This document discusses acetabular defects and their reconstruction. It begins by describing common causes of acetabular deficiency like dysplasia, trauma, and loosening. Surgical goals are to restore hip mechanics, re-establish bone coverage of the acetabular component, and achieve rigid fixation. Preoperative planning involves imaging like x-rays and CT scans to evaluate the pattern and severity of bone loss. The Paprosky classification grades acetabular defects based on the amount of bone loss and ability to achieve cementless fixation. Different reconstruction techniques are described depending on the defect type, including various cup designs, bone grafting, and structural allografts.

1. ACETABULAR DEFECTS
DR. John E. Benny
Fellow in Arthroplasty
Sunshine Hopsital

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).

6. Case 1

7. Case 2

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.

11. Paprosky classification

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

14. TYPE 2A
• Oval enlargementssuperior 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

19. Structural Allograft
technique

21. Supero-Lateral Defects

22. Supero- lateral defects

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

24. Type 3 A

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

28. Non- Custom acetabular Cages

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

33. Pelvic Discontinuity

36. <2 cm
Press Fit

37. Case 1

38. Case 1

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.

40. INTRA-OP PICS
COURTESY Dr. Vishesh

41. Case 1

42. Case 2

43. Case 1

44. Case 1

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.

47. ACETABULAR DEFECTS IN BONE
TUMOURS

51. When in doubt!!!!!!!