A 73-Year-Old Woman

and Iain McNamara¹

(1)

Trauma & Orthopaedics, Norfolk & Norwich University Hospital, Norwich, United Kingdom

A lady aged 73 years old was sent for a second opinion 2 years after a right posterior-stabilised total knee replacement. Over the course of the previous 2 years, her patella had gradually subluxated laterally. Her immediate post-operative X-ray showed the patella congruent with the trochlea. At the same time her mobility worsened, principally due to anterior knee pain and an inability to achieve extension actively.

The referring surgeon wondered if the implant was internally rotated.

Past Medical History

Fit and well

Examination

There was a palpable defect in the medial retinaculum along the length of the wound; she had had a medial parapatellar approach. The patella lay laterally. She could extend to 10^° actively and flex to 90^°.

X-rays

Question 1

What do the plain films show?

Question 2

What are the reasons for this?

Question 3

What further imaging needs to be undertaken?

Follow-Up

She returned with CT scans reported as:

The femoral component lies in 4 ^° external rotation. The tibial component lies in 20 ^° internal rotation. Lateral tilt of the patella noted with advanced patellofemoral osteoarthrosis.