gms | German Medical Science

Objectives: Osteoporosis with its accompanying fractures has become a growing burden on the health care system, leading to longer hospital stays and increased mortality and morbidity rates, especially in the aging population. Our study investigated the effect of ESWT on the time and quality of fracture healing in an osteoporotic rat model.

Methods: We utilized 144 3-month old female Sprague-Dawley rats. 132 were ovariectomized and developed manifest osteoporosis within the following 8 weeks. 12 were sham-operated (non-osteoporotic control group "SHAM"). Bilateral, metaphyseal tibia-osteotomies and mini T-plate fixations were conducted in each animal. Out of the 11 groups, 2 groups (SHAM and the osteoporotic control group) did not receive ESWT. The other 9 received, over a 35-day period, different combinations of ESWT-intensities (0.15 mJ/mm2, 0.35 mJ/mm2, or 0.55 mJ/mm2) and application-frequencies (day 1 or 1/11/26, or 1/8/15/22/29). The harvested tibiae were qualitatively tested with a 3-point bending/breaking test (investigating the newly formed callus for stiffness (S), yield load (yL), maximum force (Fmax), and failure load (fL)). Further the tibiae underwent quantitative and dynamic evaluation through high-resolution micro-CT imaging, histomorphometric analyses and immunofluorescence labeling. Gene-expression analysis was done through PCR for the transcripts of osteocalcin, IGF-1, Collagen 1-alpha, Estrogen-Receptor-alpha, and tartrate-resistant acid phosphatase.

Results and Conclusion: There was a significant improvement in thr healing of the osteoporotic fractures subjected to ESWT compared to the SHAM group and the osteoporotic animals not undergoing ESWT treatment.

We found higher average results under ESWT for S, yL, Fmax and fL in the biomechanical analyses. The application of 3 x 0.15 mJ/mm² was superior to the more intensive treatment groups, with average values of S=96N/mm, Fmax=41N, and yL=37N being significantly higher compared to the SHAM (54N/mm, 33N and 28N) and the osteoporotic control group (50N/mm, 40N and 33N). In groups 9-11, the intensity was higher, but the S, yL, Fmax, and fL were lower, narrowing down the range of beneficial intensities. The PCR analysis demonstrated a higher transcription of osteo-anabole/-catabole gene-products, signaling, in the ESWT-treated groups, a higher bone turnover. Micro-CT and histomorphometric analyses showed similar trends, resulting in significantly more formation of callus under ESWT-treatment.

This study shows that ESWT is capable of improving osteoporotic fracture healing regarding quantitative and qualitative aspects. Further, it showed ESWT intensities and application-frequencies that achieve optimal fracture healing. And in light of the fact that the properties of rat-bone(-metabolism) are very similar to those of humans, this could prove to be a tremendous improvement and advancement in human osteoporotic fracture therapy-strategies, patient health, and health care cost reductions.