Soft tissue fillers: an overview

The worldwide search for the ideal soft tissue filler material continues. The authors focus on the stringent safety and efficacy requirements for soft tissue fillers and provide an overview of the current natural and synthetic materials. (Aesthetic Surg J 2001;21:469-471.).

The effects of dynamic tension and reduced graft size on muscle regeneration in rabbit free muscle grafts

In a study of 28 adult New Zealand White rabbits, the influence of tension and size on muscle regeneration in tibialis anterior free muscle grafts (without vascular anastomoses) was examined 6 months after transplantation. Three laboratory models were studied: (1) whole dynamic (WD) graft (allowing ankle excursion and, therefore, variable dynamic physiologic tension), (2) whole static (WS) graft (constant, fixed length and, thus, only isometric tension), and (3) longitudinally sliced (reduced radius) dynamic (SD) model. Bilateral orthotopic grafts of the tibialis anterior muscle were performed in 24 rabbits (eight animals in each of the three different model groups). Controls consisted of normal tibialis anterior muscle from four age-matched rabbits. All tibialis anterior muscle grafts were examined histologically (fiber counts) and functionally (determined by in situ contractile properties under maximal stimulation conditions). The WD grafts demonstrated a significantly higher number of regenerated fibers per muscle cross section (4819 +/- 589) than the WS (2221 +/- 603) or SD (1919 +/- 732) grafts. The amount of tetanic tension in the WD grafts was 35 percent of the control and twice as much as that of the WS grafts (WD 1.0 +/- 0.2 kg versus WS 0.5 +/- 0.4 kg; p less than 0.05). The SD grafts produced approximately one-third as much maximum tetanic tension as the WD grafts (0.3 +/- 0.1 kg versus 1.0 +/- 0.2 kg), demonstrating that the amount of recovery was similar in these two dynamic models, since only the longitudinal middle third of the muscle was grafted in the SD model. Free muscle grafts under dynamic tension, which allows excursion, have shown a greater amount of muscle-fiber regeneration and restoration of function compared with a graft with fixed length. The positive effect of dynamic mechanical tension on small autogenous free muscle grafts (without vascular anastomoses) is clinically significant in the reconstruction of facial and hand neuromuscular deficits when blood vessels are not available for reanastomosis. Future studies using the tibialis anterior WD and SD transplant models will strengthen our understanding of the events of spontaneous revascularization and skeletal muscle regeneration.

The effect of rigid internal fixation on cranial growth

As the use of rigid internal fixation of the facial skeleton has become routine in adults, many craniofacial surgeons have expanded its use to the pediatric population. The effects of miniplate and screw fixation on subsequent craniofacial growth, however, have not been examined. Using 6-week-old rabbits as an experimental model, miniplates were placed across the right coronal suture. Calvarial changes were measured by direct osteometry on dry skull preparations. Compared with the control group, a significant reduction in growth was noted across the plated suture and adjacent bones. Because secondary growth disturbances can be produced with the use of these fixation devices, their use in the pediatric population should be viewed cautiously.