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Austin Moores ProsthesisIts Relevance Today
no aner a r s eo ar r un a wanConsultants
Choithram Hospital & Research Centre, Indore, India
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Improper technique Desi n of Im lant
Design of instruments
THR dominated
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hypertrophy of the bone all around.
months. success u ong s an ng eve op
some osteolysis of the bone.
Osteolysis in THR seen late and damgebecomes a problem
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mechanostat of bone after implant surgery.
Proximal fixation at or above the level of
cancellization of cortical bone in the
.
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the success of the surgery.
,
and allow the grafts in the fenestration to, -
device.
s preven s over- oa ng o ca car nosubsidence, no loosening, no failure.
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.
influences on bone strength and. .
1997;8:6070.
-----------------------------------------------------------
Bone loading - Bone strength
Bone modeling hypertrophy / normal
Bone remodelin h otro h / atro h
-----------------------------------------------------------
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Bone modeling by drifts
(A) An infants long bone with its original size
an s ape s own n so ne. o eep s s apeas it grows in length and diameter, modeling
r s move s sur aces n ssue space as e
dashed lines suggest. Formation drifts makean con ro new os eo as s o u some
surfaces. Resorption drifts make and control
new os eoc as s o remove one rom o ersurfaces.
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(B) A different drift pattern can correct the fracture
-.shows the endocortical as well as the periosteal drifts
that do the correction.
(C) How the drifts in B would move the whole segment
.
reduces the bones bending moments; it does not
, .
when and where they are needed, and they include
capillaries, precursor and supporting cells, and some
wandering cells. They are multicellular entities in thesame sense as renal nephrons, and they usually act to
m n m ze pea one s ra ns
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BMU Renal Nephron
Bone remodeling BMUs. Top row: an activation event on a bone
surface at (A) makes a packet of bone resorption begin
, .
The BMU makes and controls the new osteoclasts andosteoblasts that do this. Second row: this emphasizes the
amounts of bone resorbed (E) and formed (F) by completedBMUs. Third row: in these BMU graphs (G) shows a small
excess of formation over resor tion. H E ualized resor tion andformation as on haversian surfaces and in conservation-mode
remodeling.
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(I) A net deficit of formation, as in disuse-moderemodeling of endocortical and trabecular bone. Bottom
BMUs of the kind immediately above on the local bone .
needed and include a capillary, precursor and supporting
cells, and some wandering cells. They are multicellular
entities in the same sense as renal.
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implantation of an Austin Moore
SB Murphy, PS Walker and AL Schiller
J Bone Joint Surg Am. 1984;66:437- 443.
The calcar and proximal regions are
understrained because much of the loads
and moments are transferred to the bonearound the distal half of the stem.
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-
resistance to axial force, whereas the distal halfof the stem may carry little axial load. The varus
moment on the stem is counteracted by forces at
the medial part of the calcar and the distal tip, ina more concen ra e manner an n a
cemented stem. The radiographic appearance
hypertrophy in the whole proximal area,
es eciall mediall , and local thickenin at a
point level with the tip of the prosthetic stem.
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,hemiarthroplasties have been reviewed in the
,
stem. Results from our finite-element analysis, - ,
the stresses in the stem are small because
bone are uncoupled and, consequently, do not
head and abductor forces.
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resultant bending moment is shared, high stressesin the stem are redicted such stresses are
inconsistent with the complete absence of fractures
of these prostheses. The results of the finite-element analysis further showed that loss of calcar-
collar support with proximal fixation through the
and stress shielding of the proximal medial cortex.
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The uncoupled prosthesis also may be modeled with
a car o ar uppor
a free-body diagram as a three-force member loadedat the head, stem tip, and in the proximal region. With
,
the stem tip, and thus the peak bending stress in the
-, .
If there is no calcar-collar support, proximal support
must be provided by some combination of integration
of bone in the fenestrations and wedging due to thelateral-medial taper of the device..
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Stresses on Stem
Stresses in the stem are largest when there is no
we g ng, ut g stresses eve op n t e
cancellous bone in the fenestrations. When there
, ,
stresses in the supporting cancellous bone can
be hi h additional roximal su ort throu h the
fenestrations substantially reduces these bone
stresses
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Stresses on Stem
. If reduced stresses in the
stable device, these mechanisms
Moore prosthesis have not occurred
in normally loaded hips because
load was transferred primarily eitherthrough the collar or by wedging,
w a ona suppor a e
fenestrations
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-
Loose Prosthesis
a car a sorp on
Subsidence of the prosthesis oss o varus a gnment n t e cana
Acetabular cartilage erosion
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Elderly
Wide canal
n er our con ro Faulty operative technique
Over reaming by improper Rasp
Improper selection of Implant
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Effect of neck resection on torsional stability of cementless total hip replacement.
, , .
Biomechanical Research Laboratory, St. Louis, Missouri, USA.
Loosening of the femoral component in total hip
arthroplasty commonly results from inadequate
.
human cadaver femora to determine the effect of
-the femoral component. All specimens were prepared for
fixation with the Impact modular total hip replacement.
Each femoral diaphysis was overreamed 2 mm toachieve only proximal fixation. The specimens were then
v e n o groups o ve an mp an s were nser e
with the precision press-fit technique.
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Without distal fixation, the femoral
com onent is hi hl de endent on roximalgeometry for resistance to torsional loading.
Preservin the femoral neck rovides an
effective means of resistance. Maintainingthe entire femoral neck most effectivel
reduces miromotion at low loads, but
maintainin the midshaft area of the femoralneck appears to most effectively control
micromotion at higher torsional loads.
Resection below the midshaft of the neckmarkedly decreases the torsional load-
bearing capacity of the proximal femur.
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-incidence of calcar resorption. Sufficient cementation
incidence of calcar resorption, as did neutral andvalgus positioning of the femoral component.
Loosening of the acetabular component occurred
more often in the group with calcar resorption. Middle-age pa en s an men were more prone o eve op
resorption of the calcar. Calcar resorption may be
.
operative technique is recommended, with emphasis
on correct val us or neutral osition of the femoral
component, a positive calcar-collar contact, and
improved cementation
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Proximal Fixation
Tips & Tricks
- .
Proper neck cut.
vo comm nu ng a car emor s.
Save at least 1cm of neck at Calcar Insert canal finder from Piriformis Fossa
, .
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Proximal Fixation
Tips & Tricks
proximal femur without increasing.
Use a artery forcep in the prosthesis
,
rotation control during insertion.
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Proximal Fixation
Tips & Tricks
The most important area is the medial side nearcalcar. Graft should be inserted when nearly half of
the prosthesis has gone inside.
Fill the fenestrations of the prosthesis with bone
, .
The color of the implant should not over-hang on the
calcar.
If done properly, it should rest on the neck and willcompress the grafts.
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-uncemented Austin Moore prosthesis is relatively
.
and consultants were not significantly different.
demanding operation; the prosthesis is difficult to
.
Greater selectivity should be exercised when
femoral neck fractures.
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(1)Inadequate length of the neck remnant (12
lesser trochanter to the resection margin at the
.
remnant was identified on postoperative,
trochanter to the level of the fracture on
.(2) Inadequate calcar seating (>1 mm)-measured
.
prosthesis collar seated on the medial calcar was
.
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(3) Difference in prosthetic head size compared
with the contralateral normal femoral head usincircular overlays-a diameter of prosthesis up to 2
mm lar er to account for articular cartila e was
considered satisfactory. If the contralateralfemoral head was not suitable for anal sis due to
disease or previous prosthetic replacement), the
i silateral femoral head on reo erativeradiographs was used for assessment of the
appropriate prosthetic head size.
(4) Intra-operative periprosthetic fracture- fractureclassification was conducted using the Vancouver
system.
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147 patients were treated with the unipolar
time period: 128 (87%) had surgery performed by
-
officers, 57% by training registrars, and 17% by
performed by a consultant surgeon.
patients; only 76 (52%) had no errors in
, ,(12%) had 2 errors, and
. .
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1: Injury. 2002 Jun;33(5):419-22.
Austin Moore hemiarthro last : technical as ects and their effects on outcome, in atients with fractures of the neckof femur.
Sharif KM, Parker MJ.
Orthopaedic Department, Peterborough District Hospital, Peterborough PE3 6DA,
UK. khalidsharif doctors.or .uk
In order to determine which technical aspects of the Austin Moore hemiarthroplasty
procedure affect the outcome, we reviewed 243 patients with a non-pathologicalintracapsular femoral neck fracture who had, Austin Moore uncemented
. - -
alignment of the prosthetic stem, calcar seating, length of the neck remnant,
leg length discrepancy and size of the head, compared with the contralateral femur.
All patients were followed-up for 1 year. Significant pain at 1 year and/or revisionof the prosthesis for loosening were considered as unfavourable outcomes.
Inadequate calcar seating was significantly associated with pain and revision
of the prosthesis (P = 0.04 and 0.01, respectively). Length of the neck remnant
. . ,
respectively). Difference in head size was associated with pain, but not withloosening (P = 0.01 and 0.08, respectively). The rest of the parameters were not
significantly associated with the outcome. We recommend that when inserting an
Austin Moore hemiarthroplasty, particular attention must be paid to the seating of
the collar of the prosthesis on the calcar and correct choice of head size.
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Injury. 2004 Oct;35(10):1020-4.
Critical radiolo ical anal sis after Austin Moore hemiarthro last .Yau WP, Chiu KY.Department of Orthopaedic Surgery, The University of Hong Kong, Queen Mary
Hospital, No. 102, Pokfulam Road, Hong Kong, PR China. peterwpy@hkucc.hku.hk
treated with Austin Moore hemiarthroplasty (AMA). The clinical and radiologicaloutcomes were documented in a quantitative manner after 7 years follow-up of 144
patients. At the time of final follow-up, 52 patients had died and 48 patients were lost
to follow-up, leaving a total of 44 patients for analysis. Immediate post-operative
X-rays were studied for the initial alignment of prosthesis, the fit of the prosthesis
and the degree of osteoporosis. X-rays on latest follow-up were studied for evidence.
special surgery. It was found that hip pain was significantly related to subsidence
and pivoting of the prosthesis (P = 0.014 and 0.035, respectively).
Significant increase in subsidence was noted if the stem of prosthesis was not fitting
well within the shaft of femur (P = 0.006). When the patient was younger than73 years old at the time of operation, there was more subsidence of the prosthesis at
the final follow-up (P = 0.001). It was concluded that the fill of AMA within the shaft
.
patients with acute fracture of the neck of femur should be treated by methods other
than cementless AMA.
Injury 2004 Oct;35(10):1020 4
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Injury. 2004 Oct;35(10):1020-4.
Critical radiological analysis after Austin Moore hemiarthroplasty.
Yau WP, Chiu KY
was conc u e a e o w n e s a ofemur should be greater than 70% to avoid early
.
fracture of the neck of femur should be treated bymethods other than cementless AMA.Injury. 2002 Jun;33(5):419-22.
Austin Moore hemiarthroplasty: technical aspects and their effects on outcome, in
patients with fractures of the neck of femur.ar , ar er .
Inadequate calcar seating was significantly associated
with ain and revision of the rosthesis P = 0.04 and
0.01, respectively). Length of the neck remnant was alsosignificantly associated with these two outcomes (P =
0.05 and 0.023, respectively). Difference in head size
was associated with pain, but not with loosening
J Trauma 2001 Jul;51(1):84 7
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J Trauma. 2001 Jul;51(1):84-7.
The effect of intramedullary corticocancellous bone plug for hip hemiarthroplasty.
Kligman M, Zecevic M, Roffman M.
Application of a corticocancellous bone plug in uncemented
hi hemiarthro last for treatment of femoral neck fractures
can decrease the incidence of early thigh pain in the first 6
months.
Scand J Surg. 2002;91(4):357-60.
The long-term results of Lubinus interplanta hemiarthroplasty in 228 acute femoral neckrac ures. re rospec ve s x-year o ow-up.
Isotalo K, Rantanen J, Arimaa V, Gullichsen E.
, ,
diaphyse) angle and a longer stem compared to Thompson and
Moore implants. The need for resection of calcar cortex is also
limited. These biomechanical facts may explain the good long-
term results of Lubinus hemiarthroplasty.
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Loading of the calcar leading to Neck over hang & absorption
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Impaction Grafting
Calcar Femoris
Day One
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Tight Femoral CanalThree Point Fixation
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Proximal Fixation
.
Proximal Fixation
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14 years PO
Broken stem
Not a Failure
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Not a Failure
20 ears FU
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Bone in the fenestration
A broken stem is not a failure
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Too Much Valgus Too Mush Varus
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u s ence
No proximal Fixation
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Subsidence
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Ideal Prosthesis Fitting
or mo erate y w e cana1.Correct offset
.
3. Correct Varus setting4. Three oint fixation
For Narrow canal the junctionbelow the fenestrations is too much
,
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Intra operative error during AMP
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Intra-operative error during AMP
. .Weinrauch, P
pat ents were treate w t t e un po ar uncemente
Austin Moore prostheses over the time period: 12887% had sur er erformed b relativel unior
doctors-14% by senior medical officers, 57% by training
registrars, and 17% by principal house officers; 19 (13%)
were per orme y a consu an surgeon.
84 errors in implantation were identified in 71 patients;
onl 76 52% had no errors in im lantation while 52
(35%) had one error, 17 (12%) had 2 errors, and 2 (1.4%) had 3 errors.
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. . . .
188 patientsn ec on .
Dislocation 3.4%Loosening 3.4%
-
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- quality of lifepat ents average yrs
7% dislocation
4% deep infection
pros rus o
2% loosening of prosthesis
5 yrs -- > 60% mortality in both groups
move independently.
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Peri-prosthetic fracture
AMP was well fixed
Could not be removed
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Could not be removed
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. .
From University hospital of Cleveland Ohioourna o r rop as y
AMP Bipolar7% died(3 months) 11% died
.
(55 to 92) (60 to 94)
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must be paid to theseating of collar of
e pros es s on
choice of head size.
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be learnt.
Cost effective, well
patients
German article
154 AMP for 10 yrsAt 3yrs 46% community
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y y
35% non functionalambulance
Men had better than women
arr s p score -- yrs59 10yrs
.
10 yrs 7.7%Revision rate -- > 5 rs - 4.5 %
10 yrs 5.2%
A case of THR done 14 Years ago
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g
ow e s ow ng e orma onNo complaints A.M.P. 16 years ago.
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satisfactory function in elderly
Average ortho surgeon can perform
set-up.
an e surgery e ore an asfor appropriate stem width according
o emora cana .
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Summary
Carefully reaming in narrowfemoral canal.
No reaming in Osteoporotic
. Use bone grafts from femoral
Always fill the fenestrations
w one gra s.
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satisfactory.
THR cemented bi olar has ot their own
indications, & they are also not free from serious
complications.
AMP is Cost effective,
Bone cement can be used as last option.
Further improvement in the implant design isrecommended.
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Fracture N/F
AVN 1998
AMP working since then
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-
Friction failure emen sease
Design failure
Particle disease
Mechanical failure - Mechanostat
Proxima Depuya conservative meta h seal im lant
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Proximal Fixation
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Well fixed AMPProxima DePuy
AMP Still working
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Dont throw awa
t e
DISCLAIMER
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Information contained and transmitted by this presentation is
Choithram Hospital & Research centre, Indore, India, during last
25 years.It is intended for use onl b the students of ortho aedic sur er .Views and opinion expressed in this presentation are personalopinion.Depending upon the x-rays and clinical presentations, viewers
.For any confusion please contact the sole author for clarification.Every body is allowed to copy or download and use the material
.
arise out of this presentation.For any correction or suggestion please contactnaneria@yahoo.com
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