EE & ANOTHER EE WERE REPAIRING THE EMULSION LINENEAR THE LONGWALL POWER CTR. INJ EE WAS USING A CRESCENT WRENCH ATTEMPTING TO HOLD A COUPLER IN PLACE AS OTHER EE USED A PIPE WRENCH TO TIGHTEN THE BOLTS ON THE SAME COUPLER. WHILE PERFORMING THIS TASK INJ EE EXPERIENCED SOME PAIN IN UPPER RIGHT ARM HE IS NOW MISSING WORK DUE TO PROBLEM HOWEVER COMPLETED DIAGNOSIS HAS NOT BEEN MADE