Aims: determine functional outcome of revision Avon patellofemoral replacements (PFR), converted from primary Lubinus PFR.

Materials and Methods:

Prospective review of 11 knees (8 patients, 6 female).

Average age at primary PFR – 64 years

Indication – isolated patellofemoral osteoarthritis (11), patellofemoral instability (3)

9 knees (7 patients) temporarily improved.

Revision Avon PFR at average 83 months after primary procedure.

Indication – polyethylene wear

polyethylene synovitis

femoral component malposition

At review:

average 61 months after revision

age – 70 years 10 months.

fixed flexion contracture 1.7°

maximum flexion 111°.

Bristol knee score improved from average of 54.5 to 77.2. Pain score component averaged 25, functional component averaged 16.9. No malalignment or instability.

Average American Knee Society Score 132.8

Bartlett patellar score 19.8

Three patients (4 knees) had medical problems contributing to their functional incapacity.

No radiological complications except minor polyethylene wear on lateral facet of one patella. Progression to tibiofemoral osteoarthritis (Ahlburgh grade 1) in 3 knees.

Discussion: Primary Lubinus PFR temporarily improved 82% of knees. Maltracking/polyethylene wear was usual cause for failure. Revision to Avon PFR resulted in substantial improvement of pain and function.

Conclusion: revision Avon PFR can provide a suitable alternative to revision to total knee replacement.

Trochlear dysplasia is an important anatomical abnormality in symptomatic patellar instability. Our study assessed the mismatch between the bony and cartilaginous morphology in patients with a dysplastic trochlea compared with a control group.

MRI scans of 25 knees in 23 patients with trochlear dysplasia and in 11 patients in a randomly selected control group were reviewed retrospectively in order to assess the morphology of the cartilaginous and bony trochlea. Inter- and intra-observer error was assessed.

In the dysplastic group there were 15 women and eight men with a mean age of 20.4 years (14 to 30). The mean bony sulcus angle was 167.9° (141° to 203°), whereas the mean cartilaginous sulcus angle was 186.5° (152° to 214°; p < 0.001). In 74 of 75 axial images (98.7%) the cartilaginous contour was different from the osseous contour on subjective assessment, the cartilage exacerbated the abnormality.

Our study shows that the morphology of the cartilaginous trochlea differs markedly from that of the underlying bony trochlea in patients with trochlear dysplasia. MRI is necessary in order to demonstrate the pathology and to facilitate surgical planning.