Determination of calcaneal ultrasound properties ex situ: reproducibility, effects of storage, formalin fixation, maceration, and changes in anatomic measurement site.
The objective of this study was to determine the reproducibility of ultrasonic bone properties with a system for measuring calcanei ex situ; the influence of changes of the measurement site; and the effects of fixation, storage, and maceration. We examined 14 fixed calcanei and 12 fresh bones. Ultrasonic measurements were performed ex situ after degassing, using an Achilles+ system and a special positioning device. The instrument precision was 0.16% for speed of sound (SOS), 1.4% for broadband ultrasonic attenuation (BUA), and 1. 8% for the stiffness index (SI). The short-term precision was 0.54%, 1.9%, and 2.8%, respectively. A defined shift of the measurement site (5 mm distal of the middle) led to unpredictable changes in ultrasound (US) properties (r = 0.65 for SOS, 0.82 for BUA, and 0.75 for SI). Embalment with 4% formalin/96% alcohol caused a systematic decrease in SOS, an increase in BUA, and a decrease in SI (mean = -12.7 units; P < 0.001), the effect increasing with time. However, values at 6 months of fixation and later were highly correlated with those in fresh specimens (r = 0.95 for the SI). Two weeks storage in degassed and normal solution had only modest effects on ultrasound properties. Maceration did not lead to a systematic increase or decrease of ultrasound variables, but introduced unpredictable changes (r = 0.64-0.94). We conclude that in comparative biomechanical studies it is feasible to measure calcaneal specimens embalmed in formalin/alcohol ex situ, if the primary interest is not in the absolute values but in the correlation with mechanical failure loads at other skeletal sites.
Pöpperl
G
G
I. Frauenklinik der Ludwig-Maximilians-Universität München, Maistr. 11, D-80337 München, Germany.
Lochmüller
E
E
Becker
H
H
Mall
G
G
Steinlechner
M
M
Eckstein
F
F
D000368:Aged; D000369:Aged, 80 and over; D002111:Calcaneus / Q000000981:diagnostic imaging*; D005260:Female; D005404:Fixatives; D005557:Formaldehyde; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D013048:Specimen Handling; D016707:Tissue Fixation; D014463:Ultrasonography
D005404:Fixatives; D005557:Formaldehyde