Radiograph view influences patient selection and patient-reported outcomes in injection therapy for knee osteoarthritis

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Purpose: Knee injection therapy for osteoarthritis (OA) is less effective in advanced disease states, specifically Kellgren-Lawrence (KL) grade 4, and these patients are often excluded from knee injection trials. Evidence suggests KL grade is best determined utilizing a flexion posteroanterior (PA) radiograph; however, recent randomized trials have largely based study inclusion upon an extension AP radiograph. This study sought to determine how use of a 45-degree flexion PA radiograph influences a) patient selection for knee injection therapy and b) patient-reported outcomes following knee injection therapy. Methods: Four raters independently graded extension AP and flexion PA radiographs from 91 patients previously enrolled in a knee injection trial. Patients were excluded if they received a KL grade 4 on the extension AP radiograph by any single rater. Among included patients, those receiving a KL grade 4 on the flexion PA radiograph by at least two raters constituted Group 2, while remaining patients constituted Group 1. Demographic data and patient-reported outcome scores before injection and at six-weeks, three-months, six-months, and twelve-months post-injection were compared between groups. Results: Overall, 64 patients were included in the study, of which 19 patients (30%) constituted Group 2 (KL grade 4 on flexion PA radiograph). As compared to Group 1, patients in Group 2 were significantly older (58.7 vs. 52.3 years, p=0.02); had worse VAS pain scores before (3.4 vs. 4.7, p=0.03) and six months after injection (4.7 vs. 6.5, p=0.01); had less improvement in both Lysholm (8.5 vs. 20.5, p=0.02) and SF-12 Physical (−2.2 vs. 1.7, p=0.03) from pre-injection to six months post-injection; and, had less improvement in both Lysholm (1.6 vs. 13.1, p=0.03) and KOOS Sport (−2.1 vs. 16, p=0.01) from pre-injection to twelve months post-injection. Conclusions: As compared to the commonly used extension AP radiograph, one in three subjects were upgraded to a more advanced disease state using the flexion PA radiograph. These patients were significantly older, had significantly more pre-injection pain, and reported significantly worse post-injection outcomes. This study suggests that radiograph view can significantly influence both patient selection and outcome following knee injection therapy.Tabled 1Table 1: Patient Reported Outcomes Scores at different stages of knee injection therapy for Groups 1 and 2.Pre-injectionPost-injection (6 months)DeltaGroup 1 (n=45)Group 2 (n=19)P valueGroup 1 (n=45)Group 2 (n=19)P valueGroup 1 (n=45)Group 2 (n = 19)P valueLysholm48 ± 1551 ± 180.5268 ± 1859 ± 170.0620 ± 178.5 ± 200.02*IKDC42 ± 1440 r 130.6259 ±2050 ± 160.1615 ± 1610 ± 150.37KOOS Pain56 ± 1763 ± 170.1472 ± 1772 ± 180.9617 ±2010±210.28 Symptoms56 ± 1760 ± 230.5271 ± 1768 ±200.5513 ± 147.7 ± 190.22 ADL66 ± 2169 ± 170.7281 ± 1980 ± 170.7313 ± 188.0 ± 180.41 Sport31 ±2032 ± 140.8546 ±2839 ± 190.3714 ±206.0 ± 230.19 QOL31 ± 1942 ±210.04**51 ±2755 ±230.5520 ±2213 ±320.32WOMAC Pain7.2 ± 3.75.5 ±3.60.104.4 ±3.63.9 ±3.10.64-2.9 ±4.2-1.9 ± 4.10.41 Stiffness3.3 ± 1.83.3±2.00.992.1 ± 1.62.3 ± 1.90.75-1.2 ± 1.8-0.9 ± 2.70.64 Function23 ± 1421 ± 120.7213 ± 1314 ± 120.73-9.0 ± 12-5.4 ± 120.41 TOTAL34 ± 1930 x 170.5820 ± 1720 ± 160.92-I2± 16-7.7 ± 190.46 VAS pain (10 = best)4.7 ± 1.93.4±2.30.03**6.5 ± 2.34.7 ±2.50.01*1.7 ±2.21.2 ±2.70.47SF-12 Physical39 ± 5.940 ± 7.30.7241 ±5.637 ± 6.70.05*1.7 ±5.8-2.2 ± 70.03* Mental55 ± 9.551 ± 130.1757 ± 7.658 ± 110.581.2 ±9.56.6 ± 180.12** = statistically significant (p < 0.05).BMI = body-mass index; IKDC = International Knee Documentation Committee; KOOS = Knee Injury and Osteoarthritis Outcome Score; ADL = activities of daily living; QOL = quality of life; WOMAC = Western Ontario and McMaster Universities Osteoarthritis Index; VAS visual analog scale; SF-12 = Short Form-12. Open table in a new tab ** = statistically significant (p < 0.05). BMI = body-mass index; IKDC = International Knee Documentation Committee; KOOS = Knee Injury and Osteoarthritis Outcome Score; ADL = activities of daily living; QOL = quality of life; WOMAC = Western Ontario and McMaster Universities Osteoarthritis Index; VAS visual analog scale; SF-12 = Short Form-12.