Measuring limb length : an intra and inter-rater reliability study.

Abstract

Background

Limb Length Discrepancy (LLD) is defined as a condition in which paired limbs are unequal. The difference in limb length may result in a number of clinical problems affecting gait such as low back pain, hip osteoarthritis, stress fractures, altered balance and associated running injuries. Measurement of LLD can be performed in a number of ways, with the gold standard being the use of radiographic methods which, however have significant drawbacks in being expensive, expose patient to radiation and are time consuming. Measuring LLD with a tape measure is cheap, readily available and is the fastest method; however its reliability is questionable.

Aim

The aim of this study was to investigate the Intra- and Inter-rater reliability of measuring LLD using a Tape Measure by raters of different clinical experience. Research Design and Method A convenience sample of thirty healthy participants, with a mean age of 19.97 years (SD- 1.47 years) enrolled in this study. Participants were assessed for LLD using a Tape Measure. Three Podiatrists, with varying years of experience, performed the required tests. The measurements were taken from the Anterior Superior Iliac Spine to Medial Malleolus and from Anterior Superior Iliac Spine to Lateral Malleolus. The same measurements were taken for a second time after a period of 15 days. The raters were blinded throughout all the data collection.

Results

This study found low Intra and Inter-rater Reliability when using the Tape Measure to calculate LLD in healthy individuals. The lntra-rater reliability results for Limb Length Discrepancy measured over the medial side had an Intra Class Con-elation Coefficient (ICC) of 0.324 and 0.481 for raters B and C, respectively. The results for the measurements taken over the Lateral side had an ICC of 0.324 and 0.317 for raters B and C, respectively. The results for rater A were not significant and had to be discarded. The Inter-rater measurements taken over the lateral aspect on Day 0, resulted in an lnter-rater reliability of ICC 0.206. The other three results had to be discarded since they were not significant. Results showed that the years of clinical experience had no significant effect on the reliability of the measurements taken.

Conclusion

The study confirmed that there is poor Intra-rater reliability when measuring LLD; thus it is questionable whether these measurement techniques can be utilized clinically. Both measurements taken over the Medial and Lateral aspect showed almost equal reliability, with the Medial aspect proving to be slightly more reliable, though still considered as poorly reliable. Inter-rater reliability was lower than the lntra-rater reliability results. The results confirmed that the reliability of the tape measure is not dependant on the duration of clinical experience of the raters and caution should be exercised when applying this test to clinical decision making.