Acetabular defects
- 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.
- 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 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
- 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
- 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
Editor's Notes
- #6: Metal Artifact Reduction Sequence MRI
- #10: 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.
- #16: Migration of the component occurs superior and lateral because the acetabular rim is deficient.
- #17: 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.
- #24: 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.
- #31: 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