Look for law firms that have a team approach to representing clients. This allows you to access several attorneys within the firm all with different areas of expertise. This is often much more strategic that a sole lawyer that needs to be knowledgeable on every aspect of the case.
Medical malpractice is a very highly technical field and cases will typically require expert testimony by other medical professionals. An attorney that specializes in medical malpractice will have access to these professionals and can arrange for testimony or depositions for trial.