1. Primary Total Hip Arthroplasty
Majdi S Qutob MD, FRCSC, MSc, MBA

2. History
1891 Themistocles Glück ( ) 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

3. 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:

4. 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

5. Normal ROM
IR- 35°
ER - 45°
Flexion - 135°
Extension - 15°
Abduction - 45°
Adduction - 25°

6. Non-Surgical Intervention
Activity Modification
Weight Loss
Cane/walker
Physical Therapy
Medications:
NSAIDs
COX-2 Inhibitors
Nutritional supplements
Injections:
Corticosteroid
Viscosupplementation

7. Joint Anatomy Femoral Head Diameter 46mm
Neck Shaft Angle Average 130 degrees
> 135 deg coxa valga
< 120 deg, coxa vara
Femoral Anteversion Angle 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

9. 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

10. 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

12. 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

13. Singh et. al. JBJS (52-A)

14. Singh Classification for Femoral Neck Osteoprosis
Singh et. al. JBJS (52-A)

15. 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.

16. Types of Total Hip Arthroplasty
Cemented vs Uncemented

17. 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”

18. 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)

19. 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

20. Cemented Femoral Implants
Two Schools of Thought
Surface Properties
Implant-to-cement adhesion
Increase roughness, precoating, macroscopic grooves
Debonding and increased wear debris
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

21. 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)

22. 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)

23. 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

24. Press Fit Femoral Implants
Types
Tapered- metaphysis wedge fixation
Cylindrical- diaphyseal and metaphyseal fixation
Anatomic-metaphyseal fill in coronal and sagittal plains
Porous Coating
Grit Blasting
HA Coating

25. Press Fit Femoral Implants
Metallurgy
Cobalt-Chrome
High Modulus of Elasticity (Stress Shielding)
Stainless Steel
Lower fatigue strength
Corrosion
Lower cost, easy workability
Titanium-alloy
Lower elastic modulus (reducing stress shielding)
Titanium-oxide corrosion resistance
Osseointergration
Easily scratched and notch sensitivity decrease fatigue life

26. 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)

27. Rules of 50’s Implant-to-host distance minimum 50um
Excessive Interface motion >50um (30-150um)leads to fibrous non-union
Pore Density of implant 50%
Pore Size < 500um ( um)
Gaps Less than 0.5mm
Under Reaming 3-4mm significantly increases risk of fracture

28. 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

29. Bearing Surfaces Hard-on-Hard
Ceramic-on-Ceramic, Metal on Metal, Ceramic-on-Metal
Initial wear in period self-polishing (2.5-5 um/yr)
Aseptic lymphocytic Vasculitis Associated Lesions (ALVAL)
Delayed Type Hypersensitivity
COC um/yr
COC volumetic wear 0.004mm/year
Failure rates of 0.004% (Catastrophically!!!)

30. 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

31. Aseptic Loosening & Osteolysis
Four Mechanisms of Cemented Component Failure
Pistoning of stem/cement causing subsidence
Medial Stem Pivot- varus position stem causes failure in proximo-medial and distolateral areas
Calcar Pivoting- distal aspect of stem shifts within distal mantle
Cantilever Bending (Fatigue)
"Modes of failure" of cemented stem-type femoral components: a radiographic analysis of loosening. Gruen TA, McNeice GM, Amstutz HC 1979

32. Gruen Zone Classification for Femoral Prosthesis Loosening

33. Aseptic Loosening & Osteolysis
micrometres in size (most potent )

34. 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)

36. 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

37. Abductor Tensioning

38. Abductor Tensioning Women Shorter femoral necks Thinner femoral shafts
Lower cervio-diaphyseal angles
Lower femoral offsets
Greater femoral neck anteversion

39. 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

40. Clinical Assessment of a Difficult THA
GOLDEN STEPS!
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

41. 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

43. Step 1: Choosing the Right Patient
Assess Gait and Hip ROM
Evaulation knee, lumbosacral spine
Actual Limb-Length Discrepancy- ASIS to medial malleolus
Functional Limb-Length Discrepancy- Using blocks until patient feels equal

44. 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

45. Step 2: The Right Operation
Altering the THA to suit the patient
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

46. Step 2: The Right Operation
High Risk Dislocation Patients after THA
Initial Leg Length >2cm
Fixed Pelvic Tilt
Elderly, Cachectic female patient
Hypermobility
Neuromuscular Problems
Fusion Takedown/no Abductors
Multiple Previous Surgeries
Demented/Substance Abuse Patients
Post Fracture neck of femur
Patient with a previous spinal fusion

47. 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

48. Step 4: Xray Landmarks
Hips in degrees internal rotation (true AP of femoral neck)
Marker of known diameter between legs (coin)

49. 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%)

50. Step 4: AP Xray Landmarks
Tear Drops
Superolateral edge of Acetabulum
Centre of rotation of Head
New Centre of rotation of hip joint
Lesser Trochanters

51. Step 4: Lateral Xray Landmarks

52. 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)

53. Step 5: Check the Template
Key Radiographic Landmarks
Tear Drop
Ilioischial line
Superolateral margin of the acetabulum

54. Step 5: Check the Template
Acetabular Templating
Cup sized when placed at 40degrees (+/- 10) of abduction medial boarder approximates ilioischial line
Must have adequate lateral coverage
Inferior boarder cup level with inferior tear drop
If cemented uniform cement mantle of 2-3mm
Lateral coverage lacking metal augments or bone (number 7 graft)
Center of rotation is marked and compared to opposite side

55. Step 5: Check the Template
Protrusio Acetabuli
Template to anatomic position lateral to tear drop and Kohler’s line with peripheral rim contact
Measure medial defect for graft filling

56. THA for Acetabular Protrusio
Causes:
Osteogensis imperfecta
Osteomalacia
Paget’s Disease
Bone Tumors
Rheumatoid Arthritis
Ankylosing Spondylitis
Trauma

58. Step 5: Check the Template
Lateralized Acetabulum
Acetabulum reamed until pulvinar, ligamentum teres, cotyloid notch and transverse acetabuluar ligament (beware medial osteophytes!!!)

59. Step 5: Check the Template
Dysplastic Acetabulum
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 non-anatomic position

60. 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”

63. 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

64. 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

65. 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%)

66. 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)

67. 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

68. Adult Congenital Hip Disease

69. THA for Congenital Hip Disease
Classifications
Crowe Classification
<50%
50-75%
75-100%
>100%

70. New Classification Dysplastic Contained in true acetabulum
High Dislocation
Femur superior posterior
Segmental defect rim
Increased bone posterosuperior
Excessive anteversion
Iliac wing hypoplastic and anterverted
FN Shorter and anterverted
Diaphysis is hypoplastic narrow and thin cortices
Dysplastic
Contained in true acetabulum
Superior defect
Fossa osteophytes
Low Dislocation
Femoral Head articulates false acetabulum
Anterio-superior defect
Increased anteversion
Lack posterior bone
FN short

71. Preoperative Planning
Low and High Dislocations obtain CT
Estimates bone stock, accurate sizes and anteversion acetabulum and femoral neck
Plain films for templating

72. 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

73. Technical Difficulties

74. 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

75. THA for Arthrodesed Hips

76. 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

77. 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

78. 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

81. 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)

82. 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    

83. 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

84. Complications:
deep infection % (higher in conversion of surgical fusion)
dislocation %
sciatic nerve palsy %
femoral nerve palsy 3.6%

85. CASES

86. SH 58yo female High Speed MVA (t-boned) 1yr ago ORIF Rt Acetabulum
Referred to office for increasing right hip pain

88. Post Op

89. Today

91. Next Step?

92. Options?

95. 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

98. 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

100. 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

102. BP What about the femoral deformity distal to plate?
1. Try to bypass (+/- osteotomy)
2. Ignore

104. 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

106. 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

108. 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

111. DS Approach? 1.Transtrochanteric 2. Iliofemoral 3. Direct lateral
4. Posterior
5. Invent a new one

112. DS Hardware removal… 1. Plan to stage 2. Remove all – at time of THA
3. Try to ignore at time of THA

113. Managed to ignore most of the hardware
Lateral approach with unintentional transtrochanteric component