Principles Of Total Hip Replacement

Y
Principles of THR
Moderator: Dr Geletaw Tessema (Trauma & Arthroplasty
Surgeon)
Presenter: Yasin Awil (OSR)
Outline
• History
• Anatomy of hip
• Biomechanics
• Design and selection of components
• Preoperative Templating
• Procedure
• complications
History
 1891
• Dr. Gluck performs first reported attempt at a hip
replacement with ivory.
 1940
• Austin Moore performs first metallic hip replacement
surgery (hemiarthroplasty)
 1952
• Austin Moore prosthesis developed
 1960s
• Sir John Charnley introduces concept of low friction arthroplasty
• Concept
• termed "low friction" as a small femoral head was used to reduce wear
• Components
• metal femoral stem
• polyethylene acetabular component
• acrylic bone cement
Hip anatomy
 Acetabulum
• Anteverted 15 degrees
• Abducted 45 degrees
• Divided into four quadrants
• Proximal femur
• Femur head
• Femur neck
• anteverted 15 degrees
• neck shaft angle of 125 degrees
Principles Of Total Hip Replacement
Applied Hip Biomechanics
 Forces acting on the hip:
Forces producing torsion of stem.
• Forces acting on hip in coronal plane:
• Tend to deflect stem medially
• Forces acting in sagittal plane especially with hip
flexed or when lifting:
• Tend to deflect stem posteriorly.
• . Combined, they produce torsion of stem.
Clinical implications
 Actions that decrease joint reaction force include:
• increase in ratio of A/B (shift center of rotation medially)
• acetabular side
• moving acetabular component medial, inferior, and anterior
• Femoral side
• Increasing offset of femoral component
• Long stem prosthesis
• Lateralization of greater trochanter
CONT…
• Patient's gait:
• Shifting body weight over affected hip
• This results in Trendelenburg gait
• Cane in contralateral hand
• Reduces abductor muscle pull and decreases the moment arm
between the center of gravity and the femoral head
• Carrying load in ipsilateral hand
• Produces additional downward moment on same side of
rotational point
STRESS TRANSFER
TO BONE
 Bone Morphology
• Dorr classification:
• Type A – funnel
shape/champagne flute
appearance
• Type B – medial and posterior
cortex are minimally lost
• Type C – stovepipe appearance
Cont…..
 Stress shielding:
• Proximal femoral bone loss in the setting of
a well-fixed stem
• Risk factors:
• Stiff femoral stem
• Large diameter stem
• Extensively porous coated stem
• Greater preoperative osteopenia
DESIGN AND SELECTION OF
TOTAL HIP COMPONENTS
• No implant design or system is appropriate for every patient
• Selection is based on:
• Patient’s needs,
• Patient’s anticipated longevity
• Level of activity,
• Bone quality and dimensions,
• Ready availability of implants and proper instrumentation,
• Experience of the surgeon
FEMORAL COMPONENTS
• The primary function of the femoral component is:
• Replacement of the femoral head and neck after resection of the
arthritic or necrotic segment
• The ultimate goal of a biomechanically sound, stable hip joint
is to restoration of the normal center of rotation of the
femoral head.
• This location is determined by three factors:
• Vertical height (vertical offset),
• Medial offset(Horizontal offset)
• Version of the femoral neck
Cont….
• Vertical height and offset increase as the neck is
lengthened.
• In most modern systems, neck length is adjusted by
using modular heads with variable internal bores.
• Vertical height (vertical offset) is determined primarily
by the:
• base length of the prosthetic neck plus the length gained
by the modular head used.
Cont….
• Offset ( horizontal offset):
• distance from the center of the femoral head to a
line through the axis of the distal part of the stem
• Inadequate restoration of offset shortens the
moment arm of the abductor musculature
• Offset can be increased by simply:
• using a longer modular neck.
• reducing the neck-stem angle
• attaching the neck more medial position
CONT..
• Head-to-neck ratio of implants,
• Large-diameter head with trapezoidal neck
has greater ROM and less impingement than
smaller diameter head..
• ROM with different head sizes,
• Jump distance
• distance the head must travel to escape the rim
of the socket
• approximated to be half the diameter of the
head
CEMENTED FEMORAL COMPONENTS
• Rely on cement fixation
• The stem should be fabricated of high-strength superalloy,
• Cobalt-chrome or stainless steel
• Most common
• Reduce cement stresses
• Titanium
• Prone to micromotion and debonding
• less stiff than cobalt-chrome or stainless steel stems
Cont..
• The cross section of the stem should have:
• Broad medial border
• Broader lateral border
• To load the proximal cement mantle in compression
• Sharp edges produce local stress risers
• Collar aids in determining the depth of insertion
• Stem shape:
• Noncircular shapes ( rounded rectangle, ellipse)
• surface irregularities (grooves or a longitudinal slot)
CONT…
• Stems should be available in a variety of sizes,
• Allow the stem to occupy 80% of the cross section of the
medullary canal
• with an optimal cement mantle of approximately 4 mm
proximally and 2 mm distally
• the optimal length of the stem depends on:
• Geometry and size of the femoral canal
• The lengths of current stem designs range from 120
to 150 mm.
Cont…..
• Cement fixation is optimized by:
• limited porosity of cement
• cement mantle > 2mm
• stiff femoral stem
• stem centralization
• smooth femoral stem
• absence of mantle defects
• proper component positioning within femoral cana
Radiographic analysis
 Barrack and Harris grading system:
• grade A
• complete filling of medullary canal
• "white-out" of cement-bone interface
• grade B
• slight radiolucency of cement-bone interface
• grade C
• radiolucencies > 50% of bone-cement interface or incomplete cement mantles
• grade D-gross radiolucencies and/or failure of cement to surround tip of
stem
CEMENTLESS FEMORAL COMPONENTS
• Rely on biologic fixation:
• Immediate mechanical stability at the time of surgery
• Intimate contact between the implant surface and viable host bone
• Two materials most commonly used:
• Titanium alloy with one of a variety of surface enhancements
• Cobalt-chromium alloy with a sintered beaded surface
• A variety of surface modifications
• Porous coatings, grit blasting, plasma spraying, and hydroxyapatite coating
CONT…
 Biologic fixation
• Mechanism:
• Ingrowth:
• bone grows into porous structure of implant
• Optimum pore size for ingrowth – b/n 100 and 400 µm
• Ongrowth:
• bone grows onto the microdivots in the grit blasted surface.
Cont…
• Biologic fixation is optimized with:
• pore size 50-300um
• porosity of 40-50%
• gaps < 50um
• micromotion < 150um
• maximal contact with cortical bone
CONT…
 Classification system for cementless stems based
on shape:
• Types 1 -5 are straight stems,
• Type 6 is an anatomic shape
• Type 1 stems (single-wedge stems)
• Flat in the AP plane
• Tapered in the mediolateral plane
• Fixation is by cortical engagement only in the mediolateral
plane and by three-point fixation along the length of the
stem.
• Type 2 stems( double-wedge)
• engage the proximal femoral cortex in both ML and AP planes
• used safely in Dorr type A femurs
• Type 3 (Tapered)
• Tapered in two planes,
• Fixation is achieved more at the metaphyseal-diaphyseal
junction
• Has 3 subgroups
• Type 4
• Extensively coated implants
• With fixation along the entire length of the stem
• . Canal preparation requires distal cylindrical
reaming and proximal broaching
• Excellent long-term results
• Femoral stress shielding and thigh pain
• Type 5 (modular stems)
• Separate metaphyseal sleeves and diaphyseal
segments
• Separate preparation
• Recommended for patients with altered
femoral anatomy,
• Used for all Dorr bone types,
 Type 6(anatomic femoral Stem)
• incorporate a posterior bow in the metaphyseal
portion
• anterior bow in the diaphyseal portion
• Corresponding to the geometry of the femoral
canal
• Right and left stems are required,
Radiographic analysis
• signs of a well-fixed cementless femoral component
• Spot-welds
• new endosteal bone that contacts porous surface of implant
• absence of radiolucent lines around porous portion of
femoral stem
• proximal stress shielding in extensively-coated stems
• absence of stem subsidence on serial radiographs
SPECIALIZED AND CUSTOM-MADE FEMORAL
COMPONENTS
• used most commonly in
minimally invasive anterior
approaches
• Used salvage procedures
• some malignant or aggressive
benign bone
CEMENTED ACETABULAR
COMPONENTS
• Thick-walled polyethylene cups
• Addition of Vertical and horizontal grooves to external
surface
• increase stability within the cement mantle
• wire markers were embedded
• better assessment of position on postoperative radiographs
• PMMA spacers (3mm height)
• To avoid buttoming out
• A flange at the rim
• aids in pressurization of the cement
CEMENTLESS ACETABULAR
COMPONENTS
• Circumferentially Porous coated for bone ingrowth
• oversizing of the implant 1 to 2 mm larger than the reamed
• Fixation of the porous shell with transacetabular screws
• Most systems use
• Metal shell with an outside diameter (40 to 75 mm)
• Typically accommodates head sizes 22-40mm
• Secure liner to the cup
• Failure- back wear
Cont…..
CONT…
 Constrained acetabular component includes:
• Mechanism to lock head to the liner
• Tripolar mechanism
• A locking ring applied to the rim
• Indications:
• Insufficient soft tissues,
• Weak abductors,
• Neuromuscular disease
• Recurrent hip dislocation despite well-
positioned prosthesis
 Dual mobility acetabular component:
• Unconstrained Tripolar design
• Porous coated shell
• Polished interior
• Large polyethylene ball
• Smaller metal or ceramic head
• 2 sites of motion
• External bearing – b/n polyethylene and metal Moves at extremes of
motion
• Internal bearing – b/n head and polyethylene
 Custom components (reconstruction):
• Rarely indicated
• Most deficient acetabula can be restored to a hemispherical
shape
• A cementless acetabular component
• With modular porous metal augments
• used instead of a large structural graft
• Augments of various sizes are screwed into bony defects
• The augments are joined to the implant with the use of bone
cement
• Antiprotrusio rings and cages.
Bearing surfaces
 Metal-on-polyethylene:
• Metal (cobalt-chrome) femoral head on polyethylene acetabular line
• Benefits:
• longest track record of bearing surfaces
• lowest cost
• most modularity
• Disadvantages:
• higher wear and osteolysis rates
• smaller head leads to higher risk of impingement
 Metal-on-metal
• Benefits:
• Better wear properties than metal-on-polyethylene
• Lower linear wear rate
• Debris particles much smaller
• larger head allows for increased ROM before impingement
• Disadvantages:
• more expensive than metal-on-polyethylene
• increased metal ions in serum and urine
• May form pseudotumors
 Ceramic on Ceramic
• Benefit:
• best wear properties of all bearing surfaces
• lowest coefficient of friction of all bearing surfaces
• inert particle
• Disadvantages
• more expensive than metal-on-polyethylene
• worst mechanical properties
• Squeaking
• stripe wear
 Ceramic on polyethylene
• Benefits:
• Standard of care
• Alumina ceramic heads
• Results in less polyethylene wear than metal-on-polyethylene
• Disadvantages:
• zirconia undergoes tetragonal to monoclinic phase
transformation with time
Indications for THR
• Original primary indication:
• alleviation of incapacitating arthritic pain in patients>65 yrs
• whose pain could not be relieved by non surgical means
• For whom the only surgical alternative was resection arthroplasty (Girdlestone resection
arthroplasty) or arthrodesis.
• Secondary importance was:
• the improved function of the hip.
Principles Of Total Hip Replacement
Contraindications to THR
• Absolute:
• Active infection of the hip or any other region
• Medical unfit for surgery
• Relative:
• Morbid obesity
• Severe dementia
• Tobacco use
• Severe osteoporosis
• Untreated skin infection
• Absent or insufficient abductor musculature
Preoperative Patient Evaluation And
Optimization
 Hx:
• Pain: groin, lateral hip, anterior thigh and knee,
• Worse during activity, relieved by rest and limited weight bearing
• Through medical evaluation
• Cardiopulmonary disease, Renal insufficiency, infection, Malignancy and DM
• Anticoagulant medication:
• D/C Aspirin, clopidogrel 7-10 days before surgery
• D/C warfarin 5 days prior surgery
Cont….
• Pyogenic skin lesions should be eradicated
• Preoperative skin preparation with chlorhexidine
• Dental problems, and urinary retention should be addressed
• Preop counselling:
• Expectations
• Social support
• VTE prophylaxis
• Anesthesia
• Pain management plan
CONT…
 Physical exam- includes:
• Spine
• upper and lower extremities.
• Inspection
• Skin-Discoloration, wounds, or gross deformity
• Bony-Length, Position
• Gait-Antalgic, Trendelenburg
Cont…
 Palpation
• Greater Trochanter / Bursae
• Anterior Superior Iliac Spine
• Ischial tuberosity
• Iliac crest
• Iliotibial band / TFL
• NV-motor/sensory, pulses, reflexes
Cont…..
 ROM
• Flexion-120-135 deg
• Thomas test
• Evaluates hip flexion contractures
• Extension-20-30 deg
• Abduction-40-50 deg
• Adduction-20-30 deg
• Internal rotation 30 deg
• External 50 deg
 Special test:
• FADIR test
• hip Flexed to 90 deg, Adducted and Internally Rotated
• Positive test if patient has hip or groin pain
• Can suggest possible labral tear or FAI
• FABER test (aka Patrick's test)
• hip Flexed to 90 deg, ABducted and Externally Rotated
• positive test if patient has hip or back pain or ROM is limited
• suggest intra-articular hip lesions, iliopsoas pain, or sacroiliac
disease
Harris hip score
PREOPERATIVE RADIOGRAPHS
• Minimum requirement –AP pelvis showing proximal femur
and lateral view
• Review the integrity of the acetabulum
• Review width of femoral canal
• Look for femoral bowing, malrotation or occult fracture
• Templating
• Spine and knee x-rays maybe needed
• Obturator oblique and iliac oblique
• For patients with previous acetabulum fracture
• CT with 3D rendering is also recommended
Preoperative Templating
 Importance
• allows surgeon to anticipate potential difficulties
• reproduce hip biomechanics
• minimizes leg length inequality
• Accuracy
• 52-98% accurate +/- one size
• related to experience and practice
Cont…..
 Steps
• obtain appropriate radiographs
• record vital patient information on template (age, height, weight, etc)
• establish radiographic landmarks
• establish limb length discrepancy
• template acetabular component
• template femoral component
Appropriate radiograph
LLD
Template acetabular component
Template femoral component
Cont….
THA Stability Technique
• Four important variables that help determine the stability of THA:
• Component design
• Position component
• Soft-tissue tensioning
• Soft tissue function component
PREPARATION AND DRAPING
• Appropriate operating table
• Positioning devices
• Preop tranexamic acid
• hip and entire limb are prepared with a
suitable bactericidal solution
• a U-shaped plastic drape are applied
• Protect bony prominences
SURGICAL APPROACHES AND
TECHNIQUES
• The choice of specific surgical approach is:
• Matter of personal preference
• Training
• prior incisions
• obesity
• risk for dislocation
• implant selection and degree of deformity
• Anterior
• Supine
• medial border of TFL muscle;
Cont….
 Anterolateral
• Charnley- supine with GT osteotomy
• Amstutz-lateral with GT osteotomy
 Direct lateral-supine or lateral with split of abductors
• Dall- removed the abductor with a flake of bone
• Head-reflect vastus lateralis & G. medius together
 Posterolateral- lateral with hip delivery
 Extensile
Principles Of Total Hip Replacement
Principles Of Total Hip Replacement
THA Through Posterolateral Approach
EXPOSURE AND PREPARATION OF
THE ACETABULUM
Reaming of acetabulum
Acetabular cup placement (cementless)
Cont….
IMPLANTATION OF CEMENTED
ACETABULAR COMPONENT
EXPOSURE AND PREPARATION OF
THE FEMUR
Reaming of Femoral Canal
Femoral stem placement (cementless)
Femoral stem placement (cemented)
THA THROUGH THE
DIRECT ANTERIOR APPROACH
THA Postoperative Inpatient Management
• Care can be broken down into different
phases including:
• Preoperative teaching
• Inpatient acute care (hospital)
• Inpatient extended care (rehab)
• outpatient home care
Principles Of Total Hip Replacement
Acute complications
• Periprosthetic Fracture
• Dislocation
• Sciatic Nerve Palsy
• Leg Length Discrepancy
• Vascular Injury & Bleeding
Principles Of Total Hip Replacement
Chronic complications
• Aseptic Loosening
• Iliopsoas Impingement
• Trunnionosis
• Pseudotumors
References
• Campbell's OPERATIVE ORTHOPAEDICS 14TH EDITION
• Orthobullets
• CLINICAL ORTHOPAEDICS AND RELATED RESEARCH
• BMC musculoskeletal disorder
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Principles Of Total Hip Replacement

  • 1. Principles of THR Moderator: Dr Geletaw Tessema (Trauma & Arthroplasty Surgeon) Presenter: Yasin Awil (OSR)
  • 2. Outline • History • Anatomy of hip • Biomechanics • Design and selection of components • Preoperative Templating • Procedure • complications
  • 3. History  1891 • Dr. Gluck performs first reported attempt at a hip replacement with ivory.  1940 • Austin Moore performs first metallic hip replacement surgery (hemiarthroplasty)  1952 • Austin Moore prosthesis developed
  • 4.  1960s • Sir John Charnley introduces concept of low friction arthroplasty • Concept • termed "low friction" as a small femoral head was used to reduce wear • Components • metal femoral stem • polyethylene acetabular component • acrylic bone cement
  • 5. Hip anatomy  Acetabulum • Anteverted 15 degrees • Abducted 45 degrees • Divided into four quadrants • Proximal femur • Femur head • Femur neck • anteverted 15 degrees • neck shaft angle of 125 degrees
  • 7. Applied Hip Biomechanics  Forces acting on the hip:
  • 8. Forces producing torsion of stem. • Forces acting on hip in coronal plane: • Tend to deflect stem medially • Forces acting in sagittal plane especially with hip flexed or when lifting: • Tend to deflect stem posteriorly. • . Combined, they produce torsion of stem.
  • 9. Clinical implications  Actions that decrease joint reaction force include: • increase in ratio of A/B (shift center of rotation medially) • acetabular side • moving acetabular component medial, inferior, and anterior • Femoral side • Increasing offset of femoral component • Long stem prosthesis • Lateralization of greater trochanter
  • 10. CONT… • Patient's gait: • Shifting body weight over affected hip • This results in Trendelenburg gait • Cane in contralateral hand • Reduces abductor muscle pull and decreases the moment arm between the center of gravity and the femoral head • Carrying load in ipsilateral hand • Produces additional downward moment on same side of rotational point
  • 11. STRESS TRANSFER TO BONE  Bone Morphology • Dorr classification: • Type A – funnel shape/champagne flute appearance • Type B – medial and posterior cortex are minimally lost • Type C – stovepipe appearance
  • 12. Cont…..  Stress shielding: • Proximal femoral bone loss in the setting of a well-fixed stem • Risk factors: • Stiff femoral stem • Large diameter stem • Extensively porous coated stem • Greater preoperative osteopenia
  • 13. DESIGN AND SELECTION OF TOTAL HIP COMPONENTS • No implant design or system is appropriate for every patient • Selection is based on: • Patient’s needs, • Patient’s anticipated longevity • Level of activity, • Bone quality and dimensions, • Ready availability of implants and proper instrumentation, • Experience of the surgeon
  • 14. FEMORAL COMPONENTS • The primary function of the femoral component is: • Replacement of the femoral head and neck after resection of the arthritic or necrotic segment • The ultimate goal of a biomechanically sound, stable hip joint is to restoration of the normal center of rotation of the femoral head. • This location is determined by three factors: • Vertical height (vertical offset), • Medial offset(Horizontal offset) • Version of the femoral neck
  • 15. Cont…. • Vertical height and offset increase as the neck is lengthened. • In most modern systems, neck length is adjusted by using modular heads with variable internal bores. • Vertical height (vertical offset) is determined primarily by the: • base length of the prosthetic neck plus the length gained by the modular head used.
  • 16. Cont…. • Offset ( horizontal offset): • distance from the center of the femoral head to a line through the axis of the distal part of the stem • Inadequate restoration of offset shortens the moment arm of the abductor musculature • Offset can be increased by simply: • using a longer modular neck. • reducing the neck-stem angle • attaching the neck more medial position
  • 17. CONT.. • Head-to-neck ratio of implants, • Large-diameter head with trapezoidal neck has greater ROM and less impingement than smaller diameter head.. • ROM with different head sizes, • Jump distance • distance the head must travel to escape the rim of the socket • approximated to be half the diameter of the head
  • 18. CEMENTED FEMORAL COMPONENTS • Rely on cement fixation • The stem should be fabricated of high-strength superalloy, • Cobalt-chrome or stainless steel • Most common • Reduce cement stresses • Titanium • Prone to micromotion and debonding • less stiff than cobalt-chrome or stainless steel stems
  • 19. Cont.. • The cross section of the stem should have: • Broad medial border • Broader lateral border • To load the proximal cement mantle in compression • Sharp edges produce local stress risers • Collar aids in determining the depth of insertion • Stem shape: • Noncircular shapes ( rounded rectangle, ellipse) • surface irregularities (grooves or a longitudinal slot)
  • 20. CONT… • Stems should be available in a variety of sizes, • Allow the stem to occupy 80% of the cross section of the medullary canal • with an optimal cement mantle of approximately 4 mm proximally and 2 mm distally • the optimal length of the stem depends on: • Geometry and size of the femoral canal • The lengths of current stem designs range from 120 to 150 mm.
  • 21. Cont….. • Cement fixation is optimized by: • limited porosity of cement • cement mantle > 2mm • stiff femoral stem • stem centralization • smooth femoral stem • absence of mantle defects • proper component positioning within femoral cana
  • 22. Radiographic analysis  Barrack and Harris grading system: • grade A • complete filling of medullary canal • "white-out" of cement-bone interface • grade B • slight radiolucency of cement-bone interface • grade C • radiolucencies > 50% of bone-cement interface or incomplete cement mantles • grade D-gross radiolucencies and/or failure of cement to surround tip of stem
  • 23. CEMENTLESS FEMORAL COMPONENTS • Rely on biologic fixation: • Immediate mechanical stability at the time of surgery • Intimate contact between the implant surface and viable host bone • Two materials most commonly used: • Titanium alloy with one of a variety of surface enhancements • Cobalt-chromium alloy with a sintered beaded surface • A variety of surface modifications • Porous coatings, grit blasting, plasma spraying, and hydroxyapatite coating
  • 24. CONT…  Biologic fixation • Mechanism: • Ingrowth: • bone grows into porous structure of implant • Optimum pore size for ingrowth – b/n 100 and 400 µm • Ongrowth: • bone grows onto the microdivots in the grit blasted surface.
  • 25. Cont… • Biologic fixation is optimized with: • pore size 50-300um • porosity of 40-50% • gaps < 50um • micromotion < 150um • maximal contact with cortical bone
  • 26. CONT…  Classification system for cementless stems based on shape: • Types 1 -5 are straight stems, • Type 6 is an anatomic shape • Type 1 stems (single-wedge stems) • Flat in the AP plane • Tapered in the mediolateral plane • Fixation is by cortical engagement only in the mediolateral plane and by three-point fixation along the length of the stem.
  • 27. • Type 2 stems( double-wedge) • engage the proximal femoral cortex in both ML and AP planes • used safely in Dorr type A femurs • Type 3 (Tapered) • Tapered in two planes, • Fixation is achieved more at the metaphyseal-diaphyseal junction • Has 3 subgroups
  • 28. • Type 4 • Extensively coated implants • With fixation along the entire length of the stem • . Canal preparation requires distal cylindrical reaming and proximal broaching • Excellent long-term results • Femoral stress shielding and thigh pain
  • 29. • Type 5 (modular stems) • Separate metaphyseal sleeves and diaphyseal segments • Separate preparation • Recommended for patients with altered femoral anatomy, • Used for all Dorr bone types,
  • 30.  Type 6(anatomic femoral Stem) • incorporate a posterior bow in the metaphyseal portion • anterior bow in the diaphyseal portion • Corresponding to the geometry of the femoral canal • Right and left stems are required,
  • 31. Radiographic analysis • signs of a well-fixed cementless femoral component • Spot-welds • new endosteal bone that contacts porous surface of implant • absence of radiolucent lines around porous portion of femoral stem • proximal stress shielding in extensively-coated stems • absence of stem subsidence on serial radiographs
  • 32. SPECIALIZED AND CUSTOM-MADE FEMORAL COMPONENTS • used most commonly in minimally invasive anterior approaches • Used salvage procedures • some malignant or aggressive benign bone
  • 33. CEMENTED ACETABULAR COMPONENTS • Thick-walled polyethylene cups • Addition of Vertical and horizontal grooves to external surface • increase stability within the cement mantle • wire markers were embedded • better assessment of position on postoperative radiographs • PMMA spacers (3mm height) • To avoid buttoming out • A flange at the rim • aids in pressurization of the cement
  • 34. CEMENTLESS ACETABULAR COMPONENTS • Circumferentially Porous coated for bone ingrowth • oversizing of the implant 1 to 2 mm larger than the reamed • Fixation of the porous shell with transacetabular screws • Most systems use • Metal shell with an outside diameter (40 to 75 mm) • Typically accommodates head sizes 22-40mm • Secure liner to the cup • Failure- back wear
  • 36. CONT…  Constrained acetabular component includes: • Mechanism to lock head to the liner • Tripolar mechanism • A locking ring applied to the rim • Indications: • Insufficient soft tissues, • Weak abductors, • Neuromuscular disease • Recurrent hip dislocation despite well- positioned prosthesis
  • 37.  Dual mobility acetabular component: • Unconstrained Tripolar design • Porous coated shell • Polished interior • Large polyethylene ball • Smaller metal or ceramic head • 2 sites of motion • External bearing – b/n polyethylene and metal Moves at extremes of motion • Internal bearing – b/n head and polyethylene
  • 38.  Custom components (reconstruction): • Rarely indicated • Most deficient acetabula can be restored to a hemispherical shape • A cementless acetabular component • With modular porous metal augments • used instead of a large structural graft • Augments of various sizes are screwed into bony defects • The augments are joined to the implant with the use of bone cement • Antiprotrusio rings and cages.
  • 39. Bearing surfaces  Metal-on-polyethylene: • Metal (cobalt-chrome) femoral head on polyethylene acetabular line • Benefits: • longest track record of bearing surfaces • lowest cost • most modularity • Disadvantages: • higher wear and osteolysis rates • smaller head leads to higher risk of impingement
  • 40.  Metal-on-metal • Benefits: • Better wear properties than metal-on-polyethylene • Lower linear wear rate • Debris particles much smaller • larger head allows for increased ROM before impingement • Disadvantages: • more expensive than metal-on-polyethylene • increased metal ions in serum and urine • May form pseudotumors
  • 41.  Ceramic on Ceramic • Benefit: • best wear properties of all bearing surfaces • lowest coefficient of friction of all bearing surfaces • inert particle • Disadvantages • more expensive than metal-on-polyethylene • worst mechanical properties • Squeaking • stripe wear
  • 42.  Ceramic on polyethylene • Benefits: • Standard of care • Alumina ceramic heads • Results in less polyethylene wear than metal-on-polyethylene • Disadvantages: • zirconia undergoes tetragonal to monoclinic phase transformation with time
  • 43. Indications for THR • Original primary indication: • alleviation of incapacitating arthritic pain in patients>65 yrs • whose pain could not be relieved by non surgical means • For whom the only surgical alternative was resection arthroplasty (Girdlestone resection arthroplasty) or arthrodesis. • Secondary importance was: • the improved function of the hip.
  • 45. Contraindications to THR • Absolute: • Active infection of the hip or any other region • Medical unfit for surgery • Relative: • Morbid obesity • Severe dementia • Tobacco use • Severe osteoporosis • Untreated skin infection • Absent or insufficient abductor musculature
  • 46. Preoperative Patient Evaluation And Optimization  Hx: • Pain: groin, lateral hip, anterior thigh and knee, • Worse during activity, relieved by rest and limited weight bearing • Through medical evaluation • Cardiopulmonary disease, Renal insufficiency, infection, Malignancy and DM • Anticoagulant medication: • D/C Aspirin, clopidogrel 7-10 days before surgery • D/C warfarin 5 days prior surgery
  • 47. Cont…. • Pyogenic skin lesions should be eradicated • Preoperative skin preparation with chlorhexidine • Dental problems, and urinary retention should be addressed • Preop counselling: • Expectations • Social support • VTE prophylaxis • Anesthesia • Pain management plan
  • 48. CONT…  Physical exam- includes: • Spine • upper and lower extremities. • Inspection • Skin-Discoloration, wounds, or gross deformity • Bony-Length, Position • Gait-Antalgic, Trendelenburg
  • 49. Cont…  Palpation • Greater Trochanter / Bursae • Anterior Superior Iliac Spine • Ischial tuberosity • Iliac crest • Iliotibial band / TFL • NV-motor/sensory, pulses, reflexes
  • 50. Cont…..  ROM • Flexion-120-135 deg • Thomas test • Evaluates hip flexion contractures • Extension-20-30 deg • Abduction-40-50 deg • Adduction-20-30 deg • Internal rotation 30 deg • External 50 deg
  • 51.  Special test: • FADIR test • hip Flexed to 90 deg, Adducted and Internally Rotated • Positive test if patient has hip or groin pain • Can suggest possible labral tear or FAI • FABER test (aka Patrick's test) • hip Flexed to 90 deg, ABducted and Externally Rotated • positive test if patient has hip or back pain or ROM is limited • suggest intra-articular hip lesions, iliopsoas pain, or sacroiliac disease
  • 53. PREOPERATIVE RADIOGRAPHS • Minimum requirement –AP pelvis showing proximal femur and lateral view • Review the integrity of the acetabulum • Review width of femoral canal • Look for femoral bowing, malrotation or occult fracture • Templating • Spine and knee x-rays maybe needed • Obturator oblique and iliac oblique • For patients with previous acetabulum fracture • CT with 3D rendering is also recommended
  • 54. Preoperative Templating  Importance • allows surgeon to anticipate potential difficulties • reproduce hip biomechanics • minimizes leg length inequality • Accuracy • 52-98% accurate +/- one size • related to experience and practice
  • 55. Cont…..  Steps • obtain appropriate radiographs • record vital patient information on template (age, height, weight, etc) • establish radiographic landmarks • establish limb length discrepancy • template acetabular component • template femoral component
  • 60. THA Stability Technique • Four important variables that help determine the stability of THA: • Component design • Position component • Soft-tissue tensioning • Soft tissue function component
  • 61. PREPARATION AND DRAPING • Appropriate operating table • Positioning devices • Preop tranexamic acid • hip and entire limb are prepared with a suitable bactericidal solution • a U-shaped plastic drape are applied • Protect bony prominences
  • 62. SURGICAL APPROACHES AND TECHNIQUES • The choice of specific surgical approach is: • Matter of personal preference • Training • prior incisions • obesity • risk for dislocation • implant selection and degree of deformity • Anterior • Supine • medial border of TFL muscle;
  • 63. Cont….  Anterolateral • Charnley- supine with GT osteotomy • Amstutz-lateral with GT osteotomy  Direct lateral-supine or lateral with split of abductors • Dall- removed the abductor with a flake of bone • Head-reflect vastus lateralis & G. medius together  Posterolateral- lateral with hip delivery  Extensile
  • 67. EXPOSURE AND PREPARATION OF THE ACETABULUM
  • 69. Acetabular cup placement (cementless)
  • 72. EXPOSURE AND PREPARATION OF THE FEMUR
  • 74. Femoral stem placement (cementless)
  • 76. THA THROUGH THE DIRECT ANTERIOR APPROACH
  • 77. THA Postoperative Inpatient Management • Care can be broken down into different phases including: • Preoperative teaching • Inpatient acute care (hospital) • Inpatient extended care (rehab) • outpatient home care
  • 79. Acute complications • Periprosthetic Fracture • Dislocation • Sciatic Nerve Palsy • Leg Length Discrepancy • Vascular Injury & Bleeding
  • 81. Chronic complications • Aseptic Loosening • Iliopsoas Impingement • Trunnionosis • Pseudotumors
  • 82. References • Campbell's OPERATIVE ORTHOPAEDICS 14TH EDITION • Orthobullets • CLINICAL ORTHOPAEDICS AND RELATED RESEARCH • BMC musculoskeletal disorder

Notas do Editor

  1. Lever arms acting on hip joint. A, Moment produced by body weight applied at body’s center of gravity, X, acting on lever arm, B-X, must be counterbalanced by moment produced by abductors, A, acting on shorter lever arm, A-B. Lever arm A-B may be shorter than normal in arthritic hip. B, Medialization of acetabulum shortens lever arm B1-X, and use of high offset neck lengthens lever arm A1-B1. C, Lateral and distal reattachment of osteotomized greater trochanter lengthens lever arm A2-B2 further and tightens abductor musculature
  2. Calculated peak contact forces across the hip joint during gait range from 3.5 to 5.0 times the body weight and up to six times the body weight during single-limb stance. Experimentally measured forces around the hip joint using instrumented prostheses generally are lower than the forces predicted by analytical models, in the range of 2.6 to 3.0 times the body weight during single-limb stance phase of gait. When lifting, running, or jumping, however, the load may be equivalent to 10 times the body weight. Excess body weight and increased physical activity add significantly to the forces that act to loosen, bend, or break the femoral component
  3. The quality of the bone before surgery is a determinant in the selection of the most appropriate implant, optimal method of fixation, response of the bone to the implant, and ultimate success of the arthroplasty
  4. The material a stem is made of, the geometry, length, and size of the stem, and the method and extent of fixation dramatically alter the pattern in which stress is transferred to the femur. Adaptive bone remodeling arising from stress shielding compromises implant support and predisposes to fracture of the femur or the implant itself. Stress transfer to the femur is desirable because it provides a physiologic stimulus for maintaining bone mass and preventing disuse osteoporosis.
  5. Version refers to the orientation of the neck in reference to the coronal plane and is denoted as anteversion or retroversion. Restoration of femoral neck version is important in achieving stability of the prosthetic joint. The normal femur has 10 to 15 degrees of anteversion of the femoral neck in relation to the coronal plane when the foot faces straight forwa
  6. Inadequate restoration of offset shortens the moment arm of the abductor musculature and results in increased joint reaction force, limp, and bone impingement, which may result in Dislocation Offset can be increased by simply using a longer modular neck, but doing so also increases vertical height, which may result in overlengthening of the limb. y reducing the neck-stem angle (typically to about 127 degrees) or by attaching the neck to the stem in a more medial position
  7. The size of the femoral head, the ratio of head and neck diameters, and the shape of the neck of the femoral component have a substantial effect on the range of motion of the hip the degree of impingement between the neck and rim of the socket, and the stability of the articulation This impingement can lead to dislocation, accelerated polyethylene wear, acetabular component loosening, and liner dislodgment or fracture The ideal configuration of the prosthetic head and neck segment includes a trapezoidal neck and a larger diameter head without a skirt.
  8. Nonetheless, worldwide registry data suggest that in patients older than 75 years outcomes are better with cemented femoral fixation, owing mainly to a lower risk of periprosthetic fracture
  9. Summit stem. Integral proximal polymethyl methacrylate spacers and additional centralizer facilitate proper stem position and uniform cement mantle. Spectron EF stem. Rounded rectangular shape and longitudinal groove improve rotational stability
  10. Omnifit EON stem. Normalized proximal texturing converts shear forces to compressive forces. A, Standard offset. B, Enhanced offset Collarless, polished, tapered (CPT) hip stem. CPT design allows controlled subsidence and maintains compressive stresses within cement mantle
  11. In the mid-1970s, problems related to the fixation of femoral components with acrylic cement began to emerge. As a result, considerable laboratory and clinical investigations have been performed in an effort to eliminate cement and provide for biologic fixation of femoral components Current cementless stem designs differ in their materials, surface coating, and shape Porous coatings have historically been created by either beads or fiber mesh applied to the stem by sintering or diffusion bonding processes . Both processes require heating of the underlying substrate
  12. Types of bone ingrowth surfaces. Traditional surfaces produced from sintered beads (A) and diffusion bonded fiber mesh (B). C, Newer highly porous tantalum more closely resembles structure of trabecular bone. Types of bone ongrowth surfaces. A, Grit-blasted surface. More highly textured plasma-sprayed surfaces: titanium (B) and hydroxyapatite (C) Grit blasting involves the use of a pressurized spray of aluminum oxide particles to produce an irregular surface ranging from 3 to 8 μm in Plasma spray techniques use high-velocity application of molten metal onto the substrate in a vacuum or argon gas environment and produce a highly textured surface The thickness of the coating is typically 50 to 155 μm. depth
  13. The femoral canal is prepared by broaching alone, with no distal reaming is important to ensure that the stem is wedged proximally Dorr type A femurs, distal engagement alone risks fracture or rotational instability many of these designs have been modified with reduced distal sizing to avoid this problem These stems have performed well in Dorr type B and C femurs.
  14. Type 3A stems are tapered with a round conical distal geometry. Longitudinal cutting flutes are added to type 3B stems (Fig. 3.23). These implants have recently gained popularity in complex revision cases. Type 3C implants are rectangular and thus provide four-point rotational support (Fig. 3.24). Such implants have been used extensively in Europe with success Type2:Femoral preparation typically requires distal reaming followed by broaching of the proximal femur
  15. Type 5 or modular stems have separate metaphyseal sleeves and diaphyseal segments that are independently sized and instrumented. Such implants often are recommended for patients with altered femoral anatomy, particularly those with rotational malalignment such as developmental dysplasia. Both stem segments are prepared with reamers, leading to a precise fit with rotational stability obtained both proximally and distally. This feature makes modular stems an attractive option when femoral osteotomy is required
  16. anteversion must be built into the neck segment. Anatomic variability in the curvature of the femur usually requires some degree of overreaming of the canal; if the tip of the stem is eccentrically placed, it impinges on the anterior cortex. This point loading has been suggested to be a source of postoperative thigh pain. The popularity of anatomic stems has declined over the past decade in favor of straight designs
  17. , micromotion between the nonarticulating side of the liner and the interior of the shell may be a source of polyethylene debris generation, or “backside wear.” Recognition of this problem has led to improvements in the fixation of the liner within the metal shell, and some designs also have included polishing the interior of the shell. Monoblock acetabular components with nonmodular polyethylene also have been produced to alleviate the problem of backside wear but have not proven to be superior to modular implants.
  18. Array of liner options available with contemporary modular acetabular system: standard flat liner (A), posterior lip without anteversion (B), 4-mm lateralized flat (C), and anteverted 20 degrees (
  19. A constrained acetabular component includes a mechanism to lock the prosthetic femoral head into the polyethylene liner. The tripolar-style mechanism features a small inner bipolar bearing that articulates with an outer true liner (Fig. 3.34A). The bipolar segment is larger than the introitus of the outer liner, preventing dislocation. Other designs use a liner with added polyethylene at the rim that deforms to capture the femoral head. A locking ring is applied to the rim to prevent
  20. The design effectively increases the head size and the head-neck ratio of the construct. Implant impingement is reduced and stability is improved without reducing the range of motion as with constrained implants
  21. The preferred devices are those with superior and inferior plate extensions that provide fixation into the ilium and the ischium (Fig. 3.38). Success with these devices depends on selection of the proper device and careful attention to technique. Implantation of the antiprotrusio cage requires full exposure of the external surface of the posterior column for safe positioning and screw insertion. Alternatively, the inferior plate can be inset into a prepared recess in the ischium without the need for inferiorly placed screws. For all types of devices, dome screws are placed before the plates are attached to the external surface of the ilium
  22. more expensive than metal-on-polyethylene increased metal ions in serum and urine (5-10x normal) serum metal ion concentration highest at 12-24 months correlates with the initial "wear in" or "run-in" phase of increased particle generation, but then followed by a "steady state" phase of decreased particle generation no proven cancer link may form pseudotumors hypersensitivity (Type IV delayed type hypersensitvity) mediated by T-cells metals sensitize and activate T-cells (nickel > cobalt and chromium) however, most participating cells are macrophages (only 5% are lymphocytes) antigen-activated T-cells secrete cytokines that activate macrophages activated macrophages have increased ability to present class II MHC and IL-2, leads to increased T-cell activation the cycle continues
  23. disadvantages more expensive than metal-on-polyethylene worst mechanical properties (alumina is brittle, low fracture toughness) small 28mm heads only exist in zirconia because of alumina's inferior mechanical properties squeaking increased risk with edge loading impingement and acetabular malposition third-body wear loss of fluid film lubrication thin, flexible (titanium) stems less modularity with fewer neck length options stripe wear caused by contact between the femoral head and rim of the cup during partial subluxation results in a crescent shaped line on the femoral head
  24. disadvantages zirconia undergoes tetragonal to monoclinic phase transformation with time increased with prolonged in vivo implantation >8yr pressure temperature has lower heat conductivity than alumina (joint temperature can reach 99oC for zirconia, and 50oC for alumina)
  25. Process of anticipating the size and position of implants prior to surgery Right selection of implant to restore hip COR Provide best femoral fit Determine level of bone resection Selection of neck length to restore limb length and offset
  26. If we decide to use screw – PS is safest to use Use 6.5 mm screw If screw in the posterior quadrant is used – screw can be bicortical Palpate through the sciatic notch to make sure the screw doesn’t catch sciatic nerve, if it does, use shorter screw The screw head must sit perfectly center in the screw hole to avoid scewing the liner and malpositioning the cup Add a second screw if cup is still unstable or consider using cement If it is a must to use anterior screw – use a short drill bit and constantly stop to make sure we are still in bone and avoid plunging. Screw to be used must be less than 20 mm unless the screw is in the superior ramus. Use depth gauge carefully Finally, use a curved osteotome to remove any osteophyte in the rim, specially anteroinferiorly which will block flexion and internal rotation predisposing to dislocation. Irrigate the cup before inserting the liner
  27. Thick nonmodular acetabular cup Drill 6 mm holes in the bone for cement intrusion Thoroughly dry blood as it interferes in the cement bonding Apply cement in these drill holes first and pressurize with small pressurizer nozzles Then apply cement in the acetabulum and pressurize with the pressurizer Then apply the cup which has spacers to prevent bottoming out of the cement Apply gentle pressure until cement hardens Then check stability. Remove if cup is unstable Stability depends on immediate postop radiolucency behind the cup – correct technique is paramount to success