1. Kennemer Gasthuis, Department
of Orthopedic Surgery, Boerhaavelaan 22, 2035
RC Haarlem, the Netherlands.
2. Isala Clinics, PO
Box 10500, 8000 GM Zwolle, the
Netherlands.
3. University Medical Center Utrecht, PO
Box 85500, 3508 GA Utrecht, the
Netherlands.
4. University of Groningen, University Medical
Center Groningen, Department of General Practice, University
of Groningen, PO Box 196, 9700
AD Groningen, the Netherlands.