UIImage* image = [UIImage imageNamed:@"back_button.png"];

[item setBackButtonBackgroundImage:[image resizableImageWithCapInsets:UIEdgeInsetsMake(0, image.size.width, 0, 0)] forState:UIControlStateNormal barMetrics:UIBarMetricsDefault];

[item setBackButtonTitlePositionAdjustment:UIOffsetMake(-400.f, 0) forBarMetrics:UIBarMetricsDefault];

self.navigationItem.backBarButtonItem = item;