Association of incidence rate of spontaneous tendon rupture and renal bone disease in end-stage renal disease patients' cohort.

Introduction: Spontaneous tendon rupture (STR) is one of the complications related to hyperparathyroidism. This study aims to verify this and to elucidate the feasibility of combined incidence rate of STR and bony fracture to assess clinical management of renal bone disease in dialysis cohort.

Method: This is a clinical audit of cases of STR and fracture with 5504 patient-year dialysis vintage over 10 years. In order to verify the risk factor, comparison of cases of tendon rupture, the gender, and dialysis vintage matched patients without tendon rupture were done, followed by comparison with post-parathyroidectomy patients.

Result: Six cases of STR involving eight tendons were identified, including a case of concurrent tendon rupture and bony fracture. These include two cases of double tendons ruptures. During this time, there were 15 cases of bony fracture without tendon rupture. The overall incidence rate for STR and fracture was of 0.0011 and 0.0029 incidence per year of dialysis vintage or one case per 917 and 344 patient-year dialysis vintage, respectively. For patients with PTH ≥ 600 pg/mL, the incidence rate of tendon rupture and fracture was 0.0199 and 0.0430 incidence per person-years or one case per 50 and 23 person-years, respectively. For patients with PTH < 600 pg/mL, the respective rate was 0 and 0.0006 incidence per person-years or one case per >5202 and 1734 person-years. There was significant difference for incidence rates of tendon rupture and fracture between these two groups, with six incidences of tendon rupture per 302 patient-dialysis-years of PTH ≥ 600 pg/mL versus 0 incidence per 5202 patient-year dialysis vintage of PTH < 600 pg/mL (p < 0.001). In similar comparison, there was also significant difference for incidence rate of fracture with 13/302 versus 2/5202 (p < 0.001). In the 5 yearly audit over 10 years, the incidence rates of tendon rupture and fracture have dropped from 0.0052 to 0.0028 or one incidence per 192 to 356 person-years. Among 35 patients post-parathyroidectomy, there was an incidence of tendon rupture in a patient with recurrence of hyperparathyroidism, 5 years after surgery. Comparing six survived patients with tendon rupture versus 12 age-gender-dialysis vintage matched patients, hyperparathyroidism has been shown to be most important risk factor. And subsequently, comparing them with six post-parathyroidectomy patients, reduction of alkaline phosphatase (ALP) has been shown to be associated with lower risk of tendon rupture. Median survival in patients with history of tendon rupture and those with history of fracture was 5.9 and 2.2 years, respectively (p = 0.192).

Conclusion: Although rare, end-stage renal failure patients on dialysis with PTH > 600 pg/mL had high risk of tendon rupture and bony fracture. Parathyroidectomy might reduce the risk of tendon rupture and fracture with lowering ALP signifying reduction in bone turn over. Combined incidence rate of tendon rupture and fracture could be used to assess the control of hyperparathyroidism related issues in dialysis center.