paper. Gruen
et al. reported that among the 7 femoral components requiring revision were 2 fractured
femoral components both of which had failed
in mode IV.
Figure 5.20 Gruen modes of cemented femoral stem failure.
Copyright 2014 Springer-Verlag London
20. Answer C. Fourt h generation involves using
distal and proximal centralisers to ensure an
even cement mantle
The specific technical details of what exactly each
generation of cementing technique entails is
often unclear and mixed up between various
textbooks.
Our understanding is that fourth generation
involves both proximal and distal cement centralisers. The proximal centraliser may also be used
to enhance pressurisation after insertion of the
stem.
The importance of a complete cement mantle
is recognised and led to the development of both
91
Nicholas Wei and Paul Banaszkiewicz
distal and proximal centralisers. These centralisers facilitate the ability to reproducibly create an
adequate cement mantle by placing the stem in
the centre of the cavity.
Fourth generation cementing also includes
refinements of stem design and advances in
material science. In a number of books only three
generations of cementing techniques are mentioned, the third being known as contemporary.
As such option E is correct but less correct than
option C.
Late insertion of an implant into viscous
cement is widely practiced and considered part
of third-generation cementing technique.
‘First-generation’, cementing techniques did
not involve bone preparation (i.e. washing or
drying) before cement insertion. In addition,
the cement was inserted antegrade by hand with
no attempt at pressurisation beyond finger
packing. An intramedullary plug was not used.
These techniques caused the potential for cement
lamination, inclusion of blood or voids within
the cement, inadequate cement mantles, and
poor penetration of the cement into the interstices of the cancellous bone. Despite these limitations there are many reports of good long-term
survivorship of prostheses inserted using this
technique.
‘Second-generation’ techniques involve the
bone being (thoroughly) cleaned before cement
insertion, using an intramedullary plug, and the
cement inserted retrograde to reduce blood laminations and cement voids (gun and restrictor).
‘Third-generation’ cementation techniques
introduced the concept of maintaining pressurisation of the cemen t before and during insertion
of the femoral stem. This was achieved by placing
a rubber seal around the nozzle of the cement
gun, which effectively sealed the proximal end of
the femoral canal. After retrograde insertion of
the cement, further cement was delivered
through the seal. The medullary canal was thus
sealed distally and proximally. As more cement
was inserted, the pressure increased, and the
cement was forced into the interstices of the
surrounding bone.
Third generation includes serial pulsed
lavage, vacuum mixing of cement, obtaining a
thoroughly dried femoral canal to improve bone
cement penetration.
Figure 5.21 Fourth generation involves using distal and proximal
centralisers to ensure an even cement mantle. (a) no centralisers, (b)
distal centraliser and (c) proximal and distal centralisers. Copyright
Springer.
Figure 5.22 Proximal centraliser used intraoperatively
92
Hip III Structured SBA
Pulsed lavage appears to jump between second
and third generations of cement depending on
what textbook is read. However, pulsed lavage
is probably best thought of as third-generation
cementing. Vacuum mixing results in porosity
reduction of the cement.
Surface modifications of the implant include
the avoidance of sharp edges and a broader lateral surface.
Learmonth ID. The evolution of contempor-
ary cementation techniques. Orthopaedics
2005;28:S831–S832.
21. Answer C. Pathophysiology is an inappropriate
differentiation of pluripotent mesenchymal stem
cells
The radiograph demonstrates heterotopic ossification (HO). The osteoblastic cell responsible for
HO is believed to result from inappropriate differentiation of pluripotent mesenchymal
stem cells.
Typically HO is asymptomatic, but higher
Brooker grades can result in impairment of hip
arthroplasty function due to pain, impingement,
instability, decreased ROM, troc hanteric bursitis
and nerve irritation.
The overall incidence of HO originally
reported in Brooker’s paper (21%) is substantially
lower than that accepted these days. A systematic
review by Vavken et al. (2009) has reported an
incidence of 43% and that of severe HO (Brooker
grades III/IV) of 9%.
Risk factors include
Intraoperative muscle ischaemia.
Direct lateral approach.
Extent of soft-tissue dissection.
Bone trauma.
Persistence of bone debris (reamings,
marrow within the surgical field).
HO can be a serious complication after THA
particularly when the amount of bone interferes
with hip motion or produces pain.
Instability is a potential complication of HO
after THA if the periarticular mass of bone contributes to impingement with limitation of hip excursion and initiation of dislocation.
There is a need to ensure the HO is mature
prior to excision (1 year to 18 months) otherwise
Figure 5.23
Brooker
classification of
heterotopic
ossification. (a)
Islands of bone in
the soft tissues. (b)
Bone spurs arising
from the proximal
femur/pelvis with
1cm joint space
between ends. (c)
Bone spurs arising
from the proximal
femur/pelvis with
<1cm joint space
between ends. (d)
Apparent
bony ankylosis
bleeding and reoccurrence can occur. Surgery is
not normally recommended.
Vavken P, Castellani L, Sculco TP.
Prophylaxis of heterotopic ossification of the hip:
systematic review and meta-analysis. Clin Orthop
Rel Res. 2009;467:3283–3289.
22. Answer D. Ankylosed hip
Heterotopic ossification is the abnorma l formation of mature lamellar bone in soft tissues. All
the options provided, except for cementless prosthesis, are valid risk factors. In a meta-analysis by
Zhu et al. (2015) reviewing the risk factors for
HO following THA, they identified male sex,
ankylosing spondylitis, cemented prosthesis,
bilateral hip joint arthroplasty and hip joint
ankylosis as significant risks. Hip ankylosis had
the strongest association (odds ratio = 9.85).
Regarding the cemented prosthesis, it was
suggested that contamination of the surgical field
and activation of osteoprogenitor cells during
preparation of the femoral canal increased the
risk of HO. This is less likely to occur in preparing the femur for an uncemented prosthesis as
the endosteal bone is compacted.
Surgical approach, prosthesis type, and use of
trochanteric or femoral osteotomy also appear to
affect the risk of HO formation. Anterolateral
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