Cementless acetabular cups

cementless acetabular cup; history and evolution

1. Cementless Acetabular Cups By Ihab El- Desouky (M.D.) Asst. Prof. Pelvis and Reconstruction unit Member of A.A.H.K.S. Kasr Al- Ainy Cairo University Egypt

2. Very Easy The End

3. Cementless Acetabular Cups History: (Human Survival) Early THR was cementless THR: by Wiles , London , 1938 . (mechanical, screws- Stainless Steel). One case remained after WWII. - McKee : (mechanical, screws- Stainless Steel)

4. Cementless Acetabular Cups Ring: 1964 ( Austin-Moore stem + Long threaded cone cup) Mechanical – Co Cr . 5-12 y: 66% failure. ================ CEMENTED CUPS ================== 1970s (against cement disease) Threaded cups : promising results: mechanical( press-fit + screws) CoCr ,30% revision

5. Cementless Acetabular Cups Topics: (more durability & less complications) 1- Cup metal materials: biocompatible 2- Cup metal shapes: adequate contact with host bone 3- Surface coatings: adequate biologic fixation . 4- Liners and modularity: wear and joint instability 5- Methods of fixation: initial stabilization. 6- Survivorship of cementless cups.

6. Cementless Acetabular Cups 1-Cup metal Materials: Cobalt-chromium( CoCr )/ Titanium (Ti)/ Tantalum (Ta) All: biocompatible- reasonably inert– bone in growth. Titanium: - more bone in growth, -lower mo dulus of elasticity– less stress shielding -more fl exible ---easier insertion during press- fit—less insertional acetabular f racture risk. -High cost Tantalum: close to bone properties + more porosity------- -more bone osteointegration Higher cost --- use in massive bone loss, pelvic irradiation

7. Cementless Acetabular Cups 2-Cup metal shapes:(GEOMETRY ) cup/bone contact. Morscher et al., 1983, classified the cups into 1-Cylindrica 2-Square 3-Cone (± threads) 4-Ellipsoid 5-Hemispherical

8. Cementless Acetabular Cups Threaded cups: Mechanical Macro-interlock stabilization. Difficult preparation &positioning (vertical cups). Loosening : no perfect bone contact pressure necrosis by screws. ---mechanical failure. Revision rate up to 30% Modified Threaded cups:(biological) Porous coating or grit-blasted surfaces, longer stability .

9. Cementless Acetabular Cups But same: Difficult insertion – vertical cups (edge-loading) -- high polyethylene wear Early 1980s : HEMISPHERICAL CUPS Most successful, Ease of insertion ( mimics acetabulum) Started by: Porous Coated Anatomic PCA ( Howmedica ), Harris- Galante (Zimmer) & Anatomic Medullary Locking AML ( Depuy ) CoCr Ti CoCr Beads Ti fibers Beads 2 pegs screws 3 spikes PCA H-G AML

10. Cementless Acetabular Cups HEMISPHERICAL CUPS Current Design: (+ porous coatings) 1- Single geometry : Uniform outer diameter. 2 -Dual geometry: abruptly enlarged outer diameter,2mm) maximize bone contact & ingrowth, but, less contact at dome of cup Not fully seated ( not recommended) 3- Hemi-ellipsoid : gradual transition from periphery (2mm) to dome (0 mm)---- no discontinuity between bone and cup ( well-seated )

11. Cementless Acetabular Cups 3-Surface Coating: Definition: coverage of the outer cup surface by a material has either: 1- Porous coating ----bone In growth. Or 2- Surface Roughness- --bone On growth . +/- Hydroxyapatite coating ( osteo -conductive ) allows Biological fixation+ long-term stabilization .

12. Cementless Acetabular Cups 4-Liners and Modularity Polyethylene liner Monoblock Modular Metal shell+ moulded liner Metal shell+ separate liner+ locking one piece two pieces Adv : Adv : -No backside wear. -Customizable (lipped, offset, -Low stresses on PE constrained liners) -No failures of the locking -Liner revision (wear or dislocation) mechanism ( liner dissociation) -Supplementary fixation (screws) - 3 rd generation less backside wear and liner dissociation

13. Cementless Acetabular Cups Polyethylene liner and modularity This was not easy Evolution of Cementless Hemispheric Modular Cups -Early 1980s: 1 st generation cementless hemispheric cups e.g.: PCA, H-G, AML & Triloc ( Depuy ) UHMW –PE -Gamma irradiation in Air (fatigue ) Thin liner rim + overhanging Poor congruity between liner dome &metal shell --Rim fracture and LINER DISSOCIATION

14. Cementless Acetabular Cups The Evolution of the Cementless Hemispheric Cups -Early 1990s: 2 nd generation cementless hemispheric cups e.g.: Duraloc ( Depuy ). Triology (Zimmer) UHMWPE: non-gamma irradiation. or HXL-PE ) Thick rim + Better congruity (locking at thick PE rim) So no Liner dissociation BUT Liner impingement (thick rim): wear

15. Cementless Acetabular Cups The Evolution of the Cementless Hemispheric Cups -Early 2000s: 3 rd generation cementless hemispheric cups e.g.: Pinnacle ( Depuy ). Tantalum Continuum (Zimmer) HXL-PE (Highly Cross Linked-PE) No rim protrusion on the shell Recessed locking mechanism (not at rim) -No liner dissociation -No impingement with femoral taper.

16. Cementless Acetabular Cups PE Liners configurations: Neutral: Lipped Offset ±lip (LLD): Captive (Constrained)

17. Cementless Acetabular Cups Other bearing surfaces:

18. Cementless Acetabular Cups 5-Methods of acetabular Fixation: (initial stabilization) Press fit or Line-to-line 1-Press-fit: -Under-reaming 1-2 mm (not more) -Bone is viscoelastic—deformation and recoil around the cup – hoop stress maintain s cup. -± screws. -Stable than line to line. -Dual geometry is not favoured.

19. Cementless Acetabular Cups 2-Line-to-line: (screw supplementation) -If Inadequate initial stability after hammering of the cup , use screw -Acetabular quadrant. -Less stable alone than press-fit. Dis: of screws fixation Pathway for wear particles. Fretting corrosion (motion) Neuro-vascular injury.

20. Cementless Acetabular Cups 6-Survivorship of cementless hemispheric cup: 10-years survivorship: up to 96% (end point revision for any reason) 20-years survivorship (AML): 85-90% But:

21. Cementless Acetabular Cups - Meta-analysis 2013 , 81 articles reviewed , minimum 10 years -26,576 primary total hip arthroplasties (13,509 cemented cups & 13,067 cementless cup). - Similar outcome between both cups (about 95% survival) -Weakness: Old designs were included.

22. Take Home Message -Evolution of the cementless acetabular cup developed in many directions ( material, geometry, surface coating, modularity). -Press-fit is the main method of fixation, if not sure of its adequacy ----add screws. -Long-term follow-up yields up 95% survival , however, it is comparable to the cemented cups THANK YOU