Adult ; Age Factors ; Burnout, Professional ; epidemiology ; Female ; Health Status ; Humans ; Male ; Marital Status ; Mental Health ; Occupational Health ; Orthopedic Surgeons ; statistics & numerical data ; Pain ; epidemiology ; Personnel Staffing and Scheduling ; Sex Factors ; Singapore ; epidemiology ; Social Behavior ; Stress, Psychological ; epidemiology ; Surveys and Questionnaires ; Work Schedule Tolerance