Table 3.

Classification systems for acetabular defects

1. D’Antonio et al. classification [3]
Type I	Segmental deficiency a. Peripheral (superior, anterior or posterior) b. Central (medial wall absent)
Type II	Cavitary a. Peripheral (superior, anterior or posterior) b. Central (medial wall intact)
Type III	Combined
Type IV	Pelvic discontinuity
Type V	Arthrodesis
2. Engh and Glassman classification [5]
Mild	Cavity = hemispherical, cancellous, intact rim = round, strong, intact
Moderate	Cavity = nonhemispherical, sclerotic, perforated rim = round, strong, intact
Severe	Cavity = nonhemispherical, sclerotic, perforated rim = out of round, weak or broken
3. Gross et al. classification [11]
Protrusio	Contained defect with intact rim and columns
Shelf	Defect in rim and cavity with loss of 50% of acetabulum
Acetabular	Defect in one or both columns with 50% loss of acetabulum
4. Gustilo and Pasternak classification [12]
Type I	Minimal cavitary enlargement, loosening of the cement-prosthesis interface
Type II	Thinned, nonperforated wall, loosening of the cement-prosthesis interface
Type III	Local wall defect only a. Anterior b. Posterior c. Superior d. Central
Type IV	Massive and global collapse or defect involving one or both columns
5. Paprosky et al. classification [19]
Type I	Supportive rim with no bone lysis or migration
Type II	Distorted hemisphere with intact supportive columns and 2-cm superomedial or superolateral migration a. Superomedial b. Superolateral (no dome) c. Medial only
Type III	Superior migration 2-cm and severe ischial and medial osteolysis a. Kohler’s line intact, 30–60% of component supported by graft (bone loss: 10 o’clock to 2 o’clock position) b. Kohler’s line not intact, 60% of component supported by graft (bone loss: 9 o’clock to 5 o’clock position)
6. Saleh et al. classification [20]
Type I	No significant bone loss
Type II	Contained loss of bone stock where there is cavitary enlargement of the acetabular cavity but no wall deficiency
Type III	Uncontained loss of bone stock where there is b50% segmental loss of the acetabulum involving anterior or posterior column
Type IV	Uncontained loss of bone stock where there is N50% segmental loss of the acetabulum affecting both anterior or posterior columns (if there is N50% loss of the acetabulum, involving mostly the medial wall but the columns are intact, then this type of defect is considered type II because of the availability of the columns for reconstruction)
Type V	Acetabular defect with uncontained loss of bone stock in association with pelvic discontinuity