Cross-Sectional Comparison of Extended Anteroposterior and Posteroanterior Fixed Flexion Positioning to Assess Radiographic Osteoarthritis at the Knee: The Johnston County Osteoarthritis Project

University of North Carolina, Chapel Hill, NC 27599-7280, USA.
Arthritis care & research 09/2010; 62(9):1342-5. DOI: 10.1002/acr.20210
Source: PubMed

ABSTRACT To compare values for Kellgren/Lawrence (K/L) scale grade, joint space narrowing (JSN), and osteophytes in anteroposterior (AP) extended and fixed flexion posteroanterior (PA) radiographs obtained during a single clinic visit (the first followup of the Johnston County Osteoarthritis Project).
All films (n = 1,664 bilateral knees) were read by an experienced musculoskeletal radiologist. For each subject, AP and PA fixed flexion films were read in one sitting. K/L scale grades (range 0-4) and JSN and osteophytes (ranges 0-3) were assessed using standard atlases. Descriptive statistics were calculated for demographic and clinical variables. AP and PA fixed flexion results were compared by contingency table methods to obtain frequencies for K/L scale, JSN, and osteophyte grades using percent agreement and kappa coefficients. Results from the right and left knees were similar; data for the right knee are presented.
There was substantial agreement between AP and PA fixed flexion reads for radiographic osteoarthritis, defined as a K/L scale grade ≥ 2 (89% agreement; κ = 0.73, 95% confidence interval 0.69-0.76). Substantial agreement was also seen for tibial osteophytes and medial JSN; slightly lower kappa values were observed for femoral osteophytes and lateral JSN.
The requirements of large observational cohort studies are different than those of clinical trials, and sensitivity is less of an issue because of longer followup times. In cohort studies such as the Johnston County Osteoarthritis Project, there is substantial agreement by K/L scale grade for AP and PA fixed flexion radiographs, allowing incorporation of older films in longitudinal analyses.


Available from: Todd Schwartz, Jan 08, 2015
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    ABSTRACT: Although osteoarthritis (OA) commonly involves multiple joints, no widely accepted method for quantifying whole-body OA burden exists. Therefore, our aim was to apply factor analytic methods to radiographic OA (rOA) grades across multiple joint sites, representing both presence and severity, to quantify the burden of rOA. We used cross-sectional data from the Johnston County Osteoarthritis Project. The sample (n = 2092) had a mean age of 65 ± 11 years, body mass index (BMI) 31 ± 7 kg/m2, with 33% men and 34% African Americans. A single expert reader (intra-rater κ = 0.89) provided radiographic grades based on standard atlases for the hands (30 joints, including bilateral distal and proximal interphalangeal [IP], thumb IP, metacarpophalangeal [MCP] and carpometacarpal [CMC] joints), knees (patellofemoral and tibiofemoral, 4 joints), hips (2 joints), and spine (5 levels [L1/2 to L5/S1]). All grades were entered into an exploratory common factor analysis as continuous variables. Stratified factor analyses were used to look for differences by gender, race, age, and cohort subgroups. Four factors were identified as follows: IP/CMC factor (20 joints), MCP factor (8 joints), Knee factor (4 joints), Spine factor (5 levels). These factors had high internal consistency reliability (Cronbach's α range 0.80 to 0.95), were not collapsible into a single factor, and had moderate between-factor correlations (Pearson correlation coefficient r = 0.24 to 0.44). There were no major differences in factor structure when stratified by subgroup. The 4 factors obtained in this analysis indicate that the variables contained within each factor share an underlying cause, but the 4 factors are distinct, suggesting that combining these joint sites into one overall measure is not appropriate. Using such factors to reflect multi-joint rOA in statistical models can reduce the number of variables needed and increase precision.
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