Transcript Primary Total Hip Arthroplasty

Primary Total Hip Arthroplasty
Majdi S Qutob MD, FRCSC, MSc, MBA
History
• 1891 Themistocles Glück (1853-1942) carried out
the first reported Femoral Hemiarthroplasty in
Germany, using ivory to replace the femoral head
• 1940 Dr. Austin T. Moore (1899–1963), first
metallic (Vitallium) Femoral Hemiarthroplasty
• 1960 Dr. San Baw (1922 –1984) ivory Femoral
Hemiarthroplasty for neck fractures
• 1970 Dr Sir John Charnley (1911 –1982) Low
Friction Arthroplasty
Demographics
By 2030, the demand for primary total hip
arthroplasties is estimated to grow by 174% to
572,000
The Journal of Bone & Joint Surgery. 2007; 89:780-785
Arthritis
• Arthritis is the second most common chronic
condition in the US (sinusitis is first)
– Most common among elderly
• 20-30% of people over age 70 suffer from
osteoarthritis (OA) of the hip
• Arthritis affects over 32 million people in the US
• Total costs associated with arthritis are over
$82B/year, including hospital and drug costs, nursing
home costs, and lost productivity and work
Normal ROM
IR- 35°
ER - 45°
Flexion - 135°
Extension - 15°
Abduction - 45°
Adduction - 25°
Non-Surgical Intervention
•
•
•
•
•
Activity Modification
Weight Loss
Cane/walker
Physical Therapy
Medications:
– NSAIDs
– COX-2 Inhibitors
– Nutritional supplements
• Injections:
– Corticosteroid
– Viscosupplementation
Joint Anatomy
• Femoral Head Diameter 46mm
• Neck Shaft Angle Average 130 degrees
– > 135 deg coxa valga
– < 120 deg, coxa vara
• Femoral Anteversion Angle 12-15 degrees
• Femoral Offset variable
• Acetabular Anteversion Average 15 (0-20)
degrees
• Acetabular Abduction Angle 45 degrees (30-50)
• AP Curve of Femur is about 4 degrees
Biomechanical Considerations
• 1-2million steps/year
• 3-6x body weight due to abductors- 7-8x
sporting activities
• Descending stairs causes highest JRF
• Abductors provide two thirds of the hip joint
force parallel to the long axis of femur
• Increasing the offset and cup medialization
reducing the joint reaction force by increasing
the abductor lever arm
Biomechanical Considerations
• Increasing the offset and cup
medialization reducing the joint
reaction force by increasing the
abductor lever arm
• 10mm increase femoral offset
decreases 10% abductors force
requirement
Bone Biomechanics
• Young’s Modulus (flexibility) =stress/strain
– Stress =force/area
– Strain= change in length
• Bone is anisotropic (compression>shear)
• Exhibits creep: constant pressure will deform
at a decreasing rate
• Strain rate low with rapid application of
modest force leads to fracture
Singh et. al. JBJS. 1970 (52-A) 457-467
Singh Classification for Femoral Neck Osteoprosis
Singh et. al. JBJS. 1970 (52-A) 457-467
Dorr suggested that there are three types of proximal femur, A is the normal taper
top and thick cortex, C is a clear loss of taper and thin cortex, and B is in between.
Types of Total Hip Arthroplasty
Cemented vs Uncemented
GOALS of THA
• “Position the primary arc range of the
prosthetic hip in the centre of the functional
range of motion required by the patient, in
order to optimize the range of motion and
reduce the chances of dislocation”
Patient’s Goals
• “Patients’ satisfaction with hip replacement
depends on the surgeon’s ability to relieve
pain, equalize leg length and produce a stable
hip which will not dislocate” Dr. Charles Engh
(2007)
Cemented Components
• Polymethylmetacrylate (PMMA)
interdigitates within bone (grout)
• Endosteal heat necrosis 500
micrometers
• Cement mantle of minimum 2mm
circumferentially
• Cement in Gruen Zone 7 allows load
in proximal third femur
• Third Generation Techniques
Cemented Femoral Implants
Two Schools of Thought
1. Surface Properties
–
–
–
Implant-to-cement adhesion
Increase roughness, precoating,
macroscopic grooves
Debonding and increased wear debris
2. Implant Shape
–
–
–
Smooth stem with straight taper to
allow subsidence and create hoop
stress
Broad laterally than medially diffuse
compressive stresses and increase
torisional and bending rigidity
Less debris
Cemented Femoral Implants
Indications
• Dorr Type C Femurs
• Singh Grades 1-3
• Poor Bone Quality
Failure Rates
• Revision rates 0-5% in 10yrs
• Poor Operative Technique
• Revision outcomes worse (26% failure rate)
Cemented Acetabular Component
• “Not Suitable for younger active patients”
• Lower demand with soft bone (rheumatoids,
acetabular protrusio)
• High failure rates (10-23% at 10yrs)
• Causes of failure
– Poor operative techniques
– Failure to remove peripheral cartilage
– Poor pressurization
– Poor design of implant (flanged sockets)
Uncemented Components
“Potential life long dynamic
bond between host bone and
implant”
• Decreased failure rates in
young patients
• Surgical trauma causes
mesenchymal stem cells to
become osteoblasts and
intramembranous bony
ingrowth or on-growth into
the prosthesis
Press Fit Femoral Implants
Types
1. Tapered- metaphysis wedge fixation
2. Cylindrical- diaphyseal and metaphyseal fixation
3. Anatomic-metaphyseal fill in coronal and sagittal
plains
1. Porous Coating
2. Grit Blasting
3. HA Coating
Press Fit Femoral Implants
Metallurgy
1. Cobalt-Chrome
–
High Modulus of Elasticity (Stress Shielding)
2. Stainless Steel
–
–
–
Lower fatigue strength
Corrosion
Lower cost, easy workability
3. Titanium-alloy
–
–
–
–
Lower elastic modulus (reducing stress shielding)
Titanium-oxide corrosion resistance
Osseointergration
Easily scratched and notch sensitivity decrease fatigue life
Cortical Defects Perils
• Stress patterns of tubular bone return to
normal 2 cortical diameters past
• Stem must bypass 2-3 internal bone diameters
• 4-5cm of distal femoral isthum and implant
• Stem greater than 90% canal fill
• Stem stiffness fourth power of diameter
(higher causes more stress shielding)
Rules of 50’s
• Implant-to-host distance minimum 50um
• Excessive Interface motion >50um (30150um)leads to fibrous non-union
• Pore Density of implant 50%
• Pore Size < 500um (100-400um)
• Gaps Less than 0.5mm
• Under Reaming 3-4mm significantly increases
risk of fracture
Bearing Surfaces
• Hard-on-Soft
– Acetabular Liner polyethylene(PE) and fermoral
heads of Cobalt-Chrome, Ceramic, Titanium
– UHMWPE with vitamin E
– CC-PE 0.28mm/yr volumetric wear
– C-PE 150um/yr volumetric wear
Bearing Surfaces
• Hard-on-Hard
– Ceramic-on-Ceramic, Metal on Metal, Ceramic-onMetal
– Initial wear in period self-polishing (2.5-5 um/yr)
– Aseptic lymphocytic Vasculitis Associated Lesions
(ALVAL)
– Delayed Type Hypersensitivity
– COC 0.5-2.5um/yr
– COC volumetic wear 0.004mm/year
– Failure rates of 0.004% (Catastrophically!!!)
Mechanisms of Wear in THA
• Abrasive Wear- two surfaces of differing
hardness
• Adhesive Wear-PE sheared off and deposit in
joint space
• Fatigue
• Delamination
• Third Body Wear- particles trapped between
joint space causing wear of softer surface
Aseptic Loosening & Osteolysis
• Four Mechanisms of Cemented Component
Failure
1. Pistoning of stem/cement causing subsidence
2. Medial Stem Pivot- varus position stem causes
failure in proximo-medial and distolateral areas
3. Calcar Pivoting- distal aspect of stem shifts
within distal mantle
4. Cantilever Bending (Fatigue)
"Modes of failure" of cemented stem-type femoral components: a radiographic analysis of
loosening. Gruen TA, McNeice GM, Amstutz HC 1979
Gruen Zone Classification for
Femoral Prosthesis Loosening
Aseptic Loosening & Osteolysis
• 0.1-10 micrometres in size (most potent 0.1-0.5)
Head and Head-Neck Ratios
• Head Size
– Less volumetric wear secondary to small arc of
motion
– Greater Linear wear because JRF distributed over
smaller area
– 28mm Head trade-off between volumetric and linear
wear (new PE allows 32mm head)
– Optimal ratio HN is 2:1
• Hard on Hard Articulations
– Hydrodynamic lubrication and low volumetric wear
(with suction effect)
Abductor Tensioning
• Increasing lateral offset and neck length
increases abductor lever arm and tension,
stability and reduces JRF
• Increases torsional stresses on implant
• Increases trochanteric bursitis
• Increases leg length discrepancy
• Average femoral offset 45mm
• Sex differences
Abductor Tensioning
Abductor Tensioning
• Women
– Shorter femoral necks
– Thinner femoral shafts
– Lower cervio-diaphyseal angles
– Lower femoral offsets
– Greater femoral neck anteversion
Leg Length Discrepancy
• Lateral Decubitus highest risk
• Pre-op templating critical
• Intra-op assessment of patients feet
and knees in symmetrical knee
flexion
• Measuring height of femoral cut
from top of LT
• Assess relationship of GT to femoral
centre before and after osteotomy
Clinical Assessment of a Difficult THA
• GOLDEN STEPS!
1.
2.
3.
4.
5.
6.
7.
Choosing the right patients
Is it the right operation
What is the operative plan
What are the x-ray land marks
Check the template
Identify Surgical Landmarks
Getting the Leg Length Right
Step 1: Choosing the Right Patient
• Groin Pain or Thigh Pain or Knee Pain!!!
• Back Pathology
– Bilateral Hip Pain
– No Groin Pain
– Unable to Localize pain
– Negative leg roll test
– Back movement reproduces the pain
• If in doubt interventional radiology assisted
intraarticular injection
Step 1: Choosing the Right Patient
• Assess Gait and Hip ROM
• Evaulation knee, lumbosacral spine
• Actual Limb-Length DiscrepancyASIS to medial malleolus
• Functional Limb-Length
Discrepancy- Using blocks until
patient feels equal
Step 1: Choosing the Right Patient
• Difference actual and functional lengths
evaluate for
– Suprapelvic Obliquity (scoliosis, DD spine) persists
with sitting
– Intrapelvic Obliquity (necrosis, arthritis, infection,
malunions, congenital hemihypertrophy, etc…)
corrects with sitting
• Equalization of functional limb length
improves gait and increased comfort
Step 2: The Right Operation
• Altering the THA to suit the patient
1.
2.
3.
4.
5.
High dislocation risk patient
Young active patient
Small CDH or Juvenile Rheumatoid Patients
The Deformity Patient
Short Varus Neck Patients
• Surgical Approach
• Components
– Constrained Cups, Modular Implants, etc
Step 2: The Right Operation
• High Risk Dislocation Patients after THA
1. Initial Leg Length >2cm
2. Fixed Pelvic Tilt
3. Elderly, Cachectic female patient
4. Hypermobility
5. Neuromuscular Problems
6. Fusion Takedown/no Abductors
7. Multiple Previous Surgeries
8. Demented/Substance Abuse Patients
9. Post Fracture neck of femur
10. Patient with a previous spinal fusion
Step 3: Planning the Operation
Plan A-D
• Plan A: Usual default for THA used in 95% of
cases
• Plan B: If “Plan A” Fails (e.g. sterility of
instruments breached or implants not available)
• Plan C: Hand over complex case to senior
colleague
• Plan D: At time of surgery things are going wrong
and not able to obtain satisfactory outcome.
– Call a senior surgeon
– Close without an implant with skin or skeletal traction
Step 4: Xray Landmarks
• Hips in 10-15 degrees internal rotation (true AP
of femoral neck)
• Marker of known diameter between legs (coin)
X-ray minus 15° rotation
X-ray plus 30° rotation
• True femoral offset will be underestimated if
hips are externally rotated
• Magnification is proportional to the distance
between pelvis and film (20%+/-6%)
Step 4: AP Xray Landmarks
1.
2.
3.
4.
5.
Tear Drops
Superolateral edge of Acetabulum
Centre of rotation of Head
New Centre of rotation of hip joint
Lesser Trochanters
Step 4: Lateral Xray Landmarks
Step 5: Check the Template
• Should follow steps of surgery
– acetabular side first then femoral
• Horizontal reference line base of teardrops
(most accurate landmark) (can use SI or ischial
tuberosities)
Step 5: Check the Template
Key Radiographic Landmarks
1. Tear Drop
2. Ilioischial line
3. Superolateral margin of the acetabulum
Step 5: Check the Template
Acetabular Templating
1. Cup sized when placed at 40degrees (+/- 10) of
abduction medial boarder approximates ilioischial line
2. Must have adequate lateral coverage
3. Inferior boarder cup level with inferior tear drop
4. If cemented uniform cement mantle of 2-3mm
5. Lateral coverage lacking metal augments or bone
(number 7 graft)
6. Center of rotation is marked and compared to
opposite side
Step 5: Check the Template
Protrusio Acetabuli
1. Template to anatomic position lateral to tear drop
and Kohler’s line with peripheral rim contact
2. Measure medial defect for graft filling
THA for Acetabular Protrusio
Causes:
• Osteogensis imperfecta
• Osteomalacia
• Paget’s Disease
• Bone Tumors
• Rheumatoid Arthritis
• Ankylosing Spondylitis
• Trauma
Step 5: Check the Template
Lateralized Acetabulum
1. Acetabulum reamed until pulvinar, ligamentum
teres, cotyloid notch and transverse acetabuluar
ligament (beware medial osteophytes!!!)
Step 5: Check the Template
Dysplastic Acetabulum
1.
2.
3.
Insufficient acetabular coverage and superolateral migration of femoral
head
Mild/Moderate dysplasia well developed posteriosuperior wall
(70%coverage)
Additional coverage more proximal (high hip center) or medial nonanatomic position
Step 5: Check the Template
Femoral Templating & Restoration of
Leg Length
GOAL
“Achieve adequate alignment and
fixation to restore femoral offset and
optimize leg length”
Step 5: Check the Template
Femoral Templating & Restoration of Leg Length
Center of Rotation
• Line perpendicular to femoral shaft at the level of the
tip of the GT inaccurate
• Coxa Valga- center of rotation is above the GT
• Coxa Vara or Coxa Brevis- COR below the GT
Normal
130
Coxa Vara
<120
Coxa Valga
>140
Step 5: Check the Template
Femoral Offset
•
•
•
•
Restoration of original offset
Beware xray rotation!!!!
Template off normal contralateral side
Measure distance center of rotation to tip GT before
neck cut
• Measure distance proximal LT to COR
• Measure distance proximal LT to proposed neck cut
• Cemented stem
– Optimal diameter distal centralizer, plug size, and depth
insertion
X-ray minus 15° rotation
X-ray plus 30° rotation
• True femoral offset will be underestimated if
hips are externally rotated
• Magnification is proportional to the distance
between pelvis and film (20%+/-6%)
Step 5: Check the Template
Utility of Preoperative Templating
• Eggli et al 1998 (JBJS)
–
–
–
–
–
–
90% agreement cup size
92% agreement stem size
Actual difference COR hip 2.5 +/- 1.1mm vertical
4.4 +/- 2.1mm horizontal
Mean LLD 3 +/- 1mm clinically, 2 +/- 1 mm radiographically
80% difficulties were anticipated (trochanteric osteotomy,
acetabular autografts, reinforcement rings and resection
osteophytes)
Adapting the Preoperative Planning to
Intraoperative Findings
• Feedback during acetabular reaming and
femoral broaching
• Reduction of trial prosthesis
– ROM (removal osteophytes)
– Soft tissue tension with correct LLD then increase
stem with increased offset
– Elderly tolerate LLD
Adult Congenital Hip Disease
THA for Congenital Hip Disease
• Classifications
– Crowe Classification
<50%
75-100%
50-75%
>100%
New Classification
High Dislocation
• Femur superior
Dysplastic
Low Dislocation
posterior
• Segmental defect rim
• Contained in true • Femoral Head
• Increased bone
articulates false
acetabulum
posterosuperior
acetabulum
• Superior defect
• Excessive anteversion
• Iliac wing hypoplastic
• Fossa osteophytes • Anterio-superior
and anterverted
defect
• FN Shorter and
• Increased anteversion anterverted
• Lack posterior bone • Diaphysis is hypoplastic
narrow and thin
• FN short
cortices
Preoperative Planning
• Low and High Dislocations obtain CT
• Estimates bone stock, accurate sizes and
anteversion acetabulum and femoral neck
• Plain films for templating
Technical Difficulties
• Narrow diaphysis and angular deformities of
femur
– Trochanter osteotomy
•
•
•
•
•
Restoration true vs high hip center
Acetabulum osseous coverage 80%
Small 40-42mm cup with thin poly
Augmentation superior defects
Cotyloplasty
Technical Difficulties
Technical Difficulties
• High Hip Center
– Lever arm body weight longer than abductors
causing excessive shearing and loading forces of
the hip
– Does not correct leg length limp and low back pain
• Shortening of femur if >4cm lengthening
(subtrochanteric osteotomy)
• Stem short cementless conical distal bearing
THA for Arthrodesed Hips
THA for Arthodesed Hips
• Indications for Conversion:
– painful pseudarthrosis
– pseudorthrosis rates are 0-10% using modern
techniques for fusion
– mechanical low back pain -#1 complaint
– multi-level arthritic changes seen in LS spine
– malposition (especially increased abduction) is a
major cause
– excessive leg length inequality
– knee pain/instability
• Adduction causes ipsilateral pain
• Abduction causes contralateral pain
THA for Arthodesed Hips
Preoperative Evaluation:
• Physical exam and EMG (abductors)
• AP pelvis, cross table lateral and Judet Views
to identify bone stock
• CT scan heterotopic bone to neurovascular
structures an abductor muscle mass
Surgical Considerations
• Anterior approach, posterior approach or a direct
lateral or a trans-trochanteric (Gaunz) Osteotomy
• Indications for an trochanteric osteotomy
– Exposure
– decrease injury to atrophied/weakened abductors during
the case
– advancement (improve stability)
• Existing hardware and HO should be removed
• Neck cut in situ; proximal cuts results in fractures of
the pubis and the ischium
• if in doubt, place guide pins and obtain a radiograph
• soft tissue releases (ilio psoas, adductors, etc.) PRN
• Acetabular component:
– structural grafting (metal
augments)
– one should be prepared to cement
the socket if the shell has <50 %
contact with native bone
– a constrained liner is frequently
required because of insufficient
soft tissue tension post-op (esp.
abductors)
• Femoral component:
– modular femoral
components
– if the trochanter is bald
and there are no
abductors, the proximal
femur can be sewn to
the tensor fascia lata
anteriorly and the
gluteus maximus and ITB
posteriorly
Results:
• relief of low back pain occurs 70-95% of the
time
• leg lengths can usually be improved
• ipsilateral knee pain typically improves but it
persists in at least 1/3 (especiailly if instability
was a problem pre-op)
• a trendelenberg gait typically persists though
abductor function improves for 2-5 years
• results from conversion of spontaneous
fusions are typically better than results
of conversion of surgical fusions
Complications:
• deep infection 1.9-15.3% (higher in
conversion of surgical fusion)
• dislocation 1.7 - 6.25%
• sciatic nerve palsy 1.8-13.4%
• femoral nerve palsy 3.6%
CASES
SH
•
•
•
•
58yo female
High Speed MVA (t-boned) 1yr ago
ORIF Rt Acetabulum
Referred to office for increasing right hip pain
• Post Op
• Today
Next Step?
Options?
SR
• 63 yr male, previous Lt femoral osteotomy for
OA – uncomplicated index surgery plus
subsequent hardware removal.
• Incapacitating pain Lt hip
• Otherwise well
• Severely restricted RoM, well healed scars,
T/berg/antalgic gait
BP
• 51 yr female, brain damage, LTC resident,
recurrent seizures
• Previous Rt bipolar for subcap.#
• Previous Lt DHS for Intertroch #
• Remote Lt femoral shaft #
• Pain Lt Hip, unable to weightbear
• Afebrile
BP
• Family and caregivers request solution for pain and
inability to mobilize…
•
•
•
•
•
•
1. No surgery
2. Remove hardware only
3. Stage hardware removal and bipolar
4. Remove hardware and Bipolar
5. Stage hardware removal and THA
6. Remove hardware and THA
BP
• What about the femoral deformity distal to
plate?
• 1. Try to bypass (+/- osteotomy)
• 2. Ignore
KK
•
•
•
•
•
34 yr male, OA Lt hip secondary to LCPD
Previous periacetabular osteotomy 6ys prior
Severe pain and functional limitation
30° external rotation deformity
2.5cm short
KK
•
•
•
•
Direct lateral approach
Entire acetabulum retroverted 30°
Tight external rotators – released
Ant column “shaved” and Ant column screw
advanced to reduce femoral impingement in flexion
• Iliac screws removed via separate incisions
• “External landmarks” for cup orientation
• Posterior aspect shell 20-30% uncovered
DS
• 58yr male, previous acetabular fracture (MVA)
– ORIF 12 yrs prior
• 8hr procedure, transtrochanteric approach, no
reported postop complications
• Severe pain etc
• No systemic symptoms
• Fit and good health
DS
• Approach?
•
•
•
•
•
1.Transtrochanteric
2. Iliofemoral
3. Direct lateral
4. Posterior
5. Invent a new one
DS
• Hardware removal…
• 1. Plan to stage
• 2. Remove all – at time of THA
• 3. Try to ignore at time of THA
Managed to ignore
most of the
hardware
Lateral approach with
unintentional
transtrochanteric
component