Bone microarchitecture, bone strength, and correlation with joint score. (A) Representative HR-pQCT images at a nominal isotropic resolution of 82 μm of the distal radius in a 43-year-old male patient with severe hemophilia A (Tb.N, 1.82; Tb.Th, 0.061; Ct.Th, 0.94; Ct.Po, 2.23) and an age- and sex-matched control subject (Tb.N, 2.02; Tb.Th, 0.07; Ct.Th, 1.12; Ct.Po, 1.18). (B) Failure load (higher failure load = better mechanical bone strength) at the distal tibia in PWH and controls. The upper and lower boundaries of the box plot represent the interquartile range, the diamond represents the mean, the line dividing the box plot represents the median, and the whiskers indicate the maximum and minimum values. (C) Failure load at distal tibia vs total Gilbert joint score (higher joint score = more severe arthropathy) in 17 PWH (the remaining patient did not have Gilbert joint score available). Open square data points (□) indicate subjects who received primary prophylaxis (only 4 of 5 receiving primary prophylaxis shown, as 1 did not have joint score available) and as a whole appears to have lower Gilbert joint scores and higher failure load. The outlier (X) with the lowest tibial failure load has liver cirrhosis secondary to hepatitis C virus infection and HIV, which likely explains the lower tibial failure load and BMD. When the outlier is excluded from the correlation analysis, the statistically significant inverse correlation of Gilbert joint score and tibial BMD and failure load still stands (tibial failure load: R = −0.601 [P = .0139]; tibial BMD: R = −0.66 [P = .005]; R = Spearman ρ).