Your content marketing must begin with one thing in mind; your customer. One way to help you figure this out is to create a customer avatar. The avatar can help you narrow down your customers based on demographics, income, interests and other metrics.
So maybe your main customers are the elderly with hip and back pain, mothers with pelvic pain after childbirth, or high school athletes who are suffering from a concussion.
Each of these customers will have a different interest in your content and a different way they should be approached. Maybe the seniors like printed newsletters and the mother spends her freetime on Facebook.