Histomorphometric characteristics of the tibialis anterior muscle and the peroneal nerve in experimental repair of post-resection tibial defect using the Ilizarov external fixation and the masquelet technique

Objective Explore structural changes in the tibialis anterior muscle (TAM) and the peroneal nerve (PN) in repair of postresection tibial defect using the Ilizarov external fixation and a cement spacer. Material and methods A defect-nonunion was simulated in the proximal tibia of 10 mongrels using the Ilizarov external fixation followed by use of a cement spacer to fill the 2.5 cm defect-diastasis. The spacer was removed after 30 days and tibia distraction commenced with the rate of 1 mm performed 4 times/day following transverse osteotomy in the distal tibia to achieve docking of bone fragments. Animals were sacrificed after 60-day fixation (F60) and 30 days after frame removal (FR30). Histomorphometric parameters of the TAM and PN samples were examined. Results TAM appeared to be denervated with death or decreased size of myons and angular contours noted at F60 and FR30. Degenerated and intact muscle fibers (MF) were shown to increase by 32.5 % and by 1 %, respectively, at FR30. The peak of histogram distributing MF by diameters at F60 indicated to ischemic muscles, and a 2-fold decrease in muscle diameter and the histogram skewed to the left by 4 classes showed increase in muscle atrophy at FR30. Reactive destructive changes were noted in at least 5.4 % of myelinated nerve fibres of the PN at F60 and FR30. A 1.6-to-1.7 times decrease in larger and a 1.6-to-1.8 times increase in smaller fibers, the presence of regenerative clusters indicated to previous destruction of a large number of motor and sensory nerves. Changes in the population structure, destruction of myelinated fibers and loss of non-myelinated fibers were associated with obliteration of epineurial vessels and loss of endoneurial capillaries at F60. Conclusion Reactive destructive changes in the TAM and PN revealed in bone defects repaired with the Ilizarov external fixation and the Masquelet technique should be considered in planning of postoperative pharmacologic thearapy and rehabilitation.