A common complication of reconstructive surgery is muscle contracture and consequent loss of joint motion. This particularly occurs in surgical lengthening procedures where the muscle adaptive capacity seems to limit the extent of possible lengthening. We used intraoperative laser diffraction to determine the skeletal muscle adaptation that occurred in a 16-year-old girl who had 4-cm femoral lengthening for a leg-length discrepancy secondary to posttraumatic growth arrest. Fascicle length changed dramatically during distraction from a starting value of approximately 9 cm to a new length of 19 cm. In vivo vastus lateralis sarcomere length measured intraoperatively at the initial surgery was 3.64 µm, whereas sarcomere length measured 8 months later was 3.11 µm. The fact that fascicle length increased dramatically and in vivo sarcomere length decreased slightly reveals an increase in serial sarcomeres from 25,000 to 58,650. This direct measurement of fascicle length and sarcomere length confirms sarcomerogenesis in human skeletal muscle secondary to chronic length change, and shows the capacity of human muscle to adapt to length changes.

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