Primary Total Hip ReplacementCemented vs Un cemented

Total Hip ReplacementTypes ( based on fixation technique )

• Cemented• Un cemented• Hybrid• Reverse hybrid

Implant selection

• Patients age• Underlying bone pathology• Type of medullary canal

DORR classification

Cemented stems

• Elderly patients , particularly females• Inflammatory and metabolic bone disease• Cylindrical morphology of proximal femur ( DORR C )

Cement less stems

• Younger and relatively younger patients• AVN, osteoarthritis, Post traumatic arthritis• Funnel shaped proximal femur ( DORR A )

Cemented stem designs

• Taper slip• Composite beam

Taper slip design

• Collar less, tapered• Subsidence results in tighter wedging• Shear converted into compressive stresses

Composite beam design

• Collared• Rough surface• Co-Chrome (stiff ) stem• Strain on cement mantle reduced

Cementing technique

• Broach only technique• Antibiotic cement• Third generation cementing• Uniform cement mantle 2 to 3 mm thick

Cement less ( Press fit ) designs

• Tapered• Cylindrical• Anatomic

Tapered stem design

First generation• Load femur proximally only• Proximally coated• Tapered AP and ML• No collarSecond generation• Rotational ridges and polished tip

Cylindrical stem design

First generation• Cylindrical distally and distal press fit• Extensively porous coated• Usually collaredSecond generation• Better proximal fit• Distal flutes and coronal slots• Polished tip

Anatomic stem design

First generation• Better proximal fill and fit• Anteverted necks ( right and left )• Significant thigh pain and osteolysis

Second generation• Bowed tip eliminated• Flattened posterior and lateral sides

Types of porous coatingSecondary stability

• Sintering• Diffusion bonding• Plasma spraying

Optimal pore size 100 to 400 µm

Interphase dynamics

• Gap should be < 0.5 mm• Micro motion should be < 50 µm

Ceramic coating

• Hydroxyapatite • Tri calcium phosphate

• Fills Bone Implant gaps• Bioactive and bio-absorbable

• Particulate disease• Heterotopic bone

Cemented acetabular component

All poly cup

• Hypotensive anaesthesia• Good cancellous bed• Proper cement pressurization

Cement less acetabular component

• Hemispheric cups with porous coating• Fixation with press fit or screws

Cement less acetabular component

• Screw holes eliminated or reduced• Polished inner surface• Improved socket liner conformity and locking

Out comes

• Medium and long time Survival rates are good for both types of femoral components

• Pelvic osteolysis is still a problem with both types of cups

• Loosening is a problem with cemented acetabular components after the first decade

Technique and time

Cemented THR is technically more demanding

• Blood less field• Cement pressurization• Uniform and homogenous cement mantle

Post op. weight bearing

Cemented immediate

Un cemented 4 to 6 weeks immediate if fill and fit is good

Peri-prosthetic fractures

• More common with un cemented• More on the femoral side and in elderly

females

• Intra op. fractures 0.3 % ( cemented ) 5.4 % ( un cemented ) ( Mayo clinic registry )

Deep infections

No difference between the types-

when Cemented THR is done with antibiotic impregnated cement

Dislocations

More common with un cemented due to imperfect version and soft tissue balancing

Cost

• Manufacturing cost of un cemented implants is more

• With cemented THR - cement , related equipment, increased operating room time

• Cost difference is $ 300

Recent Trends

Swedish Hip Registry 2008 Australian Jt Registry 2009

Summary Cemented or un cemented

Elderly patients , particularly females with poor bone quality ----- cemented hip.

Otherwise ------ un cemented hip

SummaryUn cemented hips

Implants

Femur Tapered, proximally coated Acetabulum Hemispheric cup without holes

SummaryUn cemented hips

• Appropriate implant size• Careful insertion• Primary implant stability with press fit For adequate osseous integration• Literature does not support routine usage of

ceramic coated implants

SummaryCemented hips

Implants

Femur tapered, collar less, smooth surface Acetabulum Highly cross linked all poly

SummaryCemented hips

• Blood less cancellous acetabular bed• Cement pressurization

• Third generation cementing technique• Uniform, homogenous cement mantle

• Be ware of embolic manifestations in cardio-pulmonary compromised patients

Thank you