Managing bone defects using large acetabular cups and highly porous augments

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Revision total hip arthroplasty (rTHA) is a difficult surgical procedure. The key challenge of this procedure is the potentially significant bone loss and the often encountered poor bone quality. Although much advancement in surgical techniques, technologies, and materials has been made in recent years and has helped improve the treatment of complex acetabular defects, several topics remain controversial, and a systematic incorporation of the technical advancement into treatment paradigms is still needed [1]. In this article, George A Macheras, Head of the Orthopedic Department in the Henry Dunant Medical Center, Athens, Greece, shares his experience and his strategies in managing acetabular bone defects. Examples of how cases of severe bone loss were managed using advanced techniques are also presented.

George A Macheras

Henry Dunant Medical Center, Athens, Greece

The Paprosky Classification

To perform a successful rTHA, it is crucial to accurately assess the severity and the pattern of bone loss so as to predict the ability of the remaining host bone to support the implants and maximize the amount of initial stability until bone ingrowth can occur [2]. The goal of an optimal solution is to restore hip biomechanics and achieve rigid fixation for long-term results.

As has been addressed in Part 1, among the various classification systems, the Paprosky Classification has demonstrated good validity and moderate reliability. When a surgeon is trained in this system, it can provide good reliability [3]. It is also the most clinically oriented because it assesses both the amount of acetabular bone loss and the ability of the remaining host bone to support the initial stability of the acetabular components [4]. In case of severe bone loss, the Paprosky Classification is a particularly useful treatment guide [1, 5].

Four radiographic features are important in determining the Paprosky types, ie, the teardrop, ischium, Köhler’s line, and superior migration (Figure 1). These four features indicate the integrity of the medial wall (teardrop), posterior column (ischium), anterior column (Köhler’s line), and superior dome (superior migration of the hip center) [6]. The criteria for the Paprosky Classification are summarized in Table 1 [4].

Figure 1. Radiographic features used in the Paprosky Classification. (Image courtesy of George Macheras.)
Table 1. The Paprosky Classification, a summary.

Ask the expert

We asked George Macheras how accurate a preoperative assessment of bone loss is in general. He told us that, intraoperatively, one should always be ready to encounter greater bone loss than predicted by the preoperative assessment. A meticulous debridement that rids the acetabulum of necrotic bone and scar tissue is pivotal, which should be followed by reaming the defects until bleeding healthy bone. Only then can the true bone loss be evaluated. For this reason, one should always have more than one reconstruction option available at the time of surgery.

Some general principles in treating acetabular bone loss are presented below.

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  • The Paprosky Classification
  • Did you know?
  • Modern advancement to enhance biological fixation
  • Jumbo cups
  • Highly porous metal augments
  • Type I defects
  • Principles in`Paprosky type II management
  • Type IIA defects
  • Type IIB defects
  • Type IIC defects
  • Principles in Paprosky type III management
  • Type IIIA defects
  • Type IIIB defects
  • Conclusion

Part 1 | Acetabular bone defects: classification and diagnosis

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Part 3 | Management strategies for pelvic discontinuity

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AO Recon resources

Contributing experts

This series of articles was created with the support of the following specialists (in alphabetical order):

Theofilos Karachalios

University General Hospital of Larissa at the University of Thessaly, Larissa, Greece

Thomas Kostakos

Henry Dunant Medical Center, Athens, Greece

George A Macheras

Henry Dunant Medical Center, Athens, Greece

The authors thank Maio Chen, medical writer at AO Innovation Translation Center, Switzerland, for contributing to the writing and editing of the articles.

References

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