In theory, there shouldn't be major problems. Exactly how your specialist training is recognised depends somewhat on the Landesärztekammer you register with on your return. In general, jobs of less then 6 months will not be recognised. Jobs in Accident and Emergency (A&E) can be difficult as there is no comparable speciality in Germany. Non-training posts can cause problems, too. GP training is still a problem because the training structure and content are so different in both countries.

It might well be necessary that you have to work for some months at a lower level when returning to Germany to get to know the system (coding, dealing with insurance, etc.)