Background/Purpose:

Involvement of the hips are relatively common in AS and associated with a higher degrees of disability and worse prognosis. The measurements of spinal mobility could be used for predicting clinical involvement and monitoring disease severity. In this regard, intermalleolar distance (IMD) < 100 cm suggests hip disease in AS. There are two reccommended methods of measuring IMD. First, distance between the two medial malleoli is measured, with the patient lying in a supine position with the hips fully abducted. Second, the patient stands and separates the legs as far as possible and the distance between the medial malleoli is measured. Alternatively, some physicians measure IMD in sitting position, while keeping knees and the legs straight in contact with the resting surface, patient is then asked to take legs as far apart as possible, and the distance between the medial malleoli is measured. Today, it is not known whether these three methods are in agreement with each other. In this study, we evaluated the agreement of IMD measurement methods performed during standing, sitting and supine positions.

Methods:

In total of 61 consecutive AS patients (44.1±12.3 years; 35 male, and 26 female) , were included in the study. Each patient was examined independently by two observers. Reproducibility of the methods and reliability of observers were evaluated by means of the single measures intraclass correlation coefficient (ICC) values. For the analysis of intra- and interobserver variability, ten randomly chosen patients were reexamined by the observers on two different occasions (2 weeks apart). An ICC value of > 0.75 indicated good agreement.  

Results:

The three measurement methods of IMD showed good agreement between each other (Table 1). The ICCs obtained by each observer were as follows : 1- measurements performed by the observer 1: 0.81 (95% CI= 0.73-0.88), and 2- measurements performed by observer 2: 0.81 (95%CI= 0.72-0.87). Both intra- and interobserver reliability of the observers also showed good agreement (Table 1). 

Conclusion:

In this study we showed that IMD measurements (supine, standing and sitting) were in good agreement with each other. It is of note that this finding obtained independently by both observers who had also good intra- and interobserver reliability. According to the results of our study investigators can reliably use any IMD measurement methods in their studies.

Table 1: Comparison of agreement between three methods of IMD measurements and intra- and inter-observer reliability of the examiners.

 

	Observer 1	Observer 2
Comparison of agreement between three methods of IMD measurements	0.81 (0.73-0.88)	0.81 (0.72-0.87)
Intra-observer reliability of observers
Supine	0.98 (0.91-0.99)	0.99 (0.97-0.99)
Standing	0.97 (0.88-0.99)	0.99 (0.97-0.99)
Sitting	0.88 (0.6-0.97)	0.98 (0.94-0.99)
Inter-observer reliability of observers
Supine	0.96 (0.85-0.99)
Standing	0.99 (0.98-0.99)
Sitting	0.99 (0.97-0.99)

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/a-comparison-of-three-methods-of-measuring-intermalleolar-distance-in-patients-with-ankylosing-spondylitis/