Is suryamaskara helpful in curimg back ache?

Yes if taught well: Surya namaskara known as sun salutations is a common sequence of asanas in yoga. I advise you to take lessons from a certified yoga instructor and tell the instructor of your back ache so they can adjust your positions and accomodate you. And of course see your doctor to make sure it is common muscle spasm/back ache.

Yoga back pain: Back issues are generally helped by stretching yoga and specifically the pose u speak of helps back issues.