Bias og confounding. Søren Kold, overlæge, ph.d., klinisk lektor Aalborg Universitetshospital

Transkript

1 Bias og confounding Søren Kold, overlæge, ph.d., klinisk lektor Aalborg Universitetshospital

2 Bias og confounding Kritisk litteraturlæsning Introduktion Øvelse Information 5 min. Gruppearbejde 20 min. Diskussion og afrunding 10 min.

3 Kritisk litteratur læsning. Kan man ikke bare læse artiklens konklusion eller abstract? Det perfekte studie findes ikke! Peer-reviewed artikler indeholder også mulige fejlkilder Open access journals: ikke peer-reviewed: øget behov for forståelse af faldgrupper

4 23 årig, sund og rask mand Tacklet under fodbold Åben tibiafraktur Gustilo IIIA/IIIB Intakte neurovaskulære forhold distalt Ingen compartment

5 Åben reponering, marvsømning og lukning af sår samme aften

6 4. døgn udviklet dyb infektion Resektion af nekrotisk muskulatur fra den anteriore loge det meste af m. tibialis anterior, m. extensor halucis longus og m. extensor digitorum longus Partiel resektion af peroneus muskulaturen + tibialis posterior

7 Temporær ekstern fiksation: span, scan, plan Hvor hurtigt skal man foretage temporær ekstern fiksation?

8 ØVELSE Mini-review af artikel: Early vs. Delayed Spanning External Fixation for High-Energy Tibial Plateau and Plafond Fractures. Er I enige i konklusionen? Hvis nej, hvorfor ikke? Skal studiet publiceres?

9 AIM The study investigates whether complication rates to high energy tibial plateau and plafond fractures might be reduced with early (within 12 hours) spanning external fixation compared to delayed (more than 12 hours) spanning external fixation.

10 DESIGN The study is a retrospective review. Minimum clinical follow-up: six months. The timing of application of the external fixation was decided by the on-call surgeon.

11 Inclusion criteria: DESIGN Temporizing external fixation in patients above 17-years old at University of Utah Level 1 trauma center. Exclusion criteria: External fixation applied at another facility Inadequate records Less than 6 months clinical follow-up

12 DESIGN Outcome parameters: Infection rates (superficial and deep) Compartment syndrome Time to definitive fixation Length of hospitalization Secondary surgeries after definitive fixation

13 254 patients were included. 95 patients were excluded (78 due to followup of less than 6 months). The remaining 159 patients (87 plateaus and 72 plafonds) were analyzed.

14 EEF: early external fixation. DEF: delayed external fixation

15 EEF: early external fixation. DEF: delayed external fixation

16

17 Time to Fixation: time from application of external fixation to final osteosynthesis

18

19 Conclusion

20 ØVELSE Mini-review af artikel: Early vs. Delayed Spanning External Fixation for High-Energy Tibial Plateau and Plafond Fractures. Er I enige i konklusionen? Hvis nej, hvorfor ikke? Skal studiet publiceres?

21

22 Confounding: En konkurrerende sygdomsårsag som er skævt fordelt mellem eksponerede og ikke eksponerede individer. Confounding variabel er associeret med både outcome og behandlingsgruppe. Der er mindst risiko for at confounding er årsag til forskel mellem to grupper, hvis der udføres et randomiseret studium. Bias: Bevirker at studiets resultater afviger systematisk fra den sande værdi

23

24 The major limitation of study is the retrospective design without a standardized protocol for the decision-making of when to apply the external fixation. The timing of application of the external fixation was decided by the on-call surgeon. This introduces the risk of confounding in the study population. It might be that a substantially higher number of injuries that actually benefits from early external fixation (compared with delayed fixation) were included in the early group. There is a potential risk that the current study therefore falsely concludes that external fixation can be delayed for more than 12 hours without increasing the complication rates

25 Investigates an important and clinical relevant problem. Does the time from injury to application of a temporary spanning external fixation influence the risk of subsequent complications?

26 There were significantly more open plafond and plateau fractures in the early fixation groups compared with delayed fixation. The authors used linear regression modeling to control for open fracture and found no difference in infection between early and delayed fixation.

27 There were significantly more open plafond and plateau fractures in the early fixation groups compared with delayed fixation. The authors used linear regression modeling to control for open fracture and found no difference in infection between early and delayed fixation.

28 Important data are provided in the study. The external fixation was applied up to 168 hours after injury. It would be interesting to know if this patient waiting seven days before spanning external fixation developed serious complications. Two patients in the tibial plafond group ended up with an amputation. What were the primary fracture characteristics of these fractures and what were the indications for amputation.