Table 2.

Acetabular defect classification and management based on 3‑point fixation

Classification	Acetabular bony configuration	Revision cup needed
Type I	Possible 3‑point fixation within the boundaries of the acetabular wall, hemispherical configuration of the acetabulum	Hemispherical (preferably cementless; cemented only in case of adequate cancellous bone structure and absence of bone defects) ± allogenic cancellous bone
Type II	Possible 3‑point fixation within the boundaries of the acetabular wall, cavitary/oval configuration of the acetabulum	Cementless oval cups or spherical cups with augmentation parts ± allogenic cancellous bone
Type III	Impossible 3‑point fixation within the boundaries of the acetabular wall, cavitary configuration of the acetabulum with severe bone loss or pelvic discontinuity	Cementless acetabular cup with cranial strap ± iliac stem + allogenic cancellous bone or cup-cage system + allogenic cancellous bone
Type IV	Impossible 3‑point fixation within the boundaries of the acetabular wall, pelvic discontinuity with major bone loss and destruction of iliac bone	Custom-made partial pelvic replacement