A fetal lamb model of amniotic band syndrome (ABS) was developed to study the pathophysiology of banded extremities and evaluate the possibility of in utero treatment with the potential for functional recovery. Eight fetal lambs underwent banding of their extremities with umbilical tape at 100 days' gestation. Two lambs aborted after the open fetal surgery. The limbs of two unoperated newborn lambs served as controls in addition to five sham-operated control limbs that had no bands applied. Nine limbs were banded without reducing blood flow assessed by laser doppler (group 1), and 6 limbs were similarly banded and released fetoscopically at 125 days' gestation. Four limbs were banded, with a mean reduction in blood flow to the limb of 18.7% (group 2) by laser doppler flowmeter. Shortly after birth the lambs were killed, and segmental limb length, circumference, joint range of motion, and histology were evaluated. At birth, banded limbs showed marked brawny edema and absence of wool distal to the band. Segmental limb measurements showed shorter distal forelimbs in banded limbs compared with controls (10.97 +/- 0.59 versus 12.98 +/- 0.69, P < .05). Banded limbs were associated with progressive increase in hoof circumference (P < .03) and a decrease in joint range of motion (P < .003). In sharp contrast, there were no differences between fetoscopically released limbs and control limbs in any of the parameters measured. Histology of banded extremities showed edema, venous and lymphatic congestion, and fibrosis compared with controls. This model of ABS in fetal lambs is simple, reproducible, and replicates all the clinical features of extremity ABS.(ABSTRACT TRUNCATED AT 250 WORDS)