Is there any way to subscribe a topic in message_filter and not filtering it?

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Hi, I am subscribing two topics (servo position and laser scan) in message_filter for my application. Now, when I use approximate_time_synchronizer, as laser scan publishes in low frequency, callback function provides servo data at the laser scan frequency. I also need to use the original servo position topic along with these two (laser and servo) that comes as output of message_filter. I am finding trouble in using shared_memory access to access the original servo data across multiple processes. Is there any provision in ros message_filter that I subscribe some topic in message_filter and do not use it during filtering and that is accessible in the callback as well. Please let me know if any thing like that is feasible?

code:

void callback(const dynamixel_msgs::JointState::ConstPtr& msg, const sensor_msgs::LaserScan::ConstPtr& scan_in)
{
    ROS_ERROR("Enter Publish");
    servo_pos = servo_position.push_front();
    lidar_scan = laser_frame.push_front();
}

int main(int argc, char** argv)
{
    ros::init(argc, argv, "message_filter_node");
    //  ros::Time::init();
    ros::NodeHandle nh;
    //  ROS_INFO("start message filter");
    // subscribers *********************************************************************************
    message_filters::Subscriber<dynamixel_msgs::JointState> position_sub(nh, "/tilt_controller/state", 1);
    message_filters::Subscriber<sensor_msgs::LaserScan> Hokuyo_sub(nh,"/scan" , 1);
    // *********************************************************************************************
    typedef message_filters::sync_policies::ApproximateTime<dynamixel_msgs::JointState, sensor_msgs::LaserScan> MySyncPolicy;

    // ApproximateTime takes a queue size as its constructor argument, hence MySyncPolicy(10)
    message_filters::Synchronizer<MySyncPolicy> sync(MySyncPolicy(10), position_sub, Hokuyo_sub);
//    message_filters::Cache<std_msgs::String> cache(position_sub, 10);
//    cache.registerCallback(callback);
    //  message_filters::TimeSequencer<std_msgs::String> seq(sub, ros::Duration(0.1), ros::Duration(0.01), 10);
    sync.registerCallback(boost::bind(&callback, _1, _2));

    ros::spin();
    return 0;
}