Controls for power tools or instruments including bone saws and drills including safety and directional control and haptic feedback

A handheld system to control a bone resection in a patient, the system comprising

• a power tool or power instrument;
• a battery;
• and
• a control unit,
• wherein the power tool or power instrument comprises a member, wherein the member comprises a first connecting mechanism configured to connect with the battery, wherein the battery comprises a second connecting mechanism configured to connect to the first connecting mechanism,
• wherein the battery comprises a plurality of electrical contacts, wherein the power tool or power instrument comprises a plurality of electrical contacts,
• wherein the plurality of electrical contacts of the battery and the plurality of electrical contacts of the power tool or power instrument are configured to facilitate flow of electrical current from the battery to the power tool or power instrument,
• wherein the control unit is configured to be interposed between the member and the battery,
• wherein the control unit comprises a third connecting mechanism configured to connect to the first connecting mechanism,
• wherein the control unit comprises a fourth connecting mechanism configured to connect to the second connecting mechanism,
• wherein the control unit comprises a plurality of electrical contacts configured to connect to the plurality of electrical contacts of the battery and the plurality of electrical contacts of the power tool or power instrument,
• wherein the control unit comprises a wireless receiver, wherein the control unit is configured to adjust, regulate, interrupt or restore the electrical current flowing from the battery to the power tool or power instrument based on data received by the wireless receiver,
• wherein the data is derived from tracking data, and
• wherein the power tool or power instrument is configured to receive a tissue cutter.