This paper investigates prospective utilisation review for tympanostomy. In
the studied procedure, a medical corporation reviews cases for third-party
payers (insurance companies), and used explicit criteria to determine whet
her a case is appropriate for surgery. Earlier findings that inappropriate
decisions to approve surgery are strongly related to previous surgeries for
the same condition are investigated to trace the emergence of this theme w
ithin the review process and its consolidation into a 'precedent' for furth
er surgery, notwithstanding the explicit criteria which the reviewers are m
andated to enforce. The significance of previous surgeries as a factor favo
uring further surgery emerges at all levels of the review process, indicati
ng a medical culture that validates precedent in medical decision making de
spite the absence of evidence-based findings that would support it.