ABSTRACT
Peroneal neuropathy is one of the complications of orthopaedic leg lengthening. Methods of treatment include slowing of distraction and decompression both of which may lead to additional complications. The purpose of this study was to analyse the changes in histologic peroneal nerve structure during experimental orthopaedic lengthening using various modes of manual or automatic distraction. The obtained data provide the basis for better understanding of peroneal neuropathy pathogenesis and refinement of prophylaxis and preventive treatment protocols. Four experimental models of canine leg lengthening using the Ilizarov fixator were studied: 1 (n = 10)-manual distraction-1 mm/day divided into four increments; 2 (n = 12)-automatic distraction-1 mm/day in 60 increments, 3 (n = 9) and 4 (n = 9)-increased rate of high frequency automatic distraction: 3 mm/day in 120 and 180 increments, respectively. In peroneal nerves semi-thin sections cross-sectional fascicular areas, content of adipocytes in epineurium, endoneurial vascularisation, morphometric parameters of nerve fibres were assessed by computerised analysis at the end of distraction and of consolidation periods and 30 days after fixator removal. In Groups 1-2 massive nerve fibre degeneration along with epineural vessels obliteration was revealed in two cases from 22, whereas in Groups 3-4 there were 10 from 18 (p < 0.01). Injuries of perineurium and endoneurial vessels were noted in Group 3, and long-lasting thinning of nerve fascicles in Group 4. The decrease in epineurial fat tissue was revealed in all groups, more drastic in 3. Modifications and injuries of nerve sheaths and blood vessels depending on distraction rate and frequency contribute to peroneal neuropathy. Its mechanical, circulatory and metabolic causes are discussed.
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.
ABSTRACT
PURPOSE: This pilot study aimed to test the theory that different lengthening methods affect the microscopic structure of knee joint synovium in diverse ways. METHODS: This was a descriptive and analytical cross-sectional study of synovium carried out in two experimental models of canine leg lengthening using the Ilizarov fixator. Group 1 (n = 6) used manual gradual distraction most commonly used in clinical practice at one millimetre/day divided into four equal increments, 0.25 mm at each increment. Group 2 (n = 7) used an increased rate of automatic distraction at three millimetres/day divided in 120 increments, 0.025 mm at each increment. At the end of distraction and after fixator removal, the animals were euthanised. Control was via intact dogs. The thickness of the synovial lining layer, number of synovial cell rows, and numerical density of subsynovial microvessels were assessed in digital images for semiautomated computerised analysis of semi-thin sections stained with toluidine blue and methylene blue-basic fuchsin. Comparison of synovitis manifestation was made with grading scale. The vascular and nerve changes in the subsynovial layer were also compared. RESULTS: Group 1 developed marked synovitis, synovium hypervascularisation, degeneration of the nerve fibres in subsynovial nerves with the tendency to regeneration. Group 2 had moderate to mild degree of synovitis with progressive degenerative changes in subsynovial vessels and nerves. CONCLUSION: Both methods used are unfavourable for the state of the joint synovium, but modify it in different ways.
