The effects of tibial fracture and Ilizarov osteosynthesis on the structural reorganization of sciatic and tibial nerves during the bone consolidation phase and after fixator removal.

Tatyana N Varsegova,Marat S Saifutdinov,Mikhail A Stepanov,Mikhail M Shchudlo,Natalia A Shchudlo

doi:10.1007/s11751-015-0227-1

Abstract

Reactive and adaptive changes in mechanically uninjured nerves during fracture healing have not been studied previously although the status of innervation is important for bone union and functional recovery. This study explores whether subclinical nerve fibre degeneration occurs in mechanically uninjured nerves in an animal fracture model and to quantify its extent and functional significance. Twenty-four dogs were deeply anaesthetized and subjected to experimental tibial shaft fracture and Ilizarov osteosynthesis. Before fracture and during the experiment, electromyography was performed. In 7, 14, 20, 35–37 and 50 days of fixation and 30, 60–90 and 120 days after fixator removal, the dogs were euthanized. Samples from sciatic, peroneal and tibial nerves were processed for semithin section histology and morphometry. On the 37th postoperative day, M-response amplitudes in leg muscles were 70 % lower than preoperative ones. After fixator removal, these increased but were not restored to normal values. There were no signs of nerve injuries from bone fragments or wires from the fixator. The incidence of degenerated myelin fibres (MFs) was less than 12 %. Reorganization of Remak bundles (Group C nerve fibres—principally sensory) led to a temporal increase in numerical nerve fibre densities. Besides axonal atrophy, the peroneal nerve was characterized with demyelination–remyelination, while tibial nerve with hypermyelination. There were changes in endoneural vessel densities. In spite of minor acute MF degeneration, sustained axonal atrophy, dismyelination and retrograde changes did not resolve until 120 days after fracture healing. Correlations of morphometric parameters of degenerated MF with M-response amplitudes from electromyography underlie the subclinical neurologic changes in functional outcomes after tibial fractures even when nerves are mechanically uninjured.

Highlights

The shaft of the tibia is the commonest site of closed and open fractures, but the optimum treatment option remains the subject of debate
The peroneal nerve was characterized with demyelination–remyelination, while tibial nerve with hypermyelination
Ilizarov osteosynthesis is considered as a preferred, safe and effective method in open, wedged and complex tibial fractures [7,8,9,10,11], but one disadvantage is the use of wires situated close to nerves [12]

Summary

Introduction

The shaft of the tibia is the commonest site of closed and open fractures, but the optimum treatment option remains the subject of debate. The standard treatment for tibial diaphyseal fractures is intramedullary nailing. This treatment option has resulted in a good ability for the patients to return to work, especially after interlocked nailing [1]. Ilizarov osteosynthesis is considered as a preferred, safe and effective method in open, wedged and complex tibial fractures [7,8,9,10,11], but one disadvantage is the use of wires situated close to nerves [12]. The well-known classification of nerve injuries are applied usually to clinical

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