Effects of hyperbaric oxygen therapy on rabbit skeletal muscle during extremity lengthening

Extremity lengthening through distraction osteogenesis is limited by the surrounding skeletal muscle and neurovascular structures rather than the bone itself. The purpose of this study is to evaluate the effects of hyperbaric oxygen therapy on skeletal muscle during distraction osteogenesis.

Twenty New Zealand white rabbits were randomly divided into two groups. Right tibia of all rabbits was distracted at a rate of 0.125 mm per 6 h (0.5 mm/day) for 10 days with circular external fixator. Experimental group rabbits (N=10) underwent 2.5 ATA hyperbaric oxygen therapy for 2 h everyday for 20 days, control group rabbits (N=10) did not receive any corresponding treatment. Skeletal muscle perfusion was evaluated with scintigraphy before and after the distraction period. Serum CPK, LDH and AST levels were measured before and after the distraction period. All animals were killed on the 27th day. The right tibias of all animals were removed and tibialis posterior muscle was harvested for histopathologic and histomorphometric assessment with light and electron microscopy.

Skeletal muscle perfusion was decreased in the control group in comparison with pre-distraction level (P=0.008). However, no significant decrease was observed in the experimental group (P=0.678). There were no statistical differences in serum CPK, LDH and AST levels between groups (P=0.340, P=0.077, P=0.796). The mean area of the muscle fibers was measured as 398.66+/-9.16 micro2 in the experimental group and 349.44+/-5.76 micro2 in the control group (P=0.000) with light microscopy. Mild fibrosis was observed in connective tissue component of muscle tissue in control group. An average of 26 myofibrils (20-32) was counted in a 16-cm2 unit area in experimental group and 50 myofibrils (35-65) in the control group with electron microscopy. Enlargement in the sarcoplasmic reticulum, degenerative changes in nuclear cytoplasm and increase in myofibril diameter were observed in the control group, which was not observed in the experimental group

Results of this study suggest that HBO treatment alleviates the detrimental effects of distraction on skeletal muscles and preserves its ultrastructure.