An ultrasonic medical instrument having a handpiece and medical ultrasonic blade assembly including a vibration antinode, a handpiece, and a medical ultrasonic blade. The blade is threadably engaged by the handpiece proximate the vibration antinode. The blade is in ultrasound-transmitting physical contact with the handpiece proximate the vibration antinode and apart from where the medical ultrasonic blade is threadably engaged by the handpiece. A medical-instrument connection assembly for transmitting ultrasonic vibrations includes first, second, and third connecting members. The first connecting member is adapted to be ultrasonically vibrated and has a longitudinal axis. The second connecting member is capable of being positioned to be substantially coaxially aligned with the longitudinal axis and in ultrasound-transmitting physical contact with the first connecting member. The third connecting member surrounds, and is rotatably or fixedly attached to, the second connecting member and is threadably engageable with the first connecting member.