Re: "High prevalence of heterotopic ossification in critically ill patients with severe COVID-19" by Stoira et al

The Unrecognized Orthopedic Burden of COVID-19: Heterotopic Ossification of the Hip Joint

COVID-19 has extensively affected the health-care organization with varying impact on different medical specialties. Long term ICU admission is associated with a less familiar complication: the formation of heterotopic ossifications (HO). In this case report we would like to emphasize the unrecognized burden of the coronavirus pandemic in patient care from the perspective of the orthopedic surgeon. We describe two patients with major HOs around their hip joints after COVID-19. Current literature underlines the increased prevalence of HO formation in COVID-19 patients requiring long-lasting mechanical ventilation and ICU admission including prone positioning. Preventing HO formation remains a difficult undertaking without obvious evidence supporting a golden standard treatment. We advice early passive mobilization during ICU stay, also during prone positioning, serum ALP follow-up during admission, NSAID administration if possible and a low threshold in the use of radiotherapy of joints with a limited range of motion.

Computer Navigation-Assisted Resection of Heterotopic Ossification Around the Hip: A Technical Note

Heterotopic ossification is a rare but debilitating situation. It occurs in patients who have undergone paralysis and/or immobilization. Hip osteoma is one of the most frequent locations and is associated with a significant functional handicap. Its treatment is based on surgical resection, which is a risky surgery that is not devoid of complications such as infections, hematoma, and recurrence. We describe in this paper a new surgical technique that adds to the classic hip osteoma resection: guidance with a navigation system coupled to a 3D imaging tool. We performed this technique on two patients (three hips, one bilateral case). We think that this technique makes the surgery safer with fewer complications.

Heterotopic Ossification after a Prolonged Course of COVID-19: A Case Report and Review of the Literature

We report the case of a 20-year-old male who developed severe HO of the left hip secondary to a prolonged course of COVID-19 pneumonia. Upon extubation, he was found to have debilitating left hip pain and significant functional deficits with regard to his range of motion and functional status. There are numerous known causes of heterotopic ossification (HO), including trauma, surgery, and traumatic brain or spinal cord injuries. An increased incidence of HO has also been reported in patients who undergo prolonged intubation. While the COVID-19 virus has many known respiratory and medical complications, it has also resulted in unforeseen complications that present long-term challenges for patients. When treating patients with coronavirus, physicians should be aware of HO as a possible complication and consider it as a cause of musculoskeletal pain.

Neurogenic Heterotopic Ossifications Recapitulate Hematopoietic Stem Cell Niche Development Within an Adult Osteogenic Muscle Environment

Hematopoiesis and bone interact in various developmental and pathological processes. Neurogenic heterotopic ossifications (NHO) are the formation of ectopic hematopoietic bones in peri-articular muscles that develop following severe lesions of the central nervous system such as traumatic cerebral or spinal injuries or strokes. This review will focus on the hematopoietic facet of NHO. The characterization of NHO demonstrates the presence of hematopoietic marrow in which quiescent hematopoietic stem cells (HSC) are maintained by a functional stromal microenvironment, thus documenting that NHOs are neo-formed ectopic HSC niches. Similarly to adult bone marrow, the NHO permissive environment supports HSC maintenance, proliferation and differentiation through bidirectional signaling with mesenchymal stromal cells and endothelial cells, involving cell adhesion molecules, membrane-bound growth factors, hormones, and secreted matrix proteins. The participation of the nervous system, macrophages and inflammatory cytokines including oncostatin M and transforming growth factor (TGF)-β in this process, reveals how neural circuitry fine-tunes the inflammatory response to generate hematopoietic bones in injured muscles. The localization of NHOs in the peri-articular muscle environment also suggests a role of muscle mesenchymal cells and bone metabolism in development of hematopoiesis in adults. Little is known about the establishment of bone marrow niches and the regulation of HSC cycling during fetal development. Similarities between NHO and development of fetal bones make NHOs an interesting model to study the establishment of bone marrow hematopoiesis during development. Conversely, identification of stage-specific factors that specify HSC developmental state during fetal bone development will give more mechanistic insights into NHO.