Q) We were operating on a 58-year-old woman for a subcapital fracture of her right hip. The orthopedist mentioned that the patient had kidney disease and that it probably caused her hip fracture. I didn’t know kidney disease causes hip fractures. Is this true?
Evolving evidence suggests an association between diminishing renal function and increased risk for fracture. Here’s a look at the available data:
Atherosclerosis Risk in Communities (ARIC) Study. During a median 13 years’ follow-up of 10,955 community-based older adults, investigators identified higher albuminuria level and decreased creatinine-based estimated glomerular filtration rate (eGFR) as significant risk factors for fracture. Other risk factors included older age, race (Caucasians had the highest incidence), and sex (women were more likely than men to sustain a fracture). A nonlinear relationship was observed between eGFR and fracture diagnosis, with a graded association between fracture and albuminuria level. 7
Cardiovascular Health Study. In this study of 4,699 older community-based adults, kidney function was assessed by measurement of serum cystatin C. During a mean follow-up of 7.1 years, higher cystatin C levels correlated to a higher risk for hip fracture in both sexes. In women, there was a significant association between diminishing renal function and hip fracture status: Those with lower eGFRs had a higher incidence of fractures. There was a similar magnitude of association among men, but it was not significant. 8
Health, Aging and Body Composite Study. In 2,754 older adults, an association was noted between decreased femoral neck bone mineral density (BMD) and increased risk for fracture in those with and without CKD stage 3 to 5. With a concurrent diagnosis of osteoporosis, there was a 110% increased risk for nonspinal fracture in those with CKD and a 63% increased risk for those without CKD. 9 In a study of 485 adult hemodialysis patients, decreased total hip and femoral neck BMD was associated with an increased risk for fractures in women with parathyroid hormone levels on the lower range of acceptable in this population (intact parathyroid hormone level [IPTH] < 204 pg/mL) and for spinal fractures in both genders. 10
Bone changes associated with deterioration of renal function are complex and multifactorial. Human bone is a composite of protein fused to mineral crystals, primarily calcium and phosphate. Bone is dynamic, being broken down and rebuilt throughout adulthood, with the skeleton almost completely rebuilt every 10 years. 11
CKD–mineral and bone disorder (CKD–MBD) is a systemic disorder seen in those with kidney disease that affects bone and mineral metabolism. Its manifestations include abnormalities in the bone, calcifications of vascular and/or soft tissues, abnormal vitamin D metabolism, and disruptions in the phosphorus, calcium, and parathyroid hormone levels. These components, and the severity of the condition, vary by stage of CKD. One component of CKD–MBD, renal osteodystrophy, is associated with changes in bone morphology and is definitively diagnosed by bone biopsy. 12
Care of these patients is complex and can be compounded by osteoporosis and/or loss of bone strength. Osteoporosis, like CKD, increases in incidence with age and is associated with fracture risk. 11