Review Question - QID 2873

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Unicompartmental Knee Replacement Complications Stress fractures QID: 2873 (OBQ09.60)

QID 2873 (Type "2873" in App Search)

A 61-year-old male had a minimally-invasive unicompartmental knee replacement 8 months ago. He did well until recently when he developed persistent right knee pain that is worse with weight bearing. He denies any fevers or recent trauma. He does report that he had been exercising more over the past few months in an attempt to lose weight. WBC, ESR and C-reactive protein levels are normal. An AP radiograph and bone scan are shown in Figure A and B. What is the most likely cause of his symptoms?

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Component failure/ polyethylene failure

290/3208

Infection

37/3208

Pes anserine bursitis

103/3208

Stress fracture

86%

2751/3208

Complex regional pain syndrome

13/3208

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The patient has knee pain following a unicompartmental knee replacement with a normal radiograph and uptake under the prosthesis on bone scan. This is consistent with a stress fracture.

Brumby et al. reported on tibial plateau stress fractures after UKA due to the guide pin holes placed in the proximal tibia. All of their cases required a revision to a TKA. They recommend that if 3 or more pin holes are created that the surgeon be aware of this potential complication. Pandit et al. report similarly on tibial plateau fractures after medial Oxford UKA.

Hamilton et al. retrospectively reviewed minimally invasive versus open unicompartmental arthroplasty. They found the MIS group to have a higher incidence of aseptic loosening and re-operations when compared to the open group.

Incorrect Answers: The patient's presentation is not consistent with infection, pes bursitis, or complex regional pain syndrome. Radiographs do not show component or polyethylene failure.