Does overstuffing of the patellofemoral joint in total knee arthroplasty have a significant effect on postoperative outcomes?

Background: There is ongoing debate in the literature as to whether or not patellofemoral joint overstuffing has a clinically significant effect on postoperative outcomes following total knee arthroplasty (TKA). This study investigates the effect of patellofemoral joint overstuffing on patient-reported outcomes using novel methods of radiographic measurement.

Methods: The study population consisted of a prospective cohort of 266 patients receiving a Triathlon® (Stryker, Kalamazoo, MI, USA) TKA between 2006 and 2009. Participants completed the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire preoperatively and at 12 months postoperatively. Pre- and postoperative radiographic measurements were taken according to a defined protocol to assess for patellofemoral overstuffing. Measurement reproducibility was assessed using inter-observer intraclass correlation coefficients. Associations between radiographic measurements and patient-reported outcomes were analysed using linear regression analysis.

Results: A total of 107 patients had adequate images and were included in the analysis for this study. Three different radiographic measurements were used to identify patellofemoral overstuffing all with good intra- and inter-observer reliability. There was no association identified between combined (patella and trochlea) patellofemoral overstuffing measurements and WOMAC scores. However, a statistically significant association was identified between an increase in anterior trochlear offset and worse knee pain and function scores (P < 0.05).

Conclusions: There is no identifiable association between true patellofemoral overstuffing and clinical outcome; however, there is a small association with the anterior trochlear offset though further studies are warranted to confirm the clinical significance of this finding.