Learning objectives
Imaging evaluation of aseptic and infective loosening usually involves conventional radiographs and nuclear imaging.
To be able to identify patterns of uptake on Tc99m MDP scan and In111 white cell scan in infective and aseptic loosening.
Background
Total knee replacements have a 10- to 15-year survival rate greater than 90%.
Despite the ling term success of knee replacements,
failure does occur.
Common causes of failure include aseptic loosening,
instability,
infection,
polyethylene wear with or without particle disease (osteolysis) and extensor mechanism failure.
The most common cause of early failure (< 2years after initial surgery) are infection and instability.
More than 2 years after primary implantation,
the most common causes of failure are polyethylene wear and aseptic loosening.
Imaging findings OR Procedure Details
The most common cause of early failure (< 2years after initial surgery) are infection and instability.
More than 2 years after primary implantation,
the most common causes of failure are polyethylene wear and aseptic loosening.
Periprosthetic infection
The prevalence of deep infection after TKA is approximately 0.4-2% but it is higher (up to 10%) in revision arthroplasty.
The cause is usually haematogenous seeding associated with a distant infection.The diagnostic work-up for infection includes ESR and CRP and joint aspiration for suspected infection.
Radiographic findings of...
Conclusion
Imaging is an important aspect of the identification and management of loosening of total knee replacement prosthesis.
Plain radiographic findings may be nonspecific.
Triple phase Tc99m bone scan and Indium leukocyte scanning have important role in differentaiting between infected andaseptic loosening.
References
1.
Current concepts in knee replacement:Complications.
Mulcahy H,
Vhew FS.
AJR 2014;202:W76-W86
2.
Imaging of total knee arthroplasty.
Math KR,
Zaidi SF,
Petchprapa C,
Harwin SF.
Seminars in musculoskeletal radiology (2006) 10,1:47-63.
3.
Palestro CJ,
Swyer AJ,
Kim CK,
et al.
Infected knee prosthesis:diagnosis with In-111 leukocyte,
Tc-99m sulphur colloid,
and with Tc99m MDP imaging.
Radiology 1991;179:645-648.
Personal Information
Dr Alok Arya
MSK Radiology Fellow
Royal National Orthopaedic Hospital
Stanmore,
London
UK
Dr Kanupriya Agrawal
Consultant Radiologist
Watford GeneralHospital
Watford,
Herts,
UK