Friday, July 01, 2011

Total Knee Arthroplasty for Radiologist


A total knee replacement complains of pain. Xray AP and lat show good alignment of the components along with possible loosening of the tibial stem with no periosteal response or sign of osteomyelitis. Case by Dr MGK Murthy



Best TKA accepted today is Cemented Total Knee replacement(life span=finite period, depends on use). Knee ligaments to be preserved or not is still debated .Results are equal for both  though gait is better if ligaments are preserved. Types- Fixed bearing/Medial pivot/Rotating platform and mobile bearing/PCL retaining/PCL substituting

Pre Op Radiographic workup

X -rays-Standing—AP/Lat/Skyline view
Long leg X -ray for malalignment
Standing X -ray with Knee in extension  or 45°flexion(Rosenberg view)(can show cartilage degeneration better)


Contraindications
-sepsis/Extensor mechanical dysfunction/secondary vascular disease/Recurvatum secondary to muscular weakness with neuropathic joints and obesity being relative contraindications

Surgical alternatives to TKR
-proximal tibial osteotomy(for medial compartment disease)
-Distal femoral varus osteotomy(for lateral compartment disease)
-Unicompartmental Knee replacement

Post Operative Radiographs

-       Malalignment

-       Aseptic loosening of stem (either bone ) more often tibial
5-10%of patients at 10-15 yrs have loosened stem
cause is not known, but possibly polyethylene debris ---------- alteration leading to bone--------mechanical instability---Treatment is with revision surgery with bone grafting


-Arthrofibrosis
cause is not known
basically excessive scar tissue
more in young and on warfarin patients
Less than 1% of TKRs lead to this
conservative treatment or revision surgery with resection is the answer









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