The use of spect/ct in the evaluation of heterotopic ossification in para/tetraplegics

The Survey of Cells Responsible for Heterotopic Ossification Development in Skeletal Muscles-Human and Mouse Models

Heterotopic ossification (HO) manifests as bone development in the skeletal muscles and surrounding soft tissues. It can be caused by injury, surgery, or may have a genetic background. In each case, its development might differ, and depending on the age, sex, and patient's conditions, it could lead to a more or a less severe outcome. In the case of the injury or surgery provoked ossification development, it could be, to some extent, prevented by treatments. As far as genetic disorders are concerned, such prevention approaches are highly limited. Many lines of evidence point to the inflammatory process and abnormalities in the bone morphogenetic factor signaling pathway as the molecular and cellular backgrounds for HO development. However, the clear targets allowing the design of treatments preventing or lowering HO have not been identified yet. In this review, we summarize current knowledge on HO types, its symptoms, and possible ways of prevention and treatment. We also describe the molecules and cells in which abnormal function could lead to HO development. We emphasize the studies involving animal models of HO as being of great importance for understanding and future designing of the tools to counteract this pathology.

The added value of SPECT-CT in the detection of heterotopic ossification on bone scintigraphy

PURPOSE

Heterotopic ossification (HO) is the abnormal osteogenesis in non-skeletal tissue. It can be difficult to detect, as it can mimic other conditions clinically and on imaging studies. The purpose of this study was to find the added value of SPECT-CT in accurate detection of HO.

MATERIALS AND METHODS

A total of 1780 reports on the PACS system of patients underwent bone scintigraphy at the Department of Nuclear Medicine and were filtered for the term "HO" or "heterotopic bone formation" and "SPECT-CT". Thirty-four patients fulfilled this criterion. All patients had bone scintigraphy and SPECT/CT in the same occasion. Images were reviewed by two nuclear medicine physicians blindly. The certainty of the presence of extra-skeletal soft tissue ossification on the planar with SPECT was graded as "definitely present", "maybe present", or "not present", and the same was determined on planar with SPECT-CT images.

RESULTS

Based on SPECT/CT, 23 (67.6%) patients were found to have HO, and 11 (32.4%) did not have confirming findings. Of the 23 positive patients on SPECT/CT, eight (34.8%) showed "definitely present" and 12 (52.2%) patients were under "maybe present" on SPECT only. Three (13%) patients were negative on the SPECT and showed evidence of HO on CT. Of the 11 patients that did not demonstrate definite evidence of HO on SPECT/CT, seven (63.6%) were negative on SPECT alone and, four (36.4%) were under "maybe present" on SPECT. The definite detection of HO was statistically significant higher when CT is added to SPECT.

CONCLUSIONS

Our findings suggest that adding the CT component to SPECT is valuable in the detection of HO.

The traumatic bone: trauma-induced heterotopic ossification

Heterotopic ossification (HO) is a common occurrence after multiple forms of extensive trauma. These include arthroplasties, traumatic brain and spinal cord injuries, extensive burns in the civilian setting, and combat-related extremity injuries in the battlefield. Irrespective of the form of trauma, heterotopic bone is typically endochondral in structure and is laid down via a cartilaginous matrix. Once formed, the heterotopic bone typically needs to be excised surgically, which may result in wound healing complications, in addition to a risk of recurrence. Refinements of existing diagnostic modalities, like micro- and nano-CT are being adapted toward early intervention. Trauma-induced HO is a consequence of aberrant wound healing, systemic and local immune system activation, infections, extensive vascularization, and innervation. This intricate molecular crosstalk culminates in activation of stem cells that initiate heterotopic endochondral ossification. Development of animal models recapitulating the unique traumatic injuries has greatly facilitated the mechanistic understanding of trauma-induced HO. These same models also serve as powerful tools to test the efficacy of small molecules which specifically target the molecular pathways underlying ectopic ossification. This review summarizes the recent advances in the molecular understanding, diagnostic and treatment modalities in the field of trauma-induced HO.

Heterotopic Ossification and Hypertrophic Scars

Burns and trauma cause superficial and deep soft tissue wounds that cannot heal to the preinjury state. Healing requires cell proliferation and differentiation into the injured tissue type, laying down extracellular matrix, often as collagens. Heterotopic ossification causes severe pain, nonhealing wounds, and restricted range of motion. Treatment includes radiation therapy, nonsteroidal anti-inflammatory drugs, bisphosphonates, and possibly surgical excision and prophylactic measures. Hypertrophic scars, nonosseous lesions caused by excessive collagen deposition, are often painful, functionally limiting, and aesthetically displeasing. Treatment includes CO2 laser application, steroid injections, and excision with skin grafting. This article reviews the management of these pathologic wounds.

Heterotopic Ossification Following Upper Extremity Injury

Heterotopic ossification (HO) presents a substantial barrier to rehabilitation for patients with severe burns or trauma. Although surgical excision is a mainstay of management for this condition, this is unable to address the chronic sequelae of HO, including chronic pain, joint contractures, nerve dysfunction, and open wounds. Current therapeutic modalities are aimed at excision and the prevention of recurrence using nonsteroidal antiinflammatory drugs (NSAIDs) or radiation therapy. Research is now focused on identifying alternative strategies to prevent the initial occurrence of HO through NSAIDs and novel inhibitors of the bone morphogenetic protein signaling pathway.