Morphological Changes in the Tibial Nerve During the Treatment of Large Tibia Defects Using Ilizarov Apparatus Combining with the Masquelet Technique: Experimental Study

Abstract

Background. The use of Masquelet technology in combination with non-free osteoplasty according to Ilizarov in order to compensate large defects of the lower leg bones provides proper bone union and recurrence-free course of the disease, but the problem of patient rehabilitation remains relevant. The course and duration of the recovery period depend on the morphofunctional state of the tibial nerves. The purpose of this study was to determine morphological changes in the tibia nerve of dogs during the experimental treatment of large tibial defects using Ilizarov apparatus combining with the Masquelet technique. Materials and Methods. A defect of the upper third of the tibia in the form of false joint was created in 10 mongrel dogs. Then this defect was replaced with 25 mm diastasis, into which a cement spacer was placed. After 30 days, the latter was removed. At the level of the lower third, transverse osteotomy was performed, as well as distraction of 1 mm rate for 4 times per day, until complete contact of the fragments in the defect zone. The tibial nerves were studied within the periods of 60 days of fixation (F60) and 30 days after the fixator removal (FR30). Results. There were no mechanical damages of the nerves. During the experiment a part of epineural veins and arteries had obliterated lumens, two-fold decrease in the numerical density of endoneural arterioles, venules and capillaries was observed in FR30 — 97.5±2.5 in 1 mm2 (normally — 182.0±22.0), that evidenced of microcirculatory disorders progressing towards the end of the experiment. Patterns of Wallerian degeneration were found along with typical damages to fibers during distraction osteosynthesis demyelination and axonal degeneration. In F60 the proportion of modified fibers was 7.7±1.5%, which was 4.8 times higher (р = 0.52×10-5) above normal, the numerical densities and dimensional characteristics of fibers decreased. At the end of the experiment, the proportion of modified conductors 2.3-fold exceeded the norm (p = 0.33×10-4) — 3.7±0.4%, the numerical density of fibers remained 10.2% below the norm (p = 0.0362), making up 17436±865, but the average axon diameter and thickness of myelin sheaths were restored. Conclusion. Microcirculatory dysfunction, axonal atrophy, demyelination, Wallerian degeneration of a part of myelin nerve fibers and a decrease in their number revealed in the tibial nerves during the treatment of large tibia defects using the Masquelet technique combining with Ilizarov non-free bone grafting indicated the need for the use of adequate neurometabolic pharmacotherapy and effective rehabilitation.

Keywords

• tibia defect
• masquelet technique
• tibial nerve
• histomorphometry