High‐intensity focused ultrasound as a potential treatment modality for heterotopic ossification.

Abstract

Heterotopic ossification (HO) is the growth of bone in abnormal locations such as soft tissue. HO is a frequent secondary complication of common trauma, e.g., amputation or spinal cord injury. HO causes pain, motion restriction, and poor prosthetic fitting. Current HO treatments include non‐steroidal anti‐inflammatory drugs, radiation, surgery, and shock‐waves, but HO often returns. In this work, feasibility of HO treatment using high‐intensity focused ultrasound (HIFU) is studied. HIFU may induce destruction of HO nodules by a combination of thermal ablation and mechanical erosion through bubble activity. In preliminary experiments bone sections from rodent proximal tibiae embedded in polyacrylamide gel were used as tissue phantoms; subsequent experiments were performed on HO induced in a mouse calf muscle. A 2‐MHz focused transducer was used to generate pulses of shock waves with peak positive pressure of 67 MPa, duration of 10–100 ms, and 1%–10% duty cycle. High‐resolution microCT imaging of the samples was performed prior to and following HIFU exposure. Both mechanical damage of the porous bone structure and thermal denaturation of the bone were observed. The data obtained suggest that HIFU may be an option for non‐invasive treatment of HO. [Work supported by NSBRI_SMSTO1601 and NIH_DK007742].