Spinal trauma is a common problem with hamsters if they are dropped or if they fall from a height, (never put your hamster in a transparent ball on a table where it could fall and cause serious injury to your pet), this type of injury is also seen in hamsters which are allowed to roam freely around the house and then get trodden upon, unfortunately spinal injury is not something which can be treated, and it is usually kindest to put the hamster to sleep.
Lack of exercise can cause problems in these small pets since the muscles will grow weak. It is a good idea to provide activities for your hamster. I would recommend tunnels and climbing apparatus rather than wheels and transparent balls which can themselves cause injury to hamsters.
Sometimes a diet deficient in vitamins D and E can cause myopathies (muscle problems), this type of disorder can usually be reversed if the diet is improved. Offer a good quality proprietary food to avoid this type of problem.
There is also a sex linked cage paralysis which affects male hamsters of approximately 8-10 months of age. In females this problem is mild and rare.