[1] UNIV ZURICH,DEPT ORTHOPED SURG,CH-8006 ZURICH,SWITZERLAND
[2] UNIV ZURICH,DEPT MED,CH-8006 ZURICH,SWITZERLAND
[3] FREE UNIV BRUSSELS,DEPT RHEUMATOL,B-1050 BRUSSELS,BELGIUM
[4] NATL INST BIOL STAND & CONTROL,LONDON NW3 6RB,ENGLAND
[5] NATL INST MED RES,LONDON NW3 6RB,ENGLAND
[6] KENNEDY INST RHEUMATOL,LONDON W6 7DW,ENGLAND