Trabecular Metal™ Acetabular Revision System:

An algorithmic approach

While other algorithmic approaches may be used to discuss acetabular revision, this brochure uses Paprosky’s classification of acetabular defects to explain the usage of Trabecular Metal Acetabular Revision System Components. This approach provides preoperative indications to predict defects and solutions intraoperatively. It is based on the severity of bone loss and the ability to obtain cementless fixation for a given bone-loss pattern.8 This system can be used as a guide to maximize contact between the host bone and the Trabecular Metal Components, thus optimizing mechanical stability.

Paprosky Classification (8)

Defect Type

Defect Characteristics

I

Acetabular rim, anterior column, and posterior column intact and supportive; small, local, contained defects

IIA

Moderate superomedial migration <3cm; >50% host-bone contact

IIB

Moderate superolateral migration <3cm; >50% host-bone contact

IIC

Isolated medial migration, medial to Kohler’s line; intact rim

IIIA

Severe superolateral migration >3cm; 40-60% host-bone contact; inadequate stability; defect <½ circumference

IIIB

Severe superomedial migration; <40% host-bone contact; inadequate stability; medial to Kohler’s line; risk of pelvic discontinuity

Pelvic Discontinuity

Partial or complete fracture

Reconstruction Options

The integrity of the host-bone stock determines the reconstruction option available:

  • Completely supportive acetabulum (ingrowth likely)—Trabecular Metal Shell
  • Partially supportive acetabulum (ingrowth possible)—Trabecular Metal Shell with Augments
  • Non-supportive (ingrowth unlikely)— Trabecular Metal Shell with Buttress Augments and/or Cage

Four Landmarks

Indications for component revision are dependent upon four radiographic criteria:

  1. Kohler’s line—integrity of medial wall and superior anterior column
  2. Acetabular tear drop—integrity of medial wall and inferior portion of anterior and posterior column
  3. Ischial lysis—integrity of posterior wall and posterior column
  4. Vertical migration—integrity of superior dome

“In today’s environment, technological change has become a routine part of surgical practice. The Zimmer Institute is designed to help today’s surgeon bridge the gap between the classroom and the operating room.” - Aaron G. Rosenberg, MD, FACS

Example Type I and Type II

......Radiograph of Defect

.........Defect

........Algorithmic Repair

Quick Links

Overview

Modularity = Flexibility

Augments and Cages

References

8. Paprosky W, Perona P, Lawrence J. Acetabular defect classification and surgical reconstruction in revision arthroplasty. A 6-year follow-up evaluation. J Arthroplasty, 1994;9:33-44.