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. 2023 Apr;31(4):1412-1419.
doi: 10.1007/s00167-022-07085-1. Epub 2022 Sep 13.

A radiological index that influences the outcome following patellofemoral joint arthroplasty: the anterior trochlea offset ratio

Osama Aweid  1 , Nathanael Ahearn  1 , Andrew J Metcalfe  1 , Jonathan Eldridge  1 , Andrew Porteous  1 , James R Murray  2 ; Bristol Knee Group
Collaborators, Affiliations

A radiological index that influences the outcome following patellofemoral joint arthroplasty: the anterior trochlea offset ratio

Osama Aweid et al. Knee Surg Sports Traumatol Arthrosc. 2023 Apr.

Abstract

Purpose: Although largely successful, patellofemoral joint arthroplasty (PFA) has a less than satisfactory outcome in some patients. It was hypothesized that certain factors can be identified on radiological review that correlate with poor patient reported outcomes following PFA.

Methods: A retrospective cohort review of 369 patients undergoing PFA at our institution between 2005 and 2018 identified 43 "poor outcome" patients with an Oxford Knee Score (OKS) of less than 20 at 2 years follow up. These cases were matched by sex and age with 43 "good outcome" patients who had an OKS above 40 at 2 years post-op. Multiple radiological measurements were performed including anterior trochlea offset ratio (ATOR), component flexion/extension, component varus/valgus, component to bone width ratio and retinacular index. The OKS PROM was the primary outcome of the study. Stepwise logistic regression was performed to analyze the differences in radiological indices between the two groups.

Results: Intraclass correlation coefficients for inter-observer and intra-observer reliability were 0.90-0.98 for all indices measured. The only index demonstrating statistical significance between the groups was the ATOR (p = 0.003). The good outcome group had a mean ATOR of 0.19 whereas the poor outcome group had a mean ATOR of 0.24.

Conclusions: Lower ATOR on radiological review was strongly associated with improved outcomes following PFA. The surgeon should therefore take particular care to prevent increasing the anterior offset of the trochlea component when performing PFA.

Level of evidence: Retrospective cohort study, Level III.

Keywords: Component position; Functional outcome; Knee; Patellofemoral joint arthroplasty; Radiological review.

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Conflict of interest statement

The authors disclose no conflict of interest.

Figures

Fig. 1
Fig. 1
Flow chart of patient recruitment and data collection
Fig. 2
Fig. 2
Measurement of component anterior trochlea offset ratio (ATOR)
Fig. 3
Fig. 3
Measurement of component flexion/extension
Fig. 4
Fig. 4
Measurement of component retinacular index
Fig. 5
Fig. 5
Measurement of component varus/valgus
Fig. 6
Fig. 6
Measurement of component width ratio
Fig. 7
Fig. 7
A clinical photograph of the Avon Patellofemoral joint Arthroplasty (PFA)
See this image and copyright information in PMC

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