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Weerasekara I1,2, Osmotherly P1, Snodgrass S1, Tessier J1, Rivett D1
1School of Health Sciences, The University of Newcastle, Callaghan, Australia, 2Faculty of Allied Health Sciences, University of Peradeniya, Peradeniya, Sri Lanka
Background: Radiographic assessment is frequently used in determining the diagnosis and the management of ankle instability. Anterior positioning of the distal fibula following injury has been proposed as a factor in patients with chronic and recurrent ankle sprains and CAI. Previous radiographic studies of fibular position in such populations have reported conflicting findings as to the existence of an abnormality, possibly due to differences in subject positioning and radiographic measurement methods. No studies to date have reported diagnostic utility or cut-off scores for an abnormally positioned fibula in relation to the tibia. Further, reliability of measures of fibular position from weight-bearing radiographs have not been reported.
Purpose: To assess the reliability, specificity and sensitivity of measures of fibular position (normalised to tibial width; normalised fibular position=fibular position/ maximum tibial width) x 100) from weight-bearing radiographs.
Methods: Sixty-six participants ≥18 years (CAI group=33, healthy group=33) were included in this case-control study. A weight-bearing radiograph was taken with the participant standing on the imaged ankle, with the other leg simulating the mid-stance phase of the gait cycle. The distance between the anterior edge of the distal fibula and the anterior edge of the distal tibia on the lateral X-ray was recorded as the absolute fibular position. Fibular position was normalised as a proportion of the maximum tibial width (maximum distance between anterior tibial process and posterior tibial process within the distal epiphysis), and compared between the two groups using the independent t-test.
Two independent reviewers performed measurements of fibular position and tibial width on randomly selected radiographs (n=24). Intra-class correlation coefficients (ICC2,1) were calculated to determine reliability.
A receiver operating characteristic curve was used to determine sensitivity, specificity and appropriate cut-off scores (minimal clinically important difference) that best differentiate individuals with CAI from those with healthy ankles, for normalised fibular position. The minimal detectable change (MDC) was also calculated for normalised fibular position.
Results: Normalised fibular position was significantly different (mean difference=3.01%, 95%CI=0.19-5.83, p=0.04) between the two groups. The MDC was 3.67%. Intra-rater reliability was excellent (ICC2,1=0.99, 95%CI=0.98-1.00), as was inter-rater reliability (0.98, 95%CI=0.96-.99). The threshold normalised fibular position was 27%, with a score more than 27% indicating a greater chance of being in the CAI group. Sensitivity was 69.7% and specificity 54.5%.
Conclusion(s): A more anteriorly positioned fibula in relation to the tibia was observed in participants with CAI. Weight-bearing radiographic measurement can be used with excellent reliability and reproducibility in quantifying normalised fibular position. Specificity and sensitivity scores for normalised fibular position indicate that it has very little ability to predict CAI alone.
Implications: Weight-bearing lateral radiographs are a simple and reliable way to assess relative fibular position in individuals with CAI. With further investigation, it may also prove a useful tool in defining CAI in conjunction with other diagnostic factors. Clinically, this measurement of fibular position may also be useful in determining treatment progress. Future research should include an assessment of reliability, validity and responsiveness of this measure across different subgroups (eg, structural, functional) of CAI.
Keywords: Fibular Abnormality, Validity, Ankle Instability
Funding acknowledgements: None
Purpose: To assess the reliability, specificity and sensitivity of measures of fibular position (normalised to tibial width; normalised fibular position=fibular position/ maximum tibial width) x 100) from weight-bearing radiographs.
Methods: Sixty-six participants ≥18 years (CAI group=33, healthy group=33) were included in this case-control study. A weight-bearing radiograph was taken with the participant standing on the imaged ankle, with the other leg simulating the mid-stance phase of the gait cycle. The distance between the anterior edge of the distal fibula and the anterior edge of the distal tibia on the lateral X-ray was recorded as the absolute fibular position. Fibular position was normalised as a proportion of the maximum tibial width (maximum distance between anterior tibial process and posterior tibial process within the distal epiphysis), and compared between the two groups using the independent t-test.
Two independent reviewers performed measurements of fibular position and tibial width on randomly selected radiographs (n=24). Intra-class correlation coefficients (ICC2,1) were calculated to determine reliability.
A receiver operating characteristic curve was used to determine sensitivity, specificity and appropriate cut-off scores (minimal clinically important difference) that best differentiate individuals with CAI from those with healthy ankles, for normalised fibular position. The minimal detectable change (MDC) was also calculated for normalised fibular position.
Results: Normalised fibular position was significantly different (mean difference=3.01%, 95%CI=0.19-5.83, p=0.04) between the two groups. The MDC was 3.67%. Intra-rater reliability was excellent (ICC2,1=0.99, 95%CI=0.98-1.00), as was inter-rater reliability (0.98, 95%CI=0.96-.99). The threshold normalised fibular position was 27%, with a score more than 27% indicating a greater chance of being in the CAI group. Sensitivity was 69.7% and specificity 54.5%.
Conclusion(s): A more anteriorly positioned fibula in relation to the tibia was observed in participants with CAI. Weight-bearing radiographic measurement can be used with excellent reliability and reproducibility in quantifying normalised fibular position. Specificity and sensitivity scores for normalised fibular position indicate that it has very little ability to predict CAI alone.
Implications: Weight-bearing lateral radiographs are a simple and reliable way to assess relative fibular position in individuals with CAI. With further investigation, it may also prove a useful tool in defining CAI in conjunction with other diagnostic factors. Clinically, this measurement of fibular position may also be useful in determining treatment progress. Future research should include an assessment of reliability, validity and responsiveness of this measure across different subgroups (eg, structural, functional) of CAI.
Keywords: Fibular Abnormality, Validity, Ankle Instability
Funding acknowledgements: None
Topic: Musculoskeletal: lower limb; Musculoskeletal; Sport & sports injuries
Ethics approval required: Yes
Institution: The University of Newcastle
Ethics committee: Human Research Ethics Committee
Ethics number: H-2017-0217
All authors, affiliations and abstracts have been published as submitted.
