Background: Although distraction osteogenesis is a recently established method of limb lengthening, it is not well known how soft tissues behave during bone lengthening. Because skin is tissue that can be easily and directly observed, we analyzed skin extension during limb lengthening to study the condition of soft tissues.
Method: We examined three achondroplastic and two hypochondroplastic patients who underwent bilateral tibial lengthening with unilateral bone lengtheners. To analyze skin extension during leg lengthening, the bilateral skin surface was marked in a latticework pattern, starting 10 cm proximal to the knee joint down to 10 cm distal to the ankle joint, with black ink. The longitudinal length and the area of lattices, and the circumferential length of legs were measured.
Results: We found that: (1) the longitudinal extension of the skin during leg lengthening occurs not only in the bone lengthening portion between fixator pins but also around the knee or ankle joints; (2) circumferential length of legs was decreased, and soft tissue volume also does not increase in proportion to the increase in leg length. Soft tissue volume started to increase in the central region of the legs after a 30% increase in leg length was obtained, resulting in the 10% increase in the volume at the end point.
Conclusions: These data suggest that soft tissue extension precedes soft tissue neogenesis at least during the initial period of leg lengthening, possibly based on its viscoelastic properties. After a 30% increase in leg length is obtained, soft tissue neogenesis takes place in the central region of the leg.