A Star League era medical innovation, the Myomer-Implantation Device automatically replaces or repairs damaged (but still attached) human musculature with Myomer fibres. The underlying technology which made such devices possible became lostech in the Inner Sphere during the Succession War era, but this does not prevent doctors from using the device. Though the recovery of knowledge necessary for the surgical implantation of myomer has made the MID largely unnecessary following the Fourth Succession War, a few devices do exist in working order and (when functioning properly) can dramatically increase the speed at which myomer is implanted.   
While operating the MID does require some medical skill, though not to the level required for surgical myomer implantation, in general the operator places a length of myomer fiber in the receptacle and places the injured limb into device (or clamps over for larger sections) and follows the on-screen directions, letting the device do its job. In less than thirty minutes a damaged hand or foot can be completely repaired, while an entire limb takes only one hour.  
As these devices are at least two hundred or more years old, malfunctions can and do occur to varying degrees. In most cases this will result in minor faults to the affected body part; only when something goes horribly, horribly wrong will the patient's life be in danger.  
- MechWarrior: The BattleTech Role Playing Game, p. 31 "Equipment - Medical Equipment - MID (4/R)"
- MechWarrior Compansion, p. 88 "Equipment - Medical Equipment - Myomer Implantation Device (MID)"
- Lostech: The MechWarrior Equipment Guide, p. 112 "Miscellaneous Gear - Medical Equipment and Procedures"