D Reimplantation Acetabulum

Principles of Acetabular reconstructionRevision Acetabulum Post Paprosky Type IIIC

 

Restore centre of rotation
Restore acetabular integrity
Component containment
Secure fixation


Preoperatively planning


Know components in situ (esp if leaving femur)
Quantify and grade bone defects
Beware intrapelvic cement / cup (angiogram)

 

Basic Guidelines

 

> 50% host bone contact

- use press fit uncemented cup augmented with screws

 

< 50% host bone contact

- use metal augment in elderly to reconstruct defect

- use allograft augment in young to reconstruct defect

- press fit cup if able

- otherwise must use cage


Paprosky Type I, II A and B

 

I Rim intact

II A Mild superior migration / superior rim intact

II B < 30% superior rim missing


1.  Uncemented Jumbo rim fit cup


Indications
- > 50% host bone available for ingrowth
- > 2/3 rim intact


Technique
- implant in usual position
- preferentially ream anteriorly
- preserve posterior column
- some uncovering superiorly allowed
- usually augment with screws
- +/- postoperatively NWB 6/52


Results
- 12-15 year survival between 81-96%

 

Revison THR Type I AcetabulumRevision THR Jumbo Cup 2

 

2.  Impaction Bone Graft +/- Mesh + Cemented Cup

 

Revision Acetabulum Type IIIBRevision Acetabulum Type IIB Superior Mesh and Impaction Bone Graft

 

Type IIC

 

Type IIC: Medial wall deficiency but intact


Options


A.  Particulate graft medially, jumbo cup

 

Revision THR Type IIC AcetabulumRevision THR IIC Jumbo Cup + medial bone graft

 

B. Impaction bone graft, cemented cup

 

Revision Acetabulum Type IICRevision Acetabulum Type IIC Impaction Bone Grafting

 

C.  Cement +++

 

Indicated in elderly patients

 

Revision Acetabulum Type IIcRevision Acetabulum Cement +++

 

Segmental Medial Wall deficiency


A.  Allograft + Antiprotrusio Cages + Cemented Cup

 

Types
- Ganz / Muller / Burch Schneider

- variations on them

- hook or screws into ilium

- hook or screws onto ischium

- can have extension for screws onto pubis

 

Revision THR Burch Schneider Cage
 

B.  Mesh + Impaction Bone grafting

 

Type IIIA defects

 

Type IIIA

- Rim < 50% missing, > 40% host bone contact

- want to reconstruct defect but don't need cage

 

1.  Uncemented rim fit cup / screws / Structural bone graft


Indications
- defect superolateral rim < 50% to support cup
- > 50% host bone contact

- allograft will not grow onto uncemented cup

- allograft to reconstuct defect


Technique
- femoral head allograft reconstruction (no 7 shape)
- fix with 6.5 mm screws
- tap first to prevent fracture
- ream into bone


2.  Impaction bone graft +/- mesh + cemented cup
 

Revision THR Type IIC AcetabulumRevision THR Impaction Bone Graft Acetabulum

 

Technique


1.  If required, convert uncontained defect into contained defect
- use titanium mesh fixed with screws
- acetabular rim or medial wall mesh (Stryker)

 

Revision THR Type IIIC Acetabulum Mesh Impaction Bone GraftRevision THR Type IIIA Acetabulum Pre IBG


2.  Impact morcellised cancellous bone graft
- tamps or reverse reaming
- progressively smaller impactors
- need 5 mm of bone graft


3.  Insert prosthesis / Cemented poly liner


Results


- 85% 12 year survival
- 80% 15 year survival


Important Points


1.  Rigorous technique important


2.  Fresh frozen allograft
- does this perform better than irradiated BG


3.  TWB 6 – 12/52

 

3.  Trabecular metal components


New material made of element tantalum

1.  Interconnecting porous material
- 80% porous
- allows 2-3 X bony ingrowth


2.  Less stiff
- improved remodelling of BG underneath


3.  High cancellous bone coefficient of friction
- excellent initial stability
- may need less than traditional 50% host bone contact
- may not need screws


Ream host bone for press fit cut
- trial then secure trabecular augment with screws
- press fit cup with cement between augment and cup
- screw augmentation of cup
 

4.  Bilobed uncemented acetabular components

 

Bilobed Revision Cup


Indications
- superolateral deficiency
- revision
- DDH cups


Problems
- can be difficult to get version right
 

Type IIIC

 

Type IIIC

- < 50% rim intact, < 40% contact

- must reconstruct for stability

- unable to use uncemented component

- use bone graft to reconstruct

- need cage for stability

 

1.  Structural Allograft + Cage

 

Revision Acetabulum Bulk Structural Allograft + Cage


Indications
- when inadequate bone stock precludes the use of uncemented acetabular components


Theory
- cannot implant onto allograft
- graft under the cage
- secure with cage
- cement poly into it


Technique
- allograft reconstruction of rim with femoral head
- allograft particulate material in base
- secure cage to posterior column ilium and ischium
- 3 screws in each
- cement all poly cup into cage


Results
- 75% 10 – 15 year survival
 

Option:  Custom-made triflange components


CT guided model of pelvis
- custom made acetabular cage
- fits defect exactly
- flanges perfectly designed and not malleable to improve strength
- HA coated
- cement poly cup into it


Indications
- massive defects


Results
- 90% 4.5 year survival in complicated patients

 

2.  Impaction Bone Graft +/- Mesh + Cage + Cemented cup

 

Revision THR Type 3B AcetabulumRevision THR Acetabular Mesh Bone Graft Cage

 

Pelvic discontinuity

 

Revision THR Pelvic Discontinuity0001Revision THR Pelvic Discontinuity 2Revision THR Pelvic Discontinuity 3


1.  Plate and bone graft posterior column

 

Revision THR Plate Posterior ColumnRevision THR Plate Posterior Column Lateral


2.  Plate + Cage reconstruction
 

 

3.  Cup Cage Reconstruction

 

Technique

- large tantalam cup inserted for reconstitution of discontinuity

- bone graft inserted

- cage, cement in cup

 

Revision THR Cup Cage0001Revision THR Cup Cage0002Revision THR Cup Cage0003