Stress fracture of the fifth metatarsal bone as a late complication of total knee arthroplasty.

A 64-year-old man had undergone a right total knee arthroplasty (TKA) as treatment for osteoarthritis of the knee. Six months after the TKA, the patient sustained a stress fracture of the left fifth metatarsal bone, which was a contralateral side of the TKA, without any apparent trauma or cause. The fracture was treated with internal fixation using a screw and low-intensity pulsed ultrasound treatment was added. During two-year followup after internal fixation of the fifth metatarsal fracture, he had no complaints in the knee or foot. The patient felt anxiety of breakage or loosening of the implant of TKA and the patient had been walking bearing mainly on his left leg and foot which was a contralateral side of the TKA. The cause of the stress fracture of the fifth metatarsal bone was speculated to be excessive stress of weight bearing to the left foot during walking. The physicians should be aware of the risk of stress fracture of the fifth metatarsal bone as one of a rare late complication associated with TKA. It is very important to educate the patients, explaining the risk of breakage or loosening of the implant of TKA and instructing the adequate physical and mental benefits of walking.