Load a new IMG as pattern into a SVG - svg

Question

Into my page I have a SVG image wth 3 path then on other side I have 3 buttons. On click on each button I want apply a pattern to my SVG's path.
The script I did not works completly. It update the SVG structure adding all the necessary code but the result miss the image.
UPDATE Here the demo: http://jsfiddle.net/uncoke/756DS/
If on debug I copy the new SVG code and open it in a new window I see the result I want. But on live... it wont load the img pattern. Here the heart of my script:
var svgns = "http://www.w3.org/2000/svg";
var img = document.createElementNS(svgns,'image');
img.setAttributeNS(null,'height','536');
img.setAttributeNS(null,'width','536');
img.setAttributeNS('http://www.w3.org/1999/xlink','xlink:href',pattern_url);
img.setAttributeNS(null,'x','-81');
img.setAttributeNS(null,'y','-81');
img.setAttributeNS(null, 'visibility', 'visible');
def= document.createElementNS(svgns,'defs');
pattern = document.createElementNS(svgns,'pattern');
pattern.setAttributeNS(null,'id','img_pattern');
pattern.setAttributeNS(null,'patternUnits','userSpaceOnUse');
pattern.setAttributeNS(null,'width','600');
pattern.setAttributeNS(null,'height','450');
pattern.appendChild(img)
def.appendChild(pattern)
side_1 = document.getElementById('side_1');
side_1.setAttributeNS(null,"fill","url(#img_pattern)")
side_2 = document.getElementById('side_2');
side_2.setAttributeNS(null,"fill","green")
side_3 = document.getElementById('side_3');
side_3.setAttributeNS(null,"fill","url(#img_pattern)")
On this test only the "fill","green" works.
Can you hep me ?