Summary

In 263 adolescents surgically treated for patellofemoral instability and included in the JUPITER study, the BPII 2.0 score was found to be the most sensitive and the only patient-reported outcome scale without a ceiling effect.

Abstract

Background

To properly evaluate and quantify how children and adolescents with patello-femoral instability (PFI) perceive their functional status, pain level and QOL, there is great importance in identifying the optimal PROs for this patient population. A few different PRO scales have been commonly used to evaluate individuals with PFI, each designed for a different purpose. The aim of this study was to evaluate the correlation between commonly used Patient Reported Outcome (PRO) scores in assessing children and adolescents with PFI, and to evaluate their sensitivity to change following treatment.

Methods

The JUPITER study prospectively collected database was utilized to collect preoperative and 1-year postoperative PRO scores of individuals younger than 19 years of age, who were diagnosed with and treated surgically for Patellofemoral instability (PFI). Patients with a documented episode of patellar dislocation were enrolled in the study by 27 patellofemoral surgeons across 11 institutions in the US, irrespective of treatment approach. All patients completed a set of 4 PROs at the time of enrollment (baseline) and at one-year follow-up using either a paper-based or internet-based data collection sheet. BPII 2.0, IKDC, Kujala and KOOS were assessed. We analyzed the correlation between the four scores, evaluated the sensitivity to change, compared pre- and post-operative scores, and calculated minimal clinical important difference (MCID), and ceiling and floor effects.

Results

A total of 1,065 cases were reviewed, and 263 were included. The median age of the cohort was 15 (IQR 13 to 16) years, with 177 (67.3%) females. The median BPII 2.0 score was lower than the other three scores at baseline and at 1 year follow up (P<0.001, Table 2). BPII 2.0 presented the most substantial change at 1 year following surgery, increasing by a median 35.96 (IQR 14.9 to 52.35) points. The correlations between the four tested PRO scales are depicted in table 3. BPII 2.0, showed moderate correlation with the other three scores. Among themselves, Kujala, pediatric-IKDC and KOOS had strong correlations (Spearman correlation coefficient > 0.7, P<0.001). In the lower 50th percentile baseline score group the change in all PRO scores following surgery was more substantial than in the higher 50th percentile score group (P<0.001). BPII 2.0 was found to be free of a ceiling effect as only 8 (3%) patients scored the maximal 100 points at 1 year follow up. On the contrary, a total of 121 (46%) and 75 (28.5%) patients scored 100 on the 1 year follow up KOOS and Kujala scales, respectively. On the IKDC scale a borderline total count of 40 (15.2%) patients scored 100 points, but 15 (5.7%) additional patients scored 98.91 on this scale, making a total of 20.9% of the patient population at almost the top percentage of the scale.

Conclusions

BPII 2.0 score was found to be the most sensitive to change following surgery, and the only scale that did not have a ceiling effect. The moderate correlation between BPII 2.0 and the other three scales emphasizes the limited interchangeability between the scores, that measure different outcome dimensions.