Purpose Very few studies focus on lateral unicompartmental arthroplasty (LUKA) in the setting of post-traumatic osteoarthritis (PTOA). The hypothesis of our study is that LUKA is an efective procedure for isolated lateral PTOA with similar outcomes to non-traumatic LUKA. Methods Between 1990 and 2016, eighteen LUKA performed for isolated lateral tibiofemoral osteoarthritis secondary to tibial plateau fracture were retrospectively reviewed (post-traumatic group) and matched with a control group of thirty-six LUKA performed for non-traumatic OA. Clinical (International Knee Score), radiological outcomes and revision rate were compared between the two groups with a minimum follow-up of three years. Results With a mean follow-up of 10.1 years, postoperative IKS scores were similar between the two groups (IKS Knee: 89.1 (control) versus 85 (p = 0.03) and IKS Function: 85.9 (control) versus 77.9 (n.s.). Clinical improvement was greater for the post-traumatic group. No diference was observed with regard to revision rate (3/18 (16.7%) cases in the post-traumatic group and 7/36 (19.4%) in the control group, n.s.) or polyethylene wear per year between the two groups. The revision freesurvival rate was 64.8% for the post-traumatic group and 58.8% for the control group at 22-year follow-up (n.s.). Conclusion LUKA is an efective procedure at long-term for patients sufering from isolated lateral PTOA with similar clinical and radiographic results compared to LUKA performed for non-traumatic OA and without increased risk of revision or prosthetic wear. Level of evidence IV.
Purpose
The objective of this study was to analyze the intra- and interobserver variability of this measurement according to a strict methodology and on a representative sample of the general population, as well as to identify the possible difficulties of measurement in case of patellar or trochlear dysplasia.
Methods
This observational study involved radiographic analysis by three independent observers of a total of 50 patients who had a loaded patellofemoral X-ray taken with the knee flexed to 45°. An initial reading was taken to measure the angle of the trochlear sulcus, the Merchant angle, and to classify the knees according to a possible trochlear dysplasia and/or patellar dysplasia according to Wiberg. A second measurement was then performed to analyze intraobserver agreement. Interobserver agreement was measured on all radiographic measurements (n = 100).
Results
The Merchant patellofemoral congruence angle showed good intraobserver concordance ranging from 0.925 (95% CI 0.868–0.957) to 0.942 (95% CI 0.898–0.967), as well as interobserver concordance ranging from 0.795 (95% CI 0.695–0.862) to 0.914 (95% CI 0.872–0.942). Poor results were found in terms of interobserver concordance on the measurement of the Merchant angle in case of stage 3 Wiberg patella ranging from 0.282 (95% CI −0.920 to 0.731) to 0.611 (95% CI 0.226–0.892).
Conclusion
Congruence angle is one of most commonly used measurements for patellar tracking. However, the convexity of the patellar surface makes it difficult to identify the patellar apex on its intraarticular facet, making the measurement of the Merchant congruence angle unreliable and not very reproducible in cases of stage 3 Wiberg patella.
Registration N°IRB 2021/139
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