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Computed tomography scanogram compared to long leg radiograph for determining axial knee alignment.

Holme TJ, Henckel J, Hartshorn K, Cobb JP, Hart AJ - Acta Orthop (2015)

Bottom Line: Statistically significant and clinically relevant differences were found between CTS and LLR in measurement of the mechanical axis (limits of agreement: UKR -3.2° to 6.3°; native -3.2° to 5.6°) and the anatomical axis (limits of agreement: UKR -3.7° to 8.7°; native -2.0° to 8.8°).Although it is a reliable tool, CTS is not necessarily an accurate one for measurement of knee alignment when compared to LLR.We recommend that CTS should not be used as a substitute for LLR in measurement of the mechanical or anatomical axes of the knee.

View Article: PubMed Central - PubMed

Affiliation: Department of Trauma & Orthopaedics, University College London.

ABSTRACT

Background and purpose: Supine computed tomography scanogram (CTS) is a commonly used alternative to weight bearing long leg plain radiograph (LLR) in measuring knee alignment. No published studies have validated its use in the native knee and the post-unicompartmental replacement knee (UKR). We quantified the difference in measurements obtained from CTS and LLR for knee alignment.

Patients and methods: Supine CT scanograms and weight bearing long leg plain anteroposterior radiographs were obtained for 40 knees (in 25 patients), 17 of which were native, and 23 of which were post-UKR. The mechanical and anatomical axes of the tibio-femoral joint were measured. Bland-Altman plots were used to calculate the 1.96 standard deviation limits of agreement between CTS and LLR. Intraclass correlation was used to assess intra-rater and inter-rater reliability (where values > 0.81 indicate very good reliability).

Results: CTS and LLR were equally reliable in measurement of the mechanical and anatomical axes of the tibio-femoral joint (intraclass correlation coefficient (ICC) > 0.9 for all parameters). Statistically significant and clinically relevant differences were found between CTS and LLR in measurement of the mechanical axis (limits of agreement: UKR -3.2° to 6.3°; native -3.2° to 5.6°) and the anatomical axis (limits of agreement: UKR -3.7° to 8.7°; native -2.0° to 8.8°).

Interpretation: Although it is a reliable tool, CTS is not necessarily an accurate one for measurement of knee alignment when compared to LLR. We recommend that CTS should not be used as a substitute for LLR in measurement of the mechanical or anatomical axes of the knee.

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Related in: MedlinePlus

Bland-Altman plot of the differences in measurement of mechanical knee alignment between CTS and LLR (native knee).
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Figure 4: Bland-Altman plot of the differences in measurement of mechanical knee alignment between CTS and LLR (native knee).

Mentions: The correlation coefficient r was 0.83 (95% CI: 0.63–0.93; p < 0.001). 15 of 23 measurements were more than 2.5° different.


Computed tomography scanogram compared to long leg radiograph for determining axial knee alignment.

Holme TJ, Henckel J, Hartshorn K, Cobb JP, Hart AJ - Acta Orthop (2015)

Bland-Altman plot of the differences in measurement of mechanical knee alignment between CTS and LLR (native knee).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4513598&req=5

Figure 4: Bland-Altman plot of the differences in measurement of mechanical knee alignment between CTS and LLR (native knee).
Mentions: The correlation coefficient r was 0.83 (95% CI: 0.63–0.93; p < 0.001). 15 of 23 measurements were more than 2.5° different.

Bottom Line: Statistically significant and clinically relevant differences were found between CTS and LLR in measurement of the mechanical axis (limits of agreement: UKR -3.2° to 6.3°; native -3.2° to 5.6°) and the anatomical axis (limits of agreement: UKR -3.7° to 8.7°; native -2.0° to 8.8°).Although it is a reliable tool, CTS is not necessarily an accurate one for measurement of knee alignment when compared to LLR.We recommend that CTS should not be used as a substitute for LLR in measurement of the mechanical or anatomical axes of the knee.

View Article: PubMed Central - PubMed

Affiliation: Department of Trauma & Orthopaedics, University College London.

ABSTRACT

Background and purpose: Supine computed tomography scanogram (CTS) is a commonly used alternative to weight bearing long leg plain radiograph (LLR) in measuring knee alignment. No published studies have validated its use in the native knee and the post-unicompartmental replacement knee (UKR). We quantified the difference in measurements obtained from CTS and LLR for knee alignment.

Patients and methods: Supine CT scanograms and weight bearing long leg plain anteroposterior radiographs were obtained for 40 knees (in 25 patients), 17 of which were native, and 23 of which were post-UKR. The mechanical and anatomical axes of the tibio-femoral joint were measured. Bland-Altman plots were used to calculate the 1.96 standard deviation limits of agreement between CTS and LLR. Intraclass correlation was used to assess intra-rater and inter-rater reliability (where values > 0.81 indicate very good reliability).

Results: CTS and LLR were equally reliable in measurement of the mechanical and anatomical axes of the tibio-femoral joint (intraclass correlation coefficient (ICC) > 0.9 for all parameters). Statistically significant and clinically relevant differences were found between CTS and LLR in measurement of the mechanical axis (limits of agreement: UKR -3.2° to 6.3°; native -3.2° to 5.6°) and the anatomical axis (limits of agreement: UKR -3.7° to 8.7°; native -2.0° to 8.8°).

Interpretation: Although it is a reliable tool, CTS is not necessarily an accurate one for measurement of knee alignment when compared to LLR. We recommend that CTS should not be used as a substitute for LLR in measurement of the mechanical or anatomical axes of the knee.

Show MeSH
Related in: MedlinePlus