Familial positive ulnar variance with secondary radioulnar joint arthritis and extensor tendon ruptures.

A familial pattern of extensor tendon ruptures due to distal radioulnar osteoarthritis with underlying positive ulnar variance is described. Spontaneous ruptures occurred in four members of the family (one woman and three men) in middle age. Laboratory data did not indicate any sign of rheumatoid arthritis. All cases revealed significant positive ulnar variance and distal radioulnar osteoarthritis. Younger members of the family demonstrated positive ulnar variance although without osteoarthritic changes. The tendon ruptures presumably resulted from a hereditary disorder in conjunction with degenerative changes brought about by age.