Spontaneous rupture of the quadriceps tendon in patients on maintenance hemodialysis--report of three cases with clinicopathological observations.

Three patients receiving maintenance hemodialysis therapy for end-stage renal failure presented with spontaneous rupture of the quadriceps tendon(s). Biochemical data and the skeletal roentgenograms were compatible with secondary hyperparathyroidism. Histological examination of the excised quadriceps tendon specimens suggested that repeated minor avulsion fractures of the bone cortex at the tendon insertion site had preceded the final total tendon rupture and that osteitis fibrosa was responsible for these minor fractures. Serum alkaline phosphatase level had been increasing continuously for approximately five years prior to the tendon rupture in all three patients, indicating that uncontrolled osteitis fibrosa due to secondary hyperparathyroidism over these years preceded the tendon rupture.