The Knee, ISSN: 1873-5800, Vol: 23, Issue: 2, Page: 331-7

Obesity and the absence of trochlear dysplasia increase the risk of revision in patellofemoral arthroplasty

Liow, Ming Han Lincoln; Goh, Graham Seow-Hng; Tay, Darren Keng-Jin; Chia, Shi-Lu; Lo, Ngai-Nung; Yeo, Seng-Jin


  • Factors affecting the outcomes and revision of patellofemoral arthroplasty were studied.
  • Higher body mass index (BMI) led to less clinical improvement and more radiographic outliers.
  • Survivorship at a mean of 4.1 years was 92.2%, which mirrors that for total knee arthroplasty (TKA).
  • Obesity led to higher revision rates due to progression of tibiofemoral arthritis.
  • Absence of trochlear dysplasia increased revision rates due to progression of tibiofemoral osteoarthritis (TFOA).



Proper indications and patient selection are of paramount importance in patellofemoral arthroplasty (PFA). Although factors predicting outcomes in total knee arthroplasty (TKA) have been studied, there are no such studies for modern PFA. This retrospective study reports the midterm clinical and radiological outcomes and survivorship of PFA, investigating the risk factors associated with poorer outcomes and higher revision rates.


Fifty-one patients (51 knees) with isolated patellofemoral arthritis underwent PFA with a second-generation implant. The mean follow-up duration was 4.1 years (range, 2.2 to 6.1). The cohort was stratified into obese (body mass index (BMI) ≥ 30 kg/m2n = 16), overweight (BMI 25 to 29.9 kg/m2n = 20) and control (BMI 18.5 to 24.9 kg/m2n = 15) groups. The same cohort was stratified based on the presence (n = 11) or absence (n = 40) of trochlear dysplasia (TD).


The mean Knee Society objective and function scores, the Melbourne Knee score and the Physical Component Score of Short Form 36 improved significantly. Obesity was associated with no significant improvement in the Melbourne Knee score and the Knee Society function score (p > 0.05), a higher incidence of radiographic outliers and lower patient satisfaction. There was no significant difference in outcomes between the TD and non-TD groups at two years (p > 0.05), with a survivorship of 92.2%. Three revisions for progression of tibiofemoral osteoarthritis were noted in the non-TD and obese or overweight groups.


Patients with obesity and the absence of TD are at a potentially higher risk of revision surgery to TKA, and they should be counselled that PFA may represent a ‘bridging’ procedure.


Level of Evidence: III

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