8/6/2019 Acetabular Augmentation

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The Augmentation o Superior Acetabular Deects Using Cement-Screw Construct

A Clinical and Biomechanical Analysis

BA Rogers2, S Garbedian2, R Kuchinad2, T Willet1,2, AE Gross1,2,O Safr1,21 Department o Surgery, University o Toronto, Toronto, Ontario, CANADA

2 Mount Sinai Hospital, Toronto, Ontario, CANADA

Introduction

Augmentation o the superior acetabular rim is requently required to enhancethe stability o the hip joint in arthroplasty surgery. This study analyses the

clinical results and biomechanical strength o a novel technique that improvesacetabular coverage utilizing screws and cement.

Methods

We developed a technique using 6.5mm diameter bone screws inserted intothe juxta-acetabular ileum, with 15 to 20 mm o each screw shat let outside

the bone to secure and anchor bone cement that is shaped to augment theacetabular rim. We describe the outcome o 28 patients with this technique.

In addition, we are in the process o a biomechanical analysis to compare thestrength o acetabular cement augmentation with or without screws.

Results

This technique was used in primary and revision arthroplasty perormed or in-stability, inection and pathological acetabular deciencies. Good clinical sta-

bility was achieved and no dislocations have been subsequently reported.

Direction of applied force

Direction of Load

ASIS

Figure 1.

Direction of applied load rela-

tive to anterior superior iliac spine

(ASIS) and centre of acetabulum.

Position of supra-acetabular

screws shown by letters A,B,and C

Figure 2.

Position of acetabular defects

Blue 25% (with respect to ace-

tabular surface)

Greeen 50%

White 75%

AB C

Figure 3.

Diagram of control set up-

with polyethylene liner

cemented into saw-bone

acetabulum with no defect.

Cyclic load to failure

25% 50% 75%

PERCENTAGE OF ACETABULAR DEFECT +/- AUGMENT

Experimental design to create acetabular deects in sawbone modelPolyethylene liner cemented into each sawbone model with corresponding

deect +/- supplemental augmentation to deectCyclic loading o model in the laboratory until ailure Hip instability is a requent problem or hip arthroplasty, particulary when a shel-type augmentation is re-

quired or there is signicant uncoverage o the supero-lateral aspect o a cemented cup.

We describe a simple and cost-efective surgical technique to enhance stability. A useul application o this

technique is or 1st stage revision or an inected THA where previous surgeries and inection create acetabu-lar deciencies. A cement-screw construct o the acetabulum provides excellent stability and coverage or thetemporary antibiotic cement spacer o the hip prosthesis while patients wait or their denitive THA revision.

There have been no ailures or dislocations o the 28 patients we treated using this construct.

Furture biomechanical studies will analyze the screw-cement construct with varying degrees o acetabular de-ciencies to cement alone.