Effects of extracorporeal shock waves on the healing of bone nonunion in animals

Jun ZHONG; Jiayuan LI; Jianghua MING; Hao PENG; Shiqing LIU; Yiqiang WANG; Liangbo XIA

ABSTRACT

BACKGROUND:

The therapy of nonunion has been a difficult issue in orthopedics all the time. Part of nonunion can't heal even after many times of operations. The effects of non-surgical treatments are not satisfactory. Extracorporeal shock waves (ESW) is a new method that popular abroad in recent years.

OBJECTIVE:

To investigate the effect of ESW on nonunion, and preliminarily probe into its mechanism.

DESIGN:

Randomized group-division design, animal experiment.

SETTING:

Department of Orthopedics, Renmin Hospital of Wuhan University.MATERIALS The experiment was conducted in the Medical Experimental Center of Animal, Wuhan University from September 1997 to March 1999. Forty healthy male rabbits were selected to establish model of nonunion. Thirty-two rabbits with hypertrophic nonunion were taken as materials and randomly divided into treatment group and control group with 16 rabbits in each group.

METHODS:

A multifunctional ESW apparatus of type HX902Ⅲ was adopted to treat the broken ends of nonunion in the treatment group with the energy, frequency, dose and focus range of 0.54 m J/mm2, 60 times/minute,2 000 times and 1.5 cm2 respectively. The second focus of shock wave was adjusted, aiming at corresponding parts in distal and proximal sites of nonunion, and acted 1 000 times. After that, rabbits were re-fixed with external apparatus and acted freely. Rabbits in the control group were fixed with external apparatus without any other treatments.MAIN OUTCOME

MEASURES:

Examination of the healing of nonunion with radiograph, transmission electron microscope (TEM) and in histology.

RESULTS:

A total of 32 enrolled animals were involved in the analysis of results.①X-ray photograph During the treatment with ESW, the gaps of nonunion were more and more indistinct in X-rays, and the densities of two sclerotic ends were reduced, and the sclerotic marrow cavities became unobstructed. The X-rays of nonunion-gaps before ESW were significantly narrowed than those after the treatment. At 6 weeks after the treatment,nonunion in 6 rabbits of the treatment group (6/14) healed, and that in 12 animals (12/12) healed on the 12th week. However, only the nonunion in one rabbit (1/12) healed in the control group on the 12th week. Test of fourfold-table exact probability demonstrated that the healing status of nonunion in the treatment group was better than the control group, and the differences were remarkable (P＜0.001).②Examination under light microscope large quantity of osteoblasts and mesenchymal cells assembled and were active in proliferation on the 2nd week of treatment in the treatment group, and plentiful bone trabeculae formed on the 6th week, and the nonunion healed on the 12th week of treatment. However, there were chronic inflammation and few trabeculae in the control group. ③TEM examination the osteoblasts in the treatment group proliferated on the 2nd week of treatment, and there were abundant chondrosomes in the intracytoplasm,which could secrete collagen fibers with periodical transverse lines. On the 6th week, large amount of bone lacunas formed. However, little visible cells could be seen in the control group, and osteoclasts were found in act.

CONCLUSION:

The effect of ESW on hypertrophic nonunion is satisfactory, which may become a reliable and non-invasive treatment of nonunion.