Reliability and precision of single frequency bioelectrical impedance assessment of lower extremity swelling following total knee arthroplasty.
Brian J Loyd, Kristine Burrows, Jeri E Forster and 3 others
PMID 31140887WHAT IT FOUND
Single-frequency bioelectrical impedance assessment is highly reliable for measuring leg swelling after knee replacement.
It detects smaller true changes than tape measurements. A 2% reduction in swelling is considered a real change, helping therapists judge if treatment is working.
Key findings
01SF-BIA showed high test-retest reliability (ICC > 0.8) before and after surgery, whereas circumferential measurements were much less reliable.
02The minimal detectable change for SF-BIA was lower than for tape measures, meaning it can identify smaller true changes in swelling.
03A percent reduction in swelling of 2% or more using SF-BIA is considered a true detectable change.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
No a priori power analysis was performed because the study used a convenience sample from a larger trial. Reliability testing was limited to a smaller sample than the total number of participants. Only one assessor was available for many measurements, which prevented a full inter-rater reliability analysis and limited the interpretability of some statistics. The study only examined the first six weeks after surgery, so it does not provide data on swelling changes beyond this window. SF-BIA was compared only to circumferential measurements, not to other methods like MRI or water displacement.
Declared interests
The authors declare no conflict of interest.
The easy way to misread this
Do not assume SF-BIA is superior to all other swelling measures. This study only compared it to tape measures. It did not evaluate it against more expensive or complex methods like MRI or water displacement, which may still offer different advantages.