Back spasms can cause arm and hand pain if the spasms hinder communication between the spine and the nerves in the upper extremities. According to WebMD, pinched nerves in the upper or cervical spine often trigger pain, tingling, numbness or reduced strength in the shoulders, arms or hands.
Cedars-Sinai Educational Hospital describes a back spasm as an abnormal contraction of a muscle in the back. Also called a muscle strain or muscle cramp, a muscle spasm in the upper back can sometimes put a lot of strain on the spine. Pressure on the vertebrae and the cushioning between them often result in either a herniated disc or poor alignment and possibly dislocation in the spine, also known as a spinal subluxation. Both of these can cause pinched or irritated nerves.
If a spasm in the upper back or neck creates these kinds of conditions in the cervical verebrae, symptoms may manifest in the arms and hands as well as the back and neck. According to the NYU Medical Center, this is because nerves that send signals to the hands and arms originate in the upper back and neck, just like the nerves that communicate with the legs start in the lower back.
According to the Mayo Clinic, arm and hand pain can be symptomatic of a variety of ailments that are not related to the back. These include injury to the muscles, bones or joints in the arms themselves, carpal tunnel syndrome, fibromyalgia, arthritis and angina.