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Centre for Evidence-
Based Medicine

Example NNTs - Orthopedics

Condition or Disorder Intervention vs. Control Outcome Follow-up Duration Event Rates % NNT (95% CI)
CER EER
Painful stiff shoulder1 Corticosteroid injections vs. physiotherapy Treatment success 1 year 46 77 3 (2 to 8)
Subacute or chronic low back pain2 Exercise program (8 one hour sessions over 4 weeks which consisted of stretching, low impact aerobics and strengthening exercises) vs. control (standard care from GPs) Functional limitation (24 point Roland back pain disability questionnaire) 1 year 35 64 4 (3 to 8)
Lateral epicondylitis (tennis elbow)3 Local corticosteroid injection of methylprednisolone and lignocaine vs. enteric-coated naproxen Complete recovery at 4 weeks 12 months 5.7 42 3 (2 to 5)
Local corticosteroid injection of methylprednisolone and lignocaine vs. placebo Pain scores ≤ 3 at 4 weeks (on 10 point Likert scale) 50 82 4 (3 to 8)
Osteoarthritis of the knee4 Manual physical therapy and exercise vs. placebo (ultrasonography at a sub-therapeutic intensity) Knee surgery 1 year 20 5 7 (4 to 134)
Acute whiplash injuries5 Active treatment (gentle, active, small-range and small-amplitude rotational movements of the neck) vs. standard treatment (leaflet providing information about injury mechanisms, advice on suitable activities and instruction on postural correction) No pain 6 months 11 30 6 (3 to 45)
No or low pain 20 44 5 (3 to 22)

References

  1. N Engl J Med. 12 Nov 1998; 339: 1415-25
  2. BMJ. 31 Jul 1999; 319: 279-83
  3. BMJ. Oct 9, 1999; 319: 964-8
  4. Ann Intern Med. Feb 1 2000; 132: 173-81
  5. Spine. Jul 15, 2000; 25: 1782-7