Revision Acetabulum Treatment Options: Bone Graft Options

Douglas Naudie, M.D., FRCSC
Assistant Professor, University of Western Ontario
London, ON

Revision total hip arthroplasty can be extremely challenging in the face of significant bone loss. Options for reconstruction vary from isolated liner exchange (with or without bone grafting) to the use of hemispherical cups with screws, bilobed cups, cages, or porous metal cups with or without augments. The existing bone stock and the type of bone defect are the major determining factors in the surgical decision-making. The purpose of this communication is to briefly outline the bone grafting options available in revision acetabular surgery.

Although there are several classification systems that describe acetabular defects, we generally employ the classification validated by Saleh et al (2001)1. This classification specifically guides the use of bone graft and implants in revision acetabular reconstruction. This classification is divided into five classes based on host bone and component coverage: (I) no substantial bone loss; (II) contained loss of bone with intact columns and rim; (III) uncontained loss of bone stock involving less than 50% of the acetabulum; (IV) uncontained loss of bone stock involving greater than 50% of the acetabulum; and (v) pelvic discontinuity with uncontained loss of bone. Bone grafting can be employed in any of the five classes.

For type I and type II contained defects, morselized allograft bone may be used alone or with harvested autograft. Figure 1 illustrates a case of a 60-year-old rheumatoid female who presented three months following primary arthroplasty with a cup that migrated beyond the ilioischial line (protrusio), but whose anterior and posterior columns remained intact. This patient was treated with extensive morselized allografting (combined with autograft from acetabular reamings) and an uncemented porous metal shell with screws. Greater than 50% host bone contact was obtained with the revision acetabular component.

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Figure 1. Postoperative anteroposterior radiograph of the right hip of a sixty-year-old rheumatoid female following morselized allografting and acetabular revision of a Type II defect.

Pereira et al (2007) reviewed their experience with impacted morselized cancellous bone grafts in conjunction with cementless hemispherical acetabular components for contained defects at a mean of approximately eight years. They reported excellent clinical outcomes, a high rate of radiographic incorporation, and no clinical failures2. Whaley et al (2001) also reported on the use of large uncemented acetabular components in revision acetabular reconstruction3. Eighty-nine large uncemented hemispherical components were implanted for aseptic failure of the acetabulum. Particulate bone graft was used in 54 hips, and bulk allograft in nine hips. Clinical follow-up averaged 7.2 years, with 93% component survivorship.

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2A / 2B
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2C / 2D
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2E / 2F
Figures 2-a through 2-f. Technique for minor column ("Number Seven") allografting of a Type III postero-superior acetabular defect in a saw bones model.

Morselized impaction grafting in combination with the use of a cemented acetabular component has also been well described4. Schreurs et al (2004) reviewed 62 cases at a mean follow-up of 16.5 years, with 84% survivorship of the acetabular reconstruction5.

Type III and IV defects require a reconstruction that compensates for the loss of containment. Structural allograft can be employed in these defects, particularly when the area of deficiency is located superiorly. Appropriate step cuts are made to the graft and/or host bone to create interference fit with the graft, which is then secured with large fragment screws. The acetabular reconstruction is then performed with revision components that allow for appropriate loading of the graft to prevent resorption or mechanical failure.

Figure 2 demonstrates a saw bone model of the so-called "number-7" grafting technique. In this technique, a femoral head (or distal femur) is fashioned with manual saw cuts, flipped over, and secured to the lateral ilium with large fragment screws. The structural allograft can then be reamed to reconstitute a new acetabulum. A hemispherical cup (or antiprotrusio reconstruction cage) can then be inserted into the reconstructed acetabulum. Figure 3 demonstrates the technique employed in vivo.

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Figure 3. Intra-operative photograph of a Type III defect in the postero-superior acetabulum reconstructed with a minor column ("Number Seven") allograft and secured with two large fragment screws and washers.

Woodgate et al (2000) reported on the use of minor column or shelf allografts for type III defects6. Fifty-one hip reconstructions with a mean of ten years follow-up had 80% acetabular component and 94% allograft survivorship.

Type IV defects are by definition associated with an acetabular column deficiency and generally require the use of a major column allograft or whole acetabular allograft in conjunction with a reconstruction ring which is capable of spanning the defect and protecting the allograft during its incorporation. Type V defects are a distinct form of bone loss, in which the superior aspect of the pelvis is separated from the inferior aspect because of anterior and posterior columnar bone loss combined with a fracture through the acetabulum. Reconstruction generally requires restoration of at least one column with allograft and plating or a reconstruction implant capable of spanning the defect.

Type IV and V defects are generally classified together regarding their treatment (both have significant bone loss with less than 50% of host acetabular bone stock available). Saleh et al (2000) reported on the use of massive structural allograft protected with a reconstruction ring in 13 patients with an overall survivorship of 77% at 10.5 years7. Sporer et al (2005) reported on the use of structural allograft for major acetabular and pelvic bone loss in 23 patients with a mean follow-up of ten years8. These authors demonstrated a 78% implant survival.

In summary, bone grafting remains an important part of revision acetabular surgery. Even with the advent of porous metals in the form of metal augments and wedges, bone graft is advocated to encourage bone ingrowth into the augments from the host bone. Every attempt should be made to restore bone stock by grafting, especially in younger patients.

References

  1. Saleh K.J., Holtzman J., Gafni A., et al. Reliability and intraoperative validity of preoperative assessment of standardized plain radiographs in predicting bone loss at revision hip surgery. J Bone Joint Surg Am 2001; 83-A:1040.
  2. Pereira G.C., Kubiak E.N., Levine B., et al. Cavitary acetabular defects treated with morselized cancellous bone graft and cementless cups. Int Orthop 2007; 31(4):445.
  3. Whaley A.L., Berry D.J., Harmsen W.S. Extra-large uncemented hemispherical acetabular components for revision total hip arthroplasty. J Bone Joint Surg Am 2001;83-A:1352.
  4. Board T.N., Rooney P., Kearney J.N., et al. Impaction allografting in revision total hip replacement. J Bone Joint Surg Br. 2006 Jul;88(7):852-7.
  5. Schreurs B.W., Bolder S.B., Gardeniers J.W., et al. Acetabular revision with impacted morsellised cancellous bone grafting and a cemented cup. A 15- to 20-year follow-up. J Bone Joint Surg Br 2004;86-B:492.
  6. Woodgate I.G., Saleh K.J., Jaroszynski G., et al. Minor column structural acetabular allografts in revision hip arthroplasty. Clin Orthop Rel Res 2000;371:75.
  7. Saleh K.J., Jaroszynski G., Woodgate I. et al. Revision total hip arthroplasty with the use of structural acetabular allograft and reconstruction ring: a case series with a ten-year average follow-up. J Arthroplasty. 2000;15:951.
  8. Sporer S.M., O'Rourke M. Chong P., et al. The use of structural distal femoral allografts for acetabular reconstruction. Average ten-year follow-up. J Bone Joint Surg Am. 2005; 87(4):760.

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