Spondylolysis is generally attributed to stress fracture, due to movement of the affected vertebrae relative to the vertebra below and is most common in lower lumbar vertebrae. Since S1 and S2 are fused, spondylolysis of S1 due to stress fracture would unlikely to occur. Although there have been some reports of S1 spondylolysis in ancient Alaskan and Canadian Inuit skeletons, no clinical S1 spondylolysis case due to stress fracture has been reported until now.