2. Acetabular deficiency
• Dysplasia and protrusio acetabuli.
• Post-traumatic degenerative disease, secondary to acetabular trauma,
& loosening of the acetabular component.
• Hemispherical cementless cups, jumbo cups, bilobed cups, high hip
center, impaction grafting of the acetabulum, bulk structural allograft,
antiprotrusio cages, and highly porous acetabular cups
3. Goals of reconstruction
• Restore hip mechanics
• Re-establish osseous coverage of new acetabular
component
• Rigid fixation
– Acetabular component
– Graft
4. Preoperative Planning
• AP ; Lateral
• The shoot-through lateral
posterior column, which is often
obscured by the cup on other films.
• Judet oblique - pelvic discontinuity
• 3-d(CT) scans
– Pattern of the acetabular defect.
– Significant medial migration of the
acetabular component evaluate the
proximity of neurovascular structures.
5. Magenetic Resonance Imaging
• MARS MRI- greatly reduced artefact
• Osteolysis on MRI are:
• Low T1 signal and
• Intermediate to slightly increased T2
signal with a well-defined additional line
of low signal surrounding areas of
marrow replacement.
• Role
– In quantifying bone loss it is inferior to
CT
– MoM bearing THA, MRI may be a useful
pre-operative investigation for suspected
adverse reactions to metal debris
(including pseudo-tumours and
metallosis).
8. Paprosky classification
1. Severity of bone loss
2. Ability to obtain
cementless fixation for a
given bone loss pattern.
• Key to this classification
– Ability of the remaining
host bone to provide initial
stability hemispherical
cementless acetabular
component until ingrowth.
9. Migration and its impact
• Medial migration anterior
column.
– Grade 1 migration- Lateral to line and
– Grade 3 migration. - medial to the line
– Grade 2 migration to Kohler’s line or slight
remodeling of iliopubic & ilioischial lines
without a break in continuity.
• Superior migration
– Bone loss in acetabular dome involving
anterior & posterior columns
• Superior & medial anterior column.
• Superior & lateral posterior column.
10. Osteolysis
• Ischial osteolysis - inferior aspect of
the posterior column, including the
posterior wall.
• Mild < 7 mm, & severe >15 mm.
• Teardrop osteolysis - inferior &
medial aspects of the acetabulum
• Moderate osteolysis - partial
destruction of the teardrop with
maintenance of the medial limb
• Severe - complete obliteration of the
teardrop.
12. Type – I
• Acetabular rim and walls are intact and
supportive without distortion
• Anterior and posterior coloumns intact
• Acetabulum hemispherical
• No migration
• No osteolysis
• Full inherent stability is achieved,
and particulate grafting can be used
to fill the minor areas of bone loss
• Hemispherical Cup +/- graft
13.
14. TYPE 2A
• Oval enlargementssuperior bone
lysis
• Superior rim of the acetabulum is
intact
• Migration - cavitary defect is evident
medial to a thinned superior rim and is
directed superior or superior medial.
• This migration is less than 2 cm.
• Rx- particulate allograft
remaining superior rim provides a
buttress for containment of the
allograft.
15. Pap-2B• The superior acetabular rim is missing.
• <1/3rdcircumference of superior rim
deficient.
• Defect is not contained.
• Remaining anterior and posterior rims
and columns are supportive of
implant.
• Most reconstructions are done
without grafting of the segmental
defect.
• Occasionally, an allograft it is not
supportive of the implant.
16. Type - 2C
• Medial wall defect and migration of
the acetabular component medial to
the Kohler line.
• The teardrop may be obliterated
• The rim intact and will support a
hemispherical component.
• Particulate bone graft can be
placed medially to lateralize the hip
center of rotation back to its
anatomic position
17. Type 2 defect management
• Uncemented
hemispherical cup with
screws
• Graft cavitatory defects
• +/- structural allograft to
restore bone graft
• Identifying true
acetabulum
Obturator
foramen/ Pubis/
Ischium
Greatest bone
volume
18. Medialisation of inner table
• Expansion Ream at true
acetabulum until ant& Post
column contact
• Hemispherical shape
• Insert trial
• Assess bone loss
– Structural allograft
– Porous metal augument
23. Type 3A
• >1/3rd-<2/5th acetabular rim. (10 o clock and 2 o clock )
• Ischial lysis is mild to moderate, < 15 mm inferior to the obturator line.
• Trial components - partially stable, structural augment or allograft
26. Acetabular Cages
• Consider in Large Posterior
Segmental or combined
defects
• The principle - bridging an
acetabular defect by anchoring
ilium and ischium.
• 5to 7 cm of the defect by
means of a proximal flange
to the ilium and a distal nose
to the ischium.
27. “The Cage must be adapted to the bone, and the bone must be adapted to the
implant” – Gross JORR; 2004
29. CUSTOM TRIFLANGE ACETABULAR
COMPONENT
• Thin cut with 3d
reconstruction
• Achieves fixation on
– Remaining ilium,
– Ischium , and pubis with
multiple fixation
– Modular Polyethlene Liner
• Screws while the acetabular
defect is filled with
cancellous allograft bone
30. CTAC cont..
increased cost and delay in surgery
Substantial exposure of the ilium
Superior Gluteal nerve Risk
31. Triflange THA
• 26 Revision THA all 3b
– 54 months follow-up
– 88.5%(23/26) succesful
– 3 Failure due to
loosening
• Pelvic Discontinuity in all.
32. Pelvic Discontinuity
• Disruption of Anterior &
Posterior columns.
• No bony continuity between
illium and ischium/pubis
• Non-Supportive Superior
dome with >3cm migration
39. GOOGLY
• Paprosky developed the
classification evaluating 147
patients.
• Acetabular defects were graded pre-
operatively on a plain AP
radiographs.
• Intra-operatively
– 11% of grade II defects were
upgraded to type III and
– 5% of type III defects were
downgraded to type II.
• The intra- and interobserver
reliability of plain radiographs have
been found to be moderate to poor
by other authors.
45. AAOS – D’Antonio
• 83 AP and lateral xray vs
intraoperatively,
• 2categories:
– A segmental defect - complete loss
of bone in the hemisphere of the
acetabulum, peripherally or
centrally.
– A central - medial wall of the
acetabulum.
• A cavitary deficiency (type II) -
volumetric bony loss of the
acetabulum with an intact rim.
46. Aaos ..
• Combined segmental and cavitary-III
– Failed, Migrated endoprosthesis and
– Developmental dysplasia
• Pelvic discontinuity (type IV)
– Superior pelvis and the inferior pelvis are
separated.
– Visible fracture line through the anterior and
posterior columns, a break in Kohler’s line
superior & inferior pelvis are offset
– Rotation of inferior aspect hemipelvis : superior
which is often seen as asymmetry of the
obturator rings.
• Arthrodesis (type V).
• Flaw
– Identifies pattern & location ; not quantify
– management of these defects.
Kohler’s line, or the ilioischial line, is defined as a line connecting the most lateral aspect of the pelvic brim and the most lateral aspect of the obturator foramen on an anteroposterior radiograph of the pelvis.
Migration of the component occurs superior and lateral because the acetabular rim is deficient.
Reconstruction of these defects is similar to the treatment of protrusio acetabuli in the setting of a primary arthroplasty.
Radiograph demonstrating a Type 2C acetabular defect. The teardrop is obliterated and the component has migrated medially past Kohler’s line.
Type 3A acetabular defect. Bone loss along the superior rim and dome of the acetabulum. The medial teardrop is still present.
The right hip demonstrates a type 3A defect with superolateral migration of the acetabular component. The acetabular component has eroded superiorly and shifted to a vertical position. The left hip demonstrates placement of the acetabular component with a high hip center.
custom triflanged acetabular component achieves fixation on
the remaining ilium, ischium, and pubis with multiple fixation
screws while the acetabular defect is filled with cancellous
allograft bone
