Use of a Modular Acetabular Reconstruction System

CHAPTER 48 Use of a Modular Acetabular Reconstruction System




Acetabular bone deficiency is routinely encountered during revision total hip arthroplasty (THA). Factors influencing treatment include severity of bone loss, location of any defects present, and the quality, location, and vascularity of the host bone that remains. A final critical element affecting treatment choice and success rate is the amount of host bone (versus graft) available for cup support and fixation after acetabular preparation. Successful management of major bone deficiency requires careful assessment of the defect present, selection of the optimal reconstruction method, bone preparation efforts that maximize support for the revision component on host bone, stable secure initial cup fixation, and preservation or restoration of normal anatomy whenever possible.



INDICATIONS AND CONTRAINDICATIONS


Several systems for classification of acetabular bone defects have been proposed, but the system proposed by Paprosky has proven helpful in the development of treatment plans by helping predict the support that may be expected for the revision component after removal of the failed device.




Treatment Options Using a Modular Acetabular Reconstruction System


After removal of the failed implant, defect assessment, and acetabular preparation, bone grafting is routinely performed to reconstitute bone stock. Morselized cancellous graft is preferred, and structural allograft is used only when required because of massive bone deficiency. Hemispherical porous ingrowth cups fixed with multiple screws are currently the workhorse method for acetabular revision and can be applied successfully in more than 90% of revision cases encountered. Use of a hemispherical ingrowth socket with multiple screws is always our preferred and first choice, and alternatives are sought only when this method cannot be made to work or fixation status is tenuous. Use of a tantalum cup allows placement of extra screw holes and added screws via holes created with a carbide burr. Cementation of the polyethylene liner provides added stability by creating a “locking screw” effect. Once the acetabular screws are covered by cement, this prevents backing out or angulation of screws under loading.


In selected cases of massive bone loss, irregular bone defects, or impaired host bone quality (e.g., from prior radiation), alternative methods may be required. A modular system using a hemispherical cup with multiple screws in combination with matching acetabular augments can be used to fill large segmental or cavitary defects in critical support locations, allowing cup placement at or near the anatomic level. Situations involving pelvic dissociation, poor bone quality, or more massive defects that preclude achievement of stable cup support (even with augments) on host bone can be managed with a combination antiprotrusio cage and ingrowth cup (the so-called cup-cage combination).



PREOPERATIVE PLANNING AND TECHNIQUE


Descriptions of the advantages and disadvantages and the surgical technique recommendations for each of the components of this modular revision acetabular system follows.



Acetabular Augments




Mar 10, 2016 | Posted by in Reconstructive surgery | Comments Off on Use of a Modular Acetabular Reconstruction System

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