Histological evaluation of low-intensity pulsed ultrasound on osteochondritis dissecans of the humeral capitellum

Abstract Background The clinical use of low-intensity pulsed ultrasound (LIPUS) was recently evaluated in cases of osteochondritis dissecans of the humeral capitellum (elbow OCD). However, the mechanism underlying the effect of LIPUS in elbow OCD is not well understood. The aim of this study was to histopathologically evaluate the effect of LIPUS irradiation on elbow OCD. Methods Fifteen patients with elbow OCD were enrolled in this study. All patients were juvenile baseball players (average age, 13.1 years). LIPUS was performed under the same conditions as the fracture treatment for an average length of 15.1 days in the preoperative period in seven patients (LIPUS group). Cylindrical tissue specimens obtained at the time of surgery were stained with hematoxylin and eosin and alcian blue, and were also immunostained to detect type 1 collagen (Col-1), osteopontin (OPN), and Runx2. The state of the cartilage and subchondral bone and expression levels of Col-1, OPN, and Runx2 were evaluated with a semiquantitative grading system by a blinded pathologist. Histological and immunohistological findings in both groups were compared using Fisher’s exact test. Results Both groups showed reparative tissue and cartilaginous metaplasia at the separation level near the subchondral bone; Col-1 was expressed in the reparative tissue. Furthermore, OPN and Runx2 were expressed in the interstitial cells near the separation level. The cartilage and subchondral bone findings in histological evaluations did not differ significantly between the LIPUS and control groups. The distribution of OPN expression levels in the two groups was as follows: Grade 0—LIPUS group, zero patients, and control group, five patients; Grade 1—LIPUS group and control group, two patients each; Grade 2—LIPUS group, five patients and control group, one patient; Grade 3—LIPUS group, one patient and control group, zero patients. OPN expression was significantly higher in the LIPUS group than in the control group ( p = 0.04). Conclusion LIPUS stimulation increased the expression levels of OPN in elbow OCD.