title: Correlation of hip fracture with other fracture types: Toward a rational composite hip fracture endpoint.
abstract: OBJECTIVE
  With ethical requirements to the enrollment of lower risk subjects, osteoporosis trials are underpowered to detect reduction in hip fractures. Different skeletal sites have different levels of fracture risk and response to treatment. We sought to identify fracture sites which cluster with hip fracture at higher than expected frequency; if these sites respond to treatment similarly, then a composite fracture endpoint could provide a better estimate of hip fracture reduction.
  
  
  METHODS
  Cohort study using Veterans Affairs and Medicare administrative data. Male Veterans (n=5,036,536) aged 50-99 years receiving VA primary care between 1999 and 2009 were included. Fractures were ascertained using ICD9 and CPT codes and classified by skeletal site. Pearson correlation coefficients, logistic regression and kappa statistics were used to describe the correlation between each fracture type and hip fracture within individuals, without regard to the timing of the events.
  
  
  RESULTS
  595,579 (11.8%) men suffered 1 or more fractures and 179,597 (3.6%) suffered 2 or more fractures during the time under study. Of those with one or more fractures, the rib was the most common site (29%), followed by spine (22%), hip (21%) and femur (20%). The fracture types most highly correlated with hip fracture were pelvic/acetabular (Pearson correlation coefficient 0.25, p<0.0001), femur (0.15, p<0.0001), and shoulder (0.11, p<0.0001).
  
  
  CONCLUSIONS
  Pelvic, acetabular, femur, and shoulder fractures cluster with hip fractures within individuals at greater than expected frequency. If we observe similar treatment risk reductions within that cluster, subsequent trials could consider the use of a composite endpoint to better estimate hip fracture risk.
authors.affiliation: Duke University Center for the Study of Aging and Human Development, Durham, NC, United States; Durham VA Geriatric Research Education and Clinical Center, Durham, NC, United States. Electronic address: colon001@mc.duke.edu.
authors.forename: Cathleen
authors.initials: C
authors.lastname: Colón-Emeric
authors.affiliation: Duke University Center for the Study of Aging and Human Development, Durham, NC, United States.
authors.forename: Carl F
authors.initials: CF
authors.lastname: Pieper
authors.affiliation: Durham VA Health Services Research and Development Center, Durham, NC, United States.
authors.forename: Janet
authors.initials: J
authors.lastname: Grubber
authors.affiliation: Durham VA Health Services Research and Development Center, Durham, NC, United States.
authors.forename: Lynn
authors.initials: L
authors.lastname: Van Scoyoc
authors.affiliation: Durham VA Health Services Research and Development Center, Durham, NC, United States.
authors.forename: Merritt L
authors.initials: ML
authors.lastname: Schnell
authors.affiliation: Duke University Center for the Study of Aging and Human Development, Durham, NC, United States; Durham VA Health Services Research and Development Center, Durham, NC, United States; Duke University Department of Medicine, Durham, NC, United States.
authors.forename: Courtney Harold
authors.initials: CH
authors.lastname: Van Houtven
authors.affiliation: Durham VA Health Services Research and Development Center, Durham, NC, United States.
authors.forename: Megan
authors.initials: M
authors.lastname: Pearson
authors.affiliation: University of Utah, Salt Lake City, UT, United States.
authors.forename: Joanne
authors.initials: J
authors.lastname: Lafleur
authors.affiliation: Duke University Center for the Study of Aging and Human Development, Durham, NC, United States; Durham VA Geriatric Research Education and Clinical Center, Durham, NC, United States.
authors.forename: Kenneth W
authors.initials: KW
authors.lastname: Lyles
authors.affiliation: McGuire VA Medical Center, Richmond, VA, United States.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Adler
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D050071:Bone Density Conservation Agents; D002986:Clinical Trials as Topic; D015331:Cohort Studies; D005269:Femur / Q000293:injuries*; D006620:Hip Fractures / Q000453:epidemiology*; D006801:Humans; D006811:Humerus / Q000293:injuries*; D015994:Incidence; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000150:complications; D058866:Osteoporotic Fractures / Q000453:epidemiology*; D018579:Patient Selection; D010388:Pelvis / Q000293:injuries*
chemical_list: D050071:Bone Density Conservation Agents
keywords: Correlation; Fractures; Osteoporosis; Veterans