MRI FOR DIAGNOSING MENISCAL PATHOLOGY: ARE WE OVERDOING IT?

Abstract

Introduction: Meniscal tears are common and arise as a result of mainly trauma either isolated or on top of longstanding degeneration. The symptoms are restrictive and prompt diagnosis and intervention restores function and improves prognosis dramatically with long-term symptomatic relief

Purpose: Routinely diagnosing meniscal pathology via MRI is becoming commonplace, even on the background of a clear meniscal history and examination. MRI is useful in excluding tumours but evidence suggests that this can be done with an up-to-date plain x-ray. The aim of this study is to evaluate the routine practice of two knee surgeons in a District General Hospital commonly performing knee arthroscopies.

Method: A retrospective case note analysis 18/01/2007 to 2/12/2008. Patients were selected from the arthroscopy lists of two knee surgeons one largely MRI scanning the other proceeding more on clinical acumen to arthroscopy. Cohort cross-examined, isolating those with a clinical suspicion of meniscal pathology with an intention to treat on initial presentation. Suspected concurrent ACL pathology were excluded. This gave us a group of patients with likely meniscal injury that would ultimately be likely to be scoped so we could retrospectively evaluate the usefulness of MRI, in addition to clinical suspicion in detecting meniscal pathology. Clinical suspicion assumed on presence/absence of 5 key meniscal features i.e Pain, Locking, Effusion, Joint line tenderness (medial and lateral), McMurrays test positive (medial and lateral).

Results: The results in summary:

• 124 arthroscopy patients

• Mean age of the cohort was 47.7 (19–81) mostly male 2.5:1

• 2 patients not scanned had a negative arthroscopy

• Some specific and some sensitive signs and symptoms

  • Pain and Joint line tenderness – high sensitivity

  • McMurray’s and Locking – high specificity

• Combine into a scoring system (/5)

  • Shows good positive correlation with specificity (up to 97%)

  • Shows good negative correlation with sensitivity

  • Both with increasing score

• MRI scanning delays operation by a mean of 45 days (6 ½ weeks)

• Total cost of investigating and treating meniscal pathology estimated at £202,500 per year

• Costs can be reduced by using a cut off score for scanning of 3/5

Conclusion:

• ○ MRI showed excellent sensitivity and specificity for meniscal tears

• ○ Should be reserved for those with boarder-line clinical scores < 3/5 whom cannot be either operated on directly or have meniscal pathology confidently excluded on clinical grounds with ~83% certainty if > 4/5.

• ○ Clinical findings, in combination, can accurately guide treatment

• ○ Some signs display high specificity and others high sensitivity. ~83% certainty if > 4/5.

• ○ Border-line cases falling short on inclusion criteria should be investigated further (MRI) but:

  • Long waiting times will delay arthroscopy by 45 days (6½ weeks).