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- DOI: 10.1016/j.joca.2010.09.011
- PMID: 20950695
- UKPMCID: 20950695
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Does measurement of the anatomic axis consistently predict hip-knee-ankle angle (HKA) for knee alignment studies in osteoarthritis? Analysis of long limb radiographs from the multicenter osteoarthritis (MOST) study.
Sheehy, L; Felson, D; Zhang, Y; Niu, J; Lam, Y-M; Segal, N; Lynch, J; Cooke, T D V
Osteoarthritis and cartilage / OARS, Osteoarthritis Research Society. 2011;19(1):58-64.
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Full-text held externally
- DOI: 10.1016/j.joca.2010.09.011
- PMID: 20950695
- UKPMCID: 20950695
Abstract
OBJECTIVE: Researchers commonly use the femoral shaft-tibial shaft angle (FS-TS) from knee radiographs to estimate the hip-knee-ankle angle (HKA) in studies examining risk factors for knee osteoarthritis (OA) incidence and progression. The objective of this study was to determine the relationship between HKA and FS-TS, depending on the method of calculating FS-TS and the direction and degree of knee deformity. METHODS: 120 full-length digital radiographs were assigned, with 30 in each of four alignment groups (0.0°-4.9°, and ≥5.0° of varus and valgus), from a large cohort of persons with and at risk of knee OA. HKA and five measures of FS-TS (using progressively shorter-shaft lengths) were obtained using Horizons Analysis Software, Orthopaedic Alignment & Imaging Systems Inc. (OAISYS). The offsets between HKA and the different versions of FS-TS were calculated, with 95% confidence intervals (CIs). Pearson correlations were calculated. RESULTS: In varus limbs use of a shorter-shaft length increased the offset between HKA and FS-TS from 5.1° to 7.0°. The opposite occurred with valgus limbs (from 5.0° to 3.7°). Correlations between HKA and FS-TS for the whole sample of 120 individuals were excellent (r range 1.00-0.88). However, correlations for individual alignment groups were low to moderate, especially for the shortest-shaft FS-TS (r range 0.41-0.66). CONCLUSIONS: The offsets obtained using the shorter FS-TS measurements vary depending on direction and degree of knee deformity, and therefore may not provide reliable predictions for HKA We recommend that full-length radiographs be used whenever an accurate estimation of HKA is required, although broad categories of alignment can be estimated with FS-TS.