NDI Medical is taking a big step into the future of implantable surgical devices. With its new FDA approval in-hand, the Beachwood-based firm is taking its newest product to market. NDI Medicals' neurostimulation device will be implanted next month into the shoulder of a patient to alleviate chronic shoulder pain. Robert Strother, NDI Medical's vice president of engineering and chief technology officer, called implantable medical devices "an area of explosive growth." As a member of the pacemaker family, the neurostimulation device -- about the size of a silver dollar -- works where conventional pharmacology stops short. The future, Strother says, is in the "deep brain" market with products he says that could treat a number of maladies, ranging from Parkinson's disease to depression. The company at last county had 25 employees with plans to grow.