Is low-intensity pulsed ultrasound effective for revitalizing a severely necrotic small bone? An experimental rabbit model

Low-intensity pulsed ultrasound enhances bone repair in a rabbit model of steroid-associated osteonecrosis

BACKGROUND

Steroids are a leading cause of femoral head osteonecrosis. Currently there are no medications available to prevent and/or treat steroid-associated osteonecrosis. Low-intensity pulsed ultrasound (LIPUS) was approved by the FDA for treating delayed union of bone fractures. Some studies have reported that LIPUS can enhance bone formation and local blood flow in an animal model of fracture healing. However, whether the effect of osteogenesis and neovascularization by LIPUS can enhance the repair progress in steroid-associated osteonecrosis is unknown.

QUESTIONS/PURPOSES

We hypothesized that LIPUS may facilitate osteogenesis and neovascularization in the reparative processes of steroid-associated osteonecrosis. Using a rabbit animal model, we asked whether LIPUS affects (1) bone strength and trabecular architecture; (2) blood vessel number and diameter; and (3) BMP-2 and VEGF expression.

METHODS

Bilateral femoral head necrosis was induced by lipopolysaccharide and methylprednisolone in 24 rabbits. The left femoral heads of rabbits received LIPUS therapy (200 mW/cm(2)) for 20 minutes daily and were classified as the LIPUS group. The right femoral heads of the same rabbits did not receive therapy and were classified as the control group. All rabbits were euthanized 12 weeks after LIPUS therapy. Micro-CT, biomechanical testing, histologic evaluation, immunohistochemistry, quantitative real-time PCR, and Western blot were used for examination of the effects of LIPUS.

RESULTS

Twelve weeks after LIPUS treatment, the loading strength in the control group was 355 ± 38 N (95% CI, 315-394 N), which was lower (p = 0.028) than that in the LIPUS group (441 ± 78 N; 95% CI, 359-524 N). The bone tissue volume density (bone volume/total volume) in the LIPUS group (49.29% ± 12.37%; 95 % CI, 36.31%-62.27%) was higher (p = 0.022) than that in the control group (37.93% ± 8.37%; 95 % CI, 29.15%-46.72%). The percentage of empty osteocyte lacunae in the LIPUS group (17% ± 4%; 95% CI, 15%-20%) was lower (p = 0.002) than that in the control group (26% ± 9%; 95% CI, 21%-32%). The mineral apposition rate (μm/day) in the LIPUS group (2.3 ± 0.8 μm/day; 95% CI, 1.8 2.8 μm/day) was higher (p = 0.001) than that in the control group (1.6 ± 0.3 μm/day; 95% CL, 1.4-1.8 μm/day). The number of blood vessels in the LIPUS group (7.8 ± 3.6/mm(2); 95% CI, 5.5-10.1 mm(2)) was greater (p = 0.025) than the number in the control group (5.7 ± 2.6/mm(2); 95% CI, 4.0-7.3 mm(2)). Messenger RNA (mRNA) and protein expression of BMP-2 in the LIPUS group (75 ± 7, 95% CI, 70-79; and 30 ± 3, 95% CI, 28-31) were higher (both p < 0.001) than those in the control groups (46 ± 5, 95% CI, 43-49; and 15 ± 2, 95% CI, 14-16). However, there were no differences (p = 0.114 and 0.124) in mRNA and protein expression of vascular endothelial growth factor between the control (26 ± 3, 95% CI, 24-28; and 22 ± 6, 95% CI, 18-26) and LIPUS groups (28 ± 2, 95% CI, 26-29; and 23 ± 6, 95% CI, 19-27).

CONCLUSIONS

The results of this study indicate that LIPUS promotes osteogenesis and neovascularization, thus promoting bone repair in this steroid-associated osteonecrosis model.

CLINICAL RELEVANCE

LIPUS may be a promising modality for the treatment of early-stage steroid-associated osteonecrosis. Further research, including clinical trials to determine whether LIPUS has a therapeutic effect on patients with early-onset steroid-associated osteonecrosis may be warranted.

From bench to application: current practices in tissue engineering and its realisation at maxillofacial units in Germany, Austria and Switzerland

Over the last 20 years, the highly interdisciplinary field of tissue engineering (TE) has become an established subspecialty in research facilities all over the world. Numerous methods and protocols are available for various research intentions and aims, but there are no data indicating which of these methods and resources are generally used. This study is an overview of the resources and methods that are commonly applied in TE research in general, and in the field of oral and maxillofacial surgery (OMFS) in Germany, Austria and Switzerland. The DÖSAK collaborative group for TE developed a detailed questionnaire and collected information from participating university hospitals in these three countries. We evaluated the availability of research facilities, in vitro realisation and in vivo designs for animal studies in these departments. 11 units who replied, out of 35 we contacted, conducted research on bone regeneration in interdisciplinary research facilities. 10 departments used xenogeneic and alloplastic scaffolds for in vitro and in vivo applications. In this case, the most commonly utilised trademarks were Bio-Oss(®) and CERASORB(®). 9 units used osteoblasts (73%) and 10 proliferation assays in vitro, whereas rats served as the standard animal model for histology/immunohistochemistry in 6. All research units were interested in establishing a platform for research exchange and communication. This study shows that tissue engineering is well established and highly accepted in most participating university hospitals and research facilities. The presented data, together with data published in a foregoing paper will help arrange more readily available standardised procedures for further investigations.

A new treatment strategy for Kienböck's disease: combination of bone marrow transfusion, low-intensity pulsed ultrasound therapy, and external fixation

BACKGROUND

The purpose of this study was to investigate the midterm clinical and radiographic outcomes of this new treatment for Kienböck's disease.

METHODS

We applied a new method involving drilling, bone marrow transfusion, external fixation, and low-intensity pulsed ultrasound for patients with Kienböck's disease. Between 2000 and 2006, the treatment was performed in 18 patients (10 men and 8 women; 9 right wrists and 9 left wrists). The preoperative Lichtman stages were stage II in 4 cases, stage IIIa in 11 cases, and stage IIIb in 3 cases. The mean age at surgery was 44.9 years (range 16-68 years), and the mean follow-up period was 63 months (range 28-125 months). The overall results were evaluated using the Mayo wrist score and Nakamura scoring system for Kienböck's disease. Magnetic resonance imaging (MRI) was performed for all patients.

RESULTS

Wrist pain improved to no pain in 13 patients, mild pain in 4 patients, and moderate pain in 1 patient. The average wrist flexion-extension arc was 100° and averaged 120 % of the preoperative value. The average grip strength increased from 50 to 85 % relative to the unaffected side. On roentgenograms, the carpal height ratio (change from 0.53 to 0.51) and the Stahl index (change from 0.38 to 0.32) decreased slightly. On MRI, fatty marrow was recovered in 11 patients (61 %) on proton density-weighted images.

CONCLUSIONS

This method can be used as a less-invasive surgical treatment alternative for Kienböck's disease. At an average follow-up period of 6 years, this new treatment has been shown to be a reliable and durable procedure for patients with Lichtman stage II or stage III Kienböck's disease. Caution should be exercised for patients with a fragmented lunate because of the risk of collapse and nonunion of the lunate.