Acetabular Component Revision: Pelvic Discontinuity : Wheeless' Textbook of Orthopaedics

Discussion

condition in which superior aspect of pelvis is separated from inferior aspect because of bone loss or a fracture through acetabulum;
- most discontinuities represent unhealed transverse acetabular fractures which occurr through areas of pelvic bone loss;
in the study by Berry, et al (1999), the authors identified 31 cases of pelvic disontinuity out of 3505 (0.9%);
- much more common in women than men, and is more common in rheumatoid arthritis;
  - reference: Pelvic Discontinuity in Revision Total Hip Arthroplasty.
radiographs:
- fracture line through the anterior and posterior columns;
- medial translation of inferior aspect of the hemipelvis relative to the superior aspect (look< for break in Kohler's line);
- on AP view rotation of inferior aspect of hemipelvis relative to superior aspect (asymmetry of obturator rings);
- other radiographic indications include:
  - rotation of the inferior aspect of the hemipelvis relative to the superior aspect (seen as asymmetry of the obturator rings);
- w/ suspected pelvic discontinuity, consider need for CT scan;
- references:
  - Lateral and high-angle oblique radiographs of the pelvis aid in diagnosing pelvic discontinuity after total hip arthroplasty.
  - Preoperative Radiographic Evaluation of Patients with Pelvic Discontinuity

treatment may require insertion of posterior column reconstruction plate and a gap cup
intra operative exam findings:
- observe for motion between the superior and the inferior hemipelvis when applying a caudal stress to the ischium with a blunt elevator;
w/ discontinuity and severe segmental bone loss and/or cavitary bone loss have worse prognosis than those w/o bone deficiencies;
reconstructive surgery which resulted in healing of the discontinuity generally was associated w/ good results;
w/ simple discontinuity, consider use of posterior column plate to stabilize the pelvis and a porous-coated socket inserted without cement;
w/ segmental deficiency, consider use of an antiprotrusio cage augmented w/ particulate bone graft or a single structural bone graft;
sciatic nerve: requires protection throughout the case

antiprotrusio cage
- Construct Rigidity: Keystone for Treating Pelvic Discontinuity.
- Burch-Schneider antiprotrusio cage was used to reconstruct 13 hips, and the socket remained stable in all thirteen;
  - in 11 hips, the discontinuity definitely (six hips) or possibly (five hips) healed;
  - in 11 hips there was a satisfactory result;
pitfalls:
- insertion of socket with cement w/ anterior and posterior plates used to secure the discontinuity;
- 5 hips had insertion of a socket with cement and two plates without use of an antiprotrusio cage;
- none of these hips had a satisfactory result (4 hips had failure because the socket loosened;
ref: Reconstruction of AAOS type III and IV acetabular defects with Ganz reinforcement ring: high failure in pelvic discontinuity.