Cemented vs Uncemented Total hip Arthroplasty ANZCVS Resident ...

Cemented vs Uncemented Total hip Arthroplasty
ANZCVS Resident Forum 2013
Brenton Chambers BVSc (Hons) MACVSc
Lecturer in Small Animal Surgery
University of Melbourne Veterinary Hospital
250 Princes HWY WERRIBEE VIC 3030.

Lecture Outline
• Previous Exam Questions
• Indications
• Techniques
• Cemented CFX
• Uncemented BFX, Kyon, Helica
• Complications
• Operative
• Early
• Late

Previous Exam Questions
2008 Part1
2. Discuss two (2) only of the following:
• The proposed aetiology and pathogenesis of
nonseptic loosening of cemented hip
prostheses. Include in your answer a
discussion of cytokine involvement and
cellular changes

Indications for Total Hip Arthroplasty
• THR is a salvage procedure replacing the diseased
joint components (acetabulum and femoral head)
with commercially available prostheses divided into
cemented and non-cemented systems
• Indications: (Skeletally mature or near mature only)
– OA unresponsive to appropriate medical management
– Failed FHNE
– Traumatic or chronic coxofemoral luxation
– Irreparable/failed /malunion Acetabular fracture
– Irreparable/failed/malunion Femoral head and neck fracture
– Avascular necrosis of femoral head/neck (Jankovits 2011)
– Slipped Femoral Capital Physis (Gemmill 2012)

Contra-Indications
• Animals with concurrent active
infectious disease:
• Local
• Distant
• Animals with systemic illness
predisposing to infectious disease or
delayed healing
• Concurrent neurologic disease (Olmsted
1987)
• Size NOT contra-indication (Warnock 2003)

Commercial Systems
• Biomedtrix – CFX / BFX/ Hybrid
– Modular system:
• Acetabular cup UHMWPE
• Femoral Head
• Femoral Stem
– Universal, micro, nano
• Kyon/Zurich – Uncemented (Screw
Fixation)
• Helica – novel screw prosthesis
• Amplitude – Dual Mobility

Published Complications
• Luxation
• Septic loosening
• Aseptic loosening
• Fracture
• Implant failure
• Sciatic Neuropraxia
• Pulmonary Embolism
• Overall complication rate 7-22%

Cemented Technique
• Pre-operative Implant templating
radiographs
• Implant stability result of PMMA
cohesive
• Cementing technique influences mantle
quality and stability (Ota 2005, Wixon
1997)
• Antibiotic combined with cement
beneficial for prophylaxis

Cemented Technique Acetabular Preparation
• Acetabular reaming
• Establish appropriate surface for cement cohesion
• Sufficient Dorsal Support
• Sufficient Medial Support
• Alignment: (Cross 2000a,b, Dyce 2000)
• 5-10 deg closed
• 10-20 deg retroversion
• Association with luxation (Hunter 2003, Konde 1982,
Massat 1984, Dyce 2000, Nelson 2007)
• Recommended ALO 35-45 degrees

Cemented technique - Femoral Preparation
• External rotation of femur
• Trochanteric osteotomy not recommended
(Wylie 1997)
• Reamers and broaches used to prepare
femur:
• Filling of bony irregularities with debris
• Pulsatile lavage suction increases cohesion by 185%
(Askew 1984)
• Important Factors:
• Appropriate prosthesis size (2mm cement mantle)
• Correct final positioning of stem

Cemented technique - Femoral Preparation
• Prewarming stem prevents expansion/contraction with
exothermic PMMA polymerisation (Bishop 1996)
• Stem Centraliser prevents endosteal contact and
maximises uniformity of cement mantle (Schulz 1999)
• Retrograde cement fill and slow stem insertion minimises
cement mantle void formation
• Maximum collar contact reduces stress and implant failure
(Manley 1995, Shatzker 1989)
• Normo to slight anteversion
• Modular head components allow adjustment:
– Short neck predisposes to luxation
– Long neck results in external rotation and abduction
• Hip skids for reduction damage heads – aseptic loosening

Uncemented Total Hip Arthroplasty
• Short term stability provided by:
• Precise press fit (BFX)
• Monocortical screws (Kyon)
• Screw prosthesis (Helica)
• Long term Stability provided by:
• Osseous ingrowth into porous incorporated surfaces

Uncemented Total Hip Arthroplasty
• Advantages:
• Longer implant life (reduced aseptic loosening)
• Decreased post-operative/late infection
• Better stability (bone ingrowth)
• Disadvantages:
• Increased risk intra-operative femoral
fracture/fissure
• Precise preparation required

Technique Differences BFX vs CFX
• Higher Osteotomy location (isthmus)
• Acetabular reaming to EXACT templated size
• Orientation during reaming maintained for press fit
• Broaches but no reaming for femoral stem
component
• Observe cortex as final size approached:
• Circlage applied if fissures detected and size
increases abandoned
• Fractures revised with CFX – advantage of biomedtix
cross compatibility

THR in Smaller Dogs & Cats – Mini/Micro/Nano
• Technique variations:
• Burr for acetabular preparation cf reamer
• Craniodorsal capsular prosthesis due to laxity
– (Warnock 2003, Marino 2012)
• Luxation rates:
• Similar to THR in larger dogs
• 4% after falling from owners arms (Marino 2012)
• Outomes:
• Excellent to good in
• No sig difference in forceplate data btn
contralateral limb (Jankovits 2011)

Kyon/ Zurich
• Cup:
• Perforated double shell outer
titanium shell allows osseous
integration (Convection currents)
• Inner UHMWPE contact surface
• Geometry reduces contact
pressures
• Initial press-fit augmented by
screw fixation
• Modular head system
• Amorphous Diamond coating
reduces wear particles

Kyon/Zurich
• Argued press-fit, canal filling
systems cannot be stable at all
contact areas and motion (tension
on lateral, compression medial
during weight bearing) prevents
osseous integration
• Initial stability provided by bi- and
monocortical locking screw fixation
to medial cortex alone – no lateral
cortical contact allows more
effective bone ingrowth (reduces
stress shielding)

Kyon/Zurich - Complications
• Hummel (2010):
• Most common complications were intraoperative
femoral fracture, luxation and septic
loosening
• Higher overall rates than for previously reported
cemented and other cemented techniques plus
higher than previously reported for Zurich THR
• Previously performed Cemented THR or FHNA
assoc with success.

Helica
• Bone preserving prosthesis
• Self-cutting threaded titanium
alloy femoral implant screws
into femoral neck
• UHMWPE acetabular
prosthesis enclosed in titanium
shell – self threading screw
• Long-term Objective outcomes
data?

Helica
• Hach (2009):
• Implant loosening 12.5% - 0 luxations
• Short procedure
• Viefhues (2010):
• Aseptic loosening 8.1% - 0 luxations
• Andreoni (2010):
• Revision of aseptically loosened stem and cup
with kyon
• Kim (2011):
• Sig alterations in strain - decreases in medial
longitudinal compression
• Correlates with loosening seen clinically

Complications - Luxation
• Early complication (< 9 weeks) (Cross 2000)
• Trigonometric assessment of acetabular
position in 3 axes (Cross 2000) –
• Acetabular version and inclination poor
indicators of luxation.
• Tolerance of malposition
• Associated with Acetabular cup position (Dyce
2000):
• ALO > 60 degrees - *x increased risk
• Pelvic Limb amputees increased risk (44%)
(Preston 1999)

Complications – Ventral Luxation
• Ventral Luxation 4 th most
common complication (Nelson
2007)
• Risk factors:
• St Bernard Breed – risk recurrent VL
• Short Neck Extension
• High ALO ???
• Recommended ALO protective vs
ventral luxation

Luxation – Dual Mobility Prosthesis
• Recent development: (Guillaumot 2012)
• Metal backed outer acetabular component
• Inner mobile UHMWPE component
• Metallic head
• Cemented stem prosthesis
• Prospective trial of 50 dogs – no
luxation (Guillaumot 2012)

Complications – Septic Loosening
• Reports of incidence vary from 1-3.7%
• Lee (2002)
• 40% positive culture rate
• Closing culture results not assoc with success
• Increased risk positive culture with increased
surgical duration

Complications – Aseptic Loosening
• Activation of macrophages by submicron
wear products in effective joint
space results in: (Iwata 2008, Gristina
1994, Holt 2007**)
• Wear products result from biomechanical
forces and host physiologic processes
• Macrophages attempt to ingest and eliminate
wear products – chronic inflammatory reaction
• Direct enzymatic osteolysis via production of
reactive oxygen species
• Osteoclastic activation

Complications – Aseptic Loosening
• Constant remodelling mediated by both
osteoclastic and osteoblastic activity
• Imbalances in blastic vs clastic activity result
from altered cytokine expression
• Many pro-inflammatory cytokines expressed :
• TNF-a
Osteoclastogenesis
• IL-1

Aseptic Loosening – Osteoclastogenesis
RANKL-RANK-OPG-NF-κβ
• Initially termed cement disease
• PMMA wear products increase
expression of RANKL
• RANKL binding with cell surface
receptor RANK results in initiation of
NF-kb pathways resulting in
osteoclastogenesis and Activation of
mature osteoclasts
• RANKL-RANK inhibited by OPG

RANKL-RANK-NF-κβ

Complications Aseptic Loosening
• Chronic inflammation also results in a
fibro-inflammatory zone populated by
exhausted macrophages resulting in
immuno-incompetance
• Low virulence bacteria can survive and
populate in biofilms
• Advanced cementing techniques
improve mantle grade but did not affect
incidence of aseptic loosening (Ota
2005)

Aseptic Loosening Diagnosis
• Animals present with progressive
lameness
• Radiographs poorly specific
(52%) (Frankel 2004)
• Findings indicative of loosening
• Cement mantle cracks
• Cement-metal interface leucency
• Implant retroversion
• Endosteal pedestal formation

Complications - Aseptic loosening Prevention?
• Wise 2005 :
• Dose dependant effect of ZLN
• Improved amt endosteal bone @ 26 weeks
• Reduced loss of bone assoc with implant stress
shielding but not aseptic loosening
• Inconclusive and short term assessment
• Wood (2003)
• Future:
• Avoid use of uncoated hips skids
• RANK blockade (RANK;Fc Ab)
• OPG?

Complications - Fracture
• CFX:
• BFX
• 2.9% (Liska 2004)
• Intra or post operative (up to 2196 days)
• Excessive reaming, osteopathy, aseptic
loosening, altered modulus
• Plate, screw, wire ORIF
• 13% (Ganz 2004)
• Earlier complication resulting from press-fit
preparation/ undetected fissures
• ↓Canal Flare Index (Stovepipe conformation)
• Increasing age

Canal Flare Index
• Ratio of intracortical width
at level of lesser
trochanter to the
intracortical width at
isthmus A/B

Complications – Implant Failure
• Loss of stem support and cyclic cantilever
loading results in fatigue failure (Yates 2010)
• Aseptic Loosening
• Stress shielding
• Cement mantle quality
• Human literature:
• Femoral stem fracture 0.23-0.67%
• Cantilever bending assoc with 62%
• Implant design
• Metallurgical composition
• Cement mantle quality

Complications – Sciatic Neuropraxia
• Incidence 1.2-2%
• 1000 same surgeon THR (BFX/CFX/Hybrid)
• Risk Factors:
– Age at sx
– Difficulty of sx
– Traumatic pre-sx luxation
– Revision sx
• Complete recovery expected (Time
variable)
• Mean 35 days (10-120days)

Complications – Pulmonary Embolism
• Incidence: (Liska 2003) - CFX
• Perfusion defects in 82% of 44 dogs
• Assessed via:
– Scintigraphic perfusion studies
– Transoesophageal u/s
• During stem implantation – intramedullary
pressure
• Embolic sources:
• Air, PMMA, Fat, Clots
• Consequences:
• Clinically silent/spontaneous recovery
• Fatal (Terrell 2004)

Complications Tabular Summary
Author Outcome Luxation
Aseptic
Loosening Septic Fracture
Implant
Failure
Pulmonary
Embolism
Sciatic
Neuropraxia
Acetabular
Displacement
Comments
Skurla 2000
84.1% excellent or good.
Cross 2000 12% CFX
Warnock 2003 83% good to excellent 11% 5% Mini CFX
Liska 2010 91% 18% 2% 2% 2% Micro CFX in dogs and cats
Marino 2012 92% 10% 2% Micro CFX in dogs and cats
Jankovits
Micro CFX in dogs for avascular necrosis and cats
Gemmil 2012 92% good to excellent 6% Hybrid THR for slipped capital physis
Ireifej 2012 100% 25% 8% Nano CFX in dogs
Ganz 2010 13.10% BFX
Liska 2004 2.90% CFX
Hummel 2010 3.70% 3.70% 11% 2.50% 1.20% Kyon
Guererro 2009 97% 11.00% 1.50% 3% 1.5% 3% Kyon
Ota 2005 7% 2.10% 1.10% CFX examining effect of cement technique
Preston 1999 44% CFX - pelvic limb amputees
Dyce 2000 4.70% 0.50% 1% 1% CFX
Bergh 2006 6.50% 1.50% 6.40% 1.30% 4.80% CFX
Forster 2012
94% good to very good
Andrews 2008 1.90%
Liska 2003 82%
Hach 2009 0 12.50% 2% 2% Helica
Viefhues 2010 0 8.10% 2.70% Helica

Complications by System
Complication CFx BFx Zurich/Kyon Helica
Luxation 4.7-12%
18% (Nano)
44% (Amputees)
Septic 1-1.5% 1.5-3.7%
3.7-11% 0%
Aseptic Loosening 0.5-5% 8.1-12.5%
Fracture 1-6.4%
25% (Nano)
13% 3-11% 2%
Implant Failure 1.1% 1.5-2.5%
Sciatic
Neuropraxia
1.3-2% 1.3-2% 2%

Removal / Revision
• Indications:
• Aseptic Loosening of Stem / cup components
• Septic Implants
• Luxation
• Femoral Window Technique (Dyce 2002)
• Removal of infected CFX implants
• Complete cement removal in 83%
• 50% Staph aureus – 3-10 weeks Abx
• Outcome sim to FHNE
• Human Classification Systems

Removal Revision
• Torres ( 2009):
• BFX revision of 3 failed CFX
• Autogenous cancellous bone graft
• Successful in all cases despite +ve culture in 1
• Massat (1998)
• Single stage revision ( 1 x septic, 1 x aseptic)
• Revision common in humans – explantation
more common in dogs
• Single stage revision successful in both

Future Developments
• Hybrid fixation stems
(Baleani 2000)
• Combination press-fit and
cement
• Less micromotion in ex-vivo
biomech studies
• Dual Mobility Implants
• Targeted therapy vs
mechanisms of Aseptic
Loosening

Questions?