Introduction: Following previously gratifying results in older patients the study aims to quantify the outcomes and identify any contraindications in patient selection for patello-femoral replacements using the Avon pros-thesis in patients under 55 years old.

Method: We present early outcome results for a prospective cohort study of patients under 55 years of age.110 knees in 86 patients (median age 47years, range 25–54) have been treated with Avon patello-femoral replacement (88 in females and 22 in males). Diagnoses included lateral facet OA (59 knees), patella dislocation (36 knees), trochlear dysplasia (39 knees) and post patellectomy instability (7 knees). 108 knees had undergone previous surgery. 14 knees required additional intra-operative procedures (including 11 lateral releases and 2 patella realignments). All patients were assessed pre-operatively using the Oxford, Bristol and WOMAC scores.

Results: No knees have been lost to follow-up. 82 knees have post operative scores available (mean follow-up 27 months). 8 have been revised (6 due to progression of OA). The mean Oxford, Bristol and WOMAC scores all improved: 18 to 32, 56 to 83 and 39 to 25 respectively. Asymptomatic deterioration of the tibio femoral joint is seen in some cases of primary OA but not with trochlear dysplasia. 21 knees required post-operative additional procedures including 6 lateral releases, 3 patella realignments and 5 revisions. Equally good results were seen when comparing patients with the 3 main diagnoses. Trochlear dysplasia is strongly predicted by young age at onset of symptoms and patellar dislocation.

Conclusion: Many of this type of patient, with disabling symptoms, wish to “live now”. The short-term improvements are frequently dramatic. Comparison of underlying pathologies has not identified groups that are performing less well to suggest restricting current indications. As yet there is no suggestion of prosthetic failure. Revision has presented little difficulty since minimal bone is resected primarily.