KNEE Structured oralexamination question5: Unicondylar knee arthroplasty (UKA) versus total knee replacement (TKR)
EXAMINER: Have a look at these radiographs. What can you see?
(Figure 3.5.)
CANDIDATE: Non-weightbearing AP and lateral radiographs of 54-year-old man showing a left medial UKA in situ. The components look well fixed and aligned. There are no obvious periprosthetic fractures. The lateral compartment and PFJ look relatively normal.
EXAMINER: What else can you see?
CANDIDATE: (A bit hesitant and moves closer to the computer screen. This is followed by period of silence before the examiner prompts.)
EXAMINER: The patient tells you that he fell while coming down the stairs sustaining injury to the left knee. He complains of global pain and swelling of the left knee and inability to flex it. What’s going through your mind?
CANDIDATE : There is a faint radio-opaque line behind the femoral component. I would like to compare this with previous radiographs. The history and radiographs are suggestive of dislocation of mobile bearing spacer.
EXAMINER : Good. What are the advantages of UKA?
CANDIDATE: Some of the advantages of UKA are:
Preservation of bone stock.
Faster recovery and return to normal function.
Prevention of PFJ overload.
Retention of knee kinematics and increased flexion.
Less blood loss, infection rate and reduced risk of thromboembolism.
Easier revision to TKA than HTO.
EXAMINER: Does UKA perform as well as TKA?
CANDIDATE: Careful patient selection for UKA is critical if consistent and reliable results are to be obtained. In the early 1980s UKA became gradually unpopular mainly because of poor results due to poor patient selection, operative technique and polyethylene wear. With improvement in patient selection, operative technique and prosthesis design, the results of UKA became comparable to TKA. Latest reports show highly satisfactory survival rate and patient satisfaction for UKA particularly in activities requiring ROM such as going down stairs and kneeling. In a recent report from the Finnish Arthroplasty Registry, Koskinen et al. published a 10-year survival rate of between 53% and 81% depending on prosthetic model implanted. The UK National Joint Registry (NJR) 8th Report showed an overall 5-year revision rate of TKA and UKA of 3% and 9.4% respectively.
Koskinen E, Paavolainen P, Eskelinen A, Pulkkinen P, Remes V. Unicondylar knee replacement for primary osteoarthritis. A prospective follow-up study of 1,819 patients from the Finnish Arthroplasty Register. Acta Ortho Scand 2007;78(1):128–135.
