What Is the Clinical Significance of a Raised Blood C- Reactive Protein (CRP) Level in Patients with...
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What Is the Clinical Significance of a Raised Blood C-Reactive Protein (CRP) Level in Patients with Inflammatory Lesions Adjacent to Metal-on-Metal Hip Replacements on
MARS MRI?
Radiological Society of North America (RSNA)Wed Dec 01 2010 3:20PM - 3:30PM ROOM E451A
Keshthra Satchithananda, Tahir Mahmud, Adam Mitchell, Anastasia Papadaki, Donald Mcrobbie, Shiraz Sabah, John Skinner, Johann Henckel, Justin Cobb,
Angus Lewis, Alister Hart
We are interested in the mechanism of failure of metal-on-metal hip replacements
The London Implant Retrieval Centre>750 components
Painful MOM hip clinic
160 MARS MRI scans; 79 lesions found
Hart, Skinner et al JBJS Br. 2009 Jun;91-B(6):738-44;
Sabah, Skinner, Hart et al Epub J Athroplasty 2010
Plain radiographs do not explain failure:Well positioned cups, non-infected & well fixed
But MRI can detect pseudotumours
Oxford definition of pseudotumour
• “we use the term ‘‘pseudotumour’’ to encompass all masses, whether cystic or solid. Lesions described in different ways by other groups (eg. cyst, bursa, ALVAL), would be classified as a pseudotumour in our centre.” – Glynn-Jones, J Bone Joint Surg Br, 91(12): 1566-74,
2009.• It is an inflammatory problem
Difficulty differentiating between inflammation and infection for painful MOM hips
• Sierra• Biant
Purpose• a) To report the clinical correlation of CRP and MARS MRI findings on 97
patients with painful metal-on- metal (MOM) hip replacements.
• b) To guide radiologists and surgeons through the complex clinical interpretation of MARS MRI findings in patients with painful MOM hips.
• When investigating a painful hip replacement, Surgeons use raised blood CRP to indicate infection and help decide between a 1 and 2 stage revision procedure. The British Orthopaedic Association has recently recommended MARS MRI in patients with painful MOM hips because sterile inflammatory lesions can be the cause of premature failure. However, it is not known whether blood CRP is elevated in such cases.
Many papers on pseudotumoursGlyn-Jones, S.; Pandit, H.; Kwon, Y. M. et al.: Risk factors for inflammatory pseudotumour formation following
hip resurfacing. J Bone Joint Surg Br, 91(12): 1566-74, 2009.
Grammatopolous, G.; Pandit, H.; Kwon, Y. M. et al.: Hip resurfacings revised for inflammatory pseudotumour have a poor outcome. J Bone Joint Surg Br, 91(8): 1019-24, 2009.
Harvie, P.; Giele, H.; Fang, C. et al.: The treatment of femoral neuropathy due to pseudotumour caused by metal-on-metal resurfacing arthroplasty. Hip Int, 18(4): 313-20, 2008.
Kwon, Y. M.; Glyn-Jones, S.; Simpson, D. J. et al.: Analysis of wear of retrieved metal-on-metal hip resurfacing implants revised due to pseudotumours. J Bone Joint Surg Br, 92(3): 356-61.
Pandit, H.; Glyn-Jones, S.; McLardy-Smith, P. et al.: Pseudotumours associated with metal-on-metal hip resurfacings. J Bone Joint Surg Br, 90(7): 847-51, 2008.
Pandit, H.; Vlychou, M.; Whitwell, D. et al.: Necrotic granulomatous pseudotumours in bilateral resurfacing hip arthoplasties: evidence for a type IV immune response. Virchows Arch, 453(5): 529-34, 2008.
Park, S. J.; Lee, H. K.; Yi, B. H. et al.: Pseudotumour in the bladder as a complication of total hip replacement: ultrasonography, CT and MR findings. Br J Radiol, 80(954): e119-21, 2007.
Simple hypothesis
• Do patients with a lesion (pseudotumour) on MRI have a raised CRP?
Method
• 97 patients • Painful, non-infected, MOMHR • Infection was excluded by hip aspiration and extended
seven day cultures or low (<10mg/l) blood CRP level• Metal artifact reduction sequence (MARS) MRI were
performed.• Sensitivity and specificity were calculated using a
contingency table and the Chi square test was used to test for statistical significance.
MRI classification• 97 MARS MRI scans of painful MOM hips• Classification developed by 2 MSK radiologists• Blinded to clinical details
Lesion category Wall Contents Shape
Class 1 Thin walled Fluid like:T1 hypo / T2 hyper
Flat with walls mainly in apposition
Class 2A Thick walled or irregular
Fluid like: T1 hypo / T2 hyper
Not flat and >50% of the walls are not in
apposition
Class 2B Thick walled or irregular
Atypical fluid:T1 hyper / T2
variableAny size
Class 3 Solid Mixed signal Any size
Results• A raised CRP was found in 34 out
of 97 patients of which 88% of these had lesions on MARS MRI.
• In the 63 patients with a normal CRP, 53% had lesions on MARS MRI.
• CRP >10 predicts lesion on MRI with:– Sensitivity 59% – Specificity 48% – Difference in the frequency of
lesions between the normal and raised CRP groups was not statistically significant.
CRP>10 CRP<10
Lesion on MRI
30 33 63
No lesion on MRI
4 30 34
34 63 97
MRI Type 1 pseudotumour
a. Well functioning hip b. Painful hip
LesionLesion
MRI Type 2a pseudotumoura. Well functioning hip b. Painful hip
Lesion on T1 Lesion on T1
Lesion on T2Lesion on T2
MRI Type 2b pseudotumoura. Well functioning hip b. Painful hip
Lesion on T2 (coronal)
Lesion on T2 Lesion on T2
Lesion on T1
MRI Type 3 Pseudotumour
A painful hip
Solid Lesion
Conclusion
• A raised CRP was commonly found in all patients with non-infected, painful MOM hips (probably as a result of a synovitis to the metal wear debris).
• However, a raised CRP did not reliably predict the presence of a soft tissue lesion adjacent to a painful MOM hip replacement on MARS MRI.
CLINICAL RELEVANCE/APPLICATION
• This study shows that a raised CRP level in a non-infected painful MOM hip replacement does not necessarily correlate with the presence of a soft tissue lesion.
• Our latest work shows no difference in the prevalence of lesions on MRI between 28 well functioning and 30 painful MOM hip.
• CRP may indicate a synovitis as the cause of a painful MOM hip
Details of the patients groupsVariable Median
(interquartile range) 97 patients
Type of implantAdeptASR
BiometBHR
CormetDurom
Oxford hip score
3D CT measured cup inclination angle
(degrees)3D CT measured cup
version angle (degrees)
Conclusions
• 50% of well functioning and painful MOM hips had pseudotumour
• Only difference was for solid lesions: 1 painful versus zero well functioning hips
• The current definition of Pseudotumour is not clinically useful and misleading